Short communication: Bovine mastitis caused by a multidrug-resistant, mcr-1-positive (colistin-resistant), extended-spectrum β-lactamase–producing Escherichia coli clone on a Greek dairy farm

• Published in: Journal of dairy science 2020-01, Vol.103 (1), p.852-857
• Main Authors: Filioussis, George, Kachrimanidou, Melina, Christodoulopoulos, Georgios, Kyritsi, Maria, Hadjichristodoulou, Christos, Adamopoulou, Maria, Tzivara, Athanasia, Kritas, Spyridon K., Grinberg, Alex
• Format: Article
• Language: English
• Subjects: Animals; Anti-Bacterial Agents - pharmacology; antimicrobial resistance; beta-Lactamases - biosynthesis; beta-Lactamases - genetics; bovine mastitis; Cattle; Cephalosporins - pharmacology; Colistin - pharmacology; colistin resistance; Dairying; Drug Resistance, Bacterial; Escherichia coli; Escherichia coli - drug effects; Escherichia coli - enzymology; Escherichia coli - genetics; Escherichia coli - isolation & purification; Escherichia coli Infections - microbiology; Escherichia coli Infections - veterinary; Escherichia coli Proteins - biosynthesis; extended-spectrum β-lactamase (ESBL); Farms; Female; Greece; Mastitis, Bovine - microbiology; mcr-1; Microbial Sensitivity Tests; Milk; Multilocus Sequence Typing
• ISSN: 0022-0302; 1525-3198
• DOI: 10.3168/jds.2019-17320

We performed a survey aimed at analyzing milk samples collected from cows with mastitis for the presence of extended-spectrum β-lactamase (ESBL)–producing Escherichia coli. Single-quarter mastitic milk samples obtained from 400 cows in 23 Greek dairy herds with a history of E. coli mastitis were processed for the selective isolation of ESBL-producing E. coli. The antimicrobial susceptibility of the ESBL-producing isolates was analyzed using agar disk diffusion, and minimum inhibitory concentrations of colistin were determined by broth microdilution. We used PCR followed by DNA sequencing to characterize the β-lactamases and mcr-1 (colistin resistance) genes, and for phylotyping and multilocus sequence typing. We found a total of 89/400 (22.25%) E. coli isolates from 12/23 (52%) farms. Six isolates originating from 6 cows on a single farm were ESBL producers and were resistant to cefquinome, amoxicillin–clavulanic acid, aztreonam, ampicillin, and colistin. Five of these isolates were resistant to trimethoprim-sulfamethoxazole, and 5 to streptomycin. The 6 ESBL producers were mcr-1-positive and carried blaTEM-1 genes; 3 also carried blaCTX-M genes, and 3 carried blaSHV genes. All of the ESBL producers belonged to phylogroup A, multilocus sequence type ST666 (n = 5), or a single locus variant of ST666 (n = 1). To our knowledge, this is the first report of endemic bovine mastitis caused by mcr-1-positive, ESBL-producing E. coli. These results highlight the value of active surveillance of antimicrobial resistance not commonly tested by diagnostic laboratories for the early detection of novel resistant strains.