Micro 1 USMLE Flashcards by Mani Yavi

alcoholic vomits gastric contents and develops foul smelling sputum. What organisms are most likely

anaerobes

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middle age male presents w/ acute onset monoarticular joint pain and bilateral bell’s plalsy. What is the likely dz and how did he get it

lyme dz; bite from Ixodes tick

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Pt w/ mycoplasma pneumoniae exhibits cryoagglutins during recovery phase. What types of immunoglobulins are reacting

IgM

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UA of pt shows WBC casts. What is the dx?

pyelonephritis

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young child presents w/ tetany and candidiasis. Hypocalcemia and immunosuppression are found. What cell is deficient?

T cell (DiGeorge)

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pt presente w/ “rose gardener’s” scenerio (thorn prick w/ ulcers olong lymphatic drainage. What is the infectious bug.

sporothrix schencki

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25 y/o medical student has a burning feeling in his gut after meals. bx of gastric mucosa shows gram negative rods. what is the likely organism?

H pylori

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32 yo male has “cauliflower” skin lesions. Tissue bx shows broad based budding yeast. What organism is most likely?

blastomyces

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breast feeding woman suddenly develops redness and swelling of her right breast. On examination it is found to be afluctuant mass. What is the dx?

mastitis caused by S. aureus

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Young child has recurrent lung infections and granulomatous lesions. What is the defect in neutrophils?

NADPH oxidase (chronic granulomatous dz)

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20 y/o college student presents w/ lymphadenopathy, fever, and hepatosplenomegaly. His serum agglutinates sheep RBCs. What cell is infected?

B cell (EBV; infectious mononucleosis)

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One hour after eating custard at a picnic, a whole family began to vomit. After 10 hours, they were better. What is the organism?

S. aureus (produces preformed enterotoxin)

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infant becomes flaccid after eating honey. What organism is implicated, and what is the mechanism of action.

Clostridium botulinum; inhibited release of ACh.

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Man presents with squamous cell carcinoma of the penis. He has exposure to what virus?

HPV

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Pt develops endocarditis three weeks after receiving a prosthetic heart valve. What organism is suspected?

S. aureus or S. epidermidis

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55 y/o man who is a smoker and heavy drinker presents with a new cough and flulike symptoms. Gram stain shows no organisms; silver stain of sputum shows gram-negative rods. What is the dx?

legionella pneumonia

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after taking clidamycin, pt develops toxic megacolon and diarrhea. What is the mechanism of diarrhea

C. difficile overgrowth

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this bacterial structure is composed of a sugar backbone with cross linked peptide side chains. It functions to give the bacterium rigid support, and to protect against osmotic pressure

peptidoglycan

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This bacterial structure is composed of teichoic acid which induces TNF and IL-1. It functions as a major surface antigen.

cell wall/membrane in gram postitives

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this bacterial structure is composed of lipid A which induces TNF & IL-1. Polysaccharide is the antigen. It functions as a major surface Ag and a site of endotoxin.

outer membrane of gram negative

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what is the endotoxin of Gram negative bacteria

lipopolysaccaride

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this bacterial structure is composed a plasma bilayer. It fxs as a site of oxidative and transport enzymes.

Plasma membrane

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This bacterial structure is composed RNA and protein in 50S and 30S subunits. It functions as the site of protein synthesis.

ribosome

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this bacterial structure is composed of many hydrolytic enzymes, including B-lactamases. It is the space between the cytoplasmic membrane and outer membrane in gram negative bacteria.

Periplasm

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this bacterial structure is composed polysaccaride and protects against phagocytosis.

capsule.

the capsule of bacillus anthracis is unique in that it contains _________ instead of polysaccharide.

D-glutamate

This bacterial structure is composed of glycoprotein. It functions to mediate adherence of bacteria to cell surface.

pilus/fimbrae

sex pilus forms attachment between 2 bacteria during _______

conjugation

this bacterial structure is composed of protein and fxs in motility

flagellum

this bacterial structure is composed of a keratin-like coat and dipicolinic acid. It provides resistance to dehydration, heat, and chemicals.

spore

this bacterial structure is composed DNA. It contains a variety of genes for antibiotic resistance, enzymes, and toxins.

plasmid

This bacterial structure is composed of polysaccharide. It mediates adherence to surfaces, especially foreign surfaces (e.g., indwelling catheters).

Glycocalyx

in the bacterial growth curve this is the part where there is metabolic activity without division

lag

in the bacterial growth curve this is the part where there is rapid cell division

log

in the bacterial growth curve this is the part where nutrient depletion slows growth

stationary

in the bacterial growth curve this is the part where there is prolonged nutrient depletion and buildup of waste products.

death

what is the source of exotoxins

some G+ & G- bacteria

what is the source of endotoxins

cell wall of most G- bacteria and listeria

are exotoxins secreted from the cell

yes

are endotoxins secreted from the cell

exotoxins are made of _______

polypeptides

endotoxins are made of _____

lipopolysaccharides

genes for exotoxins are located where?

plasmid or bacteriophage

genes for endootoxins are located where?

bacterial chromosomes

how toxic are exotoxins

high (fatal dose is on the order of 1 ug)

What is the toxicity of endotoxins?

low (fatal dose is on the order of hundreds of micrograms)

what are the clinical effects of endotoxins?

fever & shock

what is cytokines are involved in the mode of action of endotoxins

TNF & IL1

high-titer antibodies called antitoxins can be used against these toxins

exotoxins

this toxin poorly antigenic

endotoxins

these are used as vaccines for exotoxins

toxoids

is there a vaccine available for endotoxins

what is more heat stable, endotoxins or exotoxins

endotoxins

what is the only exotoxin that is heat stable

staphylococcal enterotoxin

tetanus, botulism, & diphtheria typically cause problems due to ________ (exotoxin or endotoxins)

exotoxins

meningococcemia, causes sepsis by G- rods. Toxicity is due to ________ (exotoxin or endotoxins)

endotoxins

these binds directly to MHC II and T-cell receptor, activating large numbers of T cells to stimulate release of IL-1 & IL-2

superantigens

TSST-1 from this bug causes toxic shock syndrome (fever, rash, shock).

S. Aureus

Enterotoxins from this bug cause food poisoning.

S. Aureus

Scarlet fever-strain SPE SPE toxin from this bug causes toxic shock-like syndrome.

S. pyogenes

this exotoxin interferes with host cell fx. It has a B component and an A component.

ADP ribosylating A-B toxins.

tell me about the B component of ADP ribosylating A-B toxins

B (binding) component binds to receptor on surface of host cell, enaboling endocytosis)

tell me about the A component of ADP ribosylating A-B toxins

A (active) component attaches an ADP-ribosyl to a host cell protien (ADP ribosylation), altering protein fx.

What bugs have ADP ribosylating A-B toxins (4)

Corynebacteria diptheria Vibrio cholerae E. Coli Bordetella Pertussis

What bugs have superantigins (2)

S. aureus | S. pyogenes

this bug has an ADP ribosylating A-B toxin that inactivatess elongation factor (EF-2) causing a pharyngitis and a "pseudomembrane" in the throat

Corynebacterium diptheriae

This bugs ADP ribosylating A-B toxin acts on the G protein to stimulate adenylyl cyclase, increasing pumping of Cl- & H2O in the gut causing voluminous rice-water diarrhea.

Vibrio cholerae

This bug has a heat-labile ADP ribosylating A-B toxin, that stimulates adenylyl cyclase (cholera-like mechanism), causing watery diarrhea. Heat stabile toxin stimulates guanylate cyclase.

E. Coli

This bug has an ADP ribosylating A-B toxin that stimulates adenylate cyclase, causes whooping cough, inhibits chemokine receptor causing lymphocytosis.

Bordetella pertussis

This bug has an alpha toxin that causes gas gangrene. You will see a double zone of hemolysis on blood agar.

Clostridium perfringes.

This bug blocks the release of inhibitory neurotransmitter glycine. Causing "lockjaw"

C. Tetani

This bug blocks the release of Ach, causing anticholinergic symptoms such as CNS paralysis. Spores can be found in canned food and honey causing floppy baby.

C. botulinum

this bug has a toxin in which 1 toxin in the toxin complex is adenylate cyclases.

B. anthracis

This bug produces the shiga toxin which cleaves host cell rRNA and also enhances cytokine release causing HUS.

Shigella

what other bug produces the Shiga toxin

E. Coli O157:H7

This bug produces streptolysin O, a hemolysin and antigen for ASO antibody in rheumatic fever

S. pyogenes

this is a lipopolysaccharide found in the cell wall of gram negative bacteria

endotoxin mneu: N-dotoxin is an integral part of gram-Negative cell wall.

endotoxins are heat ______ (stable or labile)

stable)

these bugs do not gramstain well

Treponema (too thin) Rickettsia (intracellular Mycobacteria (high lipid content of cell wall) Mycoplasma (no cell wall) Legionella pneumophila (primarily intracellular) Chlamydia (intracellular) mneu:These Rascals May Microscopically Lack Color

how do you I.D. Treponema

darkfeild microscopy and fluorescent Ab staining

How do you I.D. Mycobacteria

acid fast stain

How do you I.D. Legionella

silver stain

pathogenic Neisseria species are differentiated on the basis of sugar ________

fermentation

MeninGococci ferment ________ & __________ | Gonococci ferment _______

Maltose & Glucose | Glucose

S. aureus produces a ________ pigment

yellow mneu: Aureus (latin)=gold

Pseudomonas Aeruginosa produces a ________ pigment

blue green

Serratia marcescens produces ____ pigment

red mneu: marcescens = maraschino cherries are red

______ proteases allows these organisms to colonize mucosal surfaces: Streptococcus pneumoniae, Neisseria meningitidis, N. gonorrheae, H. influenzae.

IgA proteases

special media cx requirements for isolation: | H. influenzae

chocolate agar w/ factors V (NAD) & X (hematin)

special media cx requirements for isolation: | N. gonorrheaeae

Thayer-Martin (VCN) media

special media cx requirements for isolation: | B. pertussis

Bordet-Gengou (potato) agar

special media cx requirements for isolation: | C. diptheriae

Tellurite plate, Loffler's medium, blood agar

special media cx requirements for isolation: | M. Tuberculosis

Lowenstein-Jensen agar

special media cx requirements for isolation: | Lactose-fermenting enterics

pink colonies on MacConkey's agar

special media cx requirements for isolation: | Legionella

Charcoal yeast exxtract agar buffered with increased iron and cysteine

special media cx requirements for isolation: | Fungi

Sabouraud's agair

Give the appropriate stain-- | Amyloid; apple-green bifringence in polarized light because of Beta pleated sheets

Congo red

Give the appropriate stain-- | Borrelia, Plasmodium, trypanosomes, Chlamydia

Giemsa's

Give the appropriate stain-- | stains glycogen, mucopolysaccharides, used to diagnose Whipple's dz

PAS (periodic acid-Schiff)

Give the appropriate stain--Acid-fast bacteria

Ziehll-Neelsen

Give the appropriate stain--Cryyptococcus neoformans

India ink

Give the appropriate stain--Fungi, PCP, Legionella

Silver stain

DNA transfered from 1 bacterium to another (Conjugation, transduction, or transformation)

conjugation

DNA transferred by a virus from 1 cell to another (Conjugation, transduction, or transformation)

Transduction

Purified DNA taken up by a cell. (Conjugation, transduction, or transformation)

Transformation

Conjugation, transduction, & transformation. The only transfer process done in eukaryotic (e.g., human) cells

transformation

Conjugation transfers these 2 types of DNA

chromosomal or plasmid

this classification of bacteria use an O2 dependent system to generate ATP

Obligate Aerobes.

Examples of obligate aerobes

Nocardia, Pseudomonas Aeruginosa, Mycobacterium tuberculosis, & Bacillus mneu: Nagging Pests Must Breath.

This bug is an Aerobe seen in burn wounds, nosocomial pneumonia, and pneumonias in cystic fibrosis patients

P. Aeruginosa mneu: P. AERuginosa is an AERobe

__________ HAS A PREDILECTION FOR THE APICES OF THE LUNG, WHICH HAVE THE HIGHEST PO2

M. TUBERCULOSIS

Examples of this category of bacterium include Clostridium, Bacteroides, and Actinomyces.

Obligatee anaerobes

Obligatee anaerobes lack ________ and/or ________ and thus are susceptible to oxidative damage.

catalase | superoxide dismutase

Obligatee anaerobesare generally foul smelling due to _________

short chain fatty acids

Obligatee anaerobes are difficult to culture, and produce ______ in tissue

gas (CO2 & H2)

anaerobes are normal flora in _____ but are pathogenic elsewhere.

GI tract

_________ are ineffective against anaerobes because these antibiotics require O2 to enter into bacterial cell

AminO2glycosides

These 2 bugs are obligate intracellular bugs because they can't make own ATP

Rickettsia, Clamydia mneu: Stay inside (cells) when it is Really Cold

These 8 bugs are facultative intracellular bugs.

Salmonela, Neisseria, Brucella, Mycobacterium, Listeria, Francisella, Legionella, Yersinia mneu: Some Nasty Bugs May Live FacultativeLY

Give 2 examples of encapsulated bacteria

Streptococcus pneumoniae, H. influenzae, N. meningitidis, K. pneumoniae

in encapsulated bacteria the _______ capsule is an antiphagocytic virulence factor

polysaccharide

this positive test tells you if an encapsulated bug is present--the capsule swells when specific anticapsular antiserra are added

positive quellung reaction mneu: Quellung = capsular "swellung"

in encapsulated bacteria ______ is necessary for immune response

IgG2

In pneumovax, H. influenzae, & B. meningococcii, this serves as the Ag in vaccines

capsule

these are highly resistant to destruction by heat and chemicals. They have no metabolic activity and dipicolinic acid in their core.

spores

You must do this in order kill spores (what is done to surgical equipment)

autoclave

Only this type of bug forms spores when nutrients are limited

G+ rods

gram + soil bugs (aka spore formers) are (3)

B. anthracis, C. perfringes, C. tetani

give the 2 alpha hemolytic bacteria

1) streptococcus pneumoniae | 2) Viridans streptococci

this alpha hemollytic bacteria is catalase negative and optochin sensitive

streptococcus pneumonia

this alpha hemolytic bacteria is catalase negative and optochin resistance

viridans streptococci

Give the 4 Beta hemolytic bacteria

1) Staphylococcus Aureus 2) Streptococcus Pyogenes 3) Streptococcus agalactiae 4) Listeria moncytogenes

this beta hemolytic bacteria is catalase and coagulase positive

Staphylococcus Aureus

this beta hemolytic bacteria is catalase negative and bacitracian sensitive

Streptococcus Pyogenes

this beta hemolytic bacteria is catalase negative and bacitracian resistant

Streptococcus agalactiae

this beta hemolytic bacteria exists in unpasteurized milk has tumbling motility and causes meningitis in newborns

Listeria moncytogenes

This degrades H2O2, an antimicrobial prodct of PMNs. H2O2 is a substrate for myeloperoxidase

Catalase.

_____cocci make catalase, whereas streptococci do not

staphylo- mneu: STAPH make catalase because they have more "staph".

________ makes coagulase, whereas Staph epidermidis and Staph saphrophyticus do not

Staph Aureus mneu: Bad staph (aureus, because epidermidis is skin flora) makes coagulase and toxins)

this virulence factor of S. Aureus binds Fc-IgG, inhibiting compliment fixation and phagocytosis

Protein A

S. Aureus causes these 2 things

1) Inflammatory dz- skin infxns, organ abscesses, pneumonia | 2) Toxin-mediated dz- toxic shock syndrome, scalded skin syndrome, rapid onset food poisoning

Give the toxin responsible for toxic shock syndrome?

TSST-1

Give the toxin responsible for scalded skin syndrome

exfoliative toxin

Give the toxin responsible for rapid-onset food poisoning

enterotoxins

This is a superantigen that binds to MHC II and T-cell receptor, resulting in polyclonal T-cell activation

TSST

S. Aureus food poisoning is due to ingestion of a preformed ________

toxin

this causes ACUTE bacterial endocarditis

S. Aureus

Streptococcus pyogenes (group A Beta hemolytic streptococci causes three sequelae what are they?

1) Pyogenic-pharyngitis, cellulitis, impetigo 2) Toxigenic - scarlet fever, toxic shock syndrome 3) Immunologic - rheumatic fever, acute glomerulonepritis mneu: PHaryngitis gives you rheumatic "PHever" and glomerulonepHritis" mneu2: No "RHEUM" for SPECCulation: Subcutaneous nodules, Polyarthritis, Erythema marginatum, Chorea, Carditis.

Streptococcus pyogenes is bacitratian _______.

sensitive.

Ab to ________ enhances host defences against Streptococcus pyogenes

M protein

______ titer detects recent Streptococcus pyogenes infection

ASO

Streptococcus pnemonia is the most common cause of (4 )

``` MOPS Meningitis Otitis media Pneumonia Sinusitis ```

Streptococcus pnemonia ia optochin ______

sensitive mneu: Streptococcus pnemonia MOPS are Most OPtochin Sensitive

Pt presents with rusty sputum, sickle cell anemia sepsis, and splenectomy. He has a bug that is encapsulated & has an IgA protease.

Streptococcus pneumonia

these bugs are bacitracin resistant & B hemolytic. They cause pneumonia, meningitis, and sepsis, mainly in babies.

Group B streptococci

this virulence factor of S. Aureus binds Fc-IgG, inhibiting compliment fixation and phagocytosis

Protein A

S. Aureus causes these 2 things

1) Inflammatory dz- skin infxns, organ abscesses, pneumonia | 2) Toxin-mediated dz- toxic shock syndrome, scalded skin syndrome, rapid onset food poisoning

Give the toxin responsible for toxic shock syndrome?

TSST-1

Give the toxin responsible for scalded skin syndrome

exfoliative toxin

Give the toxin responsible for rapid-onset food poisoning

enterotoxins

enterococci (2 bugs)

E. faecalis & E. faecium.

enterococci are resistant to this AB

penicillin G

enterococci cause these 2 dz

UTIs & subacute endocarditis

this lancefield group includes enterococci

Lancefield grouping is based on differences in the ___ carbohydrate on the bacterial cell wall.

enterococci grow in 6.5% ______

NaCl

entero=______ faecalis=_______ strepto=_______ coccus=_______

intestine feces twisted (chains) berry

viridans streptococci are _____ hemolytic

alpha.

viridans streptococci are normal flora of the oropharynx and cause dental caries (________) and subacute bacterial endocarditis (_________)

streptococcus mutans streptococcus sanguins mneu: sanguis=blood. There is lots of blood in the heart.

viridans streptococci are optochin ______ which differentiates them from S. pneumoniae, which is also alpha hemolytic but is optochin _______

resistant sensitive mne: viridians group strep live in the mouth because they are not afraid OF-THE-CHIN (OPTOCHIN RESISTANT)