SALMONELLA Important Gram-negative Lactose Produce H 2 S

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

Kaufman and White 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.

Cell wall O antigens: Outer cell wall polysaccharides. Used to subdivide the salmonellae into nine groups 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 Capsular Vi (virulence): Used for the typing of S. typhi.

Septicemia with metastatic Enteric fevers Accounts for 5-10% of Occurs in patients with a chronic disease (sickle cell anemia, cancer).

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

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

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

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

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

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

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

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

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

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

Enterocolitis resolves without Fluid & electrolyte therapy is 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

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

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

Apply public health and personal hygiene Proper sewage disposal and proper chlorinated water Cultures of stool of food handlers to detect Pasteurization of milk, proper cooking of poultry, eggs, and meat.

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