SALMONELLA
Under the current American CDC (Center for Disease Control) classification scheme there are two species: Salmonella enterica and Salmonella bongori. S. enterica is further divided into 6 subspecies.Classification
S. enterica contains more than 2500 serotypes (2541 in l 2004) differentiated on the O and H- Antigens Salmonella serotype (serovar) Typhimurium, Salmonella serotype Enteritidis, Salmonella serotype Typhi, Salmonella serotype Paratyphi, Salmonella serotype Cholerae suis etc. Ex.: Salmonella enterica subspecies enterica serovar Typhi or Salmonella Typhi
Although the classification of salmonellae relies primarily on serotyping of surface antigens, the typhi serotype can be differentiated from other serotypes on the basis of its relatively inert biochemical behavior. The typhi serotype is negative for Simmons citrate, gas from glucose, acetate utilization, etc.
Morphology
Gram – negative rodsuncapsulated (except S. typhi)Unsporulated.Peritrichous flagella (ensure motility)Cultural properties
Aerobe-anaerobe facultativeGrow easily on simple culture mediaOnto selective and differential media that contain biliary salts and lactose grow like lactose-negative “S” colonies.produce de H2S.Biochemical properties
Motile, Lactose negative. acid and gas from glucose, mannitol, maltose, and sorbitol. Indole test negative Methyl red test positive Voges-Proskauer test negative. Citrate positive (growth on Simmon's citrate agar) Lysine decarboxylase positive Urease negative H2S produced from thiosulfate Phenylalanine and tryptophan deaminase negative Gelatin hydrolysis negative
TSI (Triple Sugar Iron) MIU (Motility Indole Urea). Simmons Citrate medium
Epidemiology:In many countries Salmonella enteritis is the third most commonly reported form of “food poisoning”. The infection is zoonotic, and the poultry is the source of infection. Other sources of infection include milk products, food and water contaminated with animal feces or urine