Veterinary World (Jun 2014)

Pattern of antibiotic resistant mastitis in dairy cows

  • D. Chandrasekaran,
  • P. Venkatesan,
  • K. G. Tirumurugaan,
  • A. P. Nambi,
  • P. S. Thirunavukkarasu,
  • K. Kumanan,
  • S. Vairamuthu,
  • S. Ramesh

DOI
https://doi.org/10.14202/vetworld.2014.389-394
Journal volume & issue
Vol. 7, no. 6
pp. 389 – 394

Abstract

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Aim: To study the prevalence of drug resistant mastitis and their pattern of antibiotic resistance in dairy cows from Tamil Nadu. Materials and Methods: Isolation and identification of resistant pathogens were performed from acute clinical mastitis samples. Based on culture, isolation and sensitivity tests, cows with resistant mastitis were grouped as; Group I: Escherichia coli (n=119), Group II: Staphylococcus aureus (n=104) and Group III: Methicillin-resistant Staphylococcal aureus (MRSA) (n=12). The isolates were tested using agar disc diffusion method for their antimicrobial susceptibility and modified resazurin assay microdilution technique for minimum inhibitory concentration (MIC) to 8 antimicrobial drugs. The organisms were also confirmed for their identity by performing PCR on the bacterial pellet targeting the specific genes such as 16s-23s rRNA, mecA and blaZ respectively for the resistant pathogens and also confirmed by sequencing. Results: Antibiotic resistant mastitis was detected in 235 out of 401 cows accounting to 56.1%. The predominant resistant causative pathogen was E. coli (50.64%) followed by S. aureus (44.25%) and MRSA (5.11%). In vitro antibiotic sensitivity test and MIC breakpoints, E. coli, S. aureus and MRSA organisms showed more sensitivity to enrofloxacin, amoxicillin + sulbactam, gentamicin and ceftriaxone and had highest resistant to penicillin followed by amoxicillin, oxytetracycline and methicillin. E. coli and S. aureus isolates were found to be resistant to 1 or 2 antimicrobials, whereas most of the MRSA isolates were found to be multi-drug resistant i.e resistance to 3 or more of antimicrobials. Out of 235 milk samples, the specific target gene 16s-23s rRNA (E. coli ), 16s-23s rRNA (S. aureus) and MRSA (mecA and blaZ) could be amplified from 119, 104 and 12 isolates with a percentage positivity of 50.64 (119/235), 89.64 (104/116) and 10.34 (12/116) respectively. Conclusion: Prevalence of antimicrobial resistance (AMR) in bovine mastitis pathogens was high. Most MRSA pathogens were multidrug resistant. E. coli and S. aureus isolates were resistant to few antimicrobials.

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