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U6 micro > Enteric Bacteria > Flashcards

Enteric Bacteria Flashcards

1
Q

Shigella bacteriology

  • gram stain and shape
  • fermentation
  • mobility
  • respiration
  • intra vs extracellular
A 
gram (-) rods
non-lactose fermenting and not H2S producing
-non motile
-facultative anaerobe
-facultative intracellular
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2
Q

If you have a GI infection, what is going to be the general bacteriology (stain)? What is the exception? What is the general respiration?

A

Gram (-) bugs; Listeria is the exception; facultative anaerobic

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3
Q

On culture, how can you distinguish between shigella and e. coli?

A

E coli ferments lactose (bright pink on MacConkey), shigella does not

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4
Q

Shigella Pathogenicity

  • disease names (3)
  • infectious dose
  • presentation
  • mortality risk
  • complication
A

shigella enterocolitis, bacillary dysentery, and shigellosis

  • very low (~100 IUs)
  • bloody diarrhea, local inflammation, ulceration
  • worse with poor nutrition
  • Reactive Arthritis (Reiter’s syndrome)
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5
Q

Reactive Arthritis

A

“Can’t see, can’t pee, can’t climb a tree.”

  • associated w/ HLA-B27
  • conjuctivitis, urethritis, and arthritis
  • shigella and chlamydia
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6
Q

Shigella pathogenesis

  • target
  • cause of presentation
  • immune evasion
  • populations most at risk
A
  • invade epithelium of distal ileum and colon and secrete exotoxins
  • exotoxins kill adjacent cells
  • necrosis, apoptosis, host immune response and hemorrhage lead to bloody diarrhea
  • survive phagocytosis and cause macrophage apoptosis
  • children under 5, HIV+, MSM
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7
Q

Main Shigella virulence factor

  • seen in what other bacteria?
  • secretion system
A

shiga toxin: protein-synthesis-inhibiting shiga toxin is plasmid-encoded

  • can be picked up by E coli
  • type 3
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8
Q

Hemolytic uremic syndrome

A

begins when shiga toxin escapes into bloodstream, causes hemolysis, renal failure, uremia, and DIC

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9
Q

Dx Shigella: Exam

A

Very young/very old: fever, dehydration, severe headache, lethargy, watery diarrhea w/ bloody mucous

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10
Q

Dx HUS: Exam

A

hemolysis, thrombocytopenia, uremia requiring dialysis

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11
Q

Dx Shigella: Lab

A

Strain via immunoassays (agglutination); methylene blue stain of fecal sample to determine if neutrophils are present (Shigella, salmonella, campylobacter)

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12
Q

Dx HUS: Lab

A

schistocytes, decreased platelets, increased PMNs, increased lactate dehydrogenase

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13
Q

Shigella treatment

A

fluids/elect replacements; ceftriazone, fluoroquinolone, azithromycin, cefixime; NO antidiarrheal meds

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14
Q

Shigella prevention

A

sewage disposal, water chlorination, handwashing

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15
Q

E. coli bacteriology

  • stain and shape
  • fermentation
  • respiration
  • mobility
A
  • straight gram (-) rod
  • lactose fermentor, H2S/urease negative
  • facultative anaerobe
  • may be mobile (flagella) or nonmobile
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16
Q

E. coli pathologies (6)

A
  • enterotoxigenic diarrhea
  • enterohemorrhagic diarrhea
  • UTI
  • meningitis
  • pneumonia
  • intra-abdominal escape after GI perforation
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17
Q

Enterotoxigenic E coli (ETEC)

A

Traveler’s diarrhea

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18
Q

Enteropathogenic E coli (EPEC)

A

childhood diarrhea

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19
Q

Enteroinvasive E coli (EIEC)

A

causes shigella-like dysentery

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20
Q

Enterohemorrhagic E coli (EHEC)

A

infected by phage STX, produces shiga toxin, causes hemorrhagic colitis or HUS

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21
Q

Enteroaggregative E coli (EAggEC)

A

primarily associated w/ persistent diarrhea in children in developing countries

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22
Q

Enteroadherent E coli (EACE)

A

cause of childhood diarrhea and traveler’s diarrhea in Mexico and N. Africa

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23
Q

Enterotoxigenic diarrhea pathogenesis

A
  • pili attach to jejunum and ileum
  • enterotoxins (exotoxin that acts on the GI tract)
  • enterotoxin LT forces host ion channels to export, host loses fluid, potassium, and chloride
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24
Q

Enterohemorrhagic diarrhea pathogenesis

A
  • attach to mucosal epithelial cells of the colon and may invade
  • lysogenic phage STX encodes shiga toxin which becomes active inside gut cells, shuts down protein synthesis, destroys some
  • inflammation, bloody diarrhea
  • if toxin hits blood stream > HUS
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25
Q

When does HUS become a threat in EHEC

A

when antibiotics are used to treat bloody diarrhea

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26
Q

How does shiga toxin cause renal injury and anemia?

A

binds to Gb3 on RBCs and uses RBCs as transport to kidney, RBCs/toxin complex clog capillaries in the kidney via platelet-fibrin thrombi (shistocytes)

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27
Q

Dx E coli: exam

A

bloody or nonbloody diarrhea, dehydration, recent travel abroad

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28
Q

Dx E coli: lab

A

stool culture, EIA test colonies for shiga toxin

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29
Q

Enterotoxic diarrhea treatment

A

self limited, hydrate

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30
Q

Enterohemorrhagic diarrhea treatment

A

NO antidiarrhea or antibiotics! Just hydrate

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31
Q

Types of bacteria that can cause gastroenteritis with their toxins but not their virulence? How do you separate these from others clinically.

A

Staph aureus, bacillus cereus, and botulinum. Onset within hours

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32
Q

Salmonella bacteriology

  • stain and shape
  • fermentation
  • oxidase, urease, H2S
  • mobility
A
  • gram (-) rods
  • seldom lactose
  • oxidase (-), urease (-), H2S (+)
  • motile
33
Q

Salmonella pathologic presentations (4)

A

enterocolitis, enteric fever (typhoid fever), septicemia (rare and in combo w/ sickle cell), and reactive arthritis

34
Q

Salmonella Enterocolitis

  • who and where
  • presentation
  • infectious dose
A
  • children and nursing homes, ppl on antacids
  • inflammation, diarrhea, N/V
  • high (100K)
35
Q

Salmonella enterocolitis pathogenesis

A

-salmonella selectively attach to M cells of Peyer patches, are internalized by receptor mediated endocytosis

36
Q

salmonella virulence factors (5)

A
  • Ipf operon (enhances adhesion to M cell)
  • Type 3 secrection
  • SipB (causes macrophage apoptosis)
  • Spi2 (‘spy’- S. typhi uses this to turn macrophages into trojan horses for systemic spread)
  • Vi antigen (S typhi capsule for immune evasion
37
Q

Salmonella Enteric and Typhoid fevers

  • onset
  • progression
  • presentation
A

human restricted fecal-oral infections with S typhi or paratyphi

  • fever, pain, constipation
  • 3-4wks: cough, stupor, delerium, GI hemorrhage, bowel perforation, myocarditis, death
  • recent travel, hotel stay, high fever, headache, anorexia
38
Q

treat salmonella enterocolitis

A

only for very young, very old, or HIV+ (Ab sensitivity before admin)

39
Q

treat salmonella enteric fever or septicemia

A

ceftriaxone or ciprofloxacin; drain abscesses

40
Q

Yersinia enterocolitica and pseudotuberculosis bacteriology

  • stain and shape
  • fermentation
  • mobility
A

gram (-) oval rods

  • non lactose, urease (+)
  • motile at 25*C but not at body temp
41
Q

Yersinia enterocolitica pathogenicity

  • what does it cause
  • infectious dose
  • virulence factors
A
  • enterocolitis by invading intestinal mucosa and destroying tissue through the Peyer patches
  • very high (10^9)
  • carried on plasmids and chromosomes
42
Q

Yersinia enterocolitica virulence factors

A
  • pili and Inv adhesin (binding to M cells)

- CNF (dermonecrotic toxin destroys tissues)

43
Q

Yersinia enterocolitica presentation

  • who? where?
  • complication?
A
  • most common in young children, risk increased with iron overload
  • cooler climates without food processing
  • reactive arthritis
44
Q

Yersinia pseudoTB pathogenesis

  • adult presentation
  • child presentation
A
  • similar, more rare, seen in Immunocomp or pre-existing liver disease
  • Izumi fever: vasculitis w/ fever, rash, inflammation of oral cavity, erythema/edema of hands and feet
45
Q

Dx yersinia: Exam

A

diarrhea, dehydration, “false appendicitis”, recent travel

46
Q

Dx yersinia: labs

A
  • culture from stool, blood, or CSF

- grow in cold-enrichment on CIN agar

47
Q

How do you distinguish between Y. enterocolitica and pseudoTB

A

pseudoTB ferments sorbitol and has ornithine decarboxylase activity

48
Q

Treat yersinia

A
  • fluids

- if complications then trimethoprim, sulfamethoxazole, cipro

49
Q

Using Hektoen Enteric Agar to differentiate

  • no growth?
  • Blue-green growth?
  • orange growth?
  • Black growth?
A
  • listeria
  • no lactose or H2S (Shigella)
  • Lactose w/o H2S (E coli)
  • H2S (Salmonella
50
Q

Listeria bacteriology

  • stain and shape
  • respiration
  • mobility
  • colony on blood and nonblood agar
A
  • gram (+) rod
  • facultative anaerobic
  • tumbling motility
  • beta hemolytic, blue-green colonies
51
Q 
Listeria virulence (2)
-immune evasion?
A
  • listerolysin (exit macrophage lysosomes)
  • ActA (rocket thing via actin)
  • intracellular pathogen, cell to cell spread via ActA
52
Q

Listeria presentation

- who?

A

immunosuppressed, pregnant

-eating environmentally contaminated food

53
Q

Listeria outside of GI

A

meningitis, abscess, endocarditis, septic arthritis, osteomyelitis, pneumonia

54
Q

Listeria in pregnancy

A

bacteria escape GI and begin to grow in the placenta, esp in the third trimester (CMI is lowest)
- cause preterm labor, abortion, still birth, intrauterine infection

55
Q

Listeria in neonate

A
  • transmission across placenta: early onset sepsis and premature birth w/ abscesses and/or granulomas in major organs
  • transmission from vagina: late onset meningitis w/ sepsis
56
Q

Dx listeria: exam

  • pregnancy
  • CNS
A
  • fever, arthralgia, back pain, headache

- mental status change, seizure, cranial nerve deficits, strokelike hemiplegia, tremor, myoclonus, ataxia, brain abscess

57
Q

Dx listeria: lab

A

blood culture, Wet mount of CSF

- gram stain

58
Q

Treat listeria

A

Abs, IV if CNS or bacteremic

  • amp and gentamicin
  • reportable
59
Q

V. cholerae bacteriology

  • stain and shape
  • respiration
  • fermentation
  • mobility
  • reservoirs
A
  • gram (-), curved comma-shape rod
  • aerobic, facultatively anaerobic
  • sucrose fermenting, slightly lactose, oxidase (+)
  • mobile
  • humans and plankton (indian ocean)
60
Q

What marker indicated vimbrio pathogenecity

A

O cell wall antigen (O1 and O139)

61
Q

V cholerae pathogenesis

  • transmission
  • infectious dose
  • risk factors
  • virulence factors (3)
A
  • fecal-oral transmission
  • high
  • ppl on antacids, w/ gastrectomy, or with H pylori infection
  • mucinase, toxin-coregulated pilus (TCP), cholera toxin
62
Q

Cholera toxin

  • receptor
  • mechanism
A

A-B subunit enterotoxin

  • GM1 on intestinal lining
  • perisistant activation of adenylate cyclase > loss of H2O and ions
63
Q

How does V. cholera encode the toxin

A

carried by lysogenic bacteriophage CXT

64
Q

Electrolyte imbalance in cholera

A

acidosis and hypokalemia > cardiac and renal failure in hours

65
Q

Dx Cholera: exam

-children

A

-drowsy, coma, fever, hypoglycemic convulsion

66
Q

Treat cholera

A

IV lactated Ringer solution

67
Q

Non-cholera vibrio infections (2)

  • which is more common? presentation?
  • which is more lethal? presentation
A

parahaemolyticus, vulnificus

  • parahaemolyticus: gastroenteritis from undercooked shellfish
  • vulnificus: cellulitis after seawater infected wound
68
Q

campylobacter bacteriology

  • stain and shape
  • mobility
  • oxidase, catalase
  • respiration
A
  • gram (-), comma or S-shaped rod
  • motile (flagella)
  • (+)
  • microaerophilic
69
Q

Campylobacter transmission

A

fecal-oral, raw milk, undercooked chicken, sexual contact, sick pets (puppies)

70
Q

C. jejuni strongly predisposes pts to what?

A

Guillain-Barre syndrome, Reactive arthritis, HUS

71
Q

Campylobacter presentation in children

A

presents w/ watery foul-smelling diarrhea > progressing to bloody stool w/ fever and abd pain

72
Q

Dx Campylobacter: lab

- how can you tell it apart from salmonella, listeria, yersinia

A
  • campylobacter cannot grow at low temp

- grows better under low oxygen atmosphere

73
Q

Treat campylobacter

  • simple gastroenteritis
  • children, pregnancy
  • adults w/ worsening symptoms
  • meningitis
A
  • rehydrate
  • erythromycin
  • azithromycin, tetracycline, clindamycin
  • meropenem, ampicillin, chloramphenicol
74
Q

H pylori bacteriology

-stain and shape

A

curved gram (-) rod

75
Q

H pylori pathogenicity

A

peptic ulcer disease, MALT lymphoma, gastric lymphoma, adenocarcinoma of the stomach

76
Q

H pylori virulence

A
  • flagella as attachment
  • urease (break down urea into ammonia > neutral pH)
  • Vac-A (vacuolating cytotoxin)
  • Cag-A (chemotaxis of neutrophils)
77
Q

Dx H pylori: exam

A

urea breath test, biopsy, PCR for stool

78
Q

Treat H pylori

A

reduce irritation with pepto, PPIs
-kill bacteria w/ triple therapies
(omeprazole+amoxicillin+clarithromycin)
(bismuth subsalicyclate+metronidazole+tetracycline)
(lansoprazole+amoxicillin+clarithromycin)

U6 micro (6 decks)

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