Isolation, identification and antimicrobial susceptibility of public health significant organisms present in organic agricultural farms of Uttarakhand
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Date
2018-07
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
Studies are lacking in India regarding the presence of public health significant organisms in the environment and plant samples at organic farms. The present work was carried out on two highly significant public health organisms i.e. Salmonella and Listeria in five organic agricultural farms located at Kotabagh, Dhamola, Ramnagar and two locations of Pantnagar in Uttarakhand state, India. A total 500 samples, comprising 350 environmental samples viz; soil (n=227), manure (n= 66) and water (n=57) besides, 150 plant samples viz; rhizosphere (n=50), roots (n=50) and leaves/grains (n=50) were processed for isolation of Salmonella and Listeria. Standard protocols were used for isolation of both organisms. The morphological and biochemical characterization was attempted. Genus specific PCR targeting invA (284 bp) gene for Salmonella and prs (370 bp) gene for Listeria was used for molecular confirmation. A total of 11 Salmonella isolates were recovered with an overall prevalence of 2.2% while Listeria could not be isolated representing 0% prevalence. Amidst environmental sources maximum detection (8.7%) was observed from water. Three isolates each were isolated from manure (4.5%) and soil (1.32%).Highest prevalence was noticed at Ramnagar (6.4%) followed by Pantnagar-2 (3.7%) and Pantnagar-1(2.2%). Any isolate could not be detected from Kotabagh and Dhamola. Out of 11 Salmonella isolated, 7 belonged to Group C1; one was confirmed to be Salmonella Gabon and 3 Salmonella Miyazaki. Kirby-Bauer disc diffusion assay was performed for antibiotic sensitivity on all the 11 Salmonella isolates. Most frequent resistance was observed for cefotaxime (72.72%) followed by ciprofloxacin (45.45%), cefazolin (36.36%) and cefoxitin (27.27%). Nalidixic acid, streptomycin, sulphafurazole and tetracycline, each exhibited 18.18% resistance. Only 1 isolate showed resistance against gatifloxacin (9.09%). All the isolates showed susceptibility towards amoxicillin and levofloxacin. Salmonella isolates showing phenotypic resistance were screened for the presence of β lactamase genes (blaTEM, blaCTX-M-9 and blaAmpC) using simplex PCR. Three S. Miyazaki serotypes possessed blaCTX-M-9 gene. None of the isolates exhibited blaTEM and blaAmpC genes. The study focuses on the presence of the public health significant Salmonella and Listeria in environmental and plant samples of the organic agricultural farms which could be significant source of food contamination.
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