Taponen Suvi, Tölli Heikki-Tapio, Rajala-Schultz Päivi J
Department of Production Animal Medicine, Faculty of Veterinary Medicine, University of Helsinki, Saarentaus, Finland.
Front Vet Sci. 2023 Aug 17;10:1235417. doi: 10.3389/fvets.2023.1235417. eCollection 2023.
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 isolates (260 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 , , and genes investigated by PCR. Nitrocefin test assessed these isolates' beta-lactamase production. The most common NAS species were and In total, 26.6% of the isolates (18.5% of and 35.2% of all NAS) carried the gene. Penicillin resistance, based on disk diffusion, was lower: 18.8% of all the isolates (9.3% of and 28.9% of all NAS) were resistant. Based on the nitrocefin test, 21.5% of the isolates produced beta-lactamase (11.6% of and 32.0% of all NAS). Between the species, the proportion of penicillin-resistant isolates varied, being lowest in and highest in Resistance to antimicrobials other than penicillin was rare. Of the eight NAS isolates carrying the gene, six were . One isolate carried the 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 gene but isolates without or 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.
奶牛场使用抗菌药物最常见的原因是乳腺炎，了解引起乳腺炎的病原体及其对抗菌药物的敏感性应指导治疗决策。本研究的总体目标是评估芬兰乳腺炎牛奶样本中葡萄球菌的抗菌药物耐药性（AMR）。基质辅助激光解吸电离飞行时间质谱（MALDI-ToF MS）共鉴定出504株分离株（260株金黄色葡萄球菌和244株非金黄色葡萄球菌，NAS），均来自牛乳腺炎牛奶样本。采用纸片扩散法评估了这些分离株对头孢西丁、头孢噻呋、恩诺沙星、庆大霉素、苯唑西林、青霉素和四环素的表型敏感性，并通过聚合酶链反应（PCR）检测了mecA、blaZ和tetM基因的存在情况。采用硝基头孢菌素试验评估这些分离株的β-内酰胺酶产生情况。最常见的NAS菌种是表皮葡萄球菌和溶血葡萄球菌。总体而言，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mecA基因。基于纸片扩散法的青霉素耐药率较低：所有分离株中有18.8%（金黄色葡萄球菌的9.3%和所有NAS的28.9%）耐药。根据硝基头孢菌素试验，21.5%的分离株产生β-内酰胺酶（金黄色葡萄球菌的11.6%和所有NAS的32.0%）。在不同的NAS菌种之间，青霉素耐药分离株的比例有所不同，在表皮葡萄球菌中最低，在溶血葡萄球菌中最高。对青霉素以外抗菌药物的耐药情况很少见。在携带mecA基因的8株NAS分离株中，有6株是溶血葡萄球菌。1株表皮葡萄球菌分离株携带tetM基因。通过kappa系数评估，表型和基因型耐药试验之间的一致性超出偶然，为中度至高度一致。一些表型上对青霉素敏感的葡萄球菌携带mecA基因，但没有mecA或tetM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。我们的结果支持了早期的研究发现，即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药物耐药形式。
