enteric infections mohammad aboelmagd
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By Mohammad Abo El.MagdEndemic and infectious diseases Unit
Over view on Enteric Infections
OverviewThird most common syndrome seen in
general practice in the USOn the global scale, diarrheal diseases are
the leading cause of childhood deathThe frequency, type, and severity of these
infections depend on:Who you are (host factors)Where you are (Endemic areas)When you are there (times of outbreaks wet
seasons and winter)
Host factorsAge: (EPEC and rotovirus tend you affect young
children)Personal hygiene : (fecooral)Gastric acidity, physical barriersIntestinal motility (expel the pathogens.
Antimotility assoc with prolonged fever shedding shigella, complication c diff, HUS in ETEC)
Enteric microflora ( c.diffcile )Specific immunity: phagocytes, B-cell, T-
cell
Infectious doses of enteric pathogen
Shigella: 101-2
Giardia lamblia: 101-2
Entamoeba histolytica: 101-2 Campylobacter jejuni:102-6
Salmonella: 105
E. coli: 108
Vibrio cholerae: 108
Pathophysiology 1- Toxin production
Neurotoxins (preformed toxin): Bacillus cereus, Clostridium perfringens, Staphylococcus aureus
Enterotoxin: Aeromonas species, enterotoxigenic E. coli, Vibrio cholerae
Cytotoxin: Clostridium difficile, E. coli 0157:H7
Pathophysiology 2- Enteroadherence
Cryptosporidiosis (Cryptosporidium parvum)
Cyclospora species (?)Enteroadherent and enteropathogenic E.
coliHelminths :D .Latum,StrongloydesGiardiasis (Giardia lamblia)
Pathophysiology 3- Mucosal invasion
Minimal invasion: Norwalk virus, Rotavirus, other viruses
Variable invasion: Aeromonas sp., Campylobacter sp., Salmonella sp., Vibrio parahemolyticus
Severe invasion: Entamoeba histolytica, enteroinvasive E. coli, Shigella species
Clinical presentation Low-versus high-volume
diarrheaLow volume (low water): colonicHigh volume (high water): small bowel
OSMOTIC DIARRHEA: high-volume diarrhea in which the measured fecal osmolality is less than 2 [Na + K]
SECRETORY DIARRHEA: high-volume diarrhea in which the measured fecal osmolality equals 2 [Na + K]
Clinical presentation Small- versus large-bowel
diarrheaSmall bowel: large volume, watery, less
frequent, painless stools. Blood and WBCs are rare. Proctoscopy is normal. Pain is mid-abdominal.
Large bowel: small volume, often mucoid, more frequent, painful stools. Blood and WBCs are common. Proctoscopy is abnormal. Pain is lower-abdominal (left lower quadrant)
Clinical presentation Noninflammatory vs
inflammatoryNon inflammatory diarrhea: pathogens act
primarily on small intestine to induce fluid secretionsVoluminous watery diarrhea, nausea,
vomiting, abdominal cramps, low grade fever.
Inflammatory diarrhea: induce inflammation by invasion or cytotoxinsStools of small volume, fever, blood and
mucus, tenesmus, abdominal cramping.
Overview of Infectious diarrheaACUTE (symptoms 14 days)
Community-acquired: gram-negative bacterial pathogensViral pathogens
Norovirus: family clusters, winter outbreaksRotovirus: children, seasonal peak in winter
Protozoal pathogensEntamoeba Histolytica: acute colitis with
fever and dysentryNosocomial ( > 3 days after hospitalization)
Clostridium difficileTravelers:
ETEC
Overview of Infectious diarrheaPERSISTENT (symptoms > 14 days)
Parasitic: Girdia lamblia, Cryptosporidium parvum, Cyclospora, Isospora belli
Immunocompromised host: also consider microsporidium, Mycobacterium-avium complex, and cytomegalovirus
FoodNet Data, CDC 2007Incidence of Various Pathogens per
100,000 Population in U.S.Salmonella 14.92Campylobacter 12.79Shigella 6.26Cryptosporidium 2.67
(EHEC )O157:H7 1.20Yersinia 0.36Listeria 0.27Vibrio 0.24
Gram-negative Bacteria Associated with Diarrhea
Campylobacter SalmonellaShigellaEscherichia coliYersinia enterocolicaVibrio Aeromonas
Campylobacter jejuniCurved gram-negative rodsZoonotic infection and carried in GI tract of
animalsPoulty common source of infectionDisease caused by ingestion of
contaminated food or waterIncubation period 1-7 daysTwo-thirds present with fever, headache,
myalgias followed by abdominal pain and bloody diarrhea
Campylobacter jejuni
Fecal leukocytesAntibiotic therapy reserved for
immunocompromised and those with severe symptoms
Reactive arthritis 1% of patients. 1-2 weeks after diarrhea
Associated with Guillain-Barre, usually 1-3 weeks after diarrhea. 20-40% GBS cases are attributable to antecedent C. jejuni infection
Salmonella gastroenteritis Non-lactose fermenting gram-negative bacilliNon-typhoidal strains seen in the US (S.
enterica) serovars S. typhimurium, S. enteritidis, etc
Found in GI tracts of mammals, birds, reptilesAcquired from ingestion of contaminated
poultry, eggs, meat and exposure to pet reptiles
Fever, abdominal cramping, nausea, vomiting, diarrhea with fecal leukocytes
Untreated diarrhea lasts 4-10 days
Other syndromes of Salmonella
Enteric feverBacteremia with or without metastatic
diseaseAsymptomatic carrier state
Bacteremia in salmonellosisUsually transient and inconsequentialSickle cell disease: osteomyelitisAtherosclerosis: mycotic aneurysmUnderlying heart disease: endocarditisYoung children: ? meningitis
Salmonella carrier state
3% of cases of typhoid fever .0.2% to 0.6% of symptomatic non typhoidal
infections (relevant especially to food handlers)
High association with biliary tract disease and gallstones
ShigellosisNon-lactose fermenting gram-negative rodFour species:
S. dysenteriaeS. flexneriS. boydiS. sonnei
Highly infectious: infectious dose < 200 Incubation period 1-7 daysSymptoms can develop 12 hours after
ingestion
ShigellosisPresents as fever, abdominal pain, tenesmus,
bloody diarrheaBacteremia 4% of patientsReactive arthritis 1-2%, 1-2 weeks (S. flexneri)S. dysenteriae can be associated with HUSAntimotility drugs have been associated with
toxic megacolonself-limited but treatment recommended to
prevent secondary spread to contacts
E. coli gastroenteritisEnterotoxigenic: watery diarrhea
(travelers diarrhea)Enteropathogenic: diarrhea in infants
common in developing countriesEnteroinvasive: dysentery with blood
and mucusEnterohemorrhagic (E coli 0157:H7):
copious bloody diarrhea sometimes with the hemolytic-uremic syndrome
Enteroaggregative
Enterohemorrhagic E. coli(0157:H7)
Most common strain in developed countries Usually transmitted by beef, but many other
foods transmit. Associated with petting zoo Low infectious dose (as few as 100 bacteria) Shiga-toxin Crampy abdominal pain, often disproportionate
to physical findings along with bloody diarrhea with little or no fever
Complications include hemolytic-uremic syndrome in children, thrombotic thrombocytopenic purpura in adults
Clostridium difficile1970s: Found to be the cause of
enterocolitis related to the antibiotic clindamycin
Pseudomembranous colitis with yellow-white plaques; can progress to toxic megacolon
At least two toxins (A and B) cause necrosis of epithelium
Nosocomial transmission
Clostridium difficileColonization rate is 2% to 3% in healthy
adults; 20% to 40% in hospitalized patientsWidespread contamination of hospital
environmentsInfection control measures including hand
washing and gloves have been shown to reduce infection rates
Endoscopic view of multiple scattered, yellowish plaques consistent with pseudomembranous colitis. (From Iseman DT, Hamza SH, Eloubeidi MA. Pseudomembranous [Clostridium difficile] colitis. Gastrointest Endosc. 2002;56:907.)
Abdominal radiograph demonstrating markedly dilated colon, wall edema, and loss of haustration in a patient with Clostridium difficile-associated pseudomembranous colitis complicated by toxic megacolon. (From Agnifili A, Gola P, Manno M, et al. The role and timing of surgery in the treatment of pseudomembranous colitis: A case complicated by toxic megacolon. Hepatogastroenterology. 1994;41:394-396.)
Yersinia enterocoliticaCarried in GI tract of pigs, cattle, rodents,
sheep, dogs and catsInfection acquired by inadequately
cooked pork, unnpasteurized milk, contaminated water
Diarrhea, fever, abdominal painMesenteric adenitis/terminal ileitis:
fever, RLQ pain, leukocytosisReactive polyarthritis, often with
erythema nodosum Septicemia especially in children
Entamoeba histolytica (amebiasis)
Affects 10% of world’s populationIn the United States, affects up to 4%Order of involvement: ceacum, ascending
colon, rectum, sigmoidFlask-shaped ulcersLiver abscesses in up to 10%
Giardia lamblia (giardiasis)WaterborneRocky Mountains; Leningrad; but also
widespreadCan cause diarrhea by several mechanismsWeight loss (62%), cramps (61%),
steatorrhea (57%), flatulence (35%), vomiting (29%), belching (26%), fever (17%)
Cryptosporidium parvumFormerly best known as an animal
pathogen infecting numerous speciesSeverity and duration of human infection
vary directly with immunocompetenceHealthy adults: self-limited diarrhea,
usually lasting 10 to 14 daysAIDS patients: severe intractable diarrhea
Rotavirus diarrheaUsually sporadic but
can cause epidemics in institutions, including nursing homes
Winter months in temperate climates: usually infants and young children
fecal-oral transmissions
DNA virus with at least 2 sterotypes; can be demonstrated with ELISA
Norovirus diarrheaTypically epidemic, often traced to a
common sourceThroughout the yearUsually adults and school-aged childrenOften traced to contaminated food or waterAt least 3 serotypes; can be demonstrated
by immune electron microscopy or radioimmunoassay
Traveler’s diarrheaBacterial:
Enterotoxigenic E. coli (ETEC)ShigellaSalmonellaCampylobacter
Protozoa:Giardia, Entamoeba, Cryptosporidium
Virus:Norwalk, rotavirus, enterovirus
Staphylococcal food poisoningCommon food borne illnessInfections originate from asymptomatic carriers
of staphylococcus aureusCan contaminate processed meats, potato
salad, ice-creamPreformed toxin (enterotoxin) in food rather
than from direct effect of organismIncubation period about 4 hours. Symptoms last < 24 hours (no new toxin
produced by ingested bacteria)Severe nausea and vomiting along with
abdominal pain and diarrhea. No fever
Helicobacter pylori70-90% of population
in developing countries. Almost 45% in developed countries
Associated with gastritis, duodenal ulcer, gastric ulcer, gastric adenocarcinoma, MALT lymphomas
Fecal-oral transmission
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