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Basic Bacteriology Flashcards

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1
Q

Bacterial structures: Specialized structures

A

Spore:
Made of keratin-like coat; dipicolinic acid; peptidoglycan, DNA
Function: gram + only, survival - resist dehydration, heat, chemicals

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2
Q

Bacterial structures: capsule

A

Organized, discrete polysaccharide layer (except poly-D glutamate on B anthracis)
Protects against phagocytosis

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3
Q

Bacterial structures: glycocalyx

A

Loose network of polysaccharides

Mediates adherence to surfaces, esp. Foreign surfaces (e.g. Indwelling catheters)

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4
Q

Bacterial structures: Outer membrane

A

Outer leaflet: contains endotoxin (LPS/LOS)
Embedded proteins: porins and other outer membrane proteins (OMPs) - most are antigenic
Inner leaflet: phospholipids
Gram - only
Endotoxin: lipid A induces TNF and IL-1; O polysaccharide component antigenic
Porins: transport across outer membrane

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5
Q

Bacterial structures: Periplasm

A

Space between cytoplasmic membrane and outer membrane in gram (-) bacteria (peptidoglycan in middle)
Gram - only
Accumulates components exiting gram - cells, including hydrolysis enzymes (eg beta-lactamases)

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6
Q

Bacterial structures: Cell wall

A

Peptidoglycan is a sugar backbone with peptide side chains cross-linked by transpeptidase
Net like structure gives rigid support, protects against osmotic pressure damage

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7
Q

Bacterial structures: Cytoplasmic membrane

A

Phospholipid bilayer sac with embedded proteins (e.g. Penicillin-binding proteins and other enzymes)
Lipteichoic acids (gram + only) extend from membrane to exterior
Site of oxidative and transport enzymes; PBPs involved in cell wall synthesis
Lipoteichoic acids induce TNF and IL-1

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8
Q

Spherical Morphology

A

Gram +: staphylococcus (clusters), streptococcus (chains or pairs)
Gram -: moraxella catarrhalis, Neisseria

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9
Q

Rods (bacillus) morphology

A

Gram +: bacillus, clostridium, corynebacterium, gardnerella (gram variable), lactobacillus, listeria, mycobacterium (acid fast), propionibacterium
Enterics (Gram -): bacteriodes, campylobacter, E.coli, enterobacter, helicobacter, klebsiella, proteus, pseudomonas, salmonella, serration, shigella, vibrio, yersinia
Respiratory (Gram -): bordetella, burkholderia cepacia, haemophilus (pleomorphic), legionella (silver stain)
Zoonotic (gram -): bartonella, brucellosis, francisella, pasteurella

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10
Q

Branching filamentous morphology

A

Gram +: Actinomyces, Nocardia (weakly acid fast)

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11
Q

Pleomorphic morphology

A

Gram -: chlamydiae (Giemsa), Rickettsiae (Giemsa)

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12
Q

Spiral morphology

A

Gram -: borrelia (Giemsa), leptospira, treponema

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13
Q

No cell wall bacteria

A

Mycoplasma, urea plasma (contain sterols, which do not gram stain)

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14
Q

Gram Stain

A

First line lab test in bacterial identification. Bacteria with thick peptidoglycan layer retain crystal violet dye (gram +); bacteria with thin peptidoglycan layer turn red or pink (gram -) with counterstain

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15
Q

Bugs that do not gram stain well

A

These Microbes May Lack Real Color
Treponema (too thin to be visualized)
Mycobacteria (cell wall has high lipid content)
Mycoplasma, ureaplasma (no cell wall)
Legionella, Rickettsia, Chlamydia (primarily intracellular, also chlamydia lack classic peptidoglycan because of decreased muramic acid)

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16
Q

Giemsa stain

A

Certain Bugs Really Try my Patience

Chlamydia, Borrelia, Rickettsia, Trypanosomes, Plasmodium

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17
Q

Periodic acid-Schiff stain

A

Stains glycogen, mucopolysaccharidoses; used to diagnose whipped disease (tropheryma whipplei)
PaSs the SUGAR

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18
Q

Ziegler-Neelsen stain (carbon fuchsin)

A

Acid fast bacteria (mycobacteria - stains my colic acid in cell wall), Nocardia; Protozoa (eg cryptosporidium oocytes)
Alternative is auramine-rhodamine stain for screening (more sensitive but less specific)

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19
Q

India Ink stain

A

Cryptococcus neon organs; mucicarmine can also be sued to stain thick polysaccharide capsule red

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20
Q

Silver Stain

A

Fungi (eg Coccidioides, pneumocystis jirovecii), legionella, helicobacter pylori

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21
Q

Fluorescent Ab

A

Use to identify many bacteria and viruses

eg FTA-ABS for confirming syphilis

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22
Q

Selective media

A

Favors the growth of particular organism while preventing growth of other organisms
E.g Thayer-Martin agar contains antibiotics that allow the selective growth of Neisseria by inhibiting the growth of other sensitive organisms

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23
Q

Indicator (differential) media

A

Yields a color change in response to the metabolism of certain organisms
E.g. MacConkey agar contains a pH indicator; a lactose fermenter like E.coli will convert lactose into acidic metabolite –> color change

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24
Q

Special culture requirements: H.influenzae

A

Media: Chocolate agar

-factor V (NAD+) and X (hematin)

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25
Q

Special culture requirements: N.gonorrhoeae, N.meningitidis

A

Media: Thayer-Martin
Selectively favors growth by Neisseria by inhibiting growth of gram + organisms with Vancomycin, gram - organisms (except Neisseria) with Trimethoprim and Colistin and fungi with Nystatin
Very Typically Cultures Neisseria

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26
Q

Special culture requirements: B.pertussis

A

Media: Bordet-gengou agar (Bordet for bordatella); Regan-Lowe medium
Potato; charcoal, blood, antibiotic

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27
Q

Special culture requirements: C.diptheriae

A

Media: Tellurite agar; loffler medium

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28
Q

Special culture requirements: M.tuberculosis

A

Media: Lowenstein-Jensen agar

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29
Q

Special culture requirements: M.pneumoniae

A

Media: Eaton agar

Requires cholesterol

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30
Q

Special culture requirements: Lactose-fermenting enteritics

A

Media: MacConkey agar

Fermentation produces acid, causing colonies to turn pink

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31
Q

Special culture requirements: E.coli

A

Media: Eosin-methylene blue (EMB) agar

Colonies with green metallic sheen

32
Q

Special culture requirements: Legionella

A

Media: charcoal yeast extract agar buffered with cysteine and iron

33
Q

Special culture requirements: Fungi

A

Media: Sabouraud agar

Sab’s a FUN-guy

34
Q

Aerobes

A

Use an O2-dependent system to generate ATP
Examples: Nocarida, pseudomonas aeruginosa, mycobacterium tuberculosis (Nagging Pests Must Breath)
Reactivation of M.tuberculosis has predilection for the apices of the lungs

35
Q

Anaerobes

A

Examples: Clostridium, bacteriodes, fuse bacterium, Actinomyces (anaerobes Can’t Breathe Fresh Air)
They lack catalase and/or superoxide dismutase and are thus susceptible to oxidative damage (foul smelling, difficult to culture, produce gas in tissue)
Anaerobes are normal flora in the GI tract and typically pathogenic elsewhere. Aminoglycosides are ineffective against anaerobes because the antibiotics require O2 to enter into bacterial cell

36
Q

Obligate intracellular

A

Rickettsiae, CHlamydia, COxiella - rely on host ATP

stay inside cells when it’s Really CHilly and COld

37
Q

Faculties intracellular

A

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

38
Q

Encapsulated Bacteria

A

Pseudomonas aeruginosa, Streptococcus pneumoniae, Haemophilius influenzae type B, Neisseria meningitidis, E.coli, Salmonella, Klebsiella pneumoniae and group B Strep
Please SHINE my SKiS
Capsules serve as an anti phagocytic virulence factor –> then are opposites and cleared by the spleen instead. Asplenic pts have decreased opsonizing ability and thus increased risk for severe infections (give S.pneumo, HiB, & N.menigitidis vaccines)
Capsular polysaccharide + protein conjugate serves as Ag in vaccines

39
Q

Encapsulated Bacteria Vaccines

A 
Some vaccines containing polysaccharide capsule Ag are conjugated to a carrier protein, enhancing immunogenicity by promoting TC activation and subsequent class switching 
A polysaccharide Ag alone cannot be presented to TCs
PCV, PPSV, HiB, Meningococcal vaccine
40
Q

Urease-positive organisms

A 
Proteus, Cryptococcus, H pylori, Ureaplasma, Nocardia, Klebsiella, S epidermis is, S saprophyticus (*Pee CHUNKS*)
Potentiates struvite (ammonium magnesium phosphate) stones, urease hydrolyzes urea to release ammonia and CO2 --> increases pH
41
Q

Catalase-Positive organisms

A

Catalase degrades H2O2 into H2O and bubbles of O2 before it can be converted into microbicidal products by the enzyme myeloperoxidase
People with chronic granulomatous disease (NADPH oxidase deficiency) have recurrent infections with certain catalase + organisms
Examples: Nocardia, Pseudomonas, Listeria, Aspergillus, Candida, E.coli, Staphylococci, Serratia, B.cepacia, H.pylori
(Cats Need PLACESS to Belch their Hairballs)

42
Q

Pigment producing bacteria

A

Actinomyces israelii - yellow suffer granules (comprised of filaments of bacteria)
S.aureus - yellow pigment
P.aeruginosa - blue-green pigment
Serratia marcescens - red pigment

43
Q

In-Vivo biofilm producing bacteria

A

S.epidermidis - catheter and prosthetic device infections
Veridans streptococci (mutans, sanguinis) - dental plaques, infective endocarditis
P.aeruginosa - respiratory tree colonization in CF pts, contact lens-associated keratitis
Nontypeable (unencapsulated) H.influenzae - otitis media

44
Q

Virulence factor: Protein A

A

Binds Fc region of IgG. Prevents opsonization and phagocytosis
Expressed by S.aureus

45
Q

Virulence factor: IgA protease

A

Enzyme that cleaves IgA

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

46
Q

Virulence factor: M protein

A

Helps prevent phagocytosis
Expressed by group A streptococci
Shares similar epitope to human cellular proteins (molecular mimicry) possibly underlies the autoimmune response seen in acute rheumatic fever

47
Q

type III secretion system

A

Also known as “injectisome” - needle like protein appendage facilitating direct delivery of toxins from certain gram (-) bacteria
Pseudomonas, Salmonella, Shigella, E.coli) to eukaryotic host cell

48
Q

Bacterial structures: Appendages

A

Flagellum: made of proteins, function for motility
Pilus/fimbria: made of glycoproteins, function to mediate adherence of bacteria to cell surface, sex pilus forms during conjugation

49
Q

Bacterial genetics: Transformation

A

Ability to take up naked DNA (i.e. From cell lysis) from environment (AKA competence)
A feature of many bacteria - S.pneumoniae, HiB, Neisseria (SHiN)
Any DNA can be used. Adding deoxyribonuclease to environment will degrade backed DNA in medium thus no transformation is seen

50
Q

Conjugation: F+ x F-

A

F+ plasmid contains genes required for sex pilus and conjugation. Bacteria without this plasmid are termed F-.
Sex pilus on F+ bacterium contains F- bacterium. A single strand of plasmid DNA is transferred across the conjugal bridge (“mating bridge”)
No transfer of chromosomal DNA

51
Q

Conjugation: Hfr x F-

A

F+ plasmid can become incorporated into bacterial chromosomal DNA, termed high frequency recombination (Hfr) cell. Replication of incorporated plasmid DNA may include some flanking chromosomal DNA.
Transfer of plasmid and chromosomal genes

52
Q

Bacterial genetics: Transposition

A

Segment of DNA (eg transposon) that can “jump” (excision and reintegration) from one location to another, can transfer genes from plasmid to chromosome and vice versa. When excision occurs, may include some flanking chromosomal DNA, which can be incorporated into a plasmid and transferred to another bacterium.
e.g. VanA gene from vancomycin resistant enterococcus to S.aureus

53
Q

Generalized Transduction

A

A “packaging” event. Lytic phage infects bacterium, leading to cleavage of bacterial DNA. Parts of other bacterial chromosomal DNA may become packaged in phage capsid. Phage infects another bacterium, transferring these genes

54
Q

Specialized Transduction

A

An “excision” event.
Lysogenic phage infects bacterium; viral DNA incorporates into bacterial chromosome. When phage DNA is excised, flanking bacterial genes may be excised with it. DNA is packaged into phage capsid and can infect other bacterium

55
Q

Bacterial toxins encoded in lysogenic phage

A 
*ABCDs*
group A strep erythogenic toxin
Botulinum toxin
Cholera toxin
Diphtheria toxin
Shiga toxin
56
Q

Spore-forming bacteria

A 
Some bacteria forms spores at end of the stationary phase when nutrients are limited. 
Spores are highly resistant to heat and chemicals. Have dipicolinic acid in their core, have no metabolic activity. Must autoclave to potentially kill spores (as is done with surgical equipment) by steaming at 121 degrees C for 15 minutes 
Bacillus anthracis (Anthrax), Bacillus cereus (Food poisoning), Clostridium botulinum (botulism), clostridium difficle (pseudomembranous colitis), clostridium perfringens (gas gangrene), clostridium tetani (tetanus)
57
Q

Main features of Exotoxins

A

Source: certain gram + and gram - bacteria
Secreted from cell
Polypeptide
Location of genes: plasmid or bacteriophage
High amounts of adverse effects
Antigenicity: induced high-tiger Abs called antitoxins
Vaccines: toxoids used
Heat stability: destroyed rapidly at 60 degrees C (except staph enterotoxin)
Typical diseases: tetanus, botulism, diphtheria

58
Q

Main features of Endotoxins

A

Source: outer cell membrane of most gram - bacteria
Not secreted from cell
Lipid A component of LPS (structural part of bacteria; released when lysed)
Location of genes: bacterial chromosome
Low amount of adverse effects
Clinical effects: fever, shock (hypotension), DIC
MOA: inducing TNF, IL-1 & IL-6
Poorly antigenic
Vaccines: none - no toxoid formed
Heat stability: stable at 100 degrees C for 1 hr
Typical diseases: meningococcemia; sepsis by gram - rods

59
Q

Exotoxins: Inhibiting protein synthesis - C.diphtheriae

A

Toxin: diphtheria toxin (AB toxin)
MOA: inactivation of elongation factor (EF-2)
Manifestation: pharyngitis with pseudomembranes in throat and severe lymphadenopathy (bull neck)

60
Q

Exotoxins: Inhibiting protein synthesis - Pseudomonas aeruginosa

A

Toxin: exotoxins A (AB toxin)
MOA: Inactivation of EF-2
Manifestation: host cell death

61
Q

Exotoxins: Inhibiting protein synthesis - Shigella app.

A

Toxin: Shiga toxin (ST - AB toxin)
MOA: inactivate 60S ribosome by removing adenine from rRNA
Manifestation: GI mucosal damage –> dysentery; ST also enhances cytokine release, causing hemolytic uremic syndrome (HUS)

62
Q

Exotoxins: Inhibiting protein synthesis - Enterohemorrhagic E.coli (EHEC)

A

Toxin: Shiga-like toxin (SLT - AB toxin)
MOA: inactivation of 60S ribosome by removing adenine from rRNA
Manifestation: SLT enhances cytokine release, causing HUS (stereotype O157:H7), but does not invade host cells

63
Q

Exotoxins: Increase fluid secretion - Enterotoxigenic E.coli (ETEC) - Heat Labile

A

Toxin: Heat Labile toxin (LT - AB toxin)
MOA: over activates adenylate cyclase (increased cAMP) –> increase Cl- secretion in gut and H2O efflux
Manifestation: watery diarrhea (Labile in the Air (Adenylate cyclase))

64
Q

Exotoxins: Increase fluid secretion - Enterotoxigenic E.coli (ETEC) - Heat-stable

A

Toxin: Heat-stable toxin (ST - AB toxin)
MOA: over activates guanylate cyclase (increased cGMP) - decreased reabsorption of NaCl and H20 I the gut
Manifestations: watery diarrhea (stable on the Ground (guanylate cyclase))

65
Q

Exotoxins: Increase fluid secretion - Bacillus anthracis

A

Toxin: edema toxin (AB toxin)
MOA: mimic the adenylate cyclase enzyme (increased cAMP)
Manifestations: likely responsible for characteristic edematous borders of black Escher in cutaneous anthrax

66
Q

Exotoxins: Increase fluid secretion - Vibrio cholerae

A

Toxin: Cholera toxin (AB toxin)
MOA: over activates adenylate cyclase (increased cAMP) by permanently activating Gs –> increased Cl- secretion in gut and H2O efflux

67
Q

Exotoxins: Inhibit phagocytic ability - Bordetella pertussis

A

Toxin: pertussis toxin (AB toxin)
MOA: over activates adenylate cyclase (increased cAMP) by disabling Gi impairing phagocytosis to permit survival of microbe
Manifestation: Whooping cough - child cough on expiration and “whoops” on inspiration (toxin may not actually be the cause of coughs; can cause “100-day cough” in adults)

68
Q

Exotoxins: Inhibit release of neurotransmitter - Clostridium tetani

A

Toxin: Tetanospasmin (AB toxin)
MOA: protease that cleave SNARE, a set of proteins required for neurotransmitter release via vesicular fusion
Manifestation: spastic paralysis, risks sardonicus and lockjaw, toxin prevents release of INHIBITORY (GABA and glycine) NTs from Renshaw cells in spinal cord

69
Q

Exotoxins: Inhibit release of neurotransmitter - Clostridium botulinum

A

Toxin: Botulinum toxin (AB toxin)
MOA: protease that cleaves SNARE, a set of proteins required for NT release via vesicular fusion
Manifestation: flaccid paralysis, floppy baby; toxin prevents release of STIMULATORY (ACh) signals at the neuromuscular junction –> flaccid paralysis

70
Q

Exotoxins: Lyse cell membranes - Clostridium perfringes

A

Toxin: alpha toxin
MOA: phospholipase (lecithin are) that degrades tissue and cell membrane
Manifestation: degradation of phospholipids –> myonecrosis (gas gangrene) and hemolysis (double zone of hemolysis on blood agar)

71
Q

Exotoxins: Lyse cell membranes - Streptococcus pyogenes

A

Toxin: Streptolysin O
MOA: protein that degrades cell membrane
Manifestations: Lyses RBCs; contributes to Beta-hemolysis; host Abs against toxin (ASO) used to diagnose rheumatic fever (do not confuse with immune complexes of poststreptococcal glomerulornephritis)

72
Q

Exotoxins: Superantigens causing shock - Staph aureus

A

Toxin: toxic shock syndrome toxin (TSST-1)
MOA: binds to MHC II and TCR outside of Ag binding site to cause overwhelming release of IL-1, IL-2, IFN-gamma, and TNF-alpha –> shock
Manifestation: toxic shock syndrome - fever, rash, shock; other toxins cause scalded skin syndrome (exfoliating toxin) and food poisoning (enterotoxin)

73
Q

Exotoxins: Superantigens causing shock - Strep pyogenes

A

Toxin: Exotoxin A
MOA: binds to MHC II and TCR outside the Ag binding site to cause overwhelming release of IL-1, IL-2, IFN-gamma, TNF-alpha –> shock
Manifestation: Toxic shock syndrome: fever, rash, shock

74
Q

Endotoxin

A

LPS found in outer membrane of gram - bacteria (cocci and rods). Composed of O Ag + core polysaccharide + lipid A (toxic component)
Released upon cell lysis or by living cells by blebs detaching from outer surface of membrane (vs. Exotoxin which is actively secreted)
Three main effects: MP activation (TLR4), complement activation and tissue factor activation

75
Q

Facts of endotoxins

A 
*ENDOTOXINS*
Edema
Nitric Oxide
DIC/Death
Outer membrane
TNF-alpha
O-Ag + core polysaccharide + Lipid A
eXtremely heat stable
IL-1 and IL-6
Neutrophil chemotaxis
Shock

Microbiology (8 decks)

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