Prevalence of Virulence and Antimicrobial Resistance Genes in Salmonella enterica Isolated from Humans and Poultry-associated Sources in Plateau State, Nigeria

Abstract

Salmonella is a zoonotic pathogen whose virulence factors play important roles in pathogenesis. Antimicrobial resistance poses a threat to the effective prevention and treatment of bacterial infections. The aim of this study was to determine the prevalence of virulence and antimicrobial resistance genes in Salmonella isolated from humans and poultry-associated sources. Of the 1,239 samples tested, 242 (19.5%) were positive for Salmonella using Microbact 24E and VITEK 2 COMPACT systems. Antimicrobial susceptibility testing was performed on 200 Salmonella isolates purposively selected from the 242 confirmed isolates to ensure representation of isolates from the different sample types and study locations. All isolates (100%) were resistant to erythromycin, nalidixic acid and oxacillin. Additionally, high resistance was observed to ciprofloxacin (96%), cefotaxime (86%), ceftazidime (52%), and streptomycin (68%). However, the isolates showed high susceptibility to gentamicin (74%), meropenem (72%), ampicillin (51%), and amoxicillin-clavulanic acid (70%). Fourteen selected Salmonella isolates were subjected to PCR for three virulence genes (invA, spiC and pipD) and five antimicrobial resistance genes (aadA2, blaCTX-M, gyrA, tetA and mphA). The aadA2, blaCTX-M, and invA genes were detected in all the isolates (100%), while gyrA, mphA, pipD, spiC and tetA were detected in 71.4%, 7.1%, 85.7%, 14.3% and 92.8% of isolates, respectively. The study revealed that Salmonella enterica carrying antimicrobial resistance and virulence genes was recovered from humans and poultry-associated sources. Prudent antimicrobial use is therefore essential to limit the emergence and spread of multidrug-resistant Salmonella in poultry production systems.