Nested PCR based diagnosis of Salmonella enterica serovar Paratyphi A directly from blood samples

Objective: Development of a rapid, reliable PCR - based method for molecular identification of Salmonella enterica serovar Paratyphi A directly from blood samples. Methodology: S. Paratyphi A isolates were used for regular PCR targeting specific region of fliC-a gene. New primers were designed and conditions were optimized for a nested PCR that could be directly applicable on blood samples. The procedure was tested on 70 blood samples from suspected cases of typhoidal infection and comparison made with blood culture. Results: Blood culture was able to diagnose only four patients as infected with S. Paratyphi A. Regular PCR was unable to detect S. Paratyphi A directly from blood where as nested PCR detected S. Paratyphi A in blood of thirteen patients. Conclusions: S. Paratyphi A, which is emerging as a major pathogen can be detected with better sensitivity by nested PCR as compared with blood culture.