在奶牛群中使用抗菌药物的最常见原因是乳腺炎,有关引起乳腺炎的病原体及其抗菌药物敏感性的知识应指导治疗决策。这项研究的总体目标是评估芬兰乳汁样品中葡萄球菌的抗菌素耐药性(AMR)。MALDI-ToFMS共鉴定出504株葡萄球菌(260株金黄色葡萄球菌和244种非金黄色葡萄球菌,NAS)源自牛乳汁样品。头孢西丁的表型易感性,头孢噻呋酯,恩诺沙星,庆大霉素,苯唑西林,青霉素,和四环素通过圆盘扩散法和BlaZ的存在进行评估,mecA,和通过PCR研究的mecC基因。硝化氮素试验评估了这些分离株β-内酰胺酶的产量。最常见的NAS物种是S.simulans,表皮葡萄球菌,S、染色体基因,和溶血链球菌。总的来说,26.6%的分离株(金黄色葡萄球菌的18.5%和所有NAS的35.2%)携带blaZ基因。青霉素抗性,基于磁盘扩散,较低:所有分离株的18.8%(金黄色葡萄球菌的9.3%和所有NAS的28.9%)具有抗性。根据硝化冰试验,21.5%的分离物产生β-内酰胺酶(金黄色葡萄球菌的11.6%和所有NAS的32.0%)。在葡萄球菌物种之间,耐青霉素菌株的比例各不相同,在模拟链球菌中最低,在表皮葡萄球菌中最高。对青霉素以外的抗菌药物的耐药性很少。在八个携带mecA基因的NAS分离物中,六个是表皮葡萄球菌。一种金黄色葡萄球菌分离物携带mecC基因。超越偶然的协议,通过卡帕系数评估,在表型和基因型抗性测试之间,是中等到实质性的。一些表型上对青霉素敏感的葡萄球菌携带blaZ基因,但没有blaZ或mec基因的分离株很少表现出耐药性。这表明更可靠的治疗选择可能取决于基因型AMR检测。我们的结果支持早期发现,青霉素耐药性是芬兰引起乳腺炎的葡萄球菌中唯一重要的抗菌素耐药性。
The most frequent reason for antimicrobial use in dairy herds is mastitis and knowledge about mastitis-causing pathogens and their antimicrobial susceptibility should guide treatment decisions. The overall objective of this study was to assess antimicrobial resistance (AMR) of staphylococci in mastitic milk samples in Finland. MALDI-ToF MS identified a total of 504 Staphylococcus isolates (260 S. aureus and 244 non-aureus staphylococci,
NAS) originating from bovine mastitic milk samples. Phenotypic susceptibility against cefoxitin, ceftiofur, enrofloxacin, gentamycin, oxacillin, penicillin, and tetracycline was evaluated by disk diffusion method and the presence of blaZ, mecA, and mecC genes investigated by PCR. Nitrocefin test assessed these isolates\' beta-lactamase production. The most common
NAS species were S. simulans, S. epidermidis, S. chromogenes, and S. haemolyticus. In total, 26.6% of the isolates (18.5% of S. aureus and 35.2% of all
NAS) carried the blaZ gene. Penicillin resistance, based on disk diffusion, was lower: 18.8% of all the isolates (9.3% of S. aureus and 28.9% of all
NAS) were resistant. Based on the nitrocefin test, 21.5% of the isolates produced beta-lactamase (11.6% of S. aureus and 32.0% of all NAS). Between the Staphylococcus species, the proportion of penicillin-resistant isolates varied, being lowest in S. simulans and highest in S. epidermidis. Resistance to antimicrobials other than penicillin was rare. Of the eight
NAS isolates carrying the mecA gene, six were S. epidermidis. One S. aureus isolate carried the mecC gene. Agreement beyond chance, assessed by kappa coefficient, between phenotypic and genotypic resistance tests, was moderate to substantial. Some phenotypically penicillin-susceptible staphylococci carried the blaZ gene but isolates without blaZ or mec genes rarely exhibited resistance, suggesting that the more reliable treatment choice may depend upon genotypic AMR testing. Our results support earlier findings that penicillin resistance is the only significant form of antimicrobial resistance among mastitis-causing staphylococci in Finland.