Molecular characterization of non-typhoidal Salmonella serovars isolated from commercial broiler farms and retail chicken meat shops with reference to virulence and antimicrobial resistance
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Date
2019-06
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
Salmonellosis, primarily caused by Salmonella Typhimurium and S. Enteritidis, is deemed as one of the most common and most important food-borne zoonoses worldwide. The present study was undertaken to determine the prevalence, virulence genes and antimicrobial resistance of non-typhoidal Salmonella isolates obtained from commercial broiler farms and retail chicken meat shops. A total number of 556 samples were collected from five commercial broiler farms and thirty-two retail chicken meat shops situated in/around towns/cities of the Udham Singh Nagar and Nainital districts of Uttarakhand state. The samples comprised of poultry faeces (n=121), litter (n=56), drinking water (n=38) and feed (n=38) from the broiler farms (n=253), and chicken meat swabs (n=133), cutting surface/chopping board swabs (n=46), hand swabs of meat cutters/handlers (n=46), knife swabs (n=46) and meat rinsing water (n=32) from retail chicken meat shops (n=303). The overall prevalence of 5.57% (n=31) was recorded, which can be distributed as 4.35% (n=11) for the broiler farms, and 6.60% (n=21) for the chicken meat shops. The highest prevalence of Salmonella isolated from broiler farms was observed in water samples (02/38, 5.26%) and poultry faeces (06/121, 4.96%) followed by poultry litter (02/56, 3.57%) and poultry feed (01/38, 2.63%). Whereas in case of chicken meat shops, the highest prevalence of Salmonella was observed in chicken meat samples (13/133, 9.77%) followed by chopping board (03/46, 6.52), knife (02/46, 4.35%), rinsing water (01/32, 3.12%) and hand swabs of butchers (01/46, 2.17%). Geographically, the highest prevalence among broiler farms was recorded in the farm of Shantipuri (6.25%, 03/48), followed by Haldwani and Kiccha farms (5.00%, 03/60 and 02/40 respectively), followed by Kashipur farm (3.70%, 02/54) and Ramnagar farm (1.96%, 01/51). Whereas in case of chicken meat shops, a significantly higher prevalence of Salmonella was recorded from Pantnagar (8.33%, 05/60), followed by Rudrapur (7.84%, 04/51), Lalkuan (7.32%, 03/41), Haldwani (7.14%, 04/56), Kashipur (6.12%, 03/49) and Kiccha (2.17%, 1/46). Serotyping of thirty-one isolates revealed the presence of only one type of serotype viz; Salmonella Typhimurium (93.55%; 29/31), while two (6.45%; 2/31) isolates were found to be untypable (one each from poultry faeces and chicken meat). All the thirty-one isolates were screened for the presence of eight virulence genes (sipA, sopE1, fliC, mgtC, spvC, stn, sopB and gipA) by PCR. The most commonly encountered virulence gene was sipA, amplified in 100% (31) isolates, followed by mgtC 93.55% (29), sopB 87.10% (27), fliC 70.97% (22), gipA 64.52% (20), stn 64.52% (20), spvC 51.61% (16) and sopE1 16.13% (5) isolates. All 31 Salmonella isolates (100%) were multidrug resistant (MDR). Complete resistance of all the isolates was observed against Nalidixic acid and Erythromycin (100% each) followed by higher resistance against Ampicillin (87.09%), Ciprofloxacin (83.87%), Tetracycline (77.42%), Cefotaxime (74.19%), Gatifloxacin (70.97%), Cefazolin (67.74%) along with Sulphafurazole (67.74%), Streptomycin (58.06%), Levofloxacin (51.61%), Cefoxitin (38.71%) and Chloramphenicol (32.26%). Phenotypic co-resistance against Ciprofloxacin and Cefotaxime was identified in 21 (21/31, 67.74%) isolates. Three panresistant isolates, all 3 being S. Typhimurium were also identified. The most commonly expressed resistance patterns were AMP CX E LE CIP CTX GAT SF TE CZ NA S C (3/31; 22.07%), followed by AMP E LE CIP CTX GAT TE CZ NA S (2/31; 6.45%) and AMP CX E CIP CTX SF TE CZ NA S (2/31; 6.45%). All phenotypically resistant Salmonella isolates were screened for the presence of 16 corresponding antimicrobial resistance genes. Among the 28 intermediate and resistant Salmonella isolates, aadA1 gene was carried by all 28 (100%) isolates tested, while aadA2 gene was present in 11 (39.28%) isolates, strA gene in 17 (60.71%) isolates and strB gene was not detected in any of the isolates. Out of three Tetracycline resistant genes, tetA was present in 60% (15/25) isolates, whereas none of the isolates carried tetB and tetG genes. Sulphafurazole resistance encoding sul1 was harbored by 79.17% (19/24) isolates tested, while sul2 gene was not amplified in any of the isolates. Amongst the _-lactam resistance genes, blaTEM gene was detected in 100% (27/27) of the isolates, while blaPSE and blaCMY were found to be absent in all the isolates. Amid the fluoroquinolone resistance genes, gyrA and parC genes were found to be present in 93.55% (29/31) and 64.52% (20/31) of the isolates respectively, whereas none of the isolate revealed the presence of qnrA or qnrS genes. In the multiplex PCR performed among all MDR isolates for the detection of mcr-1 to mcr-5 genes coding resistance for colistin, no isolate exhibited the presence of any of the five genes targeted. Overall our study detected high prevalence of multi drug-resistant Salmonella in the broiler farms and chicken meat shops. Higher resistance to ‘critically important’ (fluoroquinolones) and ‘highly important’ (cephalosporins and tetracycline) antibiotics detected in Salmonella isolates of poultry origin is a serious public health threat which stresses on the need to curb the practice of irrational use of antimicrobials in the poultry sector in India.
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