Infectious Diarrhea Flashcards
What is the #1 cause of acute viral gastroenteritis?
Norovirus
How is acute viral gastroenteritis caused by norovirus treated?
Supportive care
What is a long term post-infectious sequelae of norovirus infection?
post-viral gastroparesis
Can norovirus cause chronic infection?
Apparently yes, looks like asymptomatic carriers can act as a reservoir
But usually, symptoms rapidly controlled within 48-72 hours
What is the most common cause of bacterial foodborne illness in the U.S>
Salmonella (S. enteriditis) a nontyphoidal infection
What are the two distinct diseases of salmonella?
Outside of U.S. = typhoid fever
In U.S. = nontyphoidal infections
How are nontyphoidal salmonella infections transmitted?
Food transmission (eggs, milk, meat, etc.)
Pet transmission (lizards, turtles, etc.)
What is the characteristic clinical presentation of typhoid fever?
Week 1: Stepwise fever and bradycardia
Week 2: Rose spots on abdomen + pain
Week 3: GI bleeding, perforation
Constipation
Do you treat salmonella with antibiotics?
Typhoid fever high mortality without antibiotics, must treat travelers
Non-typhoidal disease, no advantage to giving antibiotics because it is typically self limited (unless patient is very ill)
Can salmonella cause chronic infection?
In typhoid fever, it may persist in gallstones
In non-typhoidal disease not likely
What is the second most common food-borne bacterial infection in the U.S.
Campylobacter
What IBD can campylobacter mimic?
Crohn’s Disease since it starts in ileum/jejunum and comes to colon
What are acute complications of campylobacter infection?
Pseudo-appendicitis in kids
What are long term complications of campylobacter infection?
Reactive arthritis
Guillain-Barre polyneuropathy
What is the most common cause of bloody diarrhea worldwide?
Shigella
What is the most important virulence factor of Shigella and why is it dangerous?
Shiga toxin –> can lead to HUS
What is an E.Coli strain that also causes bloody diarrhea and HUS (very much like Shigella); what serotype is most recognized in U.S.
EHEC (Enterohemorrhagic E. Coli) aka O157:H7
Also produces shiga toxin as a virulence factor
Are antibiotics used to treat EHEC infection?
NO. Antibiotics are contraindicated because there is higher risk of HUS with antibiotic use
What triad of symptoms defines HUS
Acute renal failure
Microangiopathic hemolytic anemia
Thromboycytopenia
How are ETEC and EPEC similar?
Both cause watery, non-bloody diarrhea in kinds in developing countries
How does cholera toxin work to cause watery diarrhea?
B subunits bind to ganglioside receptor (GM1) on apical surface
A subunit enters and is cleaved into A1 and A1
A1 moves to basolateral membrane and irreversibly activates a g protein
Causes an increase in cAMP and increased Cl secretion (inhibition of NaCL transport)
Water follows ion efflux out of cell
What are clinical manifestations of cholera?
Painless, rice-water stool with fishy smell = up to 1 liter/hour
FACT: C. Difficile forms spores and is highly infectious
WASH HANDS WITH SOAP and WATER
What are the two exotoxins required for pathogenicity in C. Diff and which is more potent?
Toxin A (enterotoxin) and Toxin B (cytotoxin)
B is more potent
What are main clinical findings of C. Diff?
Watery diarrhea, abdominal cramping, fever, pseudomembranous colitis –> toxic megacolon
What is treatment for C. Diff
Metronidazole
Oral Vancomycin
Fecal Microbial Transplant (FMT)
How is Clostridium perfringens transmitted?
Food-borne –> germinates in contaminated meats
What is the enterotoxin of Clostridium perfringens?
Enteritis necroticans (pigbel)
What are risk factors for contracting Clostridium perfringens?
Consumption of pig guts (chitterlings)
Sweet potatoes
Antipsychotic drugs that decrease GI motility
What do you need to know about bacteroides fragilis?
It has a similar presentation to C. Diff
What are the two bacteria that are transmitted through pork (chitterlings)
Yersinia
Clostridium perfringens
What are the two bacteria that can present as pseudoappendicitis?
Campylobacter and Yersinia
What else comprises usual clinical presentation of Yersinia infection in children?
Dysentery Fever Pharyngitis NO abdominal pain Pseudoappendicits
Which bacteria most often infects pregnant women?
Listeria monocytogenes
primarily affects elderly, immunosuppressed, neonates
What is bacillus cereus infection classically related to?
Contraction from reheated fried rice (it can survive in extreme temps.)
What is the most common parasitic enteric pathogen in the U.S
Giardia lamblia
What is giardia lamblia highly associated with?
Contaminated water
Most common in young children
What are characteristic clinical presentations of giardia?
Foul-smelling, fatty stool, weight loss,
What is the other common parasitic enteric pathogen?
Cryptosporidium (C. parvum is most common)
What is the most common complication of cryptosporidium infection?
Primary sclerosing cholangitis (infection of biliary system which leads to strictures)
What infectious entities should be considered with chronic diarrhea
Giardia, cryptosporidium, entamoeba
