Park Hye Rim, Hong Min Ki, Hwang Sun Young, Park Young Kyung, Kwon Ka Hee, Yoon Jang Won, Shin Sook, Kim Jae Hong, Park Yong Ho
Seoul National University Department of Microbiology and Brain Korea 21 Program for Veterinary Science, College of Veterinary Medicine Seoul Korea.
University of Science and Technology Viral Infectious Disease Research Center, Korea Research Institute of Bioscience and Biotechnology Daejeon Korea.
Acta Vet Hung. 2014 Mar;62(1):1-12. doi: 10.1556/AVet.2013.054.
Pseudomonas aeruginosa is one of the causative pathogens of bovine mastitis. Most P. aeruginosa strains possess the type III secretion system (TTSS), which may increase somatic cell counts (SCCs) in milk from mastitis-affected cows. Moreover, most of P. aeruginosa cells can form biofilms, thereby reducing antibiotic efficacy. In this study, the presence and effect of TTSS-related genotypes on increase of SCCs among 122 P. aeruginosa isolates obtained from raw milk samples from mastitis-affected cows and their antibiotic susceptibility at planktonic and biofilm status were investigated. Based on the presence of TTSS-related genes a total of 82.7% of the isolates were found to harbour exoU and/or exoS genes, including the invasive (exoU-/exoS+, 69.4%), cytotoxic (exoU+/exoS-, 8.3%) and cytotoxic/invasive strains (exoU+/ exoS+, 5.0%). Milk containing exoS-positive isolates had higher SCCs than those containing exoS-negative isolates. The majority of isolates showed gentamicin, amikacin, meropenem and ciprofloxacin susceptibility at planktonic status. However, the susceptibility was decreased at the biofilm status. Based on minimum biofilm eradication concentration (MBEC)/minimum inhibitory concentration (MIC) ratios, the range of change in antibiotic susceptibility varied widely depending on the antibiotics (from ≥ 3.1-fold to ≥ 475.0-fold). In conclusion, most P. aeruginosa isolates studied here had a genotype related to increase in SCCs. The efficiency of antibiotic therapy against P. aeruginosa-related bovine mastitis could be improved by analysing both the MBEC and the MIC of isolates.
铜绿假单胞菌是牛乳腺炎的致病病原体之一。大多数铜绿假单胞菌菌株拥有III型分泌系统（TTSS），这可能会增加患乳腺炎奶牛乳汁中的体细胞计数（SCCs）。此外，大多数铜绿假单胞菌细胞可形成生物膜，从而降低抗生素疗效。在本研究中，调查了从患乳腺炎奶牛的生鲜乳样品中分离得到的122株铜绿假单胞菌中TTSS相关基因型的存在情况及其对SCCs增加的影响，以及它们在浮游状态和生物膜状态下的抗生素敏感性。基于TTSS相关基因的存在情况，共发现82.7%的分离株携带exoU和/或exoS基因，包括侵袭性菌株（exoU-/exoS+，69.4%）、细胞毒性菌株（exoU+/exoS-，8.3%）和细胞毒性/侵袭性菌株（exoU+/exoS+，5.0%）。含有exoS阳性分离株的牛奶比含有exoS阴性分离株的牛奶具有更高的SCCs。大多数分离株在浮游状态下对庆大霉素、阿米卡星、美罗培南和环丙沙星敏感。然而，在生物膜状态下敏感性降低。根据最小生物膜根除浓度（MBEC）/最小抑菌浓度（MIC）比值，抗生素敏感性的变化范围因抗生素而异（从≥3.1倍到≥475.0倍）。总之，本研究中的大多数铜绿假单胞菌分离株具有与SCCs增加相关的基因型。通过分析分离株的MBEC和MIC，可提高针对铜绿假单胞菌相关牛乳腺炎的抗生素治疗效果。
