Micro Flashcards
Causes of inflammatory diarrhea
- EHEC
- EIEC
- Shigella
- Salmonella enterica and enteritidis
- Campylobacter jejuni
- Clostridium difficile
- Yersinia enterocolitica
Causes of non-inflammatory diarrhea
- ETEC
- EAEC
- EPEC
- Vibrio cholerae, parahemolyticus, vulnificus
- S. aureus
- Bacillus cereus
anaerobes
- bacteroides fragilis
- Preotella
- Clostridium perfringens, tetani, botulinum, difficile
Most infectious diarrheas are caused by?
viruses
Most likely cause of persistant diarrhea (lasting more than 10-14 days)?
parasite
- What should you start considering in chronic diarrhea?
2. Causes of this diarrhea?
- HIV
2. Mycobacterium avium intracellulare, CMV
acute diarrhea
3 or more loose stools per day lasting less than 2 weeks
chronic diarrhea
persists greater than 4 weeks
inflammatory diarrhea
“dysentery”, bloody diarrhea
WBCs, RBCs in stool
fever, small volume
COLON
non-inflammatory diarrhea
watery diarrhea
no cells in stool
afebrile, large volume
SMALL INTESTINE
Shared characteristics of Shigella, E. coli, Salmonella
- Gram ( - ) facultative anaerobic rods
- ferment glucose with acid production
- oxidase neg.
- reduce nitrates to nitrite (dipstick test)
- motile (NOT shigella)
- O and H antigens
E. coli part of normal GI flora: don’t cause infection (lack PAI (pathogenicity associated islands)
Shigella
- lab
- transmission
- who gets it
- type of diarrhea
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
Shigella dysenteriae
epidemics in central/South America
can produce Shiga toxin (AB toxin)
HEMOLYTIC UREMIC SYNDROME
Shigella sonnei
US, mostly children
Shigella flexneri
2nd most common Shigella in US
most common worldwide
Shigella pathogenesis
resistant to acidic environment of stomach
- taken up by epithelial M cells
- proliferate intracellularly, escape into lamina propria and phagocytes by macrophages causing apoptosis
- inflammatory damage to epithelia allows invasion of cells
- spreads to adjacent cells via membrane bound protrusions (via FORMINS) that lyse membranes surrounding it, freeing it into new cell cytoplasm
Shigella
- Sx
- complications
- Tx
- self-limited diarrhea (starts watery and progresses to bloody in half), fever, abdominal pain (lasts about a week)
- reactive arthritis, urethritis, conjunctivitis, hemolytic uremic syndrome in toxin producing S. dysenteriae
- ceftriaxone, ciprofloxacin, azithromycin
Enterohemorrhagic E. coli (EHEC, STEC)
- lab
- transmission
- type of diarrhea
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%
EHEC pathogenesis
SHIGA-LIKE toxin
LEE
EHEC
- Sx
- complications
- Dx
- Tx
- similar to Shigella: fever, cramps, watery diarrhea that becomes bloody (hemorrhagic colitis) within a day; lasts up to 8 days
- HUS, AKI
- SORBITOL-MACCONKEY agar, PCR or ELISA (detect Shiga toxin)
- SUPPORTIVE, avoid antidiarrheals and antibiotics
Enteroinvasive E. coli (EIEC)
- Sx
- transmission
- who
- pathogenesis
- similar to Shigella
- food/water, person to person
- young children in developing countries
- invades intestinal cell, multiplies intracellularly, extends into adjacent cells
NO toxins
Salmonella
- lab
- type of diarrhea
Gram neg. rod
- non-lactose fermenting, produces H2S
- inflammatory
Salmonellosis pathogenesis
- attach to M cells
- type III secretion of proteins into M cells
- endocytosis
- enter lamina propr.
- inflammatory response
- kills macrophages
Salmonellosis
- transmission
- Sx
- complications
- treatment
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
Salmonella enterica
- transmission
- who
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
Salmonella paratyphi
illness similar to Typhoid fever
does NOT cause gastroenteritis
Salmonella enteritidis
Nontyphoid Salmonella
causes SALMONELLOSIS
FOOD POISONING
Which pts with Salmonellosis should be treated?
flouroquinolones
- severe infection
- atherosclerotic plaques
- endovascular/bone protheses
- immunocompromised
- sickle cell disease
Typhoid fever pathogenesis
- invade M cells
- engulfed by macrophages in lymphoid tissue
- disseminate to lymph nodes and RES then to blood: Sepsis can occur
- proliferate in submucosa: hypertrophy of Peyer’s patches can cause GI tract PERFORATION
- chronic carriage can occur in biliary tract
Typhoid fever
- first week
- second
- third
- Dx
- Tx
- prevention
- fever/chills, bacteremia; BRADYCARDIA
- ROSE SPOTS, abdominal pain
- hepatosplenomegaly, GI bleeding, perforation, secondary bacteremia
- blood cultures: may require several days incubation
- ceftriaxone, azithromycin, ciprofloxacin
- vaccine
When would you not give ciprofloxacin for typhoid fever?
pt has been to an area with high rates of fluoroquinolone resistance such as SOUTH ASIA
Campylobacter jejuni
- lab
- transmission
- Sx
- Dx
- Tx
- complications
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
Yersinia enterocolitica
- lab
- transmission
- who
G (-) coccobacilli
- BIPOLAR staining
- pork, raw milk, contaminated water, pet feces
- EUROPE
Yersinia enterocolitica
- Sx
- Dx
- Tx
ILEUM, APPENDIX, RIGHT COLON: lymph node and Peyer patch hyperplasia
- PSUEDOAPPENDICITIS, N/V, fever/diarrhea; extraintestinal: PHARYNGITIS, ARTHRALGIA, ERYTHEMA NODOSUM
- stool culture
- most don’t need it
Clostridium difficile
- transmission
- pathogenesis
- hypervirulent strands
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
Clostridium difficile
- Sx
- Dx
- watery diarrhea, cramps, fever, LEUKOCYTOSIS, PSEUDOMEMBRANOUS COLITIS, FULMINANT COLITIS, TOXIC MEGACOLON
- PCR for toxins A and B, cell culture cytotoxicity assay (takes 2 days); EIA
- metronidazole first line, severe first line: vancomycin
recurrence: metronidazole
2nd recurrence: vancomycin
other: fidaxomycin, fecal transplant
risk factors for C. diff
- advanced age
- multiple antibiotics: esp. clindamycin + penicillins; cephalosporins + fluoroquinolones
- hospitalization
- IBD
- gastric acid suppression?
enterotoxigenic E. coli (ETEC)
- transmission
- Sx
major cause of TRAVEL’S DIRRHEA
- contaminated food and water
- watery diarrhea (1-5 days)
- HEAT-LABILE TOXIN, HEAT-STABLE TOXIN
enteropathogenic E. coli (EPEC)
- who
- Sx
- pathogenesis
- children under 2, infants
- watery diarrhea with severe vomiting and dehydration
- attaching and effacing lesions and pedestal like structures: LEE
enteroaggregative E. coli (EAEC)
traveler’s diarrhea
diarrhea in children, adults, HIV patients in developed and developing countries
uropathogenic E. coli (UPEC)
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
Other E. coli infections (non-GI)
- hospital acquired: sepsis
- neonatal meningitis: K1 antigen
- UPEC
Vibrio
- lab
- where found
- transmission
curved (comma shaped) GNR motile, flagellum 1. oxidase pos. 2. SALTWATER, WARM MONTHS 3. SHELLFISH
Vibrio cholerae
- transmission
- location
- antigen
- pathogenesis
- fecal contaminated drinking water: DISASTERS
- Asia, Africa, S. America, Indian subcontinent
- O antigen
- mucinase, AB toxin
O1 (divided into E1 Tor, Classic), O139 serotypes
high infectious dose
high mortality without Tx
Vibrio parahaemolyticus
- location
- Sx
- complications
- Dx
- Tx
- JAPAN, rare in US (Gulf, Pacific)
- watery diarrhea, N/V, cramps, fever, self-limited
- bacteremia can occur in underlying conditions like liver disease; wound infections (severe in those with liver disease, DM, alcoholism: can lead to cellulitis)
- culture
- volume repletion; in severe cases: doxycycline
Vibrio vulnificus
- Sx
- complications
- Dx
- Tx
- diarrhea, severe SKIN and soft tissue infections
- septicemia in immunocompromised
- culture
- Doxy plus cefotaxime or ceftriaxone
factors predisposing to V. cholerae infection
- poor sanitation
- malnutrition
- overcrowding
- inadequate medical services
Vibrio cholerae
- Sx
- complications
- Dx
- Tx
- prevention
- watery diarrhea, dehydration, RICE WATER stools (flecks of mucous, smells fishy), vomiting
- CARDIAC and RENAL failure, ACIDOSIS, HYPOKALEMIA
NO abdominal pain - clinical suspicion, selective media: TCBS, TTGA, MacConkey agar (colorless)
- VOLUME REPLETION; antibiotics adjunctive: tetracycline, erythromycin, azithromycin, ciprofloxacin; Oral rehydration salts
- clean water, sanitation; oral vaccine in endemic areas
Bacillus cereus
- transmission
- pathogenesis
- Sx
gram (+) bacilli
- FRIED RICE
- SPORE, diarrheal enterotoxin, emetic toxin
- diarrheal syndrome, emetic syndrome
S. aureus
- enterotoxin (heat-stable), superantigen
- food handled foods left at room temperature: dairy produce, meat, egg, salad, POTATO SALAD
- within 1-6 hrs of ingestion: N/V, cramps, fever/diarrhea in minority; lasts 24 hours or less
Where are anaerobes prevalent?
gut microbiome, oral cavity, skin, colon, female genital tract
ex: Bacteroides, Clostridia
Why are anaerobes inhibited by oxygen?
no superoxide dismutase (SOD) or catalase
anaerobic infection
lack SOD and catalase
STINK
need special transport and culture
ABSCESSES: polymicrobial and reflect normal flora in that site
Bacteroides fragilis
- where found
- predisposing factors
- pathogenesis
- Sx
- Dx
- Tx
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
Prevotella melaninogenica
G (-) coccobacillus
1. oral cavity, GI tract, vagina, nasopharynx
OPPORTUNISTIC
2. oral/periodontal/pulmonary abbesses; chronic otitis, sinusitis
Clostridium
- where found
- pathogenesis
G (+) rod
SPORE, ANAEROBIC
1. colon
2. exotoxins, hydrolytic enzymes
Clostridium perfringens
- Sx
- who
- transmission
BOXCAR G (+) bacilli
- gas gangrene, food poisoning: watery diarrhea, cramps, minimal vomiting, resolves in 24 hrs
- psych inpatient facilities
- soil; meat, poultry, gravy
Clostridium tetani
- transmission
- pathogenesis
- Sx
- Tx
- wound (nail); soil; neonatal from circumcision or contaminated umbilicus
- AB neurotoxin
- spastic paralysis: trismus, risus sardonicus, opisthotonos, exaggerated reflexes, respiratory failure
- wound debridement, HTIG; metronidazole or penicillin, active immunization with tetanus toxoid (don’t have immunity after recovery)
high mortality
Clostridium botulinum
- types
- pathogenesis
- Sx of food borne
- Sx of infant
- Tx
- foodborne: CANNED FOOD, FISH; infant: RAW HONEY, spores in CARPET; wound; inhalational (bioterrorism), iatrogenic
- AB toxin
- symmetric descending flaccid paralysis, nausea, dry mouth, dysphagia, diarrhea, blurred vision, respiratory failure
- floppy baby syndrome: constipation followed by weakness, feeding difficulty, descending hypotonia, drooling, anorexia, irritability, weak cry
- MECHANICAL VENTILATION, HORSE ANTI-TOXIN for those over 1 year of age; BIG-IV; penicilin or metronidazole (NOT for infant botulism)
When are antibiotics recommended for C. botulinum?
wound botulism
NOT for infant botulism: could increase toxin release
H. pylori
- transmission
- pathogenesis
- Dx
slender, curved GNR motile, microaerophilic 1. gastric secretion, fecal-oral 2. VacA, PAI, Cag, urease 3. endoscopy, stool antigen, urea breath test, serology