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Prevalence of virulence and antimicrobial resistance genes in <i>Salmonella</i> spp. isolated from commercial chickens and human clinical isolates from South Africa and Brazil

By Oliver T. Zishiri, Nelisiwe Mkhize and Samson Mukaratirwa


<p>Salmonellosis is a significant public health concern around the world. The injudicious use of antimicrobial agents in poultry production for treatment, growth promotion and prophylaxis has resulted in the emergence of drug resistant strains of <em>Salmonella</em>. The current study was conducted to investigate the prevalence of virulence and antimicrobial resistance genes from <em>Salmonella</em> isolated from South African and Brazilian broiler chickens as well as human clinical isolates. Out of a total of 200 chicken samples that were collected from South Africa 102 (51%) tested positive for <em>Salmonella </em>using the <em>InvA</em> gene. Of the overall 146 <em>Salmonella</em> positive samples that were screened for the <em>iroB</em> gene most of them were confirmed to be <em>Salmonella</em> <em>enterica</em> with the following prevalence rates: 85% of human clinical samples, 68.6% of South African chicken isolates and 70.8% of Brazilian chicken samples. All <em>Salmonella</em> isolates obtained were subjected to antimicrobial susceptibility testing with 10 antibiotics. <em>Salmonella</em> isolates from South African chickens exhibited resistance to almost all antimicrobial agents used, such as tetracycline (93%), trimethoprim-sulfamthoxazole (84%), trimethoprim (78.4%), kanamycin (74%), gentamicin (48%), ampicillin (47%), amoxicillin (31%), chloramphenicol (31%), erythromycin (18%) and streptomycin (12%). All samples were further subjected to PCR in order to screen some common antimicrobial and virulence genes of interest namely <em>spiC, pipD, misL, orfL, </em><em>pse-1</em><em>, tet A, tet B, </em><em>ant (3")-la</em><em>, sul 1</em> and <em>sul. </em>All <em>Salmonella</em> positive isolates exhibited resistance to at least one antimicrobial agent; however, antimicrobial resistance patterns demonstrated that multiple drug resistance was prevalent. The findings provide evidence that broiler chickens are colonised by pathogenic <em>Salmonella</em> harbouring antimicrobial resistance genes. Therefore, it is evident that there is a need for prudent use of antimicrobial agents in poultry production systems in order to mitigate the proliferation of multiple drug resistance across species.</p><p><strong>Keywords: </strong>Salmonella; antimicrobial resistance; chicken; human; susceptibility; virulence gene</p

Topics: Salmonella, antimicrobial resistance, chicken, human, susceptibility, virulence gene, Veterinary medicine, SF600-1100
Publisher: AOSIS
Year: 2016
DOI identifier: 10.4102/ojvr.v83i1.1067
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