Unravelling the complex mechanisms of multidrug resistance in bovine mastitis pathogens: Insights into antimicrobial resistance genes, biofilm dynamics, and efflux systems

• Published in: Microbial pathogenesis 2024-10, Vol.195, p.106902, Article 106902
• Main Authors: Janus, A., Deepa, P.M., Vergis, Jess, Rajasekhar, R., Habeeb, Biju P., Bipin, K.C., Vinu David, P., Anand, LaliF, Ratish, R.L., Shyma, V.H., Vijayakumar, K.
• Format: Article
• Language: English
• Subjects: antibiotic resistance genes; biofilm; efflux pumps; Mastitis; Multidrug resistance
• ISSN: 0882-4010; 1096-1208; 1096-1208
• DOI: 10.1016/j.micpath.2024.106902

Mastitis remains a paramount economic threat to dairy livestock, with antibiotic resistance severely compromising treatment efficacy. This study provides an in-depth investigation into the multidrug resistance (MDR) mechanisms in bacterial isolates from bovine mastitis, emphasizing the roles of antimicrobial resistance genes (ARGs), biofilm formation, and active efflux systems. A total of 162 Staphylococci, eight Escherichia coli, and seven Klebsiella spp. isolates were obtained from 215 milk samples of clinical and subclinical mastitis cases. Antibiotic susceptibility testing identified Twenty Staphylococci (12.35 %), six E. coli (75 %) and seven Klebsiella (100 %) identified as MDR displaying significant resistance to β-lactams and tetracyclines The Multiple Antibiotic Resistance (MAR) index of these isolates ranged from 0.375 to 1.0, highlighting extensive resistance. Notably, 29 of the 33 MDR isolates produced biofilms on Congo red agar, while all exhibited biofilm formation in the Microtitre Plate assay. Critical ARGs (blaZ, blaTEM, blaCTX-M, tetM, tetA, tetB, tetC, strA/B, aadA) and efflux pump genes (acrB, acrE, acrF, emrB, norB) regulating active efflux were identified. This pioneering study elucidates the synergistic contribution of ARGs, biofilm production, and efflux pump activity to MDR in bovine mastitis pathogens. To our knowledge, this comprehensive study is the first of its kind, offering novel insights into the complex resistance mechanisms. The findings underscore the imperative need for advanced antibiotic stewardship and strategic interventions in dairy farming to curb the rise of antibiotic-resistant infections, thereby protecting both animal and public health. •This pioneering study elucidates the synergistic contribution of ARGs, biofilm production, and efflux pump activity to multidrug resistance (MDR) in bovine mastitis pathogens in Wayanad, Kerala, India.•Twenty Staphylococci (12.35 %), six E. coli (75 %) and seven Klebsiella(100 %) were identified as MDR displaying significant resistance to β-lactams and tetracyclines.•The Multiple Antibiotic Resistance (MAR) index of these isolates ranged from 0.375 to 1.0, highlighting extensive resistance.•Twenty nine isolates showed biofilm production in Congo red agar whereas all the 33 isolates produced biofilm in Microtitre Plate assay.•Antibiotic resistance genes (bla Z, bla TEM, bla CTX-M, tet M, tet A, tet B, tet C) and the efflux pump genes (acr B, acr E, acr F, emr B and norB) regulat