Kampf G, Adena S, Rüden H, Weist K
Institute of Hygiene, University Hospital Benjamin Franklin, Free University Berlin, Berlin, Germany.
J Hosp Infect. 2003 Jun;54(2):124-9. doi: 10.1016/s0195-6701(03)00119-1.
To determine the carrier rate of methicillin-susceptible mecA-positive Staphylococcus aureus (dormant MRSA) among healthcare workers (HCWs), 447 nurses and physicians from 13 general wards and intensive care units were investigated for nasal or oropharyngeal S. aureus carriage during one year whenever an MRSA patient was treated. Induction of phenotypic resistance in all mecA-positive oxacillin-susceptible aureus was attempted by 24 h exposure to oxacillin and cefotaxime. Organisms from the broth tube with the highest antibiotic concentration and visible growth after incubation were re-exposed for a total of seven repetitive exposures. Two mecA-negative oxacillin-susceptible S. aureus served as negative control. A population analysis before and after antibiotic exposure was performed. A third of the HCWs were found to be S. aureus carriers. Only three nurses were MRSA positive (0.7%). Seven isolates of dormant MRSA were isolated in six nurses and one doctor (1.6%). After four days of repetitive antibiotic exposure six of seven dormant MRSA were highly resistant to oxacillin. Resistance of the two control S. aureus without the mecA gene was not changed by repetitive antibiotic exposure. Two of the seven dormant MRSA were clonally related as shown by pulsed-field gel electrophoresis (PFGE). The PFGE pattern of one dormant MRSA (HCW) was identical to an MRSA (HCW). The pattern of another dormant MRSA was indistinguishable from an MRSA isolated from a patient who was treated at the same time on the same ward suggesting transmission from the HCW to the patient. Dormant MRSA may be isolated twice as often as MRSA from HCWs. Transmission to patients is possible, which may lead to clinical infections. It might be useful to screen methicillin-susceptible S. aureus isolates from HCWs for the mecA gene when recurrent infections with MRSA occur on a ward and a source cannot be found.
为确定医护人员中耐甲氧西林的mecA阳性金黄色葡萄球菌（潜伏性耐甲氧西林金黄色葡萄球菌）的携带率，对来自13个普通病房和重症监护病房的447名护士和医生进行了调查，在治疗耐甲氧西林金黄色葡萄球菌患者的一年期间，检测其鼻腔或口咽部金黄色葡萄球菌携带情况。对所有mecA阳性且对苯唑西林敏感的金黄色葡萄球菌，尝试通过24小时暴露于苯唑西林和头孢噻肟来诱导表型耐药。将培养后抗生素浓度最高且有可见生长的肉汤管中的菌株再次暴露，总共重复暴露7次。两株mecA阴性且对苯唑西林敏感的金黄色葡萄球菌作为阴性对照。对抗生素暴露前后进行群体分析。发现三分之一的医护人员为金黄色葡萄球菌携带者。仅3名护士耐甲氧西林金黄色葡萄球菌呈阳性（0.7%）。在6名护士和1名医生中分离出7株潜伏性耐甲氧西林金黄色葡萄球菌（1.6%）。经过4天的重复抗生素暴露后，7株潜伏性耐甲氧西林金黄色葡萄球菌中有6株对苯唑西林高度耐药。两株无mecA基因的对照金黄色葡萄球菌经重复抗生素暴露后耐药性未改变。脉冲场凝胶电泳（PFGE）显示，7株潜伏性耐甲氧西林金黄色葡萄球菌中有2株克隆相关。1株潜伏性耐甲氧西林金黄色葡萄球菌（医护人员分离株）的PFGE图谱与1株耐甲氧西林金黄色葡萄球菌（医护人员分离株）相同。另一株潜伏性耐甲氧西林金黄色葡萄球菌的图谱与同一病房同一时间治疗的1例患者分离的耐甲氧西林金黄色葡萄球菌无法区分，提示从医护人员传播至患者。潜伏性耐甲氧西林金黄色葡萄球菌的分离率可能是医护人员耐甲氧西林金黄色葡萄球菌分离率的两倍。有可能传播给患者，这可能导致临床感染。当病房中发生耐甲氧西林金黄色葡萄球菌反复感染且找不到感染源时，筛查医护人员中对苯唑西林敏感的金黄色葡萄球菌分离株的mecA基因可能会有帮助。
