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Infectious Disease > Bacteria > Flashcards

Bacteria Flashcards

1
Q

What is the minimum requirement for a plasmid to be transferred during conjugation?

A

it must have an oriT

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2
Q

What is an R plasmid?

A

one that conveys multiple antibiotic resistance

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3
Q

Name the three mechanisms of bacterial conjugation.

A
  • F+ conjugation
  • Hfr conjugation
  • conjugative transposons
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4
Q

Antibiotic resistance genes are typically found on what sort of genetic element?

A

transposons

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5
Q

What role do resident bacteria populations play in the antibiotic resistance of pathogens?

A

they provide R plasmid reservoirs that can be conveyed to pathogens

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6
Q

Long-term use of antibiotics can affect the human gut and increase a person’s risk for what four things?

A
  • infection
  • obesity
  • cancer
  • autoimmunity
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7
Q

What induces a phage to transition from a lysogenic cycle to a lytic one?

A

DNA damage, which triggers degradation of the phage repressor protein thereby permitting phage genome transcription

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8
Q

Name four important components of an F plasmid.

A
  • oriT
  • oriV
  • IS elements
  • tra operon
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9
Q

What is the tra operon?

A

an operon on F plasmids which encodes the components of the conjugation apparatus and allows for construction of the F pilus as well as nicking, unwinding, transfer of plasmid DNA

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10
Q

What is a phage repressor protein?

A

a protein expressed by lysogenic phage to prevent gene transcription and maintain the lysogenic cycle

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11
Q

Why don’t Hfr recipients become F+?

A

because transfer is terminated before F factor can be transferred

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12
Q

What is a prophage?

A

a bacteria in which lysogenic phage DNA has been incorporated into the genome

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13
Q

Where do antibiotic resistance genes typically originate?

A

in the species that makes the antibiotic

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14
Q

What happens to the donated DNA at the end of Hfr conjugation?

A

it undergoes exchange with the recipient or is degraded

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15
Q

What happens to temperate phage DNA after it first infects a bacterial cell?

A

it circularizes and either enters a lytic cycle or recombines with the bacterial chromosome at the att site

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16
Q

What is a temperate phage?

A

one capable of establishing lysogeny

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17
Q

What is an oriV?

A

the origin of replication for F plasmids

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18
Q

What are integrative conjugative elements?

A

elements within the bacterial genome that are retain the ability to excise and be transferred via conjugation

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19
Q

How does R plasmid antibiotic resistance differ from mutation-induced antibiotic resistance?

A
  • mutations are more likely to contribute to modification of an antibiotic target such that it is less susceptible
  • plasmids are more likely to convey efflux pumps or proteins capable of modifying the antibiotic itself
  • furthermore, plasmids are more likely to convey multiple antibiotic resistances rather than just one
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20
Q

What is phage conversion?

A

a change in bacterial phenotype due to expression of phage genes during a lysogenic infection

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21
Q

What are the three modes of bacterial genetic exchange?

A
  • transformation
  • transduction
  • conjugation
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22
Q

What happens to the transferred DNA after generalized transduction?

A

the DNA recombines with chromosomal DNA via homologous recombination

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23
Q

What happens to the transferred DNA after specialized transduction?

A

the DNA is inserted at the recipient att site

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24
Q

What is a Kirby-Bauer test?

A

an antibiotic resistance test involving disk diffusion

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25
Q

Bacteria typically use passive uptake to invade what host cell population?

A

phagocytic cells

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26
Q

Acid-fast stain is used to diagnose what kind of bacteria?

A

mycobacteria

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27
Q

What is CD14?

A

a membrane bound host receptor that binds LPS-binding protein and signals via a TLR to mediate toxic shock

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28
Q

Many AB exotoxins perform what function?

A

ADP-ribosylation

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29
Q

What are type I bacterial pili?

A

those that adhere to mannose receptors

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30
Q

What are type P bacterial pili?

A

those that adhere to Gal-Gal receptors

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31
Q

Describe how blood samples ought to be taken for culture.

A
  • avoiding contamination by skin flora

- in multiple across 24 hours

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32
Q

Name two classes of membrane damaging exotoxins.

A
  • phospholipases

- pore forming toxins

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33
Q

When would you collect a sputum sample?

A

if you suspected a LRTI

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34
Q

How is an ELISA performed?

A
  • antigen or antibody is fixed in place
  • sample is applied
  • a chromogenic enzyme substrate is applied
  • the color change is measured
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35
Q

In what cases are next-gen sequencing useful in diagnosing bacterial infections?

A

low complexity situations like CSF

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36
Q

What are pathogenicity islands?

A

regions of bacterial DNA that encode virulence genes, specifically T3SS

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37
Q

What is transcytosis?

A

a mechanism for cellular invasion that relies on actin polymerization and has no extracellular phase

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38
Q

What is latex agglutination?

A
  • antibody or antigen is fixed to latex beads
  • sample is applied
  • a positive test will results in visible clumping of the beads
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39
Q

What are the three components of LPS?

A
  • O antigen
  • core polysaccharide
  • lipid A
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40
Q

Which part of LPS is responsible for its toxicity?

A

lipid A

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41
Q

What is a quantitative diffusion E test?

A

a form of disk diffusion that uses a strip infused with varying concentration of antibiotic

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42
Q

What advantage does a bacterial capsule offer?

A

it can mask or prevent complement binding, thereby preventing opsonification

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43
Q

List Koch’s molecular postulates.

A
  • gene or its products should be associated with the organism
  • the gene should be isolated via cloning
  • inactivation should lead to loss of pathogenicity
  • reactivation should restore pathogenicity
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44
Q

How is acid-fast staining performed?

A
  • heat fix the specimen
  • stain with carbolfuchsin
  • promote uptake with heat
  • decolorize (acid-fast will resist this)
  • counterstain with methylene blue
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45
Q

What are southern and northern blots?

A

diagnostic techniques that utilize hybridization of nucleic acid probes against DNA or RNA, respectively

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46
Q

What is a catalase test?

A

a diagnostic technique that tests the ability of a bacteria to form gas

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47
Q

Encapsulated bacteria pose a greater problem for hosts with what kind of immune deficiency?

A

those with depressed cell-mediated immunity

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48
Q

List four types of exotoxins.

A
  • membrane damaging
  • enzymes that act on ECM
  • AB
  • superantigens
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49
Q

What group of virulence factors are largely responsible for the tissue tropism of a pathogen?

A

the adhesins it expresses

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50
Q

What are the steps of PCR?

A
  • heat to denature RNA
  • cool to allow annealing of primers
  • allow polymerase to amplify
  • repeat
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51
Q

How is pulse-field gel electrophoresis performed?

A
  • digest DNA with a rare cutter

- separate these fragments by gel electrophoresis with a switching electric field

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52
Q

What are alpha, beta, and gamma hemolysis?

A
  • alpha is partial and has a geen color
  • beta is complete hemolysis
  • gamma is no hemolysis
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53
Q

What is wright-giemsa stain?

A

a stain used to diagnose chlamydia

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54
Q

Where on the anaerobe-anaerobic spectrum do mycobacteria fall?

A

they are obligate aerobes

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55
Q

Name the two important tuberculous mycobacteria.

A
  • M. tuberculosis

- M. bovus

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56
Q

Why is M. bovus important?

A

it is the basis for the BCG vaccine against tuberculosis

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57
Q

Name the two important non-tuberculous mycobacteria.

A
  • M. kansasii

- M. avium-intracellulare

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58
Q

List seven risk factors for tuberculosis.

A
  • young or old age
  • immunocompromised state
  • exposure to persons with disease
  • chronic pulmonary disease
  • homelessness
  • alcohol or elicit drug use
  • incarceration
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59
Q

Mycobacteria have cell walls with a high __ content.

A

lipid

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60
Q

What is arabinogalactan?

A

the other significant component of the mycobacteria cell wall apart from mycolic acids and lipids

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61
Q

Which bacteria have mycolic acids and lipids in their cell wall?

A

mycobacteria

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62
Q

What is lipoarabinomannan?

A

an adhesin expressed by mycobacteria that binds the mannose receptor of macrophages

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63
Q

How does M.tb survive intracellularly in macrophages?

A

it prevents fusion of the phagosome and lysosome

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64
Q

A PPD is a example of what kind of hypersensitivity reaction?

A

a delayed type IV

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65
Q

What is cord factor?

A

a virulent protein expressed by M.tb which disrupts mitochondrial membranes and is cytotoxic for PMNs

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66
Q

Describe the histology of a M.tb tubercle.

A

a large granuloma containing bacilli, epithelioid histiocytes, and Langhans cells, surrounded by T cells and macrophages and encapsulated with collagen

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67
Q

Epithelioid histiocytes have what cell origin?

A

macrophage

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68
Q

Define Ghon focus, Ghon complex, and Ranke complex.

A
  • Ghon focus: a primary M.tb tubercle
  • Ghon complex: a goon focus that also involves the adjacent lymphatics and hilar lymph nodes
  • Ranke complex: a fibrous, calcified Ghon complex
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69
Q

How does pulmonary TB present?

A
  • night sweats
  • weight loss
  • initially unproductive cough that begins to produce a blood sputum
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70
Q

What is primary TB?

A

clinically apparent TB within two years of infection

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71
Q

In which two populations do we most often see primary TB rather than secondary TB?

A
  • children

- the immunocompromised

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72
Q

What is miliary TB?

A

widespread, hematogenous dissemination of M.tb

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73
Q

What is scrofula?

A

another name for mycobacterial cervical lymphadenitis

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74
Q

How is active TB diagnosed?

A
  • clinically

- and confirmed by skin test and radiology

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75
Q

Where in the lungs are TB lesions most common?

A

the most oxygenated

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76
Q

A PPD will not be positive until how long after the initial infection?

A

3-6 weeks

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77
Q

What are four limitations of the PPD?

A
  • anergy in immunocompromised patients
  • 3-6 weeks delay until positive
  • prior immunization may generate a false positive
  • there is some cross-reactivity with other mycobacteria
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78
Q

For which populations does a 5mm induration indicate a positive PPD?

A
  • close contact with someone TB+
  • someone with known HIV
  • someone with a history of IV drug use
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79
Q

For which populations is a 10mm induration a positive PPD?

A
  • foreign-born individuals
  • children under 4
  • HIV negative individuals with history of IV drug use
  • low income
  • residential facility occupants
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80
Q

How is an interferon-gamma release assay performed?

A
  • M.tb antigens added to whole blood
  • antigens activate TH1 cells to produce interferon
  • that production is measured with an ELISA
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81
Q

What population of T helper cells mediates M.tb reactions?

A

TH1

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82
Q

Why isn’t culture used to diagnose M.tb?

A

it is definitive but very slow

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83
Q

List the five first-line therapies for treatment of TB.

A
  • isoniazid
  • ethambutol
  • rifampin
  • streptomycin
  • pyrazinamide
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84
Q

What is XDR-TB?

A

TB resistant to isoniazid, rifampin, quinolone, and at least one second line drug

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85
Q

What is MDR-TB resistant to?

A
  • isoniazid

- rifampin

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86
Q

Who is a candidate for TB prophylaxis?

A

someone with a positive skin test and some other risk factor

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87
Q

Name four actions that have been taken to control TB.

A
  • pasteurization of milk
  • antibiotic prophylaxis for HIV
  • development of the BCG vaccine
  • better surveillance and treatment programs
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88
Q

What is the BCG vaccine?

A

a live, attenuated M. bovis vaccine

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89
Q

Why is the BCG vaccine not used in the US?

A
  • unreliable efficacy

- most US citizens are at low risk

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90
Q

HIV patients have what risk of TB?

A

7-10 percent annual risk

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91
Q

How is M. leprae transmitted?

A

close contact or aerosols

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92
Q

M. leprae targets which human cell population?

A

schwann cells

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93
Q

Armadillos are a reservoir for what pathogen?

A

M. leprae

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94
Q

How does tuberculoid leprosy differ from lepromatous leprosy?

A
  • tuberculoid is mediated by TH1 cells and there are few bacteria in lesions
  • lepromatous is mediated by TH2 humoral immunity and there are many bacteria found in lesions
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95
Q

Name three diagnostic tests for leprosy.

A
  • lepromin skin test
  • serology for PGL-1
  • acid fast stain of tissues
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96
Q

What is the two drug combination preferred for treatment of leprosy?

A
  • rifampin

- dapsone

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97
Q

Dapsone is contraindicated for which group of people?

A

those with a G6PDH deficiency

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98
Q

What is the mechanism of action of dapsone?

A

it inhibits folic acid synthesis

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99
Q

Which disease presents with a hypo pigmented, anesthetic skin patch and complaints of an electric-current-like sensation?

A

leprosy

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100
Q

Which non-tuberculous mycobacteria is ubiquitous in water?

A

M. avium-intracellulare

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101
Q

What are Runyon classifications?

A

a method for classifying mycobacteria based on the pigment produced in their colonies

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102
Q

M. avium-intracellulare is resistant to which antibiotics?

A

clarithromycin and ethambutol

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103
Q

How does M. kansasii manifest?

A

as a TB-like disease

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104
Q

How does M. marinum manifest?

A

subcutaneous abscesses and skin ulcers

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105
Q

Which mycobacteria-like pathogen has a hyphae form and also forms white-to-orange colonies?

A

nocardia

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106
Q

Where is nocardia found?

A

in the soil and decaying organic matter

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107
Q

How does nocardia evade phagocytic killing once inside macrophages?

A

by secreting catalase and SOD

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108
Q

Nocardia causes what two diseases?

A
  • bronchopulmonary disease

- cutaneous nocardiosis

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109
Q

What is nocardia bronchopulmonary disease?

A
  • a localized disease in immunocompetent patients with pre-existing pulmonary conditions
  • spreads into pleura and then into CNS and skin
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110
Q

Who is at risk for nocardia bronchopulmonary disease?

A
  • immunocompetent patients with a pre-existing pulmonary condition
  • patients with a T cell deficiency
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111
Q

Cutaneous nocardiosis comes in what two forms?

A
  • actinomycotic mycetoma

- lymphocutaneous disease

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112
Q

How does actinomycotic mycetoma present?

A
  • painless, firm subcutaneous nodules
  • erythema and sinus tract formation
  • caused by nocardia
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113
Q

How does lymphocutaneous disease present?

A
  • nodules along lymphatics

- caused by nocardia

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114
Q

How is nocardia treated?

A
  • TMP-SMX for six weeks

- possible surgical intervention

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115
Q

CD14 signals through which TLR?

A

TLR4

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116
Q

How do we subtype members of the same bacterial species?

A

based on their pattern of antigens, toxins, or bacteriophage sensitivity

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117
Q

How is gram staining performed?

A
  • apply crystal violet stain
  • apply gram’s iodine
  • decolorize
  • counterstain with safranin red
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118
Q

List four methods for phylogenetic classification of bacteria.

A
  • GC content
  • sequencing
  • comparing conserved genes (70%)
  • comparing 16S rRNA (97%)
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119
Q

Bacteria use which ribosome for translation?

A

70S

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120
Q

All bacteria have what kind of genome?

A

a dsDNA genome

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121
Q

Where in bacterial cells is the ETC and ATP synthesis machinery?

A

on the inner membrane

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122
Q

How does the composition of the phospholipid bilayer of bacterial cells differ from that of humans?

A

it lacks sterols

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123
Q

What component of tears and saliva destroy bacterial cell walls?

A

lysozyme

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124
Q

Describe the basic subunit of peptidoglycan.

A

NAG-NAM-peptide chain

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125
Q

What is leptoteichoic acid?

A

a component of the gram+ cell wall, which serves as an endotoxin

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126
Q

Describe gram- cell walls.

A
  • a thin peptidoglycan layer

- an outer, asymmetric layer of phospholipids and LPS

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127
Q

Gram- porins allow passage of what kind of molecules?

A

small, hydrophilic molecules

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128
Q

List the cell wall types in order of most to least permeable.

A
  • acid-fast
  • gram-
  • gram+
  • mycoplasma
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129
Q

What powers flagella?

A

membrane potential

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130
Q

Which group of bacteria express T3SS and T4SS?

A

gram- bacteria

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131
Q

Which bacteria are capable of forming spores?

A

gram+

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132
Q

List three endotoxins.

A
  • LPS
  • teichoic acids
  • PG fragments
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133
Q

What is the difference between facultative and aerotolerant anaerobes?

A

facultative will use oxygen if it is present, but aerotolerant will only endure it

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134
Q

Why is oxygen toxic to obligate anaerobes?

A

often because they are unable to deal with the ROS that will form

135
Q

What is superoxide dismutase?

A

enzyme that converts O^-2 to water

136
Q

What is catalase?

A

an enzyme that converts hydrogen peroxide to water

137
Q

What three mechanisms drive active transport across bacterial cell membranes?

A
  • ATP
  • the proton motive force
  • group translocation
138
Q

B-lactams are an analog for what?

A

the D-ala, D-ala terminal of peptidoglycan chains

139
Q

What is cabapenemase?

A

a beta-lactamase capable of degrading all beta-lactams

140
Q

What change mediates vancomycin resistance?

A

modification fo the terminal D-ala of peptidoglycan to prevent vancomycin binding

141
Q

Which topoisomerases are involved in bacterial DNA replication?

A

II: removes supercoils ahead of fork
IV: resolves interlocked plasmids

142
Q

Why is folic acid important for cellular processes?

A

it is needed for 1 carbon transfers in reactions used for nucleotide and amino acid synthesis

143
Q

Why aren’t human cells susceptible to sulfonamides?

A

they block synthesis of dihydrogolic acid, something we obtain from diet

144
Q

What is mcr-1?

A

a gene that modifies LPS to convey resistance to colistin (a polymixin)

145
Q

Define antiseptic.

A

a chemical agent used to reduce the concentration of microbes in tissue

146
Q

Define disinfectant.

A

an agent used to kill microorganisms but doesn’t meet the standard of sterilization

147
Q

List five sterilization methods.

A
  • radiation
  • chemical
  • gas vapors
  • heat
  • filtration
148
Q

What chemical agent is used to disinfect surgical instruments?

A

chlorine

149
Q

What are genomic islands?

A

patches of unusual sequence or GC content acquired through horizontal gene transfer

150
Q

How is plasmid replication related to genome replication?

A

both processes use the same machinery

151
Q

What is oriC?

A

the origin of replication for bacterial chromosomes

152
Q

What role does DnaA play in bacterial chromosome replication?

A

it recognizes the oriC, unwinds the DNA, and recruits the necessary enzymes

153
Q

What is the Rep protein?

A

a protein that initiates plasmid replication at oriT or oriV

154
Q

What is a polycistronic transcript?

A

one that encodes multiple genes, usually from the same operon

155
Q

What is dyad symmetry?

A

inverted repeats found at the end of bacterial transcripts which form hairpins and trigger termination

156
Q

Expression of most operons is controlled via regulation of what step?

A

transcription initiation

157
Q

What is a co-repressor?

A

a small molecule that binds a transcription repressor and alters its activity

158
Q

How is the Lac operon negatively regulated?

A

allolactose, the inducer, binds the repressor and inactivates it so it can no longer bind the operator sequence

159
Q

How is the Lac operon positively regulated?

A

falling glucose levels, increase cAMP, which binds the cAMP binding protein, which binds the DNA to serve as an activator

160
Q

Under what conditions is the Trp operon expressed?

A

low levels of tryptophan

161
Q

Describe trp attenuations.

A

when trp levels are low, transcription is stalled and avoids termination

162
Q

What are the parts of a two-component system?

A
  • sensor kinase with autophosphorylation ability

- response regulator which gets phosphorylated

163
Q

Why do bacterial populations express rare mutations more than humans?

A
  • they are haploid

- they have a rapid growth rate

164
Q

What is the most common form of DNA mutation?

A

base substitution

165
Q

What causes DNA breaks?

A

x-ray and gamma radiation

166
Q

What is the largest group of chemical DNA mutagens?

A

alkylating agents

167
Q

Through what mechanism do alkylating agents cause DNA mutation?

A

they interfere with proper hydrogen bonding of bases

168
Q

Name the two most significant base analog chemical mutagens.

A

2-aminopurine and 5-bromouracil

169
Q

What are intercalating agents?

A

DNA mutagens that insert themselves between adjacent bases and cause a frameshift mutation

170
Q

What is a common intercalating agent?

A

ethydium bromide

171
Q

How are ROS DNA mutagenic?

A

they oxidize DNA and cause mispairing

172
Q

Through what repair mechanism is UV damage resolved?

A

direct repair

173
Q

What DNA mutations are fixed via excision repair?

A

bulky adducts

174
Q

Where does the sequence come from for recombinational DNA repair?

A

the sister chromosome

175
Q

DNA polymerases have what proofreading mechanism?

A

3’-5’ exonuclease activity

176
Q

What are two non-mutagenic mechanisms for repairing thymine dimers?

A
  • light repair (aka photo reactivation)

- dark repair (nucleotide excision)

177
Q

What are LexA and RecA?

A
  • LexA is a repressor protein which inhibits SOS repair proteins
  • RecA cleaves it in response to DNA damage
178
Q

Which polymerase mediates SOS repair?

A

DNA polymerase V

179
Q

DNA damage has what three effects on bacteria?

A
  • mutation
  • induces phages
  • induces transposition
180
Q

Describe Griffith’s transformation experiment.

A
  • rough S. pneumoniae didn’t kill mice but smooth did
  • heat-killed smooth + active rough did kill mice
  • able to isolate live smooth from mice
181
Q

What is a competent bacteria?

A

one in the late log/early stationary phase, capable of transformation

182
Q

List two unique about transformation among gram+ species.

A
  • they require a competence factor (from quorum sensing)

- dsDNA is bound to the cell but only ssDNA is translocated

183
Q

List three unique things about transformation among gram- species.

A
  • only uptake DNA from closely related species
  • bind DNA via a transformasome that recognizes a specific sequence
  • only ssDNA is translocated
184
Q

What is an ampicillin rash?

A

an adverse effect of PCNs seen mostly in patients with mono

185
Q

Most inhibitors of protein synthesis target what bacterial component?

A

the 50S ribosome

186
Q

What is the main mechanism bacteria use to become amino glycoside resistant?

A

increased bacterial metabolism

187
Q

Describe the folate pathway.

A
  • PABA is converted to dihydrofolic acid

- dihydrofolic acid is converted to tetrahydrofolic acid

188
Q

List four things that make anti-mycobacterial therapy so difficult?

A
  • resistance develops quickly
  • pathogen has long periods without growth
  • pathogen is largely intracellular
  • therapy has to be long-term
189
Q

How did S. pneumonia develop penicillin resistance?

A
  • point mutations in PBPs provide resistance in nonpathogenic organisms
  • mosaic PBPs are formed via transformation with low beta-lactam affinity
190
Q

What kind of protease is the HIV protease?

A

aspartyl

191
Q

Which group of drugs are often given with cobistat and ritonavir?

A

HIV protease inhibitors

192
Q

What is the primary ART option during pregnancy?

A

atazanavir or darunavir + ritonavir

193
Q

Which HIV treatments induce and which inhibit CYP3A4?

A
  • induce: efavirenz, nevirapine, amprenavir

- inhibit: PIs, efavirenz, delavirdine

194
Q

Why is protein synthesis not a common target of anti-virals?

A

because viruses typically use host machinery

195
Q

Under what circumstances does B. anthracis form spores?

A

in rich media under aerobic conditions

196
Q

Human B. anthracis infections are ___ and not ___.

A

incidental and not contageous

197
Q

From what animals does B. anthracis originate?

A

from herbivores

198
Q

List the three ways B. anthracis enters the human body.

A
  • cutaneous via contact with infected material
  • inhalation of spores
  • ingestion of contaminated meat
199
Q

What are the symptoms of inhalation anthrax?

A
  • flu-like symptoms without runny nose
  • non-productive cough
  • radiographic evidence of mediastinal widening
200
Q

What is the incubation period of anthrax?

A

1-7 days usually, but can be up to 60

201
Q

When must anthrax be treated to prevent mortality?

A

in the first 48 hours after exposure

202
Q

Why does mediastinal widening occur in inhalation anthrax?

A
  • alveolar macrophages phagocytize the spores
  • transport them to mediastinal lymph nodes
  • spores germinate and multiple
203
Q

What are the two forms of gastrointestinal anthrax?

A
  • oropharyngeal

- intestinal

204
Q

How does oropharyngeal anthrax present?

A

local ulcerations leading to tonsillitis

205
Q

How does intestinal anthrax present?

A

an ulcer followed by bloody diarrhea or sepsis

206
Q

How does cutaneous anthrax present?

A

a painless papule that develops into a black necrotic ulcer with edema

207
Q

Describe the anthrax capsule.

A

it is an unusual poly-D-glutamic acid

208
Q

Describe the anthrax exotoxin.

A

an AB exotoxin

  • protective antigen (B) binds the anthrax toxin receptor and is cleaved to form PA63-ATR, which forms a hepatmeric complex
  • 2 active subunits, edema factor and lethal factor
209
Q

What does anthrax lethal protein cause?

A

it inactivates MAPKK

210
Q

Anthrax toxin binds what two host cell receptors?

A

tumor endothelial marker 8 and capillary morphogenesis protein 2

211
Q

How is anthrax diagnosed?

A
  • the plating and appearance of non-motile, non-hemolytic mucoid colonies on sheep’s blood agar
  • confirmed by gamma phage susceptibility
212
Q

What is the drug of choice for anthrax?

A

ciprofloxacin

213
Q

Describe the human anthrax vaccine.

A

a cell-free attenuated strain containing the protective antigen of anthrax toxin

214
Q

What are the primary sources of B. cereus?

A
  • contaminated food
  • trauma
  • IV injections
215
Q

Describe the course of B. cereus emetic gastroenteritis.

A
  • usually from contaminated rice
  • with a less than 6 hour incubation
  • vomiting, nausea, and abdominal cramps
216
Q

What causes B. cereus emetic gastroenteritis? What causes the diarrheal form?

A

a heat-stable enterotoxin causes emetic, a heat-liable enterotoxin causes the diarrheal form

217
Q

How does B. cereus emetic gastroenteritis differ from the diarrheal form?

A
  • diarrheal is usually from meat or vegetables
  • diarrheal has a more than 6 hour incubation
  • diarrheal induces diarrhea rather than vomiting
218
Q

B. cereus ocular infections are usually associated with what other factor?

A

contact-lenses

219
Q

What is panophthamitis?

A

a massive vitro retinal destruction within 48 hours of ocular surgery due to B. cereus toxins

220
Q

Why is B. cereus not diagnosed via stool samples?

A

because most GI tracts are colonized already

221
Q

How is B. cereus diagnosed?

A

culture and gram staining of contaminated food or infected specimen

222
Q

How is B. cereus treated?

A

vancomycin or clindamycin

223
Q

What is the hemolytic activity of B. cereus?

A

beta-hemolytic

224
Q

What bacteria has a “tumbling motility” at room temperature?

A

Listeria

225
Q

For which bacteria is refrigeration not sufficient to protect against food contamination?

A

listeria because it grows at 4 degrees celsius

226
Q

Listeria is classically a contaminant of what food products?

A

dairy products

227
Q

Which populations are most at risk for listeria infection?

A
  • primarily pregnant women

- neonates

228
Q

What is granulomatosis infanticeptica?

A

an in utero presentation of listeria with disseminated abscesses and granulomas

229
Q

How does late-onset neonate infection of listeria present?

A

soon after birth with meningitis, meningoencephalitis, and septicemia

230
Q

Where does a listeria infection typically begin in the human body?

A

enterocytes or M cells of Peyer’s patches

231
Q

What are internalins?

A

listeria virulence factors that mediate entry into non-phagocytic cells

232
Q

What is listeriolysin O?

A

a listeria virulence factor encoding a pore-forming hemolysin activated by acidic pH

233
Q

Which bacteria relies heavily on transcytosis?

A

listeria

234
Q

What is the function of actin-binding protein in listeria?

A

it is localized to the surface of a new pole, binds actin, and mediates polymerization to facilitate transcytosis

235
Q

What part of the immune system is critical for fighting listeria?

A

cell-mediated immunity

236
Q

Which bacteria has a tumbling motility and umbrella-like growth?

A

listeria

237
Q

What is the preferred treatment for listeria?

A

ampicillin

238
Q

Which bacteria is said to have form “chinese characters” due to it’s V- and L-shaped arrangements?

A

diphtheriae

239
Q

What is the action of diphtheria toxin?

A

it shuts down protein synthesis via ADP-ribosylation of elongation factor

240
Q

Vaccines against diphtheria include what antigen?

A

toxoids formed from diphtheria toxin

241
Q

Diphtheria toxin targets what three things?

A
  • URT
  • heart
  • nerve cells
242
Q

What is pseudomembranous pharyngitis?

A
  • aka respiratory diphtheria
  • it has a one week incubation period followed by sudden onset pharyngitis due to toxin secretion
  • see a grayish pseudomembrane difficult to dislodge which may cause stridor or asphyxiation
243
Q

What is tellurite chocolate agar?

A

a media for diagnosing diphtheria which the organism reduces to form a black pigment

244
Q

How is diphtheria treated?

A
  • immediate administration of antitoxin
  • erythromycin
  • immunization (because infection doesn’t generate protective antibodies)
245
Q

How is Staph differentiated from Strep?

A

staph has a positive catalase test

246
Q

___ is the bacterial genus most responsible for orthopedic infection.

A

Staph

247
Q

Staph is the number one cause of what three bacterial infections?

A
  • orthopedic infection
  • endocarditis
  • nosocomial bloodstream infections
248
Q

How is S. aureus spread?

A

via direct contact, so wash hands

249
Q

What is VRSA?

A

vancomycin-resistant staph aureus (also methicillin-resistant)

250
Q

Describe the changing epidemiology of S. areus.

A
  • no new genes but it overproduces virulence factors

- no longer just an opportunistic infection

251
Q

What is USA300?

A

the most common strain of MRSA in the US

252
Q

Is MRSA usually community or hospital acquired?

A

nowadays it is usually CA

253
Q

S. aureus is common in what food products?

A

meats, pastries, and milk products left at room temperature

254
Q

Describe the course of food-borne S. aureus infection.

A

rapid onset, short-lived nausea, diarrhea, stomach cramps

255
Q

What causes the pathology associated with food-borne S. aureus infections?

A

a heat stable enterotoxin

256
Q

What is the best drug used in the treatment of toxins?

A

clindamycin

257
Q

S. aureus uses what sort of exotoxin?

A

a superantigen

258
Q

What is Protein A?

A

a S. aureus adhesin that binds the Fc region of antibodies

259
Q

What skin and soft tissues diseases are caused by S. aureus?

A
  • impetigo
  • folliculitis
  • cellulitis
  • abscesses
260
Q

Describe S. aureus cellulitis.

A

warm, red, swollen soft tissue that is tender to touch

261
Q

What skin disease is characterized by “honey crusting”?

A

impetigo

262
Q

Cellulitis is most commonly associated with which two pathogens?

A

MSSA or GAS

263
Q

Where are most S. aureus abscesses located?

A

in association with the base of hair follicles

264
Q

What is scalded skin syndrome? What causes it?

A

an exfoliative dermatitis with fever and blistering caused by S. aureus toxins ETA and ETB

265
Q

Who is most often affected by scalded skin syndrome?

A

children under the age of 5

266
Q

What is TSST-1?

A

a superantigen produced by S. aureus capable of triggering toxic shock syndrome

267
Q

Describe the pathogenesis of TSST-1 mediated toxic shock syndrome.

A
  • non-specifically activates T cells
  • causes a massive cytokine storm
  • causes endothelial damage
  • causes leakage
268
Q

A child presents with sudden onset of pain over the knees, fever, redness, and a refusal to bear weight. What is the likely diagnosis?

A

S. aureus osteomyelitis

269
Q

What species is the most common cause of acute bacterial endocarditis?

A

S. aureus

270
Q

What are the three primary symptoms of bacteremia?

A
  • high fever
  • shaking chills
  • hypotension
271
Q

CAP most commonly follows what other infection?

A

influenza

272
Q

List three respiratory tract disease associated with S. aureus.

A
  • pneumonia
  • empyema
  • cystic fibrosis
273
Q

S. aureus infection often precedes a ___ infection in CF patients.

A

pseudomonas

274
Q

What are the two major host defenses against S. aureus?

A
  • neutrophils

- C3b

275
Q

Name three immune problems that are risk factors for S. aureus infection.

A
  • neutropenia
  • complement deficiency
  • reduced radial production
  • lazy leukocytes
276
Q

What is the preferred treatment for S. aureus?

A
  • topical: bacitracin
  • MSSA: cephalosporin or amoxicillin
  • MRSA: clindamycin, bactrim, doxycycline
277
Q

What mechanism is in place to make S. aureus VISA?

A

thickened cell wall

278
Q

What mechanism is in place to make S. aureus VRSA?

A

a resistance plasmid

279
Q

How are VRSA and VISA treated?

A
  • linezolid

- daptomycin

280
Q

Why is Staph saprophyticus clinically relevant?

A

it causes many UTIs in sexually active young women

281
Q

How does S. aureus differ diagnostically from S. epidermidis?

A
  • epidermidis is coagulase negative

- aureus is beta hemolytic and performs mannitol fermentation

282
Q

Strep are normal flora where in the human body?

A

skin and mouth

283
Q

How are Strep species grouped?

A
  • by their hemolytic character (alpha, beta, gamma)

- then surface antigens (A, B, etc.)

284
Q

What is Strep pyogenes?

A

a GAS that causes strep throat

285
Q

What is Strep agalactiae?

A

a GBS that causes neonatal infections and bacteremia

286
Q

What is Strep mutans?

A

an alpha-hemolytic strep known to cause dental caries and endocarditis

287
Q

What is S. enteroccocus?

A

the most relevant species of gamma-hemolytic strep

288
Q

How is S. pyogenes spread?

A

very efficiently via direct contact and respiratory droplets

289
Q

How does strep throat present?

A
  • erythematous posterior pharynx with purulent exudate
  • lasting 1-4 weeks without treatment
  • caused by S. pyogenes
290
Q

What is the preferred treatment for GAS?

A

penicillin

291
Q

What causes scarlet fever?

A

SpeA and SpeC (aka strep pyrogenic exotoxin) producing GAS

292
Q

What are the three major symptoms of scarlet fever?

A
  • “sand paper” rash on chest
  • “strawberry” tongue
  • circumoral pallor
293
Q

What are the two major complications of scarlet fever?

A
  • rheumatic fever

- glomerulonephritis

294
Q

Which species of strep commonly causes skin infections like impetigo and cellulitis?

A

GAS S. pyogenes

295
Q

What is erysipelas? What pathogen causes it?

A

a GAS skin infection characterized by raised bright-red plaques with sharply defined borders

296
Q

List three adhesins used by GAS and what each binds.

A
  • M protein
  • Protein F
  • lipoteichoic acid
297
Q

What kind of capsule do GAS produce?

A

a hyaluronic acid one that mimics host antigens

298
Q

What is streptomycin O? What pathogen produces it?

A

a pore forming toxin secreted by GAS

299
Q

What is Spe?

A
  • streptococcus pyrogenic exotoxin

- superantigen that produces scarlet fever or toxic shock

300
Q

What is streptokinase?

A

a GAS virulence factor that activates plasminogen to dissolve clots

301
Q

How is strep throat treated?

A

amoxicillin

302
Q

How is strep toxic shock syndrome treated?

A

penicillin and clindamycin

303
Q

How is strep throat diagnosed?

A
  • rapid antigen detection test for group A capsule antigen

- confirmed by a culture

304
Q

GBS are normal flora where in the body?

A

GI and GU tracts

305
Q

What are four risk factors for GBS infection in adults?

A
  • diabetes
  • kidney disease
  • increasing age
  • cancer
306
Q

GBS is a major cause of what two disease in pregnant women?

A
  • UTIs

- puerperal sepsis

307
Q

Pregnant women must get a screening for what vaginal flora?

A

GBS

308
Q

What are four risk factors for GBS disease in neonates?

A
  • mother had UTI during pregnancy
  • prolonged labor
  • premature rupture of membranes
  • maternal colonization
309
Q

GBS causes what three disease in neonates?

A
  • sepsis
  • meningitis
  • pneumonia
310
Q

What is C5a peptidase? Which organisms utilize it?

A

a GBS virulence factor that inhibits neutrophil recruitment

311
Q

What is CAMP factor? Which pathogen produces it?

A

a phospholipase produced only by GBS which lysis erythrocytes

312
Q

List four

A
  • beta-hemolyin
  • CAMP factor
  • C5a peptidase
  • capsule
313
Q

How is neonatal GBS infection treated?

A

ampicillin and gentamicin

314
Q

How is GBS endocarditis treated?

A

penicillin G and gentamicin

315
Q

What are viridans streptococci?

A

those that are alpha hemolytic

316
Q

Why are viridans streptococci so likely to cause endocarditis?

A

they can bind fibrin-platelet aggregates at damaged heart valves

317
Q

What is the most common cause of CAP?

A

strep pneumoniae

318
Q

Name four disease commonly caused by S. pneumoniae in adults and children.

A 
In adults...
- CAP
in children...
- meningitis
- otitis media
- sinusitis
319
Q

Describe S. pneumoniae pneumonia.

A
  • abrupt onset fever and shaking
  • pleurisy
  • productive, blood tinged cough
320
Q

What are the three major causes of atypical pneumonia?

A
  • mycoplasma
  • chlamydia
  • legionella
321
Q

How does atypical pneumonia compare to typical?

A

slower onset, more moderate fever, non-productive cough

322
Q

What pathogen accounts for most middle ear infections in children?

A

S. pneumoniae

323
Q

What is C polysaccharide? What pathogen produces it?

A

a capsular antigen of S. pneumoniae

324
Q

What is pneumolysin? What pathogen produces it?

A

a toxin secreted by S. pneumoniae which targets bronchial epithelial cells

325
Q

Why does S. pneumonia produce autolysin?

A

to promote release of pneumolysin and endotoxins

326
Q

What is quelling?

A

a swelling reaction to antisera that helps visualize S. pneumoniae capsules

327
Q

How is S. pneumoniae treated?

A

fluroquinolones

328
Q

Why are enterococci more antibiotic resistant than other species of Strep?

A

they have a modified peptidoglycan cell wall

329
Q

Enterococcus most often spreads from the intestines to cause what?

A

endocarditis

330
Q

Which species of Streptococci are very resilient and hardy?

A

enterococci

331
Q

What is cytolysin?

A

a virulence factor produced by enterococci

332
Q

What is aggregation substance?

A

an adhesin secreted by enterococci to promote conjugation and adherence to intestinal epithelial cells

333
Q

What is enterococcal surface protein?

A

an adhesin that promotes colonization of the urinary tract

334
Q

How are enterococci infections diagnosed?

A

they can be cultured in high salts

Infectious Disease (9 decks)

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