Prevalence and Genetic Basis of Antimicrobial Resistance in Non-aureus Staphylococci Isolated from Canadian Dairy Herds

Abstract

Emergence and spread of antimicrobial resistance is a major concern for the dairy industry worldwide. Objectives were to determine: (1) phenotypic and genotypic prevalence of drug-specific resistance for 25 species of non-aureus staphylococci, and (2) associations between presence of resistance determinants and antimicrobial resistance. Broth micro-dilution was used to determine resistance profiles for 1,702 isolates from 89 dairy herds. Additionally, 405 isolates were sequenced to screen for resistance determinants. Antimicrobial resistance was clearly species-dependent. Resistance to quinupristin/dalfopristin was common in Staphylococcus gallinarum (prevalence of 98%), whereas S. cohnii and S. arlettae were frequently resistant to erythromycin (prevalence of 63 and 100%, respectively). Prevalence of resistance was 10% against β-lactams and tetracyclines. In contrast, resistance to antimicrobials critically important for human medicine, namely vancomycin, fluoroquinolones, linezolid and daptomycin, was uncommon (< 1%). Genes encoding multidrug-resistance efflux pumps and resistance-associated residues in deducted amino acid sequences of the folP gene were the most frequent mechanisms of resistance, regardless of species. The estimated prevalence of the mecA gene was 17% for S. epidermidis. Several genes, including blaZ, mecA, fexA, erm, mphC, msrA, and tet were associated with drug-specific resistance, whereas other elements were not. There were specific residues in gyrB for all isolates of species intrinsically resistant to novobiocin. This study provided consensus protein sequences of key elements previously associated with resistance for 25 species of non-aureus staphylococci from dairy cattle. These results will be important for evaluating effects of interventions in antimicrobial use in Canadian dairy herds.

Genomic Analysis of Bovine Staphylococcus aureus Isolates from Milk To Elucidate Diversity and Determine the Distributions of Antimicrobial and Virulence Genes and Their Association with Mastitis

“…Identifying ARGs is critical to recognize and assess the pathogenic potential of S. aureus. Fewer ARGs were identified in this study than from non-aureus staphylococci (NAS) originating from the same herds (36). This corresponded with reports that S. aureus strains isolated from mastitis cases were less resistant than NAS against commonly used antimicrobials (94,95).…”

Antimicrobial resistance profiles of 5 common bovine mastitis pathogens in large Chinese dairy herds

“…aureus, resistance to daptomycin and vancomycin was only 8 and 3%, respectively, whereas 21 and 20% of NAS and 5 and 9% of Streptococcus spp. isolated from CM were resistant to daptomycin and vancomycin, respectively; this was different from other countries, for example Canada and Uganda (Saini et al, 2012;Kateete et al, 2013;Nobrega et al, 2018). Since 1989, prevalence of vancomycin-resistant infections has increased exponentially in humans.…”

Molecular epidemiology and distribution of antimicrobial resistance genes of Staphylococcus species isolated from Chinese dairy cows with clinical mastitis

“…Staphylococci can be resistant to antimicrobials, contributing to reduced efficacy of treatment with antibiotics (Barkema et al, 2006). Common antimicrobial resistance genes (ARG) detected among bovine Staphylococcus isolates included blaZ and mecA (β-lactam resistance genes); tetK, tetL, tetM, and tetO (tetracycline resistance genes); aacA-aphD, aadD, and aphA3 (aminoglycoside resistance genes); ermA, ermB, ermC, ermT, msrA, mphC, and lnuA (macrolides, lincosamides, and streptogramin B; MLS B resistance genes); dfrG and dfrK (trimethoprim resistance genes); and vanA and vanB (vancomycin resistance genes; Wendlandt et al, 2013;Nobrega et al, 2018). Furthermore, biofilm formation in Staphylococcus isolates from mastitis cases was also associated with reduced susceptibility to antimicrobials (Aslantaş and Demir, 2016).…”