Aykan Sadiye Berna, Cağlar Kayhan, Engin Evren Doruk, Sipahi Ayşe Bilge, Sultan Nedim, Yalınay Çırak Meltem
Gazi University Faculty of Medicine, Department of Medical Microbiology, Ankara, Turkey.
Mikrobiyol Bul. 2013 Jan;47(1):1-10. doi: 10.5578/mb.4409.
Development of resistance to disinfectant substances in nosocomial microorganisms is an important problem encountered during disinfectant practices. Methicillin-resistant Staphylococcus aureus (MRSA) remains a significant cause of hospital-acquired infections. Besides being resistant to several antimicrobial agents, MRSA strains can also become resistant to some disinfectant substances. Resistance to disinfectant substances may develop due to the misuse of disinfectants. This may either be due to the frequent use of disinfectant substances or use in lower concentrations than recommended. MRSA strains may harbour the qacA/B disinfectant resistance genes that may cause resistance to quarternary ammonium compounds and some cationic disinfectants. These resistance genes are found in plasmids and are responsible for decreased susceptibility or resistance. In this study, a total of 69 nosocomial MRSA strains isolated from clinical specimens in our hospital were tested for disinfectant activity and the presence of qacA/B disinfectant resistance genes in these isolates was investigated by polymerase chain reaction. We determined whether the presence of these genes caused phenotypic resistance to chlorhexidine and benzalkonium chloride by the use of bactericidal and bacteriostatic tests. For this purpose, the minimum inhibitory concentration (MIC) values of these disinfectants against MRSA isolates were detected by microdilution method with the proposals of CLSI, and bactericidal effects of these disinfectants were also detected by using quantitative suspension test according to EN13727:2003 European Standard. It has been found that 11.6% (8/69) of the isolates harbored qacA/B resistance genes. MIC values for chlorhexidine and benzalkonium chloride were found in the range of 2-8 µg/ml. Although it was observed that MIC values were higher in five of the qacA/B gene positive isolates, statistically significant difference was not found between gene positive and gene negative groups. Both 1% chlorhexidine and 1% benzalkonium chloride were found bactericidal against the isolates including the ones carrying the qacA/B resistance genes. It was concluded that the presence of the qacA/B disinfectant resistance genes did not lead to resistance to the disinfectant substances at the concentrations used in clinical practices. Furthermore, tested disinfectants still exhibited bactericidal activity even with high MIC values.
医院微生物对消毒物质产生耐药性是消毒实践中遇到的一个重要问题。耐甲氧西林金黄色葡萄球菌（MRSA）仍然是医院获得性感染的一个重要原因。除了对多种抗菌药物耐药外，MRSA菌株还可能对某些消毒物质产生耐药性。消毒物质耐药性的产生可能是由于消毒剂使用不当。这可能是由于频繁使用消毒物质或使用浓度低于推荐浓度。MRSA菌株可能携带qacA/B消毒耐药基因，这些基因可能导致对季铵化合物和一些阳离子消毒剂产生耐药性。这些耐药基因存在于质粒中，会导致敏感性降低或产生耐药性。在本研究中，对我院从临床标本中分离出的69株医院MRSA菌株进行了消毒活性测试，并通过聚合酶链反应研究了这些分离株中qacA/B消毒耐药基因的存在情况。我们通过杀菌和抑菌试验确定这些基因的存在是否会导致对氯己定和苯扎氯铵的表型耐药。为此，根据CLSI的建议，采用微量稀释法检测这些消毒剂对MRSA分离株的最低抑菌浓度（MIC）值，并根据EN13727:2003欧洲标准采用定量悬液试验检测这些消毒剂的杀菌效果。结果发现，11.6%（8/69）的分离株携带qacA/B耐药基因。氯己定和苯扎氯铵的MIC值在2-8μg/ml范围内。虽然在5株qacA/B基因阳性分离株中观察到MIC值较高，但基因阳性组和基因阴性组之间未发现统计学上的显著差异。1%的氯己定和1%的苯扎氯铵对包括携带qacA/B耐药基因的分离株在内的所有分离株均有杀菌作用。得出的结论是，qacA/B消毒耐药基因的存在不会导致在临床实践中使用的浓度下对消毒物质产生耐药性。此外，即使MIC值较高，测试的消毒剂仍表现出杀菌活性。
