Studies on non-typhoidal Salmonella isolates obtained from indigenous and exotic layers of an organized poultry farm
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Date
2019-07
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
The present study was undertaken to assess the prevalence, virulence characteristics and antimicrobial resistance at phenotypic and genotypic level of non-typhoidal Salmonella isolated from layer flocks of indigenous (Uttara fowl and Kadaknath) and exotic (RIR, White Leghorn and Australorp) breeds of an organized farm at Pantnagar. A total of 470 samples were collected from 5 layer breeds, Uttara fowl (n=220), Kadaknath (n=55), RIR (n=91), White Leghorn (n=55) and Australorp (n=49). The samples (n=470) comprised of poultry faeces (n=90), litter (n=75), feed (n=70), water (n=65), eggs (n=120) [egg surface (60) + egg content (60)] and caecal content (n=50) of dead birds.The overall prevalence of non-typhoidal Salmonella was 4.89% (23/470). Higher prevalence was observed in exotic breeds (8.21%, 16/195) than indigenous breeds (2.55%, 7/275). Among the different breeds, RIR showed the higher occurrence (17.58%, 16/91), followed by Uttara fowl (2.73%, 6/220) and Kadaknath (1.82%, 1/55). White Leghorn and Australorp did not reveal any presence of Salmonella. Of the total samples (n=470), the highest prevalence was observed in water samples (7/65, 10.77%), followed by poultry faeces (6/90, 6.67%), caecal content (3/50; 6.0%), litter (4/75, 5.33%), feed (2/70, 2.86%) and egg samples (1/120, 0.83%). Only one sample of egg surface rinse was positive (1/60, 1.67%) and none of the egg content samples (n=60) showed positive result. Serotyping revealed the presence of a single serovar viz. Salmonella Typhimurium (91.3%, 21/23), while two isolates (8.7%, 2/23) remained untypable. All 23 isolates were screened for the presence of 8 virulence genes by PCR. Majority of the isolates (22) carried sipA (95.65%) followed by sopB 17 (73.91%), sopE1 14 (60.87%), stn 13 (56.52%), fliC 11 (47.83%) and mgtC 7 (30.43%), spvC and gipA 3 each (13.04%). All 23 isolates when tested against 13 antimicrobials, showed highest resistance for Erythromycin 23 (100%) followed by Ampicillin 15 (65.22%), Nalidixic Acid 13 (56.52%), Ciprofloxacin 12 (52.17%), Cefazolin 9 (39.13%), Cefotaxime 8 (34.78%), Sulfisoxazole 7 (30.43%), Enrofloxacin 6 (26.09), Gatifloxacin 5 (21.74%), Cefoxitin and Tetracycline 4 each (17.39%), Levofloxacin 3 (13.04%) and Streptomycin 2 (8.70%). Phenotypic co-resistance against Ciprofloxacin and Cefotaxime was identified in 5 (5/23, 21.74%) isolates. Eighteen out of twenty-three isolates (78.26%) were multidrug resistant (MDR). Sixteen different antimicrobial resistance patterns were observed. Of these, common resistance patterns were CZ CTX E AMP, NA CIP LE GAT EX E AMP SF, S E, NA CIP CTX E AMP TE SF, E AMP, NA CIP CZ CX CTX E AMP and NA CIP CZ CX E AMP (all 2/23, 8.7%). The multiple antibiotic resistance (MAR) index was found in a range of 0.15-0.69. All phenotypically resistant (including intermediate) isolates were screened for 16 corresponding antimicrobial resistance genes. The most commonly occurring resistant gene was gyrA (23/23, 100%) followed by parC (22/23, 95.65%), aadA1 (2/4, 50%), sul1 (3/7, 42.86%), blaTEM (5/23, 21.74%) and qnrS (1/23, 4.35%) while blaPSE, blaCMY, aadA2, strA, strB, sul2, tetA, tetB, tetG and qnrA were not found in any of the isolates. None of the isolates exhibited Class1 integrons. Overall, our study detected low occurrence of NTS from the layer flocks of an organized farm. Co-resistance to clinically important antimicrobials, ciprofloxacin and cefotaxime observed in this study is a matter of concern that necessitates only deliberate use of antimicrobials in the poultry farms in the country.
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