Dr. Ban sahib abed al-nabi zoonotic disease unit post graduate lecture Salmonella Dr. Ban sahib abed al-nabi zoonotic disease unit post graduate lecture

Genus : Salmonella

Species In human Diseases 1. S. typhi Causes typhoid fever 2. S. para typhi causes para typhoid fever 3. S. enteritidis causes food poisoning 4. S. typhimurium In cattle & sheep 1. S. dublin Enteritis & septicaemia 2. S. typhimurium

Species in poultry & bird Species in goat Disease 1. S. typhimurium causes enteritis 2. S. enteritidis = 3. S. hadar Species in poultry & bird 1. S. pullorum causes white diarrhoea 2. S. gallinarum causes fowl typhoid 3. S. arizonae causes enteritis,septicaemia 4. S. enteritidis = 5. S. typhimurium

Salmonella as pathogens Salmonella species are facultative   intracellular pathogens .  Many infections are due to ingestion of contaminated food.  Salmonella serovars can be divided into two main groups—typhoidal and nontyphoidal Salmonella.

Nontyphoidal serovars are more common, and usually cause self-limiting gastrointestinal disease. They can infect a range of animals, and are zoonotic, meaning they can be transferred between humans and other animals.

Morphology & S taining : It is a Gram negative bacteria , cocco bacilli or straight rod with rounded ends . some times they develop into pleomorphic forms or very short coccobacilli after prolonged culture on media .

Micro scopic appearance & Incubation period : G ram stain Negative Morphology cocco bacilli or straight rod with rounded end Motility by peritrichous flagella (actively motile) except S. pullorum & S. gallinarum Capsule observed with mucoid strains Spore Non Temperature 37 c on media without any addition Time 16- 24 hours Atmosphere Aerobic & facultative an aerobic

Natural Habitat Salmonellae live in the intestinal tracts of warm and cold blooded animals. Some species are ubiquitous. Other species are specifically adapted to a particular host. In humans, Salmonella are the cause of two diseases called salmonellosis: enteric fever (typhoid), resulting from bacterial invasion of the bloodstream acute gastroenteritis, resulting from a foodborne infection . The majority of infected animals become subclinical excretors . Salmonella can survive for 9 months or more in the environment such as moist soil , water , faecal & animal feeds .

Isolation & Identification of salmonella : 1.Enrichment broth Mannitol Selenite broth & Tetera thionate broth & Soy peptone broth for salmonella isolation from stool specimen . These fluid a useful medium which allows the growth of salmonella but inhibits other enteric organisms .

1. MacConkey agar & desoxy cholate citrate agar : (DCA) The medium & colonies are pale yellow- straw smooth & non lactose Ferment . lactose fermenting Non lactose Fermenting Escherichia coli Salmonella spp Klebsiella pneumoniae Shigella proteus

2. Salmonella- Shigella agar (ss agar) : Its selective for salmonella . Colonies are colorless with black center . Non lactose ferment .

3. Xylose lysine desoxy cholate (XLD) : Red colonies with black centers of H2S producing . Non lactose ferment .

Red colonies & medium . Non lactose ferment . 4. Brilliant green agar : Red colonies & medium . Non lactose ferment . Smooth circular entire edges .

Colonies are black surrounding by metallic sheen on the surface. 5. Bismuth sulfite agar : Is highly selective for salmonella & one of the most sensitive media to detect H2S production. Colonies are black surrounding by metallic sheen on the surface.

6. Hektoen enteric agar (HE) : Colonies are blue-Green with black due to H2S production. Non lactose ferment .

Biochemicals test : salmonella don’t ferment lactose, sucrose but ferment glucose, maltose , mannitol . positive Negative

TSI/ p/y +H2S simmon citrate + Motility test/ motil +H2S

MR/ positive VP/ Negative Negative urease test -