Polymerase chain reaction (PCR) analysis of Salmonella typhi from patients in Lagos, Nigeria

The polymerase chain reaction (PCR), is a very sensitive and specific molecular method, in the identification of microorganism. Definitive diagnosis of bacterial pathogens is a major healthcare challenge in developing countries including Nigeria. PCR profiles of Salmonella typhi in Lagos, Nigeria is presented in this study. Bacteriological analysis of stool samples from patient diagnosed clinically for typhoid fever was carried using selective media such as Selenite F (SF), buffered peptone water (BPW) and trypticase soy agar (TSA) which were incubated at 37⠰C for 18-24 h. After incubation 0.1 ml of sample from each enrichment medium was inoculated into 10 ml of Rappaport Vassiliadis R10 broth which was incubated at 42⠰Cfor 24 h. One loopful of the RV10 broth was inoculated into selective media:;MacConkey agar (MA), xylose lysine deoxycholate agar (XLD), Salmonella- Shigella agar (SSA) and brilliant green deoxycholate agar (BGDA). Suspected colonies were identified biochemically and kept on nutrient agar slants at 4°C for further analysis. All the S. typhi isolates produced reproducible and distinguishable profiles from samples and were amplified and analyzed by gel electrophoresis. The chromosomal DNAs had molecular weight that ranged between 0.52kbp to 2.9Kbp. Fifty-six(83.3%) of the S. typhi harbored both 0.9kbp and 1.4Kbp molecular weight, 50 (83.3%) had 2.8Kbp, 42 (70%) had 1.8Kbp molecular weight while the isolate with the least molecular weight DNA were 20,(33.3%). All the isolates belong to five distinctive clones. PCR with RAPD was very discriminatory as isolates classified together by other methods were classified into fewer clones.