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Typhoid/ Enteric fever. Dr. Jyotsna Agarwal Professor, Dept. Microbiology KGMU. Salmonella. Salmonella is Gram-negative, rod-shaped Facultative anaerobe in family Enterobacteriaceae Motile, Non lactose fermenting Over 2400 serotypes. Faeco-oral transmission
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Typhoid/ Enteric fever Dr. Jyotsna Agarwal Professor, Dept. Microbiology KGMU
Salmonella • Salmonella is Gram-negative, rod-shaped • Facultative anaerobe in family Enterobacteriaceae • Motile, Non lactose fermenting • Over 2400 serotypes
Faeco-oral transmission • Refrigeration does not kill bacteria, Heat at 600C destroys
Pathogenesis • Bacteria penetrates intestinal cell in ileocaecal region • Inflammatory response to bacterial multiplication in the cell • Prostaglandins secreted • Increase in C-AMP
Virtually non existent in developed world • In developing countries endemic • Typhoid more common than paratyphoid
Pathogenesis of Enteric fever • M cells on Peyers patches • Invade intestinal lining cells • bloodstream (primary bacteremia) • Phagocytosis • Transported (R E system), continue to replicate
Pathogenesis contd… • Second week:re-enter bloodstream (secondary bacteremia) endotoxemia • Second to third week: gallbladder, secreted in bile,re-infect intestinal tract
Complications: Intestinal haemorrhage, perforation, cholecystitis • Less commonly: Bronchopneumonia, arthritis, osteomyelitis
Diagnosis of Typhoid Fever • Clinical: • For Lab diagnosis, specimen & diagnostic tests according to duration of fever: • Blood for Culture • WIDAL • Stool culture • Urine culture
Blood Culture • In blood culture bottle • Repeated cultures may be required • Subculture on MacConkey medium (NLF colony) • Clot culture- put clot in blood culture bottle, lyse it with streptokinase in B/C bottle • Use serum for WIDAL
Selective media for subculture from blood culture bottle: MacConkey, Wilson Blair, Tellurite blood agar • Enrichment broth for culture of stool/urine: Selenite F broth, Tetrathionate broth
Serological test- WIDAL • For detecting antibody • Agglutination test • Endemic titre • Paired sera • For carriers - antibody against Vi antigen • Rapid test- Typhi dot
Salmonella vaccines • TAB: Salmonella typhi, paratyphi A &B, killed whole cell • Oral Ty21-A: Live attenuated, Salmonella typhi vaccine • Vicapsular polysaccharide vaccine
Summary- Enteric fever • S. typhi / S. paratyphi • Mode of spread /Pathogenesis • Clinical features / Complications • Laboratory diagnosis • Treatment/vaccines