Antibiotic resistance profile of Salmonella enterica isolated from exotic and indigenous leafy green vegetables in Accra, Ghana.

Abstract

Fresh produce-borne enteric bacterial pathogens with resistance to antibiotics have posed serious challenges to food safety and public health worldwide.\xa0 This study examined the antibiotic resistance profile of Salmonella enterica (n=33), previously isolated from exotic and indigenous leafy green vegetable samples (n=328) collected from 50 vegetable farms in 12 farming areas and 37 vegetable sellers in 4 market centers in Accra, Ghana during the period of March 2016 to March 2017, and determined the distribution of integrons among antibiotic-resistant isolates. \xa0The susceptibility of the Salmonella isolates to 12 antibiotics was assayed using the standard disc diffusion assay. \xa0The minimum inhibitory concentrations (MICs) of the five most resisted antibiotics were determined using the twofold macro dilution method. \xa0PCR assay was used to detect the presence of integrons in Salmonella cells, and PCR product with amplified integron gene cassette was purified and sequenced using the Sanger sequencing technology.\xa0 The Salmonella isolates used in the study resisted at least one tested antibiotic, and multi-drug resistant (MDR) isolates were 30.3% (10/33). \xa0Most isolates (81.8%) were resistant to sulfisoxazole. \xa0The MICs of tetracycline, cefoxitin, streptomycin, ampicillin, and sulfisoxazole were 16, 32, 64, 64, and > 1,024 µg/ml, respectively. \xa0A total of five different patterns of MDR were observed among the Salmonella isolates, and the common MDR patterns were AAuFox (30.3%) and AAuFoxSSu (18.1%). \xa0One out of the 33 (3.0%) Salmonella isolates tested positive for class 1 integron with a gene cassette of about 800 bp. \xa0Nucleotide sequencing revealed the class 1 integron carried a single gene dfrA7 . \xa0Future studies are needed to confirm whether the consumption of contaminated leafy green vegetables is a route of acquiring antibiotic-resistant Salmonella by consumers in Accra, Ghana.