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First Aid Flashcards > Microbiology > Flashcards

Microbiology Flashcards

1
Q

Peptidoglycan: function and composition

A

Function: rigid support, protects against osmotic pressure

Composition: sugar backbone with peptide side chains cross linked by transpeptidase

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2
Q

Gram-positive cell wall and membrane: function and composition

A

Function: major surface antigen

Composition: peptidoglycan for support, lipoteichoic acid induces TNF and IL-1

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3
Q

Gram-negative cell wall and membrane: function and composition

A

Function: site of endotoxin (LPS), major surface antigen

Composition: lipid A induces TNF and IL-1, O-polysaccaride is the antigen

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4
Q

Plasma membrane: function and composition

A

Function: site of oxidative and transport enzymes (akin to mitochondrial membrane)

Composition: phospholipid bilayer

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5
Q

Ribosome: function and composition

A

Function: protein synthesis

Composition: 30S and 50S subunits

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6
Q

Periplasm: function and composition

A

Function: space between the cytoplasmic membrane and the outer membrane in gram-negatives

Composition: contains hydrolytic enzymes, including beta-lactamases (penicillin)

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7
Q

Capsule: function and composition

A

Function: protects against phagocytosis

Composition: polysaccharides (exception: D-glutamate in B. anthracis - anthrax)

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8
Q

Pilus/fimbria: function and composition

A

Function: mediates adherence to cell surface, sex pills forms attachment between 2 bacteria during conjugation

Composition: glycoprotein

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9
Q

Flagellum: function and composition

A

Function: motility

Composition: protein (flagellin)

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10
Q

Spore: function and composition

A

Function: resistance to dehydration, heat, and chemicals

Composition: keratin-like coat, dipicolinic acid, peptidoglycan

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11
Q

Plasmid: function and composition

A

Function: carries additional genes for antibiotic resistance, enzymes, toxins

Composition: DNA

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12
Q

Glycocalyx: function and composition

A

Function: mediates adherence to surfaces

Composition: polysaccharide

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13
Q

Gram-postive cell wall vs. Gram-negative cell wall

A

Gram-positive has lipoteichoic acid, thicker peptidoglycan layer, no outer membrane

Gram-negative has endotoxin/LPS on the outer membrane, periplasm, thinner peptidoglycan

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14
Q

Bacteria that don’t gram-stain well

A

Treponema (too thin), Rickettsia (intracellular), Mycobacteria (high lipid content in cell wall), Mycoplasma (no cell wall), Legionella (intracellular), Chlamydia (intracellular)

These Rascals May Microscopically Lack Color

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15
Q

How do you visualize Treponema?

A

Dark-field microscopy and fluorescent antibody staining

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16
Q

How do you visualize Mycobacteria?

A

Acid-fast stain

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17
Q

Bacteria visualized by Giemsa stain

A

Chlamydia, Borrelia, Rickettsiae, Trypanosomes, Plasmodium

Certain Bugs Really Try my Patience

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18
Q

Bacteria visualized by PAS (periodic acid-Schiff) stain

A

Stains glycogen, used for Whipple’s disease (Thopheryma whipplei)

PAS the sugar

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19
Q

Bacteria visualized by Ziehl-Neelsen (carbol fuschin) stain

A

Acid-fast bugs (Nocardia, Mycobacterium)

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20
Q

Organism visualized by India Ink stain

A

Cryptococcus neoformans

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21
Q

Bacteria visualized by Silver stain

A

Fungi, Legionella, Helicobacter pylori

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22
Q

H. influenzae culture requirements

A

Chocolate agar with factor V (NAD+) and X (hematin)

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23
Q

N. gonorrhoeae, N. meningitidis culture requirements

A

Thayer-Martin (VPN) media - vancomycin (inhibits gram-positives), polymyxin (inhibits other gram-negatives), nystatin (inhibits fungi)

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24
Q

B. pertussis culture requirements

A

Bordet-Gengou (potato) agar

Bordet for Bordetella

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25
Q

C. diphtheriae culture requirements

A

Tellurite plate, Loffler’s media

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26
Q

M. tuberculosis culture requirements

A

Lowenstein-Jensen agar

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27
Q

M. pneumoniae culture requirements

A

Eaton’s agar

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28
Q

Lactose-fermenting enterics culture requirements

A

Pink colonies on MacConkey’s agar

E. coli also grown on eosin-methylene blue (EMB) agar as colonies with green metallic sheen

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29
Q

Legionella culture requirements

A

Charcoal yeast extract buffered with cysteine and iron

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30
Q

Fungi culture requirements

A

Sabouraud’s agar

Sab’s a fun guy

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31
Q

Obligate aerobes

A

Nocardia, Pseudomonas aeruginosa, Mycobacterium tuberculosis, Bacillus

Nagging Pests Must Breathe

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32
Q

Obligate anaerobes

A

Clostridium, Bacteroides, Actinomyces

Anaerobes Can’t Breathe Air

Foul-smelling and difficult to culture, produce gas in tissue

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33
Q

What makes anaerobic bacteria susceptible to oxidative damage?

A

They lack catalase and/or superoxide dismutase

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34
Q

What antibiotic is ineffective against anaerobic bacteria?

A

Amin(O2)glycosides - require oxygen to enter bacterial cells

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35
Q

Intracellular bacteria

A

Obligate: Rickettsia, Chlamydia (stay inside when it’s Really Cold)

Facultative: Salmonella, Neisseria, Brucella, Mycobacterium, Listeria, Francisella, Legionella, Yersinia pestis (Some Nasty Bugs May Live FacultativeLY)

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36
Q

Encapsulated bacteria

A

Streptococcus pneumoniae, Haemophilus influenzae type B, Neisseria meningitidis, Escherichia coli, Salmonella, Klebsiella pneumoniae, group B strep

SHiNE SKiS

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37
Q

What reaction do encapsulated bacteria have?

A

Positive quellung - swells when anti-capsular antisera are added

Quellung = capsular “swellung”

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38
Q

How are encapsulated bacteria cleared?

A

Opsonized and then cleared by spleen

Asplenic people have decreased opsonizing ability and thus are at risk for severe infections (need S. pneumonia, H. influenza, and N. meningitidis vaccines)

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39
Q

Catalase-positive organisms

A

Pseudomonas, Listeria, Aspergillus, Candida, E. coli, S. aureus, Serratia

You need PLACESS for your “CAT”s

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40
Q

What does catalase do for pathogens?

A

Lets them degrade H2O2 before it can be converted to microbicidal products by myeloperoxidase

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41
Q

What types of bacteria infect people with chronic granulomatous disease (CGD)? What is their enzyme defect?

A

Catalase-positive organism

NADPH oxidase deficiency

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42
Q

Urease-positive bacteria

A

Cryptococcus, H. pylori, Proteus, Ureaplasma, Nocardia, Klebsiella, S. epidermidis, S. saprophyticus

CHuck norris hates PUNKSS

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43
Q

Pigment-producing bacteria

A

Actinomyces israelii, S. auerus, Pseudomonas aeruginosa, Serratia marcescens

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44
Q

Actinomyces israelii pigment

A

Yellow sulfur granules composed of filaments of bacteria

Israel has yellow sand

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45
Q

Staph aereus pigment

A

Yellow pigment

aureus = gold in latin

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46
Q

Pseudomonas aeruginosa pigment

A

Blue-green

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47
Q

Serratia marcescens pigment

A

Red

Red marachino (marcescens) cherries

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48
Q

Protein A

A

Bacterial virulence factor

Binds Fc region of Ig’s, prevents opsonization and phagocytosis

Expressed by Staph aureus

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49
Q

IgA protease

A

Bacterial virulence factor

Cleaves IgA

Secreted by S. pneumoniae, H. influenzae type B, Neisseria (SHiN) to colonize respiratory influenza

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50
Q

M protein

A

Bacterial virulence factor

Prevents phagocytosis

Express by group A strep

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51
Q

Polysaccharide capsule vaccine considerations

A

Have to conjugate a protein to the antigen to promote T-cell activation and class switching

Antigen alone can’t be presented to T cells

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52
Q

Types of conjugated vaccines

A

Pneumovax (NOT conjugated) vs. Prevnar (conjugated)
H. influenzae type B
Meningococcal vaccines

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53
Q

Exotoxin vs. Endotoxin: source

A

Exo: some gram-positive and some gram-negative

Endo: nearly all gram-negative (structural component)

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54
Q

Exotoxin vs. Endotoxin: secretion

A

Exo: yes

Endo: no

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55
Q

Exotoxin vs. Endotoxin: chemistry

A

Exo: polypeptide

Endo: lipopolysaccharide (structural component, released when bacteria is lysed)

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56
Q

Exotoxin vs. Endotoxin: location of gene

A

Exo: plasmid or bacteriophage

Endo: bacterial chromosome

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57
Q

Exotoxin vs. Endotoxin: toxicity

A

Exo: high

Endo: low (need a larger dose)

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58
Q

Exotoxin vs. Endotoxin: clinical effects

A

Exo: various

Endo: fever, shock (hypotensive), DIC

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59
Q

Exotoxin vs. Endotoxin: mode of action

A

Exo: various

Endo: induces TNF, IL-1, and IL-6

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60
Q

Exotoxin vs. Endotoxin: antigenicity

A

Exo: induces high-titer antibodies called antitoxins

Endo: poorly antigenic

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61
Q

Exotoxin vs. Endotoxin: vaccines

A

Exo: toxoids

Endo: no toxoids formed, no vaccine

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62
Q

Exotoxin vs. Endotoxin: heat stability

A

Exo: destroyed rapidly at 60 degrees (besides staphylococcal enterotoxin)

Endo: stable at 100 degrees for an hour

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63
Q

Exotoxin vs. Endotoxin: typical diseases

A

Exo: tetanus, botulism, diphtheria

Endo: meningococcemia, sepsis by gram-negative rods

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64
Q

Bacterial genetics: transformation

A

Ability to take up naked DNA from the environment (competence)

S. pneumoniae, H. influenze type B, Neisseria

(SHiN - mnemonic also used for IgA protease)

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65
Q

Bacterial genetics: F+ x F- conjugation

A

F+ plasmid has genes for sex pilus and conjugation

Bacteria without F+ plasmid are F-

Plasmid is transfered via pilus (no chromosomal genes)

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66
Q

Bacterial genetics: Hfr x F- conjugation

A

F+ plasmid can become incorporated into chromosomal DNA (Hfr)

Transfer of plasmid and chromosomal genes

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67
Q

Bacterial genetics: transposition

A

Segment of DNA that can jump (excision and insertion) from one location to another

Transfer of genes from plasmid to chromosomal DNA and vice versa

A way that chromosomal genes can be transferred via conjugation other than Hfr

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68
Q

Bacterial genetics: generalized transduction

A

Packaging event

Lytic phage infects bacteria, cleaves DNA and inserts itself

Part of chromosomal DNA can become packaged in viral capsid and then transferred to another cell upon the next infection cycle

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69
Q

Bacterial genetics: specialized transduction

A

Excision event

Lysogenic phage infects bateria, cleaves DNA and inserts itself

Part of chromosomal DNA can become packaged in viral capsid and then transferred to another cell upon the next infection cycle

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70
Q

What can you add to the environment to prevent bacterial transformation?

A

Deoxyribonuclease (degrades DNA)

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71
Q

Streptococcus pyogenes (GAS)

A

Bacitracin sensitive

Antibodies to M protein enhance host defenses but can also give rise to rheumatic fever

ASO titer detects infection

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72
Q

Streptococcus agalatiae (GBS)

A

Bacitracin resistant, beta-hemolytic, hippurate test positive

Colonizes vagina

Pneumonia, meningitis, sepsis

Mainly in babies

Screen pregnant women at 35-37 weeks, give intrapartum penicillin prophylaxis if positive

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73
Q

Enterococci (GDS)

A

Normal colonic flora

Enterococcus faecalis and Enterococcus faecium

Penicillin G resistant

Cause UTI, biliary tract infections, subacute endocarditis

Can grow in 6.5% NaCl and bile

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74
Q

Streptococcus bovis (GDS)

A

Colonizes the gut

Cause bacteremia and subacute endocarditis in colon cancer patients

Bovis in the Blood = Cancer in the Colon

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75
Q

VRE

A

Vancomycin-resitant enterococci

Cause of nosocomial infection

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76
Q

CAMP factor

A

Produced by group-B strep, enlarges the area of hemolysis caused by S. aureus

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77
Q

JONES criteria

A

For rheumatic fever diagnosis:

J - joints, polyarthritis
O - heart, carditis
N - nodules (subcutaneous)
E - erythema marginatum (pink rings on the trunk)
S - Sydenham's chorea
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78
Q

Pyogenic group-A strep

A

Pharyngitis (can progress to rheumatic “PH”ever and glomerulonePHritis, cellulitis, impetigo

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79
Q

Toxigenic group-A strep

A

Scarlet fever, toxic shock-like syndrome, necrotizing fasciitis

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80
Q

Immunologic group-A strep

A

Rheumatic fever, acute glomerulonephritis

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81
Q

Scarlet fever signs

A

Scarlet rash with sandpaper texture that spares face, strawberry tongue, scarlet throat

Caused by toxigenic Streptococus pyogenes (GAS)

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82
Q

Corynebacterium exotoxin: toxin, mechanism, manifestation

A

Toxin: diphtheria toxin

Mechanism: inactivate elongation factor (EF-2)

Manifestation: pharyngitis with pseudomembranes in throat and severe lymphadenopathy (bull neck)

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83
Q

Pseudomonas aeruginosa exotoxin: toxin, mechanism, manifestation

A

Toxin: exotoxin A

Mechanism: inactivate elongation factor (EF-2)

Manifestation: host cells death

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84
Q

Shigella spp. exotoxin: toxin, mechanism, manifestation

A

Toxin: shiga toxin (ST)

Mechanism: inactivate 60S ribosome by removing adenine from rRNA

Manifestation: GI mucosal damage -> dystenery, enhanced cytokine release causing HUS (hemolytic-uremic syndrome)

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85
Q

Eneterhemorrhagic E. coli (EHEC) exotoxin: toxin, mechanism, manifestation

A

Toxin: shiga-like toxin (SLT)

Mechanism: inactivate 60S ribosome by removing adenine from rRNA

Manifestation: cytokine release causes HUS (hemolytic-uremic syndrome), does NOT invade cells so no GI mucosal damage

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86
Q

Enterotoxigenic E. coli (ETEC) exotoxin: toxin, mechanism, manifestation

A

Toxin: heat-labile toxin (LT) and heat-stable toxin (ST)

Mechanism: LT: activates adenylate cyclase (cAMP), increased Cl and H2O secretion into gut. ST: activates guanylate cyclase (cGMP), decreased reabsorption of NaCl and H2O in the gut.

Manifestation: watery diarrhea

“Labile in the Air” (cAMP) and “Stable on the Ground” (cGMP)

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87
Q

Bacillus anthracis exotoxin: toxin, mechanism, manifestation

A

Toxin: edema factor

Mechanism: mimics adenylate cyclase to increase cAMP

Manifestation: characteristic edematous borders of black eschar in cutaneous anthrax

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88
Q

Vibrio cholerae exotoxin: toxin, mechanism, manifestation

A

Toxin: cholera toxin

Mechanism: overactivates adenylate cyclase by activating Gs, increases cAMP, increased Cl and H2O secretion into gut

Manifestation: voluminous “rice-water” diarrhea

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89
Q

Bordatella pertussis exotoxin: toxin, mechanism, manifestation

A

Toxin: pertussis toxin

Mechanism: overactivates adenylate cyclase, increases cAMP by disabling Gi, impairs phagocytosis to permit survival of microbe

Manifestation: whooping cough - coughs on expiration and whoops on inspiration (100 day cough in adults)

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90
Q

Clostridium tetani exotoxin: toxin, mechanism, manifestation

A

Toxin: tetanospasmin

Mechanism: cleaves synaptobrevin (SNARE protein)

Manifestation: muscle rigidity and lockjaw, prevents release of inhibitory GABA neurotransmitters

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91
Q

Clostridium botulinum exotoxin: toxin, mechanism, manifestation

A

Toxin: botulinum toxin (BOTOX)

Mechanism: cleaves SNAP-25 (SNARE protein)

Manifestation: flaccid paralysis and floppy baby, prevents release of stimulatory ACh neurotransmitters

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92
Q

Clostridium perfringens exotoxin: toxin, mechanism, manifestation

A

Toxin: alpha toxin

Mechanism: phospholipase that degrades tissue and cell membranes

Manifestation: degradation of phospholipase C -> myonecrosis (gas gangrene) and hemolysis (“double zone” on blood agar)

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93
Q

Streptococcus pyogenes exotoxin: toxin, mechanism, manifestation

A

Toxin: steptolysin O

Mechanism: protein that degrades cell membrane

Manifestation: lysing of RBCs, contributes to beta-hemolysis, antibodies against the toxin are used to diagnose bacteria

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94
Q

Staphylococcus aureus exotoxin: toxin, mechanism, manifestation

A

Toxin: toxic shock syndrome toxin (TSST-1)

Mechanism: brings MHC II and TCR in proximity to outside of antigen binding site, causes overwhelming release of IFNy and IL-2 -> shock

Manifestation: toxic shock syndrome: fever, rash, shock, scalded skin syndrome (exfoliative toxin), food poisoning (enterotoxin)

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95
Q

Streptococcus pyogenes exotoxin: toxin, mechanism, manifestation

A

Toxin: exotoxin A

Mechanism: brings MHC II and TCR in proximity to outside of antigen binding site, causes overwhelming release of IFNy and IL-2 -> shock

Manifestation: toxic shock syndrome: fever, rash, shock

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96
Q

Strep. pneumoniae: characteristics, clinical signs, optochin?

A

Lancet-shaped, gram-positive diplococci, encapsulated, IgA protease, rusty sputum,

Most common cause of: Meningitis, Otitis media, Pneumonia, Sinusitis (MOPS), sepsis in sickle cell anemia

MOPS are Most OPtochin Sensitive

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97
Q

Lag phase

A

Metabolic activity without division

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98
Q

Exponential/log phase

A

Rapid cell division

Penicillins and cephalosporins act here as peptidoglycan in cell walls is being made

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99
Q

Stationary phase

A

Nutrient depletion slows growth, spore formation in some bacteria

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100
Q

Death

A

Prolonged nutrient depletion and buildup of waste products leads to death

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101
Q

Endotoxin mnemonic

A

Edema, nitric oxide, DIC/death (disseminated intravascular coagulation), Outer membrane, TNFa, O-antigen, eXtremely heat stable, IL-1 and IL-6, Neutrophil chemotaxis

ENDOTOXIN

102
Q

Alpha-hemolytic bacteria

A

Form green ring around colonies on blood agar

Streptococcus pneumoniae (catalse negative and optochin sensitive), Viridans streptococci (catalase negative and optochin resistant)

103
Q

Beta-hemolytic bacteria

A

Form clear are of hemolysis on blood agar

Staph. aureus (catalase and coagular positive)
Strep. pyogenes (GAS, catalase negative and bacitracin sensitive)
Strep. agalactiae (GBS, catalase negative and bacitracin resistant)
Listeria monocytogenes (tumbling motility, meningitis in newborns, unpasteurized milk)

104
Q

Identification of Staph species

A

NOvobiocin - Saprophyticus is Resistant, Epidermidis is Sensitive

On the office’s staph retreat, there was NO StRESs

105
Q

Identification of Strep species

A

Optochin - Viridans is Resistant, Pneumoniae is Sensitive

OVRPS

Bacitracin - GBS are Resitant, GAS are Sensitive

B-BRAS

106
Q

Staph aureus: characteristics, clinical signs and toxins, TSS signs and toxin

A

Gram-positive cocci in grapelike clusters, protein A binds Fc-IgG, inhibiting complement fixation and phagocytosis

Inflammatory disease: skin, organ absess, pneumonia, toxin-mediated: TSS, scalded skin syndrome (exfoliative toxin), food poisoning (enterotoxin - transmission due to ingestion of toxin: short incubation period and heat stable means it’s not destroyed by cooking), MRSA: methicillin-resistant (nosocomial and community-acquired infections, has penicillin-binding protein)

TSST: super antigen that binds to MHC II and T-cell receptor, resulting in polyclonal T-cell activation. Presents as fever, vomiting, rash, desquamation, shock, and end end-organ failure. Use of vaginal or nasal tampons predisposes you

107
Q

Staph aureus food poisoning

A

Ingestion of preformed toxin

108
Q

Staph epidermidis: transmission

A

Infects prosthetic devices and IV catheters leading to biofilms

Normal skin flora, contaminates blood cultures

109
Q

Viridans group strep.: hemolysis type, transmission, optochin?

A

Alpha-hemolytic

Normal oropharynx flora, cause dental caries and suabcute bacterial endocarditis at damaged valves

Resistant to optochin

Live in the mouth because they are not afraid of-the-chin (optochin)

110
Q

Corynebacterium diphtheriae: characteristics, culture requirements, toxin, vaccine

A

Gram-positive rods with metachromatic (blue and red) granules and Elek’s test for toxin, pseudomembranous pharyngitis (gray-white membrane) with lymphadenopathy, myocarditis, and arrhythmias

Black colonies on tellurite agar, or Loffler medium

Causes diphtheria via exotoxin encoded by beta-prophage (inhibits protein synthesis by ADP-ribosylation of EF-2

Toxoid vaccine prevents diphtheria

Coryne = club shaped

ABCDEFG: ADP-ribosylation, Beta-prophage, Corynebacterium, Diphtheria, Elongation Factor 2, Granules

111
Q

Spore forming bacteria

A

Gram-positive bacteria found in soil: Bacillus anthracis, Clostridia genus

Other spore-formers: Bacillus cereus, Clostridium botulinum, Coxiella burnetii

112
Q

Clostridium tetani: toxin, clinical signs

A

Produces tetanospasmin (causes tetanus), which cleaves synaptobrevin (SNARE protein)

Paralysis: blocks glycine and GABA release (inhibitory neurotransmitters) from Renshaw cells in spinal cord. Causes spastic paralysis, trismus (lockjaw), and risus sardonicus (sustained spasm of the face that looks like grinning)

113
Q

Clostridium botulinum: toxin, transmission

A

Produces a preformed, heat-labile toxin that cleaves SNAP-25 (SNARE protein) and inhibits ACh release at the neuromuscular junction

In adults, disease is caused by ingestion of preformed toxin. In babies, ingestion of spores in honey causes disease (floppy baby syndrome)

Botulinum is from Bad Bottles of food and honey (causes a flaccid paralysis)

114
Q

Clostridium difficile: toxins, clinical signs, treatment

A

Toxin A: enterotoxin, binds to brush border in gut Toxin B: cytotoxin, destroys enterocyte cytoskeletal structure, causing pseudomembranous colitis

Often 2° to antibiotic use, especially clindamycin or ampicillin. Diagnosed by detection of one or both toxins in stool. Difficile causes Diarrhea

Treatment: metronidazole or oral vancomycin, fecal transplant

115
Q

Clostridium perfringens: toxin, disease

A

Produces alpha toxin (“lecithinase,” a phospholipase) that causes myonecrosis (gas gangrene) and hemolysis

Perfringens perforates a gangrenous leg

116
Q

Anthrax: characteristics

A

Caused by Bacillus anthraces: gram-positive, spore-forming rod that produces anthrax toxin, only bacterium with a polypeptide capsule (contains D-glutamate)

117
Q

Cutaneous anthrax: transmission, clinical signs

A

Contact -> black eschar (painless ulcer)

Can progress to bacteremia and death

Black skin lesions: black eschar (necrosis) surrounded by edematous ring. Caused by lethal factor and edema factor

118
Q

Pulmonary anthrax: transmission, clinical signs

A

Inhalation of spores -> flu-like symptoms that rapidly progress to fever, pulmonary hemorrhage, mediastinitis, and shock

Woolsorters’ disease: inhalation of spores from contaminated wool

119
Q

Bacillus cereus: characteristics,, transmission, clinical signs,

A

Gram-positive, produces spores that can survive cooking rice

Keeping rice warm results in germination of spores and enterotoxin formation. Emetic type usually seen with rice and pasta

Food poisoning: nnausea and vomiting within 1–5 hours: caused by cereulide, a preformed toxin. Diarrheal type causes watery, nonbloody diarrhea and GI pain in 8–18 hours

“Reheated rice syndrome”

120
Q

Listeria monocytogenes: characteristics, transmissions, motility, clinical signs, treatment

A

Facultative intracellular microbe

Acquired by ingestion of unpasteurized milk/cheese and deli meats or by vaginal transmission during birth

Form “actin rockets” by which they move from cell to cell. Characteristic tumbling motility

Can cause amnionitis, septicemia, and spontaneous abortion in pregnant women, granulomatosis infantiseptica, neonatal meningitis, meningitis in immunocompromised patients, mild gastroenteritis in healthy individuals

Treatment: gastroenteritis usually self-limited, ampicillin in infants, immunocompromised patients, and the elderly in empirical treatment of meningitis

121
Q

Actinomyces vs. Nocardia: gram stain and oxygen utilization?

A

Actinomyces: gram-positive anaerobe
Nocardia: gram-positive aerobe

122
Q

Actinomyces vs. Nocardia: acid-fast?

A

Actinomyces: gram-positive anaerobe

Nocardia: gram-positive aerobe

123
Q

Actinomyces vs. Nocardia: environment found in?

A

Actinomyces: normal oral flora

Nocardia: soil

124
Q

Actinomyces vs. Nocardia: clinical signs

A

Actinomyces: oral/facial abscesses that drain through sinus tracts, forms yellow “sulfur granules”

Nocardia: pulmonary infections in immunocompromised patients and cutaneous infections after trauma in immunocompetent patients

125
Q

Actinomyces vs. Nocardia: treatment

A

Actinomyces: penicillin

Nocardia: sulfonamides

126
Q

Mycobacteria: characteristics, different species and diseases caused, treatment

A

All are acid-fast organisms

Mycobacterium tuberculosis (TB, often resistant to multiple drugs), M. kansasii (pulmonary TB-like symptoms, M. avium–intracellulare (causes disseminated, non-TB disease in AIDS - often resistant to multiple drugs)

TB symptoms include fever, night sweats, weight loss, and hemoptysis

Cord factor in virulent strains inhibits macrophage maturation and induces release of TNF-α

Prophylactic treatment with azithromycin, sulfatides (surface glycolipids) inhibit phagolysosomal fusion

127
Q

PPD: what does it test for? When is it positive? When is it negative?

A

TB

PPD+ if current infection, past exposure, or BCG vaccinated

PPD– if no infection or anergic (steroids, malnutrition, immunocompromise) and in sarcoidosis

128
Q

Signs of primary TB

A

Hilar nodes and ghon focus (mid field): small area of granulomatous inflammation that can be visualized if it calcifies

129
Q

Signs of secondary TB

A

Fibrocaseous cavitary lesion (upper lobes)

Fever, night sweats, weight loss, and hemoptysis

130
Q

Miliary TB

A

Disseminated disease characterized by tiny lesions (millet seeds)

131
Q

4 possible outcomes of primary TB

A

1) Heals by fibrosis -> immunity and hypersensitivity -> Tuberculin positive
2) Progressive lung disease (HIV, malnutrition) and death
3) Severe bacteremia -> miliary TB and death
4) Preallergic lymphatic of hematogenous dissemination -> dormant tubercle bacilli in several organs -> reactivation later in life

132
Q

Extrapulmonary TB

A

CNS (parenchymal tuburculoma or meningitis), vertebral body (Pott’s disease), lympadenitis, renal, GI

133
Q

Leprosy (Hansen’s disease): bacteria, culture, reservoir, treatment

A

Caused by Mycobacterium leprae: acid-fast bacillus that likes cool temperatures (infects skin and superficial nerves—“glove and stocking” loss of sensation)

Cannot be grown in vitro

Reservoir in United States: armadillos

Treatment: dapsone, rifampin, and clofazimine for 2–5 years for Lepromatous form, multidrug therapy consisting of dapsone and rifampin for 6 months for tuberculoid form

134
Q

Lepromatous Hansen’s disease/leprosy: presentation, immune response

A

Presents diffusely over skin and is communicable

Characterized by low cell-mediated immunity with a humoral Th2 response

135
Q

Tuberculoid Hansen’s disease/leprosy: presentation, immune response

A

Limited to a few hypoesthetic, hairless skin plaques

Characterized by high cell-mediated immunity with a largely Th1- type immune response

136
Q

Klebsiella: characteristics, transmission, clinical signs

A

Gram-negative, very mucoid colonies caused by abundant polysaccharide capsule. Red “currant jelly” sputum

Intestinal flora, causes lobar pneumonia in alcoholics and diabetics when aspirated. Also cause of nosocomial UTIs.

4 A’s: Aspiration pneumonia, Abscess in lungs and liver, Alcoholics, di-A-betics

137
Q

Salmonella vs. Shigella: flagella?

A

Salmonella: have flagella (salmon swim)

Shigella: no flagella

138
Q

Salmonella vs. Shigella: transmission

A

Salmonella: hematogenous

Shigella: cell to cell spread

139
Q

Salmonella vs. Shigella: reservoir

A

Salmonella: many animals

Shigella: only humans and primates

140
Q

Salmonella vs. Shigella: hydrogen sulfide?

A

Salmonella: yes

Shigella: no

141
Q

Salmonella vs. Shigella: effect of antibiotics

A

Salmonella: prolong symptoms

Shigella: prolong excretion in feces

142
Q

Salmonella vs. Shigella: pathophysiology

A

Salmonella: invades intestinal mucosa and causes a monocytic response

Shigella: invades intestinal mucosa and causes PMN infiltration

143
Q

Salmonella vs. Shigella: clinical signs

A

Salmonella: sometimes causes bloody diarrhea

Shigella: usually causes bloody diarrhea

144
Q

Salmonella vs. Shigella: lactose fermentation?

A

Salmonella: no

Shigella: no

145
Q

Salmonella typhi: characteristics, disease caused, reservoir, clinical signs, sequelae

A

Gram-negative

Causes typhoid fever

Found only in humans

Characterized by rose spots on the abdomen, fever, headache, and diarrhea

Can remain in gallbladder and cause a carrier state

146
Q

Campylobacter jéjunum: characteristics, transmission, clinical signs

A

Gram-negative, xomma or S-shaped, oxidase positive, grows at 42°C (“Campylobacter likes the hot campfire”)

Fecal-oral transmission through foods such as undercooked meat (poultry, meat}, unpasteurized milk

Major cause of bloody diarrhea, especially in children

Common antecedent to Guillain-Barré syndrome and reactive arthritis

147
Q

Vibrio cholerae: characteristics, toxin, endemic area, treatment

A

Comma shaped, oxidase positive, grows in alkaline media

Produces profuse rice-water diarrhea via toxin that permanently activates Gs -> more cAMP

Endemic to developing countries

Treatment: prompt oral rehydration is necessary

148
Q

Yersinia entercolitica: transmission, clinical signs

A

Usually transmitted from pet feces (e.g., puppies), contaminated milk, or pork

Causes mesenteric adenitis that can mimic Crohn’s or appendicitis

149
Q

Salmonella gram stain

A

Gram negative

150
Q

Shigella gram stain

A

Gram negative

151
Q

E. coli

A

E. coli virulence factors:

Fimbriae - cystitis and pyelonephritis

K capsule - pneumonia, neonatal meningitis

LPS endotoxin - septic shock.

152
Q

EIEC: toxin and mechanism, presentation

A

Microbe invades intestinal mucosa and causes necrosis and inflammation. No toxins produced. Clinical manifestations similar to Shigella

Invasive, dysentery

153
Q

ETEC: toxin and mechanism, presentation

A

Labile toxin/stable toxin. No inflammation or invasion

Traveler’s diarrhea (watery)

154
Q

EPEC: toxin and mechanism, presentation

A

No toxin produced. Adheres to apical surface, flattens villi, prevents absorption

Diarrhea usually in children (Pediatrics)

155
Q

EHEC: toxin and mechanism, presentation

A

O157:H7 is the most common serotype. Produces Shiga-like toxin and Hemolytic-uremic syndrome (triad of anemia, thrombocytopenia, and acute renal failure)

Endothelium swells and narrows lumen, leading to mechanical hemolysis and reduced renal blood flow; damaged endothelium consumes platelets

Dysentery (toxin alone causes necrosis and inflammation)

Does not ferment sorbitol (distinguishes it from other E. coli)

156
Q

Pseudomonas aeruginosa: characteristics, clinical signs, normal environment, toxin, treatment

A

Obligate aerobic gram-negative rod, mon–lactose fermenting, oxidase positive, produces pyocyanin (blue-green) pigment, has a grape-like odor

PSEUDOmonas is associated with wound
and burn infections, Pneumonia (especially in cystic fibrosis), Sepsis (black lesions on skin), External otitis (swimmer’s ear), UTI, Drug use and Diabetic Osteomyelitis, and hot tub folliculitis

Malignant otitis externa in diabetics

Found in water sources

Produces endotoxin (fever, shock) and exotoxin A (inactivates EF-2)

Treatment: aminoglycoside plus extended- spectrum penicillin (e.g., piperacillin, ticarcillin)

Aeruginosa—aerobic. Think water connection and blue-green pigment

Think Pseudomonas in burn victims.
Chronic pneumonia in CF patients is associated
with biofilm

157
Q

Legionella pneumophila: characteristics, diseases caused, clinical test, transmission, treatment

A

Gram-negative rod. Gram stains poorly—use silver stain. Grow on charcoal yeast extract
culture with iron and cysteine

Legionnaires’ disease = severe pneumonia, fever, GI and CNS symptoms

Pontiac fever = mild flu-like syndrome

Detected clinically by presence of antigen in urine

Aerosol transmission from environmental water source habitat. No person-to-person transmission

Treatment: macrolide or quinolone.

Think of a French legionnaire (soldier) with his silver helmet, sitting around a campfire (charcoal) with his iron dagger—he is no sissy (cysteine).
Labs show hyponatremia.

158
Q

Lactose-fermenting enteric bacteria: culture and appearance, examples, carbohydrate utilization, other agar options and appearance

A

Grow pink colonies on MacConkey’s agar

Examples: Citrobacter, Klebsiella,
E. coli, Enterobacter, and Serratia

E. coli produces β-galactosidase, which breaks down lactose into glucose and galactose

Lactose is KEE

Test with MacConKEE’S agar

EMB agar—lactose fermenters grow as purple/black colonies, E. coli grows purple colonies with a green sheen

159
Q

Penicillin and gram-negative bugs

A

Gram-negative bacilli are resistant to penicillin G but may be susceptible to penicillin derivatives such as ampicillin and amoxicillin

The gram-negative outer membrane layer inhibits entry of penicillin G and vancomycin

160
Q

Neisseria: characteristics, carbohydrate utilization and Ig production

A

Gram-negative diplococci

Both ferment glucose and produce IgA proteases

MeninGococci ferment Maltose and Glucose, Gonococci ferment Glucose

161
Q

Haemophilus infleunzae: characteristics, transmission, clinical signs, culture requirements, treatment, vaccine

A

Small gram-negative (coccobacillary) rod, produces IgA protease

Aerosol transmission

HaEMOPhilus causes Epiglottitis (“cherry
red” in children), Meningitis, Otitis media, and Pneumonia

Most invasive disease caused by capsular type B. Nontypeable strains cause mucosal infections (otitis media, conjunctivitis, bronchitis)

Culture on chocolate agar requires factors V (NAD+) and X (hematin) for growth, can also be grown with S. aureus, which provides factor V (mnemonic: When a child has “flu,” mom goes to five (V) and dime (X) store to buy some chocolate)

Treat meningitis with ceftriaxone. Rifampin prophylaxis in close contacts

Vaccine contains type B capsular polysaccharide (polyribosylribitol phosphate) conjugated
to diphtheria toxoid or other protein. Given between 2 and 18 months of age

Does not cause the flu (influenza virus does)

162
Q

Neisseria gonococci vs. Neisseria meningococci: capsule?

A

Neisseria gonococci: no capsule

Neisseria meningococci: polysaccharide capsule

163
Q

Neisseria gonococci vs. Neisseria meningococci: maltose fermentation?

A

Neisseria gonococci: no

Neisseria meningococci: yes (Meningococci Maltose)

164
Q

Neisseria gonococci vs. Neisseria meningococci: vaccine?

A

Neisseria gonococci: no vaccine

Neisseria meningococci: yes, except for type B

165
Q

Neisseria gonococci vs. Neisseria meningococci: transmission

A

Neisseria gonococci: sexual transmission

Neisseria meningococci: respiratory and oral secretions

166
Q

Neisseria gonococci vs. Neisseria meningococci: clinical signs

A

Neisseria gonococci: gonorrhea, septic arthritis, neonatal conjunctivitis, PID (pelvic inflammatory disease), Fitz-Hugh-Curtis syndrome (PID complication: acute onset RUQ abdominal pain aggravated by breathing, coughing or movement, which is referred to the right shoulder

Neisseria meningococci: meningococcemia and meningitis, Waterhouse-Friderichsen syndrome (severe septicemia with fever, rigors, vomiting and headache)

167
Q

Neisseria gonococci vs. Neisseria meningococci: treatment

A

Neisseria gonococci: ceftriaxone + azithromycin or doxycycline for possible chlamdydia coinfection

Neisseria meningococci: certriaxone of penicillin G, rifampin, ciprofloxacin, or ceftriaxone prophylaxis in close contacts

168
Q

Clostridia characteristics

A

Gram-positive, spore forming, obligate anaerobes

169
Q

Helicobacteri pylori

A

Causes gastritis and 90% of duodenal ulcers, risk factor for peptic ulcer, gastric adenocarcinoma, and lymphoma

Curved gram-negative rod, urease positive (urea breath test), creates an alkaline environment for itself

Treatment: triple therapy - PPI (-prazoles), clarithromycin (macrolide), amoxicillin or metronidazole

170
Q

Spirochetes: shape, examples, culture requirements

A

Spiral-shaped bacteria with axial filaments

Borrelia (big size), Leptospira, and Treponema

Borrelia can be visualized with aniline dyes (Wright’s or Giemsa stain) in light microscopy, Treponema is visualized by dark-field microscopy and fluorescent-antibody staining

171
Q

Leptospira interrofgans: characteristics, transmission, clinical signs

A

Gram-negative spirochete

Found in water contaminated with animal urine, common among surfers and in the tropic (Hawaii)

Weil’s disease (icterohemorrhagic leptospirosis): severe form with jaundice and azotemia from liver and kidney dysfunction, fever, hemorrhage, anemia

172
Q

Lyme disease: bacteria, endemic area, stages, treatment

A

Borrelia burgdorferi, which is transmitted by the deer tick Ixodes (also carries babesia), natural reservoir is the mouse. Gram-negative spirochete

Northeastern US

1) erythema chronicum migrans (expanding bull’s eye red rash with central clearing), flu-like symptoms, 2) neurologic (facial nerve palsy) and cardiac (AV nodal block) manifestations, 3) musculoskeletal (chronic monoarthritis and migratory polyarthritis), neurological (encephalopathy and polyneuropathy), and cutaneous manifestations

FAKE a key LYME pie: Facial nerve (bilateral), Arthritis, Kardiac block, Erythema migrans

173
Q

Syphilus bacteria: characteristics and treatment

A

Gram-negative spirochete Treponema pallidum

Treatment: penicillin G

174
Q

Primary syphilus: disease, labs, site of treponemes

A

Localized disease presenting with painless chanche (ulceration)

Screen with VDRL (serum test) and confirm diagnosis with FTA-ABS (blood with fluorescent antibody and dark-field microscopy)

Treponemes are present in chancres of primary and condylomata lat a of secondary, may be directly visualized with dark-field

175
Q

Secondary syphilis: disease, site of treponemes, labs

A

Disseminated disease with constitutional symptoms, maculopapular rash (palms and soles), condylomata lata (wart-like lesions on genitals)

Treponemes are present in chancres of primary and condylomata lat a of secondary, may be directly visualized with dark-field

Screen with VDRL, confirm with FTA-ABS

Secondary = Systemic

176
Q

Tertiary syphilis: clinical signs, labs

A

Gummas (chronic granulomas), aoritisis (vasa vasorum destruction), neurosyphilis (tabes dorsalis), Argyll Robertson pupil

Broad-based ataxia, positive Romberg, Charcot joint, stroke without HTN

Test with spinal fluid VDRL

177
Q

Congenital syphilis, clinical signs, treatment

A

Saber shins (malformation of tibia, sharp bowing), saddle nose, CN VIII deafness, Hutchinson’s teeth (smaller, widely-spaced, notches on biting surfaces), mulberry molars (small, lots of enamel ridges on the top of the 1st molars)

Early prevention is key, as placental transmission typically occurs after the first trimester

178
Q

Argyll Robertson pupil

A

Constricts with accommodation but is not reactive to light

Associated with tertiary syphilis

“Prostitute’s pupil:” accommodates but does not react

179
Q

VDRL false positives

A

VDRL detects nonspecific antibody that reacts with beef cardiolipin. Used for diagnosis of syphilis, but many false positives, including viral infection (mononucleosis, hepatitis), some drugs, rheumatic fever, SLE, and leprosy

VDRL: Viruses (mono, hepatitis), Drugs, Rheumatic fever, Lupus/Leprosy

180
Q

Jarisch-Herxheimer reaction, disease and cause

A

Flu-like syndrome immediately after antibiotics are started

Due to killed bacteria releasing pyrogens.

181
Q

Zoonotic bacteria

A

Infections transmitted from animals to human

182
Q

Zoonotic bacteria - Bartonella spp.: disease and transmission

A

Disease: cat scratch disease (lympadenopathy, fever, chills, headache, back pain), bacillary angiomatosis (tumor-like growths of blood vessels)

Transmission: cat scratch

183
Q

Zoonotic bacteria - Borrellia burgdoferi spp.: disease and transmission

A

Disease: Lyme disease (FAKE a key LYME pie: Facial nerve (bilateral), Arthritis, Kardiac block, Erythema migrans)

Transmission: Ixodes (deer and mice ticks)

184
Q

Zoonotic bacteria - Borrelia recurrentis spp.: disease and transmission

A

Disease: relapsing fever (recurrent due to variable surface antigens)

Transmission: louse

185
Q

Zoonotic bacteria - Brucella spp. spp.: disease and transmission

A

Disease: Brucellosis/undulant fever

Transmission: unpasteurized dairy

186
Q

Zoonotic bacteria - Campylobacter spp.: disease and transmission

A

Disease: bloody diarrhea

Transmission: puppies, livestock (fecal-oral, ingestion of undercooked meat, especially chicken)

187
Q

Zoonotic bacteria - Chlamydophila psittaci spp.: disease and transmission

A

Disease: Psittacosis

Transmission: parrots and other birds

188
Q

Zoonotic bacteria - Coxiella burnetii spp.: disease and transmission

A

Disease: Q fever (flu-like symptoms with abrupt onset of fever and headache)

Transmission: aerosols of cattle/sheep amniotic fluid (farmers, vets)

189
Q

Zoonotic bacteria - Francisella tularensis spp.: disease and transmission

A

Disease: tularemia

Transmission: ticks, rabbits, deer fly

190
Q

Zoonotic bacteria - Ehrlichia chaffeensis spp.: disease and

A

Disease: ehrlichiosis

Transmission: Lone Star ticks

191
Q

Zoonotic bacteria - Leptospira spp.: disease and transmission

A

Disease: leptospirosis

Transmission: animal urine

192
Q

Zoonotic bacteria - Mycobacterium leprae spp.: disease and transmission

A

Disease: leprosy

Transmission: humans with lepromatous leprosy, armadillo (rare)

193
Q

Zoonotic bacteria - Pasteurella multocida spp.: disease and transmission

A

Disease: cellulitis, osteomyelitis

Transmission: animal bite, cats, dogs

194
Q

Zoonotic bacteria - Rickettsia prowazekii spp.: disease and transmission

A

Disease: endemic typhus

Transmission: louse

195
Q

Zoonotic bacteria - Rickettsia rickettsii spp.: disease and transmission

A

Disease: Rocky Mountain Spotted Fever

Transmission: Dermacentor ticks

196
Q

Zoonotic bacteria - Rickettsia typhi spp.: disease and transmission

A

Disease: endemic typhus

Transmission: fleas

197
Q

Zoonotic bacteria - Yersinia pestis spp.: disease and transmission

A

Disease: Plague

Transmission: fleas (rats and prairie dogs are reservoirs)

198
Q

Zoonotic bacteria - Anaplasma spp.: disease and transmission

A

Disease: anaplasmosis

Transmission: Ixodes ticks (deer and mice)

199
Q

Gardnerella vaginalis: characteristics, clinical signs, transmission, pathology, treatment

A

Pleomorphic, gram-variable rod

Causes vaginosis presenting as a gray vaginal discharge with a fishy smell, nonpainful.

Associated with sexual activity, but not an STD

Bacterial vaginosis is characterized by overgrowth of certain bacteria in vagina. Clue cells, or vaginal epithelial cells covered with bacteria, are visible under the microscope

Treatment: metronidazole

I don’t have a CLUE why I smell FISH in the VAGINA GARDEN

200
Q

Rickettsial diseases: bacteria characteristics and treatment

A

Rickettsiae are obligate intracellular organisms that need CoA and NAD+.

Doxycycline for all

201
Q

Rickettsial diseases and vector-borne illness with rash: types, clinical signs

A

Rocky Mountain spotted fever (tick): Rickettsia rickettsii. Broadly distributed in US (in spite
of name). Rash typically starts at wrists and ankles

Typhus: Endemic (fleas): R. typhi. Epidemic (human body louse): R. prowazekii. Rash starts centrally and spreads out, sparing palms and soles

Classic triad—headache, fever, rash (vasculitis)

“Rickettsii on the wRists, Typhus on the Trunk”

Palm and sole rash is seen in Coxsackievirus A infection (hand, foot, and mouth disease), Rocky Mountain spotted fever, and secondary Syphilis (you drive CARS using your palms and soles)

202
Q

Rickettsial diseases and vector-borne illness without rash: types, clinical signs

A

Ehrlichiosis (tick): Ehrlichia. Monocytes with morula (berry-like inclusions) in cytoplasm

Anaplasmosis (tick): Anaplasma. Granulocytes
with morula in cytoplasm

Q fever (tick feces and cattle placenta release
spores that are inhaled as aerosols): Coxiella burnetii. No arthropod vector. Presents as pneumonia

Q fever is Queer because it has no rash or vector and its causative organism can survive outside in its endospore form. Not in the Rickettsia genus, but closely related

203
Q

Mycoplasma pneumoniae: characteristics, culture requirement, clinical signs, treatment, age group and areas where it’s found

A

No cell wall. Not seen on Gram stain. Bacterial membrane contains sterols for stability. High titer of cold agglutinins (IgM), which can agglutinate or lyse RBCs

Grown on Eaton’s agar

Classic cause of atypical “walking” pneumonia (insidious onset, headache, nonproductive cough, diffuse interstitial infiltrate)

X-ray looks worse than patient.

Treatment: macrolide or fluoroquinolone (penicillin ineffective since Mycoplasma have no cell wall)

Mycoplasmal pneumonia is more common in
patients < 30 years of age

Frequent outbreaks in military recruits and
prisons

204
Q

Chlamydia trachomatis serotypes: A, B, C

A

Chronic infection, causes blindness due to follicular conjunctivitis in Africa

ABC: Africa/Blindness/Chronic infection

205
Q

Chlamydia trachomatis serotypes: D-K

A

Urethritis/PID, ectopic pregnancy, neonatal pneumonia (staccato cough), or neonatal conjunctivitis

D-K = everything else

Neonatal disease can be acquired during passage through infected birth canal

206
Q

Chlamydia trachomatis serotypes: L1, L2, L3

A

Lymphogranuloma venereum

207
Q

Chlamydia: characteristics, pathology, culture requirements, types and disease, treatment

A

Chlamydiae cannot make their own ATP. They are obligate intracellular organisms that cause mucosal infections. Cell wall is unusual in that it lacks muramic acid

2 forms: Elementary body (small, dense) is “Enfectious” and Enters cell via Endocytosis. Reticulate body Replicates in cell by fission; form seen on tissue culture

Lab diagnosis: cytoplasmic inclusions seen on
Giemsa or fluorescent antibody–stained smear

Chlamydia trachomatis causes reactive arthritis,
conjunctivitis, nongonococcal urethritis, and
PID

C. pneumoniae and C. psittaci cause atypical
pneumonia; transmitted by aerosol

Treatment: azithromycin (favored because one-
time treatment) or doxycycline

Chlamys = cloak (intracellular). Chlamydophila psittaci is notable for an avian reservoir

208
Q

Systemic mycoses: diseases caused, growth temperature, treatment, disease it can mimic

A

Cause pneumonia and can disseminate

All are caused by dimorphic fungi: cold (20°C) = mold, heat (37°C) = yeast. Exception is coccidioidomycosis, which is a spherule (not yeast) in tissue

Treatment: fluconazole or itraconazole for local infection; amphotericin B for systemic infection

Systemic mycoses can mimic TB (granuloma formation), except, unlike TB, have no person-person transmission

209
Q

Histoplasmosis: where is it found? what disease does it cause? Path?

A

Mississippi and Ohio River valleys, bird or bat droppings

Pneumonia

Macrophage filled with Histoplasma (smaller than RBC)

Histo Hides within macrophages

210
Q

Blastomycosis where is it found? What disease does it cause? Path?

A

States east of the Mississippi River and in Central America

Causes inflammatory lung disease, can disseminate to skin and bone

Granulomatous nodules, broad-based budding (same size as RBC)

Blasto Buds Broadly

211
Q

Coccidioidomycosis where, when is it found? What disease does it cause? Path?

A

Southwestern states, California. Increases after earthquakes, because spores in the dust are thrown up into the air and become spherules in the lungs

Pneumonia and menigitis, can disseminate to bone and skin

Spherule filled with endospores (much larger than RBC)

Coccidio crowds

San Joaquin Valley: “valley fever”

212
Q

Paracoccidioidomyocsis where is it found? Path?

A

Latin America

Budding yeast with “captain’s wheel” formation (much larger than RBC)

Paracoccidio parasails with the captain’s wheel all the way to Latin America

213
Q

Tinease: examples, clinical signs, culture requirements

A

Tinea pedis (foot), tinea cruris (groin), tinea corporis (ringworm, on body), tinea capitis (head, scalp), tinea unguium (onchyomycosis, on fingernails)

Pruritic lesions with central clearing resembling a ring, caused by dermatophytes (Microsporum, Trichophyton, Epidermophyton)

Mold hyphae in KOH prep, not dimorphic

214
Q

Tinea versiclor: fungus, pathophysiology, treatment, culture requirements, when does it occur?

A

Caused by Malassezia furfur

Degradation of lipids produces acids that damage melanocytes and cause hypopigmented and/or hyper pigmented patches

Treatment: topical miconazole, selenium sulfide (Selsun)

“Spaghetti and meatball” appearance on KOH prep A .

Occurs in hot, humid weather.

215
Q

Candida albicans: clinical signs, treatment

A

Systemic or superficial fungal infection

Oral and esophageal thrush in immunocompromised (neonates, steroids, diabetes, AIDS), vulvovaginitis (diabetes, use of antibiotics), diaper rash, endocarditis in IV drug users, disseminated candidiasis (to any organ), chronic mucocutaneous candidiasis

Treatment: topical azole for vaginal; fluconazole or caspofungin for oral/esophageal; fluconazole, amphotericin B, or caspofungin for systemic

alba = white

216
Q

Aspergillus fumigatus: clinical signs, toxin

A

Invasive aspergillosis, especially in immunocompromised and those with chronic granulomatous disease

Allergic bronchopulmonary aspergillosis (ABPA): with asthma or CF, aspergillomas in lung cavities, especially after TB infection

Some species of Aspergillus produce aflatoxins, which are associated with HCC

Think “A” for Acute Angles in Aspergillus. Not dimorphic

217
Q

Cryptococcus neoformans: characteristics, disease, culture requirements, pathology

A

Cryptococcal meningitis, cryptococcosis

Heavily encapsulated yeast. Not dimorphic. Found in soil, pigeon droppings

Acquired through inhalation with hematogenous dissemination to meninges

Culture on Sabouraud’s agar. Stains with India ink

Latex agglutination test detects polysaccharide capsular antigen and is more specific. “Soap bubble” lesions in brain

218
Q

Mucor and Rhizopus spp.: who gets it, pathophysiology, clinical signs

A

Mucormycosis

Disease mostly in ketoacidotic diabetic and leukemic patients

Fungi proliferate in blood vessel walls when there is excess ketone and glucose, penetrate cribriform plate, and enter brain

Rhinocerebral, frontal lobe abscesses. Headache, facial pain, black necrotic eschar on face; may have cranial nerve involvement

219
Q

Pneumocystis jirovecii: disease, organism type, predisposing factors, diagnosis, treatment

A

Causes Pneumocystis pneumonia (PCP), a diffuse interstitial pneumonia

Yeast (originally classified as protozoan). Inhaled. Most infections are asymptomatic

Immunosuppression (e.g., AIDS) predisposes to disease.

Diagnosed by lung biopsy or lavage. Disc-shaped yeast forms on methenamine silver stain of lung tissue A. Diffuse, bilateral CXR appearance

Treatment: TMP-SMX (sulfonamide), pentamidine, dapsone. Start prophylaxis when CD4 drops < 200 cells/mm3 in HIV patients

220
Q

Sporothrix schenckii: characteristics, pathophysiology, clinical signs, treatment

A

Sporotrichosis. Dimorphic, cigar-shaped budding yeast that lives on vegetation A

When spores are traumatically introduced into the skin, typically by a thorn (“rose gardener’s” disease)

Causes local pustule or ulcer with nodules along draining lymphatics (ascending lymphangitis). Little systemic illness

Treatment: itraconazole or POTassium iodide (“plant a rose in the POT”)

221
Q

Giardiasis lamblia: disease, transmission, diagnosis, treatment

A

GI protozoa

Giardiasis: bloating, flatulence, foul-smelling, fatty diarrhea (often seen in campers/hikers). Think FAT-rich Ghirardelli chocolates for fatty stools of Giardia

Cysts in water

Trophozoites or cysts in stool

Metronidazole

222
Q

Entamoeba histolytica: disease, transmission, diagnosis, treatment

A

GI protozoa

Amebiasis: bloody diarrhea (dysentery), liver abscess (“anchovy paste” exudate), RUQ pain (histology shows flask-shaped ulcer if submucosal abscess of colon ruptures)

Cysts in water

Serology and/or trophozoites (with RBCs in the cytoplasm) or cysts (with multiple nuclei) in stool

Metronidazole, iodoquional (Fe chelator) for non-symptomatic cyst passers

223
Q

Cryptosporidium: disease, transmission, diagnosis, treatment

A

GI protozoa

Severe diarrhea in AIDS. Mild disease (watery diarrhea) in non-immunocompromised

Cysts in water

Cysts on acid-fast stain

Prevention (by filtering city water supplies), nitazoxanide in immunocompetent hosts

224
Q

Toxoplasmia gondii: disease, transmission, diagnosis, treatment

A

CNS protozoa

Brain abscess in HIV (seen as ring-enhancing brain lesions on CT/MRI). Congenital toxoplasmosis = “classic triad” of chorioretinitis, hydrocephalus, and intracranial calcifications

Cysts in meat or cat feces, can cross placenta (pregnant women should avoid cats)

Serology, biopsy

Sulfadiazine + pyrimethamine

225
Q

Naegleria fowleri: disease, transmission, diagnosis, treatment

A

CNS protozoa

Rapidly fatal meningitis

Swimming in freshwater lakes (think Nalgene bottle filled with freshwater containing Naegleria), enters via cribriform plate

Amoebas in spinal fluid

Amphotericin has been effective for some survivors

226
Q

Trypanosoma brucei, T. gambiense, T. rhodesiense: disease, transmission, diagnosis, treatment

A

CNS protozoa

African sleeping sickness: enlarged lymph nodes, recurring fever (due to antigenic variation), somnolence, coma

Tsetse fly (painful bite)

Blood smear

Suramin for blood-borne disease or melarsoprol for CNS penetration (“it SURe is nice to go to sleep,
MELatonin helps with sleep)

227
Q

Plasmodium (P. vivax/ovale, P. falciparum, P. malariae): disease, transmission, diagnosis, treatment

A

Hematologic protozoa

Malaria: fever, headache, anemia, splenomegaly

P. vivax/ovale: 48-hr cycle (tertian, includes fever on first day and third day, thus fevers are actually 48 hr apart) or dormant form (hypnozoite) in liver

P. falciparum: severe; irregular fever patterns, parasitized RBCs occlude capillaries in brain (cerebral malaria), kidneys, lungs

P. malariae—72-hr cycle (quartan)

Mosquito (Anopheles)

Blood smear, trophozoite ring form A , RBC schizont with merozoites B

Begin with chloroquine, which blocks Plasmodium heme polymerase. If resistant, use mefloquine. If life-threatening, use intravenous quinidine (test for G6PD deficiency or serious methemoglobinemia may occur). Vivax/ovale—add primaquine for hypnozoite (test for G6PD deficiency)

228
Q

Babesia: disease, transmission, diagnosis, treatment

A

Hematologic protozoa

Babesiosis: fever and hemolytic anemia, predominantly in northeastern United States, asplenia: risk of severe disease

Ixodes tick (same as Borrelia burgdorferi of Lyme disease, may often coinfect humans)

Blood smear, ring form, “Maltese cross” C2, PCR

Atovaquone + azithromycin

229
Q

Trypanosoma cruzi: disease, transmission, diagnosis, treatment

A

Visceral protozoa

Chagas’ disease: dilated cardiomyopathy, megacolon, megaesophagus. Predominantly in South America

Reduviid bug (“kissing bug”), a painless bite (much like a kiss)

Blood smear

Nifurtimox

230
Q

Leishmania donovani: disease, transmission, diagnosis, treatment

A

Visceral protozoa

Sandfly

Visceral leishmaniasis (kala-azar): spiking fevers, hepatosplenomegaly, pancytopenia

Macrophages containing amistigotes

Sodium stibogluconate

231
Q

Trichomonas vaginalis: disease, transmission, diagnosis, treatment

A

STD protozoa

Vaginitis: foul-smelling, greenish discharge; itching and burning; do not confuse with Gardnerella vaginalis, a gram-variable bacterium that causes vaginosis

Sexual transmission

Mobile trophozoites on wet mount

Metronidazole for patient and partner (prophylaxis)

232
Q

Viral structure: capsid

A

Protein shell immediately surrounding nuclei acid

233
Q

Viral structure: envelope

A

Derived from plasma membranes, cover capsids

Sensitive to desiccation, heat, and detergents

234
Q

Viral genetics: recombination

A

Exchange of genes between 2 chromosomes with significant base homology

235
Q

Viral genetics: reassortment

A

When viruses with segmented genomes (influenza is an example) exchange segments. High-frequeny recombination. Ultimately responsible for flu pandemics

236
Q

Viral genetics: complementation

A

Occurs when 1 of 2 viruses infecting a cell has a mutation resulting in a nonfunctional protein. The nonmutated virus “complements” the mutated one by making a functional protein that can be used by both viruses

237
Q

Viral genetics: phenotypic mixing

A

Occurs with co-infection of a cell with 2 viruses. Genome of virus A can be partially or completely coated with the surface proteins of virus B (this is a pseudovirion)

Type B protein coat determines the tropism (which cells can be infected) of the hybrid virus, but the progeny from this infection will get a type A coat again because those genes will be translated

238
Q

DNA viral genomes

A

All DNA viruses except Parvoviridae are dsDNA

All are linear except papilloma-, polyoma-, and hepadnaviruses (circular)

All are dsDNA except “part-of-a- virus” (parvovirus) is ssDNA

Parvus = small

239
Q

Live attenuated viral vaccines

A

Induce humoral and cell-mediated immunity but have reverted to virulence on rare occasions

Killed/inactivated vaccines induce only humoral immunity but are stable

Live attenuated—smallpox, yellow fever, chickenpox (VZV), Sabin’s polio virus, MMR, Influenza (intranasal)

No booster needed for live attenuated vaccines.

Dangerous to give live vaccines to
immunocompromised patients or their close contacts

“LIVE! One night only! See SMALL YELLOW
CHICKENS get vaccinated with SABIN’S and
MMR! It’s INcredible!”

MMR = measles, mumps, rubella (live
attenuated vaccine that can be given to HIV- positive patients who do not show signs of immunodeficiency).

240
Q

Killed viral vaccines

A

Rabies, Influenza (injected), Salk Polio, and HAV vaccines

SalK = Killed. RIP Always

241
Q

Recombinant viral vaccines

A

HBV (antigen = recombinant HBsAg), HPV (types 6, 11, 16, and 18)

242
Q

RNA viral genomes

A

All RNA viruses except Reoviridae are ssRNA

Positive-stranded RNA viruses: I went to a
retro (retrovirus) toga (togavirus) party, where I drank flavored (flavivirus) Corona (coronavirus) and ate hippy (hepevirus) California (calicivirus) pickles (picornavirus).

All are ssRNA except “repeato-virus” (reovirus) is dsRNA

243
Q

Naked viral genome infectivity

A

Purified nucleic acids of most dsDNA (except poxviruses and HBV) and (+) strand ssRNA
(≈ mRNA) viruses are infectious

Naked nucleic acids of (−) strand ssRNA and dsRNA viruses are not infectious. They require polymerases contained in the complete virion

244
Q

Virus ploidy

A

All viruses are haploid (with 1 copy of DNA or RNA) except retroviruses, which have 2 identical ssRNA molecules (≈ diploid)

245
Q

DNA viral replication

A

Replicate within the nucleus. Exception: poxvirus (which carries its own DNA-dependent RNA polymerase)

246
Q

RNA viral replication

A

Replicate in the cytoplasm. Exceptions: influenza and retrovirus

247
Q

Viral envelopes

A

Naked (nonenveloped) viruses include Papillomavirus, Adenovirus, Picornavirus, Polyomavirus, Calcivirus, Parvovirus, Reovirus, and Hepevirus

Enveloped viruses acquire their envelopes from plasma membrane when they exit from cell (exceptions include herpesviruses, which acquire envelopes from nuclear membrane)

Give PAPP smears and CPR to a naked Heppy (hippy). DNA = PAPP; RNA = CPR and hepevirus

248
Q

DNA viruses: examples and characteristics

A

HHAPPPPy viruses (Hepadna, Herpes, Adeno, Pox, Parvo, Papilloma, Polyoma)

Are double stranded (except parvo)

Are linear (except papilloma and polyoma (circular, supercoiled) and hepadna (circular, incomplete))

Are icosahedral (except pox, which is complex)

Replicate in the nucleus (except pox, which carries its own DNA-dependent RNA polymerase)

249
Q

HSV identification

A

PCR is best

Tzanck test—a smear of an opened skin vesicle
to detect multinucleated giant cells commonly
seen in HSV-1, HSV-2, and VZV

Infected cells also have intranuclear Cowdry A
inclusions

Tzanck God I don’t have HSV

250
Q

EBV: virus, cells infected, clinical signs, pathology, diagnosis

A

Herpesvirus, causes mononucleosis

Infects B cells

Characterized by fever, hepatosplenomegaly, pharyngitis, and lymphadenopathy (especially posterior cervical nodes). Also associated with development of Hodgkin’s and endemic Burkitt’s lymphomas as well as nasopharyngeal carcinoma.

Peak incidence 15–20 years of age (“kissing years”)

Atypical lymphocytes seen on peripheral blood smear A are not infected B cells but rather reactive cytotoxic T cells

Positive Monospot test: heterophile antibodies detected by agglutination of sheep or horse RBCs

First Aid Flashcards (2 decks)

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