Plasmid-mediated Quinolone Resistance Genes in Salmonella typhi from Patients Attending Selected General Hospitals in Abuja Municipal, Nigeria

Abstract

This study investigated the antimicrobial resistance profile and presence of plasmid-mediated quinolone resistance (PMQR) genes in Salmonella typhi from patients attending selected general hospitals in Abuja municipal, Nigeria. Four hundred stool samples from patients with suspected typhoid fever were collected from Asokoro General Hospital Abuja (AGH), Garki Hospital Abuja (GHA), Maitama General Hospital Abuja (MGHA) and Wuse General Hospital Abuja (WGHA) and S. typhi was isolated and identified using standard microbiological methods. Antimicrobial susceptibility testing of the isolates was carried out using Clinical and Laboratory Standards Institute (CLSI) method. Molecular detection of PMQR genes in the ciprofloxacin-resistant isolates was carried out using Polymerase Chain Reaction (PCR) method. The overall occurrence of the isolates was 13.3% (53/400), with the highest hospital-related occurrence at WGHA (18.0%). The occurrence was highest at age 21-30yrs in AGHA (20.0%), GHA (33.3%) and WGHA (45.0%). The occurrence was higher in females at AGHA (12.7%) and GHA (16.0%); but higher in males at MGHA (11.4%) and WGHA (18.2%). Resistance to ciprofloxacin was the least at 30.2%, distributed as follows: AGHA (20.0%), GHA (35.7%), MGHA (36.4%) and WGHA (27.8%). The most common resistance phenotype was: NA-S-XT-AMC-TE-CRO-C-CN with overall occurrence of 9.4% (5/53) observed in AGH (10.0%), GHA (16.7%) and MGHA (18.2%) but not in WGHA. All (100%) isolates were multiple antibiotic resistance (MAR) isolates, with MAR indices above 0.2; and the commonest MAR index of 0.6 (30.0%) in AGHA, 0.8 (35.7%) in GHA; 0.8 (45.6%) in MGHA, and was 0.7 (38.9%) in WGHA. Multidrug resistance (MDR) was the commonest at 96.2% (51/53), with occurrences in the selected hospitals as follows: AGHA (90.0%), GHA (100.0%) and MGHA (100.0%) and WGHA (94.4%).The PMQR genes detected had overall frequency in the order: aac(6′)-Ib-cr (50.0%) >qnrB (37.5%) >qnrS (18.8%); qnrS was absent in AGHA and WGHA. The genes co-existed with one another with the qnrB+ aac(6′)-Ib-cr combination, present in isolates from all the hospitals, being the most common at (31.3%). Ciprofloxacin was the most effective antibiotic against the isolates; most isolates were MAR with prior exposure to antibiotics; most isolates were MDR and the ciprofloxacin-resistant isolatesharbored qnrS, qnrB and aac(6′)-Ib-cr PMQR genes, with aac(6′)-Ib-cr being the most prevalent.