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GER Unit 1 > Microbio 1 > Flashcards

Microbio 1 Flashcards

1
Q

common themes in exotoxin structure and function

A
  • encoded on plasmids
  • common strategies: superantigenicity, interference with signal transduction, depolymerization of actin
  • A-B structure: A has toxic activity and B delivers A to target
  • heat liable, inactivated toxoids are useful vaccine targets
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2
Q

virulence factors

A

gene products expressed by pathogens that directly contribute to disease process (enhances pathogenicity); often encoded on accessory DNA transferred horizontally on plasmids or by phage

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3
Q

when do commensals become pathogens or symbiotes?

A

when assumptions of commensal relationship are violated

  • escape proper containment
  • host is immunosuppressed and commensal overgrows
  • antibiotic use throws off commensal balance
  • pathogen to neonate after vaginal delivery
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4
Q

definition of endotoxin

A

innate structural components of bacteria that cause strong immune response, neither previous exposure nor vaccination is protective

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5
Q

Staph. Aureus

A 
MRSA
Tests: gram +, beta hemolytic, catalase +, coagulase+
Vir. Factors: protein A, capsule
Toxins: DNAse, TSS
Reservoir: flora of nose or skin
Transmission: direct or indirect
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6
Q

Staph. epidermis

A

piercing infections
Tests: gram +, coagulase -, novobiocin S
Reservoir: flora of skin and mucus membranes
Transmission: attaches to nylon and plastic

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7
Q

Staph. saprophyticus

A

UTI (not major cause)

Tests: gram +, coagulase -, novobiocin R

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8
Q

Strep. pneumoniae

A

Tests: gram +, catalase -, alpha hemolytic, diplococci
Vir. Factors: capsule
Reservoir: throat

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9
Q

Viridans Strep

A

dental caries and endocarditis
Tests: gram +, catalase -, alpha hemolytic
Vir. Factors: sugar-metabolizing enzymes (biofilm production)
Reservoir: teeth

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10
Q

Group A (Strep. pyogenes)

A

Strep throat
Tests: gram +, catalase -, beta hemolytic bacitracin S
Vir. Factors: pili, M Protein
Toxins: streptokinase, streptodornase, et al.
Reservoir: pharynx, skin
Transmission: carriers, infected pt

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11
Q

Group B

A 
pathogenic to neonates
Tests: gram +, catalase -, beta hemolytic, bacitracin R, CAMP +
Vir. Factors: capsule
Reservoir: genital tract of women
Transmission: vaginal birth
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12
Q

Group D

A

Tests: gram +, catalase -, gamma hemolytic
Reservoir: GI tract

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13
Q

N. Meningitis

A 
Tests: gram -, maltose +
Vir. Factors: capsule
Toxins: LPS
Reservoir: resp. tract, carriers
Transmission: droplets
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14
Q

N. Gonorrhea

A 
Tests: gram -, maltose -
Vir. Factors: pili
Toxins: LOS
Reservoir: genitals
Transmission: sex
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15
Q

Sterilization

A

eliminates all forms of microbial life, living tissue cannot be sterilized

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16
Q

Disinfection

A

eliminates many or all pathogens (except bacterial spores) on inanimate objects, base different levels of activity based on microorgs

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17
Q

Antiseptic

A

reduction of microorgs on living tissue/skin

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18
Q

Gas Plasma

A

sterilization tech.; free radicals produced with UV and H2O2 or peracetic acid disrupt microorgs

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19
Q

Irradiation

A

sterilization tech.; single-use medical supplies, RBCs to help prevent graft-vs.-host

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20
Q

what is the only liquid chemical disinfectant that can be considered a sterilant?

A

cidex

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21
Q

what is the chain of infection?

A

pathogen–> reservoir–> portal of exit–> means of transmission–> portal of entry–> susceptible host

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22
Q

what is the Ames test?

A

test using bacteria to determine if something in carcinogenic; inoculate plate with tester strain, filter disk containing test chemical
negative result: few spontaneous revertants
positive result: increased revertants near test chemical

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23
Q

Transformation

A

DNA released from dead bacteria may be taken up nonspecifically by live bacteria; DNA is incorporated into the recipient genome by homologous recombination

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24
Q

General transduction

A

bacterial gene transfer to another bacterium via a bacteriophage; typically carries only bacterial DNA and no viral DNA; special case of transformation

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25
Q

Specialized transduction

A

restricted set of bacterial genes is transferred to another bacterium; prophage excises imprecisely from the chromosome so that bacterial genes adjacent to prophage are included in the excised DNA

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26
Q

Conjugation

A

mechanism by which many antibiotic-resistance genes are transferred; male cell produces pilus, pilus attaches to recipient, mobile plasmid (contains F Factor with genes for pilus and conjugation) is transferred to recipient cell

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27
Q

Bacterial gene expression

A

operon cluster of genes whose expression is controlled by one promoter; promoter is separated from genes by an operator which regulates expression of operon; repressor or product can bind to operon to stop gene expression

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28
Q

quorum sensing

A

ability of bacteria to sense their own population density; secreted inducer, receptor for inducer, transcriptional activator that responds

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29
Q

obligate anaerobes

A

derive ATP from breakdown of glucose; cannot detoxify oxygen radicals; fermentation: use pyruvate as an electron acceptor to deoxidize the used coenzymes

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30
Q

obligate aerobes

A

efficiently derive ATP from oxidizing sugars or other organic molecules; contain oxidase, superoxide dismutase, catalase, and/or cytochrome c; glycolysis–> citric acid cycle–> ETC

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31
Q

facultative anaerobes

A

encode both fermentation and aerobic respiration, grow much faster when O2 is available (e.g., e.coli)

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32
Q

stages of bacterial cell growth in the lab

A

lag (upreg of metabolism and growth), log (rapid cell division), stationary (die and grow at same rate, nutrient depletion and waste accumulation), and death (waste kills off most remaining bacteria)

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33
Q

spores (endospores)

A

thick spherical coat forms in response to nutrient depletion in extreme environmental conditions; produces rugged, dehydrated package containing bacterial genome with minimal entourage of macromolecules, e.g. bacillus and clostridium

34
Q

bacterial ribosomes

A

70S (smaller than eukaryotes) and sediment less readily under ultracentrifugation; chemical differences make them a great drug target (>50% of antibiotics: amino glycosides, tetracyclines, and macrolides)

35
Q

glycocalyx

A

glycoprotein

  • slime layer: loose coating of polysaccharide that aids in biofilm attachment and formation
  • capsules: antiphagocytic, serologic testing, vaccine target, attachment
36
Q

examples of endotoxins

A

LPS and LOS: gram - cell wall component; teichoic acids: gram + cell wall component

37
Q

acid fast staining procedure

A

mycobac don’t hold safrinin because cell wall is waxy (mycolic layer), cook sample to get carbofuchsin stain to penetrate layers, e.g. TB

38
Q

gram staining procedure

A

fix to slide/kill bacteria, stain crystal violet, iodine treatment (+ becomes permanently purple), decolorize with alcohol (leeches purple from -), counterstain with safrinin (- becomes light pink)

39
Q

gram + characteristics

A

3 layer peptidoglycan cell wall; smaller less diverse lineage but very successful and disproportionately represented in bacteria that make us sick

40
Q

gram - characteristics

A

1 layer peptidoglycan cell wall and exterior membrane; more diverse lineage

41
Q

bacterial flagella

A

polymer of flagellin powered by proton motive force, rotates to propel bacteria forward

42
Q

eukaryotic flagella

A

complex filament structure that moves using ATP, waves side to side

43
Q

pili/fimbrae

A

gram +: simple and more recently discovered

gram -: complex, type I attachment, type II locomotion, type III and IV: secretion

44
Q

natural selection of microorganisms

A

bacteria and viruses show genetic instability, this does not produce new species but it can cause phenotypic changes through minor genetic changes; happens fast enough to observe:

  • virulence
  • host range
  • drug resistance
45
Q

enterobacteriaceae characteristics

A 
gram -
nonsporulating
straight rods
facultative aerobes
promiscuous to new DNA (acquire gut virulence factors like pili, T3SS, actin-based cell to cell motility, antibiotic resistance)
46
Q

describe how salmonella can cause enterocolitis

A

M cells in Peyer’s patch sample antigen, enterobac attaches to M cell via pili, T3SS injects, alters local macrophages and spreads to the exterior surface of the gut and lyse to escape into bloodstream

47
Q

trojan horse method of infection

A

subvert macrophage but do not immediately cause apoptosis, ride through lymphatics and invade major organs; lyse once critical density is reaches (e.g., s. typhi and y. enterocolicita)

48
Q

Hemolytic-Uremic Syndrome (HUS)

A

primarily per complication of shigella and EHe.coli caused by release of shiga toxin into the bloodstream

49
Q

Reactive Arthritis

A

autoimmune sequel of bacterial infection in patients positive for HLA-B27, commonly triggered by shigella, salmonella, yersinia, campylobacter, or chlamydia; can’t see, can’t pee, can’t climb a tree

50
Q

ICU bugs

A

extremely antibiotic resistant, seldom symptomatic in previously healthy people but are very difficult to treat once introduced; klebsiella, enterobacter, serrate, proteus, providence, and morganella

51
Q

S. Typhi

A

enteric bacteria with extra virulence factors that take infection past GI system via. trojan horse method; typhoid mary–chronic carriage in gallbladder.

52
Q

Non-facultative anaerobes

A

drive all ATP from fermentation; lack enzymes like catalase, peroxidase, superoxide dismutase

53
Q

Common themes of anaerobic pathogens

A
  • normal flora that escape compartment (form abscess)

- soil organism (enter through wound or through food)

54
Q

Major pathogenic anaerobes

A

-clostridium: gram +, needs spores (except C. diff)
-gram - anaerobic bacteria (GNAB): normal flora
Actinomyces: gram +, normal flora

55
Q

C. Tetani

A

gram +, Soil–> wound–> spores express tetanospasmin in A-B subunit structure, cleaves synaptobrevin in CNS and inhibits neural inhibition

56
Q

C. Botulinum

A

entry through food, expresses immediately and results in flaccid paralysis

57
Q

M. Tuberculosis

A
  • gram - because of nycolic cell wall (use acid fast)
  • very slow growing
  • trojan horse method of spread, strong CMI leads to latent infection in granulomas
  • DOTs with ionized
58
Q

M. Leprae

A
  • no in vitro culture system
  • slowest double time of any human pathogen
  • range of presentation from tuberculoid (PPD+) to lepromatous (PPD-)
  • 2 yr. dapsome treatment
59
Q

Common themes in spirochetes

A
  • wide variety of transmission
  • cross quickly/easily into blood stream (virulence factors for immune evasion)
  • challenging to diagnose (phases of disease, very small to see)
  • Jarisch-Herxheimer reaction
60
Q

Treponema pallidum

A

-can’t be grown in culture
-extremely sexually infectious
-penicillin treatment
1°: chancre
2°: rash with flulike symptoms (low inflamm. meningitis possible)
-latency in 2/3 of cases that proceed to 2°
3°: gummas, cardiovascular and CNS involvement

61
Q

Borrelia burgdorferi

A

-tick borne, 24 attachment to transmit
-longterm seropositivity
-doxycycline treatment for 1 mo.
1°: skin infection; bulls eye rash common
2°: immune/neurological issues
-post-lyme neuro sequela
3°: chronic lyme with more severe immune, neurofibromyalgia

62
Q

Common themes in vibrio

A
  • curved, gram -
  • most pathogens are ocean-dwelling
  • require GI virulence factors to establish locus of infection for gastroenteritis and peptic ulcers
  • can also infect wounds
63
Q

V. Cholerae

A
  • O1 genetic marker of colonization by lysogenic CTX bacteriophase that carries virulence factors
  • fecal-oral transmission, HUGE ID50
  • mucinase to attach and colonize intestine
  • choleragen: enterotoxin that causes watery diarrhea
  • self limited, antibiotics less necessary than ORS
64
Q

examples of intracellular pathogens

A

all viruses, neisseria, enterobac, mycobac, bacilli, legionella, listeria, rickettsia, chlamydia, some fungals

65
Q

themes in intracellular pathogenesis

A
  • infected macrophages for transport
  • t3SS
  • actin based motility and cell-cell spread
  • evade humoral immunity and surface defenses
  • treatment: tetracycline, antibiotics must be active in cell membrane
66
Q

facultative intracellular pathogens

A

divide independently but can enter host cells as part of pathogenesis
-ex. listeria monocytogenes: gastroenteritis found in cold-stored food (don’t eat soft cheese and deli meat when pregnant–meningitis), ActA virulence factor for actin-based motility after endocytosis

67
Q

obligate intracellular pathogens

A

require host cell resources to multiply; grown in tissue culture like viruses
-ex. chlamydia: reverse endocytosis (tiny, infectious elementary bodies (T3SS) unpack into larger reticulate bodies after cell penetration; risk of reactive arthritis; treat with doxycycline or azithromycin

68
Q

ß-lactams

A
  • bactericidal
  • inhibits cell wall synthesis by mimicking the d-ala d-ala that normally bind to transpeptidase enzyme that cross links peptidoglycan strands
  • gram +
  • broad spectrum do gram - too
  • ex. penicillan and cephalosporin
  • use carbapenems for ESBLs
69
Q

Glycopeptides

A

bactericidal

  • inhibits cell wall synthesis by irreversibly binding to d-ala d-ala
  • gram +
  • ex. vancomycin
70
Q

Macrolides

A
  • bacteriostatic
  • inhibits 50S ribosomal subunit
  • gram +
  • ex. erythromycin, z-pack
71
Q

Tetracyclines

A
  • bacteriostatic
  • inhibits 30S ribosomal subunit
  • broad spectrum
72
Q

Fluoroquinolones

A
  • bactericidal
  • inhibits nucleic acid synthesis (DNA gyrase)
  • broad spectrum
73
Q

Aminoglycosides

A
  • bacteriocidal
  • inhibit 30S ribosomal subunit
  • gram -
74
Q

Sulfonamides/Trimethoprim

A
  • bacteriostatic when alone, bactericidal together
  • inhibits nucleic acid synthesis (folate synthesis)
  • ex. bactrim
75
Q

insertion sequences

A

mobile genetic elements; may contain promoters capable of activating the expression of neighboring genes; incapable of autonomous self-replication

76
Q

interons

A

non mobile gene capture machines; can be park of a transposon or plasmid; allows for the insertion of multiple gene cassettes

77
Q

gene cassette

A

free DNA that includes a gene and an integrate specific recombination site to allow for attachment to integron; expression based on number, position, and proximity to promoter sequence

78
Q

what are the main mechanisms of antibiotic resistance?

A
  • enzymatic inactivation: ex. ß-lactamase
  • decreased permeability: change ability of antibiotic to get into cell
  • efflux: antibiotic gets in and cell kicks out
79
Q

ß-lactamase

A

inactivate ß-lactam antibiotics by hydrolysis of ß-lactam bond; clavulanate and sulbactam are suicide inhibitors that covalently bind to ß-lactamase enabling antibiotic to work

80
Q

advantages and disadvantages of gram stain for ID detection

A
  • pros: simple, reliable, provide preliminary info

- cons: takes a few days, some organisms grow slowly, not always diagnostic

81
Q

advantages and disadvantages of molecular methods for ID detection

A
  • pros: good for difficult to culture a gens, increased sensitivity, rapid diagnostic top, quantity of viral load for prognosis and response to therapy
  • cons: few FDA approved assays

GER Unit 1 (2 decks)

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