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Micro Flashcards

1
Q

Causes of inflammatory diarrhea

A
  1. EHEC
  2. EIEC
  3. Shigella
  4. Salmonella enterica and enteritidis
  5. Campylobacter jejuni
  6. Clostridium difficile
  7. Yersinia enterocolitica
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2
Q

Causes of non-inflammatory diarrhea

A
  1. ETEC
  2. EAEC
  3. EPEC
  4. Vibrio cholerae, parahemolyticus, vulnificus
  5. S. aureus
  6. Bacillus cereus
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3
Q

anaerobes

A
  1. bacteroides fragilis
  2. Preotella
  3. Clostridium perfringens, tetani, botulinum, difficile
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4
Q

Most infectious diarrheas are caused by?

A

viruses

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5
Q

Most likely cause of persistant diarrhea (lasting more than 10-14 days)?

A

parasite

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6
Q
  1. What should you start considering in chronic diarrhea?

2. Causes of this diarrhea?

A
  1. HIV

2. Mycobacterium avium intracellulare, CMV

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7
Q

acute diarrhea

A

3 or more loose stools per day lasting less than 2 weeks

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8
Q

chronic diarrhea

A

persists greater than 4 weeks

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9
Q

inflammatory diarrhea

A

“dysentery”, bloody diarrhea
WBCs, RBCs in stool
fever, small volume
COLON

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10
Q

non-inflammatory diarrhea

A

watery diarrhea
no cells in stool
afebrile, large volume
SMALL INTESTINE

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11
Q

Shared characteristics of Shigella, E. coli, Salmonella

A
  1. Gram ( - ) facultative anaerobic rods
  2. ferment glucose with acid production
  3. oxidase neg.
  4. reduce nitrates to nitrite (dipstick test)
  5. motile (NOT shigella)
  6. O and H antigens
    E. coli part of normal GI flora: don’t cause infection (lack PAI (pathogenicity associated islands)
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12
Q

Shigella

  1. lab
  2. transmission
  3. who gets it
  4. type of diarrhea
A

G ( - ) rod
1. nonmotile, non-lactose fermenting, does not produce H2S
2. fecal-oral, contaminated water/food
3. DAYCARE, migrant workers, travelers to developing countries, nursing homes
4. inflammatory
HIGHLY transmissible: low infectious dose

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13
Q

Shigella dysenteriae

A

epidemics in central/South America
can produce Shiga toxin (AB toxin)
HEMOLYTIC UREMIC SYNDROME

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14
Q

Shigella sonnei

A

US, mostly children

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15
Q

Shigella flexneri

A

2nd most common Shigella in US

most common worldwide

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16
Q

Shigella pathogenesis

A

resistant to acidic environment of stomach

  1. taken up by epithelial M cells
  2. proliferate intracellularly, escape into lamina propria and phagocytes by macrophages causing apoptosis
  3. inflammatory damage to epithelia allows invasion of cells
  4. spreads to adjacent cells via membrane bound protrusions (via FORMINS) that lyse membranes surrounding it, freeing it into new cell cytoplasm
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17
Q

Shigella

  1. Sx
  2. complications
  3. Tx
A
  1. self-limited diarrhea (starts watery and progresses to bloody in half), fever, abdominal pain (lasts about a week)
  2. reactive arthritis, urethritis, conjunctivitis, hemolytic uremic syndrome in toxin producing S. dysenteriae
  3. ceftriaxone, ciprofloxacin, azithromycin
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18
Q

Enterohemorrhagic E. coli (EHEC, STEC)

  1. lab
  2. transmission
  3. type of diarrhea
A 
1. can't ferment sorbitol
O157: H7 or non-O157:H7
2. inadequately cooked meat (HAMBURGERS), contaminated vegetables and milk, human to human
3. inflammatory
low infectious dose
HOSPITALIZATION in 25-50%
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19
Q

EHEC pathogenesis

A

SHIGA-LIKE toxin

LEE

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20
Q

EHEC

  1. Sx
  2. complications
  3. Dx
  4. Tx
A
  1. similar to Shigella: fever, cramps, watery diarrhea that becomes bloody (hemorrhagic colitis) within a day; lasts up to 8 days
  2. HUS, AKI
  3. SORBITOL-MACCONKEY agar, PCR or ELISA (detect Shiga toxin)
  4. SUPPORTIVE, avoid antidiarrheals and antibiotics
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21
Q

Enteroinvasive E. coli (EIEC)

  1. Sx
  2. transmission
  3. who
  4. pathogenesis
A
  1. similar to Shigella
  2. food/water, person to person
  3. young children in developing countries
  4. invades intestinal cell, multiplies intracellularly, extends into adjacent cells
    NO toxins
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22
Q

Salmonella

  1. lab
  2. type of diarrhea
A

Gram neg. rod

  1. non-lactose fermenting, produces H2S
  2. inflammatory
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23
Q

Salmonellosis pathogenesis

A
  1. attach to M cells
  2. type III secretion of proteins into M cells
  3. endocytosis
  4. enter lamina propr.
  5. inflammatory response
  6. kills macrophages
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24
Q

Salmonellosis

  1. transmission
  2. Sx
  3. complications
  4. treatment
A

S. enteritidis
1. DAIRY, MEAT, POULTRY, EGGS, REPTILES (TURTLES, LIZARDS), human to human
2. N/V, diarrhea, cramps, fever in some (lasts 304 days)
3. bactermia, endovascular infections, endocarditis, osteomyelitis, aortic plaques and bone protheses, reactive arthritis
Dx: stool culture
4. not required for healthy people 2-50 yrs, flouroquinolones (must test for susceptibility) for those at risk of disseminated disease

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25
Q

Salmonella enterica

  1. transmission
  2. who
A

TYPHOID fever
South-central Asia
does NOT cause gastroenteritis
1. person to person (fecal-oral, infected food handler, contaminated food/water); FOODBORNE, HUMANS sole reservoir
2. children, young adults; POOR SANITATION

26
Q

Salmonella paratyphi

A

illness similar to Typhoid fever

does NOT cause gastroenteritis

27
Q

Salmonella enteritidis

A

Nontyphoid Salmonella
causes SALMONELLOSIS
FOOD POISONING

28
Q

Which pts with Salmonellosis should be treated?

A

flouroquinolones

  1. severe infection
  2. atherosclerotic plaques
  3. endovascular/bone protheses
  4. immunocompromised
  5. sickle cell disease
29
Q

Typhoid fever pathogenesis

A
  1. invade M cells
  2. engulfed by macrophages in lymphoid tissue
  3. disseminate to lymph nodes and RES then to blood: Sepsis can occur
  4. proliferate in submucosa: hypertrophy of Peyer’s patches can cause GI tract PERFORATION
  5. chronic carriage can occur in biliary tract
30
Q

Typhoid fever

  1. first week
  2. second
  3. third
  4. Dx
  5. Tx
  6. prevention
A
  1. fever/chills, bacteremia; BRADYCARDIA
  2. ROSE SPOTS, abdominal pain
  3. hepatosplenomegaly, GI bleeding, perforation, secondary bacteremia
  4. blood cultures: may require several days incubation
  5. ceftriaxone, azithromycin, ciprofloxacin
  6. vaccine
31
Q

When would you not give ciprofloxacin for typhoid fever?

A

pt has been to an area with high rates of fluoroquinolone resistance such as SOUTH ASIA

32
Q

Campylobacter jejuni

  1. lab
  2. transmission
  3. Sx
  4. Dx
  5. Tx
  6. complications
A

MOST COMMON bacterial enteric pathogen in developed countries
TRAVELER’s DIARRHEA
1. thin, spiral GNR
2. chicken, unpasteurized milk, contaminated water
highly transmissible
3. watery diarrhea that becomes bloody in some, fever, cramps, self-limited
4. stool culture
5. only for severe disease; azithromycin, ciprofloxicin
6. GUILLAIN BARRE, ERYTHEMA NODOSUM, REACTIVE ARTHRITIS

33
Q

Yersinia enterocolitica

  1. lab
  2. transmission
  3. who
A

G (-) coccobacilli

  1. BIPOLAR staining
  2. pork, raw milk, contaminated water, pet feces
  3. EUROPE
34
Q

Yersinia enterocolitica

  1. Sx
  2. Dx
  3. Tx
A

ILEUM, APPENDIX, RIGHT COLON: lymph node and Peyer patch hyperplasia

  1. PSUEDOAPPENDICITIS, N/V, fever/diarrhea; extraintestinal: PHARYNGITIS, ARTHRALGIA, ERYTHEMA NODOSUM
  2. stool culture
  3. most don’t need it
35
Q

Clostridium difficile

  1. transmission
  2. pathogenesis
  3. hypervirulent strands
A 
anaerobic, G (+) rod
SPORE
1. fecal-oral: hospital personal
MOST common NOSOCOMIAL and ANTIBIOTIC associated diarrhea
2. Exotoxins A and B
3. NAP-1/027
36
Q

Clostridium difficile

  1. Sx
  2. Dx
A
  1. watery diarrhea, cramps, fever, LEUKOCYTOSIS, PSEUDOMEMBRANOUS COLITIS, FULMINANT COLITIS, TOXIC MEGACOLON
  2. PCR for toxins A and B, cell culture cytotoxicity assay (takes 2 days); EIA
  3. metronidazole first line, severe first line: vancomycin
    recurrence: metronidazole
    2nd recurrence: vancomycin
    other: fidaxomycin, fecal transplant
37
Q

risk factors for C. diff

A
  1. advanced age
  2. multiple antibiotics: esp. clindamycin + penicillins; cephalosporins + fluoroquinolones
  3. hospitalization
  4. IBD
  5. gastric acid suppression?
38
Q

enterotoxigenic E. coli (ETEC)

  1. transmission
  2. Sx
A

major cause of TRAVEL’S DIRRHEA

  1. contaminated food and water
  2. watery diarrhea (1-5 days)
  3. HEAT-LABILE TOXIN, HEAT-STABLE TOXIN
39
Q

enteropathogenic E. coli (EPEC)

  1. who
  2. Sx
  3. pathogenesis
A
  1. children under 2, infants
  2. watery diarrhea with severe vomiting and dehydration
  3. attaching and effacing lesions and pedestal like structures: LEE
40
Q

enteroaggregative E. coli (EAEC)

A

traveler’s diarrhea

diarrhea in children, adults, HIV patients in developed and developing countries

41
Q

uropathogenic E. coli (UPEC)

A

UTI
Sx: frequency, dysuria, pyuria, suprapubic pain, cloudy urine, cramping, afebrile
Dx: female: greater than 10^5 per ml; male: greater than 10^3
virulence: P fimbriae, PAP pili, capsule

42
Q

Other E. coli infections (non-GI)

A
  1. hospital acquired: sepsis
  2. neonatal meningitis: K1 antigen
  3. UPEC
43
Q

Vibrio

  1. lab
  2. where found
  3. transmission
A 
curved (comma shaped) GNR
motile, flagellum
1. oxidase pos. 
2. SALTWATER, WARM MONTHS
3. SHELLFISH
44
Q

Vibrio cholerae

  1. transmission
  2. location
  3. antigen
  4. pathogenesis
A
  1. fecal contaminated drinking water: DISASTERS
  2. Asia, Africa, S. America, Indian subcontinent
  3. O antigen
  4. mucinase, AB toxin
    O1 (divided into E1 Tor, Classic), O139 serotypes
    high infectious dose
    high mortality without Tx
45
Q

Vibrio parahaemolyticus

  1. location
  2. Sx
  3. complications
  4. Dx
  5. Tx
A
  1. JAPAN, rare in US (Gulf, Pacific)
  2. watery diarrhea, N/V, cramps, fever, self-limited
  3. bacteremia can occur in underlying conditions like liver disease; wound infections (severe in those with liver disease, DM, alcoholism: can lead to cellulitis)
  4. culture
  5. volume repletion; in severe cases: doxycycline
46
Q

Vibrio vulnificus

  1. Sx
  2. complications
  3. Dx
  4. Tx
A
  1. diarrhea, severe SKIN and soft tissue infections
  2. septicemia in immunocompromised
  3. culture
  4. Doxy plus cefotaxime or ceftriaxone
47
Q

factors predisposing to V. cholerae infection

A
  1. poor sanitation
  2. malnutrition
  3. overcrowding
  4. inadequate medical services
48
Q

Vibrio cholerae

  1. Sx
  2. complications
  3. Dx
  4. Tx
  5. prevention
A
  1. watery diarrhea, dehydration, RICE WATER stools (flecks of mucous, smells fishy), vomiting
  2. CARDIAC and RENAL failure, ACIDOSIS, HYPOKALEMIA
    NO abdominal pain
  3. clinical suspicion, selective media: TCBS, TTGA, MacConkey agar (colorless)
  4. VOLUME REPLETION; antibiotics adjunctive: tetracycline, erythromycin, azithromycin, ciprofloxacin; Oral rehydration salts
  5. clean water, sanitation; oral vaccine in endemic areas
49
Q

Bacillus cereus

  1. transmission
  2. pathogenesis
  3. Sx
A

gram (+) bacilli

  1. FRIED RICE
  2. SPORE, diarrheal enterotoxin, emetic toxin
  3. diarrheal syndrome, emetic syndrome
50
Q

S. aureus

A
  1. enterotoxin (heat-stable), superantigen
  2. food handled foods left at room temperature: dairy produce, meat, egg, salad, POTATO SALAD
  3. within 1-6 hrs of ingestion: N/V, cramps, fever/diarrhea in minority; lasts 24 hours or less
51
Q

Where are anaerobes prevalent?

A

gut microbiome, oral cavity, skin, colon, female genital tract
ex: Bacteroides, Clostridia

52
Q

Why are anaerobes inhibited by oxygen?

A

no superoxide dismutase (SOD) or catalase

53
Q

anaerobic infection

A

lack SOD and catalase
STINK
need special transport and culture
ABSCESSES: polymicrobial and reflect normal flora in that site

54
Q

Bacteroides fragilis

  1. where found
  2. predisposing factors
  3. pathogenesis
  4. Sx
  5. Dx
  6. Tx
A

GNR
1. predominant organism in colon, found in vagina
2. surgery, trauma, chronic disease
3. capsule (role in abscess formation)
4. pelvic/peri-rectal abscesses, lung abscess, peritonitis, baceremia, infected decubitus ulcers; diarrhea (enterotoxin strain)
5. anaerobic cultures
6. metronidazole, carbapenem, beta lactic with beta-lacatkase inhibitors
resistant to penicillin

55
Q

Prevotella melaninogenica

A

G (-) coccobacillus
1. oral cavity, GI tract, vagina, nasopharynx
OPPORTUNISTIC
2. oral/periodontal/pulmonary abbesses; chronic otitis, sinusitis

56
Q

Clostridium

  1. where found
  2. pathogenesis
A

G (+) rod
SPORE, ANAEROBIC
1. colon
2. exotoxins, hydrolytic enzymes

57
Q

Clostridium perfringens

  1. Sx
  2. who
  3. transmission
A

BOXCAR G (+) bacilli

  1. gas gangrene, food poisoning: watery diarrhea, cramps, minimal vomiting, resolves in 24 hrs
  2. psych inpatient facilities
  3. soil; meat, poultry, gravy
58
Q

Clostridium tetani

  1. transmission
  2. pathogenesis
  3. Sx
  4. Tx
A
  1. wound (nail); soil; neonatal from circumcision or contaminated umbilicus
  2. AB neurotoxin
  3. spastic paralysis: trismus, risus sardonicus, opisthotonos, exaggerated reflexes, respiratory failure
  4. wound debridement, HTIG; metronidazole or penicillin, active immunization with tetanus toxoid (don’t have immunity after recovery)
    high mortality
59
Q

Clostridium botulinum

  1. types
  2. pathogenesis
  3. Sx of food borne
  4. Sx of infant
  5. Tx
A
  1. foodborne: CANNED FOOD, FISH; infant: RAW HONEY, spores in CARPET; wound; inhalational (bioterrorism), iatrogenic
  2. AB toxin
  3. symmetric descending flaccid paralysis, nausea, dry mouth, dysphagia, diarrhea, blurred vision, respiratory failure
  4. floppy baby syndrome: constipation followed by weakness, feeding difficulty, descending hypotonia, drooling, anorexia, irritability, weak cry
  5. MECHANICAL VENTILATION, HORSE ANTI-TOXIN for those over 1 year of age; BIG-IV; penicilin or metronidazole (NOT for infant botulism)
60
Q

When are antibiotics recommended for C. botulinum?

A

wound botulism

NOT for infant botulism: could increase toxin release

61
Q

H. pylori

  1. transmission
  2. pathogenesis
  3. Dx
A 
slender, curved GNR
motile, microaerophilic
1. gastric secretion, fecal-oral
2. VacA, PAI, Cag, urease
3. endoscopy, stool antigen, urea breath test, serology

GI (12 decks)

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