Effect of dry cow therapy on antimicrobial resistance of mastitis pathogens post-calving

Frontiers in Veterinary Science

Veterinary Science

Deniece R. Williams¹  Wagdy R. ElAshmawy²  Terry W. Lehenbauer³  Sharif S. Aly³  Emmanuel Okello³ 

[1] Veterinary Medicine Teaching and Research Center, School of Veterinary Medicine, University of California, Davis, Tulare, CA, United States;Veterinary Medicine Teaching and Research Center, School of Veterinary Medicine, University of California, Davis, Tulare, CA, United States;Department of Internal Medicine and Infectious Diseases, Faculty of Veterinary Medicine, Cairo University, Giza, Egypt;Veterinary Medicine Teaching and Research Center, School of Veterinary Medicine, University of California, Davis, Tulare, CA, United States;Department of Population Health and Reproduction, School of Veterinary Medicine, University of California, Davis, Davis, CA, United States;

关键词: dry cow therapy;    antimicrobial resistance;    mastitis pathogens;    Staphylococcus;    Streptococcus;    coliforms;   

DOI  :  10.3389/fvets.2023.1132810

 received in 2022-12-27, accepted in 2023-06-26,  发布年份 2023

来源: Frontiers

【 摘 要 】

The aim of this study was to evaluate the effect of dry cow therapy (DCT) on the antimicrobial resistance (AMR) profile of mastitis pathogens post-calving. A repository of isolates based on a DCT trial was utilized for the current study. A stratified random survey sample of cows from the trial were identified within the strata of season, herd, and trial treatment resulting in 382 cows. All isolates from the 382 cows were selected for the current study, which identified 566 isolates from milk samples collected at dry off (S1), post-calving (S2), and at the first clinical mastitis event up to 150 days in milk (S3). The AMR profiles were determined using broth microdilution method. Less than 10% of the coagulase-negative Staphylococcus species (CNS) isolates (n = 421) were resistant to tetracycline, ceftiofur, penicillin/novobiocin or erythromycin, while higher proportions of resistance to sulfadimethoxine (72%) and penicillin (28%) were observed. All Staphylococcus aureus (S. aureus) isolates (n = 4) were susceptible to all tested AMD except sulfadimethoxine, to which all isolates were resistant. Similarly, all Streptococcus spp. (n = 37) were susceptible to penicillin, penicillin/novobiocin, and ampicillin while resistant to tetracycline (17%). All coliforms (n = 21) were susceptible to ceftiofur, but resistance was recorded for sulfadimethoxine (70%), cephalothin (56%), and tetracycline (43%). The increased resistance percent from S1 to S2 was observed in CNS isolates from AMD-treated cows, with the highest increase recorded for penicillin (12.2%). Parametric survival interval regression models were used to explore the association between antimicrobial drug (AMD) therapy at dry off and the AMR phenotype post-calving. The accelerated failure-time metric was adopted to minimum inhibitory concentration measurements to permit interpretation of model exponentiated coefficients. Models for cows with CNS isolated at both S1 and S2 showed increased resistance against cephalothin, oxacillin, and ceftiofur in cows that received DCT from the same drug class, or a class with a shared resistance mechanism. In contrast, resistance of CNS isolates to tetracycline were associated with any AMD therapy at dry off. Resistance of CNS isolates to Penicillin decreased in CNS isolates in cows that received any AMD therapy at dry off compared to those that didn't. The study provided evidence that dry-cow IMM AMD was associated with AMR post-calving.

【 授权许可】

Unknown   
Copyright © 2023 Okello, ElAshmawy, Williams, Lehenbauer and Aly.