Molecular typing of clinical and non-clinical Escherichia coli from Rivers State, Nigeria using amplification-based RAPD and ERIC-PCR typing methods

Due to the diverse nature of Escherichia coli, typing of these organisms is essential. This can provide key epidemiological information not just on the strains in circulation and their relationship, but also on the development and spread of drug resistant clones. Affordable PCR-based typing techniques have resulted in an increase in typing studies particularly in resource limited settings. But information from Nigeria on strain typing is limited. This study was therefore aimed at typing clinical and non-clinical strains of E. coli from Nigeria using the PCR based Random Amplification of Polymorphic DNA (RAPD) and Enterobacterial Repetitive Intergenic Consensus-PCR (ERIC-PCR) typing methods. E. coli was isolated from clinical and non-clinical sources using Eosin Methylene Blue agar. Characteristic green metallic sheen colonies associated with E. coli were purified, identities determined using standard biochemical tests and confirmed using molecular methods. Susceptibility testing was carried out using the modified Kirby-Bauer disc diffusion test and RAPD and ERIC-PCR typing carried out on 48 confirmed E. coli isolates as previously described. ERIC-PCR typing resulted in the generation of 38 unique patterns with a 0.94 diversity. Nine of these were singletons comprised of only a single isolate, while the remaining 29 patterns were grouped to 10 clusters. RAPD gave similar results of 37 patterns, 9 singletons, 0.94 diversity and 13 clusters. For ERIC-PCR, all isolates with identical patterns were from the same source. RAPD, however, had identical patterns present in isolates from different sources. Using the ERIC-PCR typing method, this study was able to identify non-clinical isolates as distinct from the clinical E. coli isolates as evidenced by 100% identical ERIC-PCR profiles of isolates from the same source and a lack of 100% relatedness in isolates from different sources.