MINIMUM BACTERICIDAL CONCENTRATION OF COMMERCIAL DISINFECTANTS ON STAPHYLOCOCCUS SPP. ISOLATED FROM MASTITIS IN GOATS AND DETECTION OF THE icaD GENE

Abstract This study aimed to evaluate the in vitro efficacy of commercial disinfectants on Staphylococcus spp., isolated from mastitis cases in goats, and to associate the observed resistance with the presence of the icaD gene. Broth microdilution was employed to evaluate the in vitro antimicrobial activity of the disinfectants, whereas the Congo Red technique was used for the evaluation of biofilm production and amplification of the icaD gene. All evaluated samples were sensitive to disinfectants, with the following ranges of activity: quaternary ammonium (0.13 - 21.33 µg/ml), chlorhexidine (4.00 - 313.00 µg/ml) and iodine (190.00 - 12500.00 µg/ml); however, the sodium hypochlorite-based disinfectant showed no bactericidal activity in the concentration range from 15.0 to 0.03 µg/ml. The icaD gene presented a frequency of 14.7% in the isolate samples. Fisher’s exact test showed a significant effect of the relation between the minimum bactericidal concentration value of the quaternary ammonium-based disinfectant and the presence/absence of the icaD gene (P <0.01). Commercial disinfectants with quaternary ammonium, chlorhexidine and iodine active ingredients presented in vitro activity even at concentrations lower than those recommended by the manufacturers. Therefore, the periodic evaluation of the sensitivity profile of the disinfectants must be performed.

摘要 本研究旨在评估从山羊乳腺炎病例中分离的葡萄球菌属（Staphylococcus spp.）菌株对商用消毒剂的体外抑菌效果，并分析所观察到的耐药性与icaD基因存在情况的关联。本研究采用肉汤微量稀释法评估消毒剂的体外抗菌活性，借助刚果红染色技术检测生物膜生成情况，并完成icaD基因的扩增检测。所有受试菌株均对上述消毒剂敏感，各消毒剂的活性浓度范围如下：季铵盐类（quaternary ammonium）：0.13~21.33 μg/ml、氯己定（chlorhexidine）：4.00~313.00 μg/ml、碘（iodine）：190.00~12500.00 μg/ml；但次氯酸钠基消毒剂在15.0至0.03 μg/ml的浓度范围内未表现出杀菌活性。受试分离株中icaD基因的检出率为14.7%。费舍尔精确检验（Fisher’s exact test）结果显示，季铵盐类消毒剂的最小杀菌浓度与icaD基因的存在与否存在显著关联（P<0.01）。含有季铵盐类、氯己定及碘活性成分的商用消毒剂，即使在低于厂商推荐浓度的条件下仍具备体外抗菌活性。因此，需定期开展消毒剂敏感性谱的评估工作。