Evidence of Salmonella enterica in Pakistani backyard poultry breeds: isolation, molecular characterization and pathology

The present study evaluated the presence of Salmonella enterica in Pakistani backyard poultry. A total 48 chickens from 4 backyard poultry breeds with the clinical presentation of S. enterica infection were randomly selected from villages in the Punjab Province. Cloacal swabs from live poultry and liver samples from the dead birds were collected for bacterial culture and biochemical identification. Liver and spleen samples from dead birds were evaluated for gross and histopathological changes. Bacterial isolates were subjected to PCR and sequencing of ratA gene. Biochemical identification revealed 5/48 (10.42%) chickens positive for S. enterica. Gross pathology included enlarged, discoloured and congested liver and congested spleen. Histopathology demonstrated congestion of sinusoidal capillaries, cellular swelling and cellular / ballooning degeneration, congestion of central hepatic vein, granular hepatocytic cytoplasm and the presence of variable-sized vacuoles in hepatocytes. The PCR yielded a S. enterica specific amplicon (1047 bp). All liver samples that were positive for S. enterica by biochemical tests, were also positive by PCR. The ratA gene sequencing revealed a close resemblance with S. enteritidis isolates from humans. The present study highlights zoonotic risk from backyard poultry and suggests that PCR can be used as an alternate method for rapid detection of Salmonella serovars.