Multi-Drug Resistant and Plasmid-Mediated Quinolone-Resistant Salmonella enterica isolated from Shellfish in Iko Creek, Nigeria

Abstract

Aim: This study investigated the occurrence of multi-drug resistant (MDR) and Plasmid-Mediated Quinolone Resistant (PMQR) genes in Salmonella enterica isolated from shellfish in Iko Creek, Nigeria. Study Design: This is an experimental research that studied Salmonella enterica isolated from shellfish to determine its association with MDR and PMQR using standard microbiological and molecular methods. Place and Duration of Study: The study was carried within Iko Creek, South-South Nigeria for a period of one year (March-July and August to February 2017). Methodology: A total of 160 shellfish samples (80 clams and 80 oysters) were analyzed for the presence of Salmonella enterica using standard bacteriological methods. In all, 22(52.4%) were positive for clams while 20(47.6%) for oysters. The bacterium was identified using phenotypic methods. The antibiotics used for the antibiotic susceptibility profiles were amoxicillin, quinolones, aminoglycosides, macrolide and sulfonamide. Confirmation of the isolates was done by DNA sequencing of 16S rRNA gene; results obtained were then compared with that in the gene bank. The isolate was identified as Salmonella enterica. Results: The mean heterotrophic bacterial counts (THBC) in clams ranged from 5.25 x 106 to 3.71 x 107 (Cfu/g) in the dry season and 3.05 x 106 to 2.33 x106 (Cfu/g) in the rainy season. The mean THB counts in oyster was 3.27 x 108 to 1.59 x 108(Cfu/g) in the dry season and 2.54 x 107 to 4.39 x 106 (Cfu/g) in the rainy season. Salmonella enterica showed resistance to all the antibiotics tested except gentamicin. Seventy-one (71) percent of the isolates in this study expressed the qnrB genes. Conclusion: The presence of qnr B genes and multi-drug resistance (MDR) in the isolate’s gene according to this study is an indicator of treatment failure with antibiotics.