Abstract
Simple SummaryWorldwide, antimicrobial resistance (AMR) is of major concern for human and animal health since infections with multidrug-resistant bacteria are often more challenging and costly. In the family Staphyloccocaceae, the species Staphylococcus aureus in particular was reported to cause severe infections. Although most of the other Staphylococcaceae members were not shown to cause severe illnesses, the transmission of AMR genes to harmful species might take place. Therefore, the monitoring of AMR potential in different environments is of high relevance. Mammaliicocci on dairy farms might represent such an AMR gene reservoir. Thus, in this study, the AMR potential of mammaliicocci isolates from German dairy farms was investigated. Whole-genome sequencing (WGS) of the isolates was conducted to evaluate the phylogenetic relationship of the isolates and analyze AMR genes. In addition, antimicrobial susceptibility testing was performed to compare the AMR genotype with the phenotype. It turned out that mammaliicocci may harbor large numbers of different AMR genes and exhibit phenotypic resistance to various antibiotics. Since some AMR genes are likely located on mobile genetic elements, such as plasmids, AMR gene transmission between members of the Staphylococcaceae family might occur.Mammaliicocci might play a major role in antimicrobial resistance (AMR) gene transmission between organisms of the family Staphylococcaceae, such as the potentially pathogenic species Staphylococcus aureus. The interest of this study was to analyze AMR profiles of mammaliicocci from German dairy farms to evaluate the AMR transmission potential. In total, 65 mammaliicocci isolates from 17 dairy farms with a history of MRSA detection were analyzed for AMR genotypes and phenotypes using whole genome sequencing and antimicrobial susceptibility testing against 19 antibiotics. The various genotypic and phenotypic AMR profiles of mammaliicocci from German dairy farms indicated the simultaneous occurrence of several different strains on the farms. The isolates exhibited a non-wildtype phenotype to penicillin (58/64), cefoxitin (25/64), chloramphenicol (26/64), ciprofloxacin (25/64), clindamycin (49/64), erythromycin (17/64), fusidic acid (61/64), gentamicin (8/64), kanamycin (9/64), linezolid (1/64), mupirocin (4/64), rifampicin (1/64), sulfamethoxazol (1/64), streptomycin (20/64), quinupristin/dalfopristin (26/64), tetracycline (37/64), tiamulin (59/64), and trimethoprim (30/64). Corresponding AMR genes against several antimicrobial classes were detected. Linezolid resistance was associated with the cfr gene in the respective isolate. However, discrepancies between genotypic prediction and phenotypic resistance profiles, such as for fusidic acid and tiamulin, were also observed. In conclusion, mammaliicocci from dairy farms may carry a broad variety of antimicrobial resistance genes and exhibit non-wildtype phenotypes to several antimicrobial classes; therefore, they may represent an important source for horizontal gene transfer of AMR genes to pathogenic Staphylococcaceae.
Highlights
Bovine mastitis is frequently related to the presence of Staphylococcus (S.) aureus, which is the most prominent species in the family Staphylococcaceae
Separate phylogenetic trees of M. sciuri and M. lentus isolates, which represent the major fractions of the analyzed isolates, show both genomic differences between the dairy farms and closely related strains within distinct farms
Since the visited dairy farms had a history of methicillin-resistant S. aureus (MRSA) detection, it was assumed that mammaliicoccal species might express distinct antimicrobial resistance (AMR) profiles
Summary
Bovine mastitis is frequently related to the presence of Staphylococcus (S.) aureus, which is the most prominent species in the family Staphylococcaceae. The genus consists of the five species Mammaliicoccus (M.) sciuri, M. fleurettii, M. lentus, M. vitulinus, and M. stepanovicii These organisms were previously reported to harbor AMR genes against several antibiotics [1] and show unusual SCCmec elements, such as a SCCmec–mecC hybrid element [3,4]. MecA genes harboring M. sciuri were recently found to be the most frequently detected species in quarter milk samples on German dairy farms with a history of MRSA detection [6]. Mammaliicocci were isolated from human clinical samples, and animal–human contact was considered one feasible transmission route [1] To their potential but rarely expressed pathogenic character, the AMR gene transmission potential of mammaliicocci in particular is of high importance. Investigating Staphylococcaceae members, such as species of the genus Mammaliicoccus, from different environments gives further insights into this topic and reveals alternative AMR mechanisms that might be of public health relevance
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