1. SALMONELLA Important Properties: @ Gram-negative rods @ Lactose negative @ Produce H 2 S

3. Nomenclature of Salmonellae: Ewing Scheme: # Divides Salmonella into three species: @ S. typhi @ Salmonella choleraesuis @ Salmonella enteritidis # In this scheme there is one serotype in each of the first two species and 1500 serotypes in the third species.

5. Kaufman and White Scheme: @ This gave 1500 different species, named after the city in which they were isolated. # Salmonella dublin in Kaufman and White Scheme would be S. enteritidis serotype dublin in Ewing Scheme. # Both schemes are used. # American Center for Disease Control and Prevention uses Ewing Scheme.

7. Antigens: @ Cell wall O antigens: Outer cell wall polysaccharides. Used to subdivide the salmonellae into nine groups A-I. @ Flagellar H antigens: There are two phases of H antigens: Phases 1 and 2. # Only one of the two phases is produced by Salmonella at any one time, depending on the gene sequence. @ Capsular Vi (virulence): Used for the typing of S. typhi.

9. Diseases: @ Septicemia with metastatic abscesses. @ Enterocolitis @ Enteric fevers Septicemia @ Accounts for 5-10% of salmonellosis @ Occurs in patients with a chronic disease (sickle cell anemia, cancer).

11. @ Bacteremia causes osteomyelitis, pneumonia, and meningitis. @ Metastatic abscesses, infarcts and aortic aneurysms may occur. Clinical Findings of Septiceamia: @ Septicemia is caused by S choleraesuis. @ The symptoms begin with fever, then proceed to other organs, e.g. bone, lung, meninges.

13. Enterocolitis @ Salmonella invades the epithelial tissue of small & large intestines. @ Salmonella penetrates the mucosal cells and causes inflammation and diarrhea. @ Infection is limited to gut & mesenteric lymph nodes; i.e. No bacteremia. @ Gastric acid is a host defense @ Gastrectomy & use of antacids increase the infection.

15. Clinical Findings of Enterocolitis: @ Begins with nausea and vomiting. @ Progresses to abdominal pain and diarrhea, with or without blood. @ Disease lasts a few days and it is self- limited. Requires treatment only in the very young and the very old. @ Caused by Salmonella typhimurium (but all species has been implicated).

17. Enteric fevers @ Begins in the small intestine with few gastrointestinal symptoms. @ Salmonella multiplies inside the phagocytes of Peyer's patches. @ Then spread by these phagocytes to the liver, gallbladder, and spleen. @ This leads to bacteremia and fever. @ In the gallbladder a carrier state occurs and Salmonella is excreted in the feces.

19. Clinical Findings of Enteric Fevers: @ Typhoid fever is caused by S. typhi, and enteric fever is caused by S. paratyphi A, B, and C. @ Onset is slow, with fever, & constipation without vomiting or diarrhea. @ Bacteraemia develops after first week leading to high fever, delirium, tender abdomen, enlarged spleen, & rose- colored spots on the abdomen.

21. @ Infection resolves by the third week. @ Complications: intestinal hemorrhage or intestinal perforation. @ 3% of typhoid fever patients become chronic carriers. @ The carrier rate is higher among women, especially those with previous gallbladder disease and gall stones.

23. Transmission: @ Associated with ingestion of food and water contaminated by human and animal wastes. @ S. typhi is transmitted only by humans. @ All other Salmonella species have an animal and a human reservoir.

25. Human sources of infection: @ Persons excreting the organism during or shortly after an attack of enterocolitis. @ Chronic carriers, excreting Salmonella for years. Animal sources of infection: @ Contaminated poultry and eggs. @ Inadequately cooked meat products @ Dogs, turtles, and other pets.

27. Laboratory Diagnosis: @ In enterocolitis: Salmonella is isolated from stool. @ In enteric fevers: a blood culture reveals Salmonella during first 2 weeks of illness. @ On Mac Conkey & EMB agar: Salmonella forms non-lactose-fermenting colonies @ TSI agar: gives an alkaline slant and an a black acid butt, with both gas and H 2 S.

29. @ S. typhi does not form gas and produces only a small amount of H 2 S. @ Salmonella is urease negative. @ Salmonella is identified and grouped by the slide agglutination test, using the O, H, and Vi antigens. @ The diagnosis can be made serologically by detecting a rise in antibody titer in the patient's serum (Fernand Widal test).

31. Treatment: @ Enterocolitis resolves without treatment. @ Fluid & electrolyte therapy is required. @ No antibiotics for enterocolitis because: # it will not shorten the illness. # it will not reduce the symptoms # it may prolong excretion of Salmonella # it increases frequency of carrier state # it forms mutants resistant to antibiotic

33. @ Antibiotics are indicated for neonates or persons with chronic diseases. @ Antibiotics are prescribed after sensitivity testing because Salmonella resistance is common @ Drugs that retard intestinal motility and reduce diarrhea are not used because they prolong duration of symptoms & the fecal excretion of Salmonella.

35. @ Treatment of choice for enteric fever & septicemia is ceftriaxone & ciprofloxacin @ Ampicillin or ciprofloxacin are used for chronic carriers of S. typhi. @ Cholecystectomy is necessary to abolish the chronic carrier state. @ Focal abscesses should be drained surgically whenever feasible.

37. Prevention: @ Apply public health and personal hygiene measures. @ Proper sewage disposal and proper chlorinated water supply @ Cultures of stool of food handlers to detect carriers. @ Pasteurization of milk, proper cooking of poultry, eggs, and meat.

39. Vaccination: @ Two vaccines are available, giving 50-80% protection against S typhi. @ One vaccine consists of acetone-killed S typhi organisms, administered I.M. @ The other vaccine is a live, attenuated S typhi and is taken orally.