First phenotypic and molecular characterization of clinical isolates of drug resistant Providencia rettgeri in Imo state, South-Eastern Nigeria.

Background: Nosocomial outbreak of drug resistant Enterobacteriaceae including those mediated by Providencia species has become a serious public health challenge across the globe – owing to the difficulty in selecting antibiotics for proper treatment especially in the face of resistance. The morbidity and mortality rate of bacteremia due to Providencia species could be high, especially among the elderly and those with pre-existing medical conditions. This study was aimed at determining the occurrence of multidrug resistance phenotypes in clinical isolates of Providencia rettgeri using both phenotypic and genotypic techniques. Methods: Clinical isolates were identified to be isolates of P. rettgeri using standard microbiological and biochemical techniques; and these were characterized with respect to antibiotic resistant patterns. Overall, 143 clinical isolates of non-duplicate P. rettgeri isolates were bacteriologically recovered from the clinical specimens which included blood/wound swab samples (n=108) and swabs from surgical instruments and suction devices (n=35). Antimicrobial susceptibility test (AST) was done using the modified Kirby-Bauer disk diffusion techniques as per the Clinical Laboratory Standard Institute (CLSI) criteria. The isolates were tested phenotypically for ESBL production by the double disk synergy test (DDST) method and the β-lactamase genes were identified using polymerase chain reaction. The strains were sequenced with ABI3500XL analyzer with a 50 cm array, using POP7. Sequences data generated were analyzed with Geneious version 9. 0. 5. Results: The result of AST showed that Providencia rettgeri isolates were resistant to ceftazidime, cefotaxime, ampicillin and tetracycline. Based on the DDST method, some of the Providencia rettgeri isolates were phenotypically confirmed to be ESBL positive (11%) and MBL positive (6%). The results of the molecular analysis showed that the P. rettgeri isolates harbored SHV genes (n=6; 12. 5%) which mediates ESBL production. However, none of the isolates harboured the CTX-M or TEM gene. Conclusion: Our study shows that the P. rettgeri isolates analyzed were multidrug resistant, and they also harbour some important phenotypes and/or genotypes that mediate the production of ESBL (extended spectrum beta-lactamase). This is the first report of ESBL detection in clinical isolates of P. rettgeri in Imo state, southeast Nigeria.