1. Bacterial Gastroenteritis
Dr. Maitham F. Jalal
M.B.CH.B- F.I.C.M.S( neurology )

2. 3 groups of gram negative bacteria account for most bacterial intestinal infections:
Vibrio cholerae (Cholera)
Enterics (Salmonella, Shigella, E. coli)
Campylobacter jejuni

3. Cholera Causative agent: Vibrio cholerae High infectious dose
Bacteria sensitive to stomach acid
Adheres to small intestine and multiply
Bacteria don’t enter cells

4. Cholera toxin Potent exotoxin
Causes intestinal cells to rapidly pump out electrolytes
Passive osmotic H2O loss follows
Metabolic acidosis
Shock

5. Untreated cases potentially fatal
Heavy loss of fluid
“rice-water stool”
Up to 20L of fluids lost per day
May discharge 1 million bacteria per ml of feces
Untreated cases potentially fatal
Fluid/electrolyte replacement
Tetracycline reduces toxin production

6. Shigellosis Causative Agent: Shigella sp. Low infecting dose
S. dysenteriae, S. flexneri, S. boydii, S. sonnei
Low infecting dose
Bacteria not sensitive to stomach acid
Characterized by fever and dysentery

7. Infects cells of large intestine and
initiates intense inflammatory
response
Dead cells slough off
Produces areas covered with pus and blood

8. All species produce enterotoxin and type III secretion systems
S. dysenteriae produces powerful endotoxin
shiga-toxin
Ciprofloxacin, rifampin or azithromycin may reduce duration and infectivity

9. Traveler’s Diarrhea Causative Agent: Escherichia coli
Multiple antigenic strains (O, H, K)
Virulent strains have fimbriae, adhesions and multiple toxins
Enterotoxigenic E. coli
Enterotoxins
Type III secretion system
Typically self limiting

10. Enterohemorrhagic E. coli
Produce potent Shiga-like toxins and type III secretion systems
Antimicrobials cause increase in toxin production

11. Salmonellosis and Typhoid Fever
Causative agent: Salmonella enterica
2000 strains (serotypes)
Typhimurium and Enteritidis commonly cause Salmonellosis
Typhi and Paratyphi cause Typhoid Fever

12. Common intestinal flora of many animals
Contaminated animal products are reservoir
Reptiles, eggs and undercooked poultry

13. Virulent strains tolerate stomach
acid and pass to intestines
Toxin induces phagocytosis in
intestinal cells
Pathogen reproduces inside
phagosome killing host cell
Bacteria (Typhi) may pass
through intestinal cells into
bloodstream

14. Typhoid fever is an enteric fever
Macrophages carry bacteria to liver, spleen, bone marrow and gallbladder
Treated with ciprofloxacin or ampicillin
Surgical removal of gallbladder

15. Campylobacteriosis Causative agent: Campylobacter jejuni
Leading cause of bacterial diarrhea in United States
Estimated 1million cases annually with ~100 deaths
Associated with poultry
Low infecting dose

16. Virulent strains possess adhesions, cytotoxins and endotoxin
Induce endocytosis in cells of intestine and initiate inflammation and bleeding lesions
Non-motile mutants are avirulent
Severe cases treated with ciprofloxacin or azithromycin

17. Guillain-Barré Syndrome
Tingling of the feet leads to progressive paralysis of the legs, arms and rest of the body
40% of cases preceded by campylobacteriosis
May be associated with autoimmune response
80% recover completely; 5% mortality with treatment

19. Bacterial Food Intoxication
Staphylococcus aureus
Halotolerent; grows well in foods at room temp
Associated with cafeterias and social functions

20. 5 heat stable enterotoxins:
1000 for up to 30 min
Stimulate muscle contractions, nausea and intense vomiting, diarrhea and cramping
Acute and self limiting
symptoms begin 4-6 hrs after consumption and end within 24 hrs

21. Botulism Causative agent: Clostridium botulinum
Obligate anaerobic, Gram +, spore forming bacillus
Produce 7 different neurotoxins
One of most deadly toxins known

22. Signs & Symptoms Dizziness, dry mouth, blurred vision
Abdominal symptoms include pain, nausea, vomiting and diarrhea or constipation
Progressive paralysis
Paralysis of respiratory muscles most common cause of death

23. 3 forms of botulism:
Food-borne botulism – progressive paralysis of all voluntary muscles due to toxin production
Wound botulism – similar symptoms
Infant botulism – bacteria grow in the intestines, producing non-specific symptoms
“floppy baby syndrome”

25. Epidemiology Food borne botulism Wound botulism Infant botulism
Commercial sterilization
Toxin destroyed by heating foods
Wound botulism
deep crushing wounds
Infant botulism
Inhalation or ingestion of spores
Commonly associated with honey or juices

26. Prevention Treatment Proper sterilization and sealing of canned food
No honey or unpasteurized juices for infants!!
Treatment
Antitoxin
Gastric washing and surgical removal of tissues
Artificial respiration may be required
Anti-microbials given to kill bacteria in infant and wound botulism