Prevalence, Antibiotic Resistance, Virulence, And Genetic Diversity Of Salmonella Serovars And Listeria Species Isolated From Vegetables, Chicken And Processing Environment In The Wet Markets Of Peninsular Malaysia
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Date
2018-08
Authors
Mustapha Goni Abatcha
Journal Title
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Publisher
Universiti Sains Malaysia
Abstract
Salmonellosis and listeriosis represent important foodborne diseases that continue to pose a major problem to the economic and health sectors, worldwide. The transmission of these two foodborne diseases is thought to be via the consumption of contaminated vegetables or undercooked poultry meat and their products. The aims of this study were to determine the prevalence, antibiotic resistance and genetic relatedness of Salmonella serovars and Listeria spp. isolated from vegetables, chicken and related processing environments. From April 2015 to May 2016, a total of 642 samples, which include 405 vegetables, 35 chicken carcasses and 202 processing environments were collected from wet markets in the Northern and Central region of Peninsular Malaysia. Culture-based and molecular methods were used for the isolation and confirmation of Salmonella and Listeria spp. The isolates were characterised by antibiogram, virulence genes using PCR, repetitive element palindromic PCR (Rep-PCR), random amplified polymorphic DNA (RAPD) and pulsed-field gel electrophoresis (PFGE) techniques. Salmonella spp. were isolated from 87/405 (21.5%) vegetable samples and 100/237 (42.1%) from the chicken carcasses and their processing environments, whereas Listeria spp. were isolated from 84/405 (20.7%) vegetables and 40/237 (16.8%) chicken processing environments, respectively. S. Corvallis, S. Brancaster, S. Albany, L. monocytogenes, L. innocua and L. seeligeri were among the predominantly isolated serovars and species of Salmonella and Listeria. The L. monocytogenes isolates were serotyped into “4b, 4d, 4e”, “1/2a,3a”,and “1/2c, 3c” which are the common serogroups known to cause foodborne outbreak. In addition, Salmonella isolates showed high resistance to streptomycin (66.6%), followed by tetracycline (44.4%) and sulphonamide (44.4%) whereas Listeria isolates were highly resistant to nalidixic acid (95.1%) and clindamycin (84.6%). Resistance determinant genes including sulI, sulII, floR, cmlA strA, strB, aadA, blaTEM-1, temB, tetA and tetB were detected among the resistant Salmonella isolates. Seventeen isolates harboured class 1 integrons with the role in the distribution and spread of antimicrobial agents. The arrays of gene cassettes identified were dfrA1, dfrA12, aadA2, blaPSE−1 and dfrA12-orf-aadA2 with an open reading frame orfC with unknown function. Important virulence determinant genes involving tolC, orgA, spaN, prgH, sipB and invA were expressed by all Salmonella isolates, whereas inlA, inlC and inlJ were harboured by L. monocytogenes, respectively. Results from Rep-PCR, RAPD and PFGE characterisation showed that Salmonella serovars and L. monocytogenes isolates from vegetables, chicken and their processing environments was heterogeneous and genetically diverse. These findings have highlighted the need for proper sanitation and hygiene standards in the wet markets so as to minimize the rate of Salmonella and Listeria. The increase in drugs resistance and virulence among Salmonella and Listeria recovered from raw vegetables and poultry is an emerging problem which can affect human through consumption of food products and thereby, causing illnesses.