infectious diseases

1. By
Mohammad Abo El.Magd
Endemic and infectious diseases Unit
Over view on Enteric Infections

2. Overview
Third most common syndrome seen in general practice in the
US
On the global scale, diarrheal diseases are the leading cause of
childhood death
The 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)

3. Host factors
Age: (EPEC and rotovirus tend you affect young children)
Personal hygiene : (fecooral)
Gastric acidity, physical barriers
Intestinal 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

4. 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

5. 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

6. Pathophysiology
2- Enteroadherence
Cryptosporidiosis (Cryptosporidium parvum)
Cyclospora species (?)
Enteroadherent and enteropathogenic E. coli
Helminths :D .Latum,Strongloydes
Giardiasis (Giardia lamblia)

7. 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

8. Clinical presentation
Low-versus high-volume diarrhea
Low volume (low water): colonic
High 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]

9. Clinical presentation
Small- versus large-bowel diarrhea
Small 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)

10. Clinical presentation
Noninflammatory vs inflammatory
Non inflammatory diarrhea: pathogens act primarily on small
intestine to induce fluid secretions
Voluminous watery diarrhea, nausea, vomiting, abdominal
cramps, low grade fever.
Inflammatory diarrhea: induce inflammation by invasion or
cytotoxins
Stools of small volume, fever, blood and mucus, tenesmus,
abdominal cramping.

11. Overview of Infectious diarrhea
ACUTE (symptoms ≤ 14 days)
Community-acquired:
gram-negative bacterial pathogens
Viral pathogens
Norovirus: family clusters, winter outbreaks
Rotovirus: children, seasonal peak in winter
Protozoal pathogens
Entamoeba Histolytica: acute colitis with fever and dysentry
Nosocomial ( > 3 days after hospitalization)
Clostridium difficile
Travelers:
ETEC

12. Overview of Infectious diarrhea
PERSISTENT (symptoms > 14 days)
Parasitic: Girdia lamblia, Cryptosporidium parvum, Cyclospora,
Isospora belli
Immunocompromised host: also consider
microsporidium, Mycobacterium-avium complex, and
cytomegalovirus

14. FoodNet Data, CDC 2007
Incidence of Various Pathogens per
100,000 Population in U.S.
Salmonella 14.92
Campylobacter 12.79
Shigella 6.26
Cryptosporidium 2.67
)EHEC) O157:H7 1.20
Yersinia 0.36
Listeria 0.27
Vibrio 0.24

17. Gram-negative Bacteria Associated with
Diarrhea
Campylobacter
Salmonella
Shigella
Escherichia coli
Yersinia enterocolica
Vibrio
Aeromonas

18. Campylobacter jejuni
Curved gram-negative rods
Zoonotic infection and carried in GI tract of animals
Poulty common source of infection
Disease caused by ingestion of contaminated food or water
Incubation period 1-7 days
Two-thirds present with fever, headache, myalgias followed
by abdominal pain and bloody diarrhea

19. Campylobacter jejuni
Fecal leukocytes
Antibiotic 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

20. Salmonella gastroenteritis
Non-lactose fermenting gram-negative bacilli
Non-typhoidal strains seen in the US (S. enterica)
serovars S. typhimurium, S. enteritidis, etc
Found in GI tracts of mammals, birds, reptiles
Acquired 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

21. Other syndromes of Salmonella
Enteric fever
Bacteremia with or without metastatic disease
Asymptomatic carrier state

24. Bacteremia in salmonellosis
Usually transient and inconsequential
Sickle cell disease: osteomyelitis
Atherosclerosis: mycotic aneurysm
Underlying heart disease: endocarditis
Young children: ? meningitis

25. 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

26. Shigellosis
Non-lactose fermenting gram-negative rod
Four species:
S. dysenteriae
S. flexneri
S. boydi
S. sonnei
Highly infectious: infectious dose < 200
Incubation period 1-7 days
Symptoms can develop 12 hours after ingestion

27. Shigellosis
Presents as fever, abdominal pain, tenesmus, bloody diarrhea
Bacteremia 4% of patients
Reactive arthritis 1-2%, 1-2 weeks (S. flexneri)
S. dysenteriae can be associated with HUS
Antimotility drugs have been associated with toxic megacolon
self-limited but treatment recommended to prevent secondary
spread to contacts

28. E. coli gastroenteritis
Enterotoxigenic: watery diarrhea (travelers diarrhea)
Enteropathogenic: diarrhea in infants common in
developing countries
Enteroinvasive: dysentery with blood and mucus
Enterohemorrhagic (E coli 0157:H7): copious bloody
diarrhea sometimes with the hemolytic-uremic
syndrome
Enteroaggregative

29. 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

30. Clostridium difficile
1970s: 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

31. Clostridium difficile
Colonization rate is 2% to 3% in healthy adults; 20% to 40%
in hospitalized patients
Widespread contamination of hospital environments
Infection control measures including hand washing and gloves
have been shown to reduce infection rates

32. 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.)

33. 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.)

34. Yersinia enterocolitica
Carried in GI tract of pigs, cattle, rodents, sheep, dogs and cats
Infection acquired by inadequately cooked pork,
unnpasteurized milk, contaminated water
Diarrhea, fever, abdominal pain
Mesenteric adenitis/terminal ileitis: fever, RLQ pain,
leukocytosis
Reactive polyarthritis, often with erythema nodosum
Septicemia especially in children

35. Entamoeba histolytica (amebiasis(
Affects 10% of world’s population
In the United States, affects up to 4%
Order of involvement: ceacum, ascending colon, rectum,
sigmoid
Flask-shaped ulcers
Liver abscesses in up to 10%

37. Giardia lamblia (giardiasis(
Waterborne
Rocky Mountains; Leningrad; but also widespread
Can cause diarrhea by several mechanisms
Weight loss (62%), cramps (61%), steatorrhea (57%),
flatulence (35%), vomiting (29%), belching (26%), fever
(17%)

39. Cryptosporidium parvum
Formerly best known as an animal pathogen infecting
numerous species
Severity and duration of human infection vary directly with
immunocompetence
Healthy adults: self-limited diarrhea, usually lasting 10 to 14
days
AIDS patients: severe intractable diarrhea

40. Rotavirus diarrhea
Usually 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

41. Norovirus diarrhea
Typically epidemic, often traced to a common source
Throughout the year
Usually adults and school-aged children
Often traced to contaminated food or water
At least 3 serotypes; can be demonstrated by immune electron
microscopy or radioimmunoassay

42. Traveler’s diarrhea
Bacterial:
Enterotoxigenic E. coli (ETEC)
Shigella
Salmonella
Campylobacter
Protozoa:
Giardia, Entamoeba, Cryptosporidium
Virus:
Norwalk, rotavirus, enterovirus

43. Staphylococcal food poisoning
Common food borne illness
Infections originate from asymptomatic carriers of staphylococcus
aureus
Can contaminate processed meats, potato salad, ice-cream
Preformed toxin (enterotoxin) in food rather than from direct
effect of organism
Incubation 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

44. Helicobacter pylori
70-90% of population in
developing countries. Almost
45% in developed countries
Associated with gastritis,
duodenal ulcer, gastric ulcer,
gastric adenocarcinoma, MALT
lymphomas
Fecal-oral transmission