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

International Journal of Research and Innovation in Applied Science (IJRIAS) | Volume VI, Issue V, May 2021|ISSN 2454-6194

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

Moro, D.D. Ph.D¹, Akinsinde, K.A. Ph.D^2
1Department of Microbiology, Lagos State University, P.M. B. 0001, Ojo, Lagos, Nigeria
²Genetics Division, Nigeria Institute of Medical Research, Yaba, Lagos, Nigeria

ABSTRACT
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 37⁰C 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 42⁰C for 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 1.4 Kbp 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.

Keywords: Genomic DNA, PCR, Molecular diagnosis, Salmonellae, Salmonella typhi, Oligonucleotides

I.INTRODUCTION

Typhoid fever (enteric fever) is a major public health problem in the developing countries of the world with an annual incidence of 540 per 100 [1, 2]. Salmonella typhi is the etiology of typhoid fever with an estimated 21.7 million illnesses with greater than 600,000 [3]. Typhoid fever is a systemic disease caused by S. typhi and is a major cause of morbidity and mortality worldwide, which emerged as a major important infection in the early 19th century [4]. Humans are the only natural host and reservoir for fever agent, with the infection occurring in all age groups. It is transmitted by ingestion of food or water contaminated with feces [2].In Nigeria, typhoid fever is not only endemic but constitute a great socio-medical problem, being responsible for many cases of pyrexia of unknown origin, high morbidity and mortality [3]. Nigeria falls within the region of estimated high incidence of typhoid fever in the sub-Saharan Africa and the causative

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