Genome analysis of methicillin resistance in Macrococcus caseolyticus from dairy cattle in England and Wales

Abstract

Species of the genus Macrococcus are widespread commensals of animals but are becoming increasingly recognised as veterinary pathogens. They can encode methicillin resistance and are implicated in its spread to the closely-related, but more pathogenic, staphylococci. In this study we have identified 33 isolates of methicillin-resistant Macrococcus caseolyticus from bovine bulk tank milk from England and Wales. These isolates were characterised to provide insight into the molecular epidemiology of M. caseolyticus and to discern the genetic basis for their methicillin resistance. Antimicrobial susceptibility testing was performed by Vitek2 and disc diffusion. Isolates were whole-genome sequenced to evaluate phylogenetic relationships and the presence of methicillin resistance determinants, mecA–D. All 33 isolates were phenotypically methicillin-resistant according to cefoxitin disc diffusion, cefoxitin Etest and oxacillin resistance assessed by Vitek2. In contrast only a single isolate was resistant in the Vitek2 cefoxitin screen. Twenty-seven isolates were positive for mecD and six were positive for mecB. mecA and mecC were not detected. The results of phylogenetic analysis indicated that these methicillin-resistant isolates represented a heterogeneous population with both mecB and mecD found in diverse isolates. Isolates had a widespread distribution across the sampled region. Taken together with the role of M. caseolyticus in veterinary infections, including bovine mastitis, and in the potential spread of methicillin resistance to more pathogenic staphylococci, this work highlights the need to better understand their epidemiology and for increased awareness among veterinary microbiology laboratories.

Typing of mecD Islands in Genetically Diverse Methicillin-Resistant Macrococcus caseolyticus Strains from Cattle

“…Phylogenetic clustering based on seven housekeeping genes showed an overall good correlation with the phylogenetic analysis based on 1,550 gene targets performed in the study of MacFadyen et al (11). The same ST was assigned to strains that were highly related based on whole-genome MLST analysis (11). The only exception was strain 5795_EF335, which was assigned to ST51 even though it was on the same terminal branch as the ST21 strains 5193_2_23 and 5818_BC116.…”

“…Thirty-four strains were isolated in Switzerland between 2015 and 2017 from bovine samples, including 13 strains from mastitis milk obtained from seven different farms at different time points, two strains from milking machines on a farm with a recurrent mastitis problem, and 19 strains from the noses of healthy calves all raised on different farms ( Table 1). The remaining 33 M. caseolyticus strains originated from the study of MacFadyen et al (11), who isolated them from bovine bulk milk tanks in England and Wales between 2015 and 2016 ( Table 2). Genetic characterization of these strains from England/Wales was performed using publicly available wholegenome sequences (NCBI BioProject PRJNA420921).…”

“…Since the first description of mecD in 2017, additional methicillin-resistant M. caseolyticus strains have been isolated from cattle in Switzerland, as well as from bulk tank milk in England and Wales (11), indicating a broader geographical dissemination. In the present study, we characterized M. caseolyticus from Switzerland using multilocus sequence typing (MLST), PCR-based McRI mecD typing, and microarray detection of antibiotic resistance genes.…”

Molecular Epidemiology of Staphylococcus aureus Lineages in Wild Animals in Europe: A Review

“…rodentium and in S. vitulinus, respectively [43]. Other homologues, with less than 70% identity, have been reported-the mecB, mecC, and mecD genes; however, mecB and mecD were initially described in in Macrococcus caseolyticus [44,45]. More recently, mecB was detected in S. aureus strains, which suggests a possible transfer between genus [46].…”

Staphylococcus aureusin the Meat Supply Chain: Detection Methods, Antimicrobial Resistance, and Virulence Factors

“…This protein has a lower affinity for β-lactam antibiotics, resulting in normal cross-linking of peptidoglycan strands during bacterial cell wall synthesis [5]. Currently, new mecA gene homologs have been described, such as mecB, mecC, and mecD, which may not be detected by conventional methods [6][7][8]. The borderline oxacillin-resistant S. aureus: (BORSA) is other mechanism in which the resistance to oxacillin is mediated by an increase of the β-lactamase production.…”