Non-inflammatory diarrhea Flashcards
Inflammation involving the mucosa of the both the small and large intestines
Enterocolitis
Bacteria associated with marine environments
Vibrio cholerae
Gram negative, rigid, curved rod with polar flagellum and darting motility. Arranged in rows on smear.
Vibrio cholerae
Facultative anaerobe, halophilic, fermentative gram negative curved rod. Grows in alkaline pH.
Vibrio cholerae
Serogroups of V cholerae that cause cholera
O1
O139
Bacteria present in algal blooms that contaminates shellfish
Vibrio cholerae
Reason infective dose of Vibrio cholerae is high
It is sensitive to gastric acid
Virulence factor that acts as a receptor for filamentous bacteriophage that codes for cholera toxin
Toxin coregulated pilus (TCP)
Virulence factors of V cholerae
Pili
TCP
Flagellum
Mucinase
Complex A-B toxin that resembles ETEC heat labile toxin
Cholera toxin
Causes increased levels of cAMP in enterocyte leading to secretory diarrhea
Cholera toxin
Incubation period of cholera
1-4 days
Pt presents with N/V, abdominal cramps, and rice-water stools after eating shellfish a few days ago
Cholera
Complication of untreated cholera
Hypovolemic shock
Yellow (sucrose) fermenting colonies on TCBS from stool specimen. Oxidase positive.
Vibrio cholerae
Drug of choice for cholera
Azithromycin
Antibiotics that can be used for cholera
Azithromycin
Doxycycline
Ciprofloxacin
Suspected in pts who give a history of ingestion of raw seafood, or wound infection after exposure to seawater
Vibrio vulnificus
Treatment for Vibrio vulnificus infection
Doxycycline
General features of Enterobacteriaceae
Gram negative bacilli
Facultatively anaerobic
Ferment glucose
Catalase positive
Oxidase negative
Reduce nitrates to nitrites
Most abundant gram negative rods in the colon and feces I
E coli
Gram negative, lactose fermenting bacilli with peritrichous flagella. Indole and citrate positive
E coli
3 antigenic structures of E coli
O antigen –> somatic
H antigen –> flagellar
K antigen –> capsule
Virulence factors of E coli
Pili
Endotoxin
Capsule
Type III secretion systems
Enterotoxins
Virulence factor of E coli responsible for gastroenteritis
Enterotoxins
E coli type associated with these exotoxins –> heat labile toxin (LT-1) and heat stable toxin (STa)
ETEC
E coli type associated with colonization factor antigens (CFA) adhesins
ETEC
E coli types associated with BFP and intimin adhesins
EPEC
STEC/EHEC
E coli type associated with aggregative adherence fimbriae (AAF) adhesins
EAEC
E coli type associated with these exotoxins –> enteroaggregative heat stable toxin and plasmid encoded toxin
EAEC
E coli type associated with shiga toxins, Stx1 and Stx2, exotoxins
STEC/EHEC
E coli type associated with invasive plasmid antigen adhesin
EIEC
E coli type associated with hemolysin (HlyA) exotoxin
EIEC
5 main groups of E coli that cause diarrhea
STEC/EHEC
ETEC
EPEC
EAEC
EIEC
Source of ETEC
Food or water contaminated with human feces
Site of action of ETEC
Small intestine
AB toxin that causes ADP ribosylation and stimulation of G proteins to activate adenylate cyclase to cause intestinal secretion
LT toxin of ETEC
ST toxin stimulates guanylate cyclase to increase cGMP
ETEC
Pathogens commonly causing traveler’s diarrhea
ETEC
Pt presents with watery diarrhea, nausea, and vomiting with low-grade fever after recent travel
ETEC
EAEC
Treatment for infection with ETEC
Fluid replacement
E coli type seen in bottle fed infants in developing countries, commonly affecting children <1 yo
EPEC
Source of EPEC
Food or water contaminated with human feces
Site of action of EPEC
Small intestine
E coli type that produces attachment and effacement lesions using T3SS, intimin, and Tir adherence factors to HEp-2 and HeLa cells causing malabsorption and diarrhea
EPEC
Most frequent isolate types of EPEC
O55:K59
O111:K58
Treatment of EPEC
Fluid replacement and supportive care
E coli strain commonly implicated in food contamination in Mexico and in infant diarrhea
EAEC
Aggregates resemble stacked bricks on light microscopy
EAEC
Site of action of EAEC
Small intestine
Plasmid coded virulence factors of this pathogen are EAST and AAF I-III causing hemorrhage and decreased fluid absorption
EAEC
Pathogen that causes formation of heavy mucus biofilm on intestinal surface, which may contribute to persistent colonization and diarrhea
EAEC
Pt presents with persistent watery mucoid diarrhea, vomiting, and low-grade fever after travel
EAEC
Diarrhea causing pathogen associated with characteristic adherence to HEp-2 cells
EAEC
Viruses causing non-inflammatory diarrhea
Rotavirus
Norovirus
Adenovirus
Astrovirus
Number one cause of serious infantile diarrhea worldwide
Rotavirus
Medium sized virus with double layered capsid in the Reoviridae family
Rotavirus
Segmented dsDNA, non-enveloped virus that looks like a hub cap
Rotavirus
Most common Rotavirus group causing endemic, severe, infantile diarrhea
Group A
Transmission of rotavirus
Feco-oral
Virus that infects cell of small intestine by attaching to sialic acid via VP4
Rotavirus
Viral protein NSP4 acts as enterotoxin, causing fluid secretion
Rotavirus
Incubation period of rotavirus
48 hrs
Sudden onset of vomiting, abdominal pain, non-bloody watery diarrhea, fever, and dehydration in infant or young child who goes to daycare
Rotavirus
Type of vaccine for rotavirus and administration schedule
Oral live attenuated vaccine
At 2, 4, and 6 mo
Naked, icosahedral, positive sense ssRNA virus of the Calciviridae family that is acid stable
Norovirus
Transmission of norovirus
Feco-oral –> contaminated food, water, and surfaces
Person to person
Foodborne pathogen commonly associated with outbreaks on cruise ships
Norovirus
Pathogen causing direct damage to intestinal enterocytes causing vomiting, diarrhea, abdominal cramps, fever, and HAs that usually resolves in 1-2 days
Norovirus
Incubation of norovirus
12-48 hrs
Diagnosis of norovirus
Reverse transcriptase PCR of feces or vomitus
Non-enveloped dsDNA virus that can cause diarrhea, but is usually associated with respiratory infection and conjunctivitis
Adenovirus
Infective serotypes of adenovirus
40 and 41
Non-enveloped ssRNA virus that often causes an asymptomatic infection where virions are shed in the stool in large quantities
Astrovirus
Protozoa causing secretory diarrhea
Giardia duodenalis
Cryptosporidium parvum
Cystoisospora belli
Cyclospora cayetanensis
Non-invasive luminal flagellate, sting-ray shaped trophozoite with 2 nuclei
Giardia duodenalis
Infective form of Giardia duodenalis
Cysts
Pt presents with steatorrhea, nausea, and abdominal cramps persisting for 6 weeks. Stool sample shows cysts.
Giardia duodenalis
Complication of Giardia infection in children
Severe malabsorption syndrome
Treatments for giardiasis
Metronidazole
Quinacrine hydrochloride
Prevention of giardiasis
Boiling, filtering, or treating water with iodine
Coccidian parasite that infects villi of lower small intestine and is resistant to chlorine
Cryptosporidium parvum
Source of Cryptosporidium parvum
Gut of cattle
Diagnosis by modified acid fast staining of stool showing oocysts
Cryptosporidiosis
Treatment for Cryptosporidiosis
Nitazoxanide –> only in immunocompromised
Common presentation of cryptosporidiosis
Asymptomatic to mild in healthy
Severe in immunocompromised
Only known host of Cystoisospora belli
Humans
Transmission of Cystoisospora belli
Ingestion of mature oocysts via feco-oral route
Pt presents with profuse, water, non-bloody, mucoid, foul-smelling diarrhea. Also has cramping, vomiting, and low-grade fever. Modified acid fast stain shows large oocysts.
Cystoisospora belli
Treatment for heavier Cystoisospora belli infections
Cotrimoxazole
TMP-SMZ
Transmission of Cyclospora cayetanensis
Feco-oral route via contaminated food or water
Diarrhea causing pathogen associated with contaminated raspberries, basil, and lettuce
Cyclospora cayetanensis
Immunocompromised pt presents with 6 wks of diarrhea, cramps, and dehydration. Stool sample demonstrates acid fast oocysts.
Cyclospora cayetanensis
Treatment for cyclospora cayetanensis
Cotrimoxazole