Saribas Suat, Bagdatli Yasar
Microbiology and Clinical Microbiology Department, Cerrahpasa Faculty of Medicine, University of Istanbul, Kocamustafapasa, Istanbul, Turkey.
Chemotherapy. 2004 Nov;50(5):250-4. doi: 10.1159/000081946. Epub 2004 Nov 3.
Tolerance can be defined as the ability of bacteria to grow in the presence of high concentrations of bactericide antimicrobics, so that the killing action of the drug is avoided but the minimal inhibitory concentration (MIC) remains the same. We investigated vancomycin tolerance in the Enterococcus faecium and Enterococcus faecalis strains isolated from different clinical specimens.
Vancomycin was obtained from Sigma Chemical Co. We studied 100 enterococci strains. Fifty-six and 44 of Enterococcus strains were idendified as E. feacalis and E. faecium, respectively. To determine MICs and minimal bactericidal concentration (MBC), we inoculated strains from an overnight agar culture to Muller-Hinton broth and incubated them for 4-6 h at 37 degrees C with shaking to obtain a logarithmic phase culture. The inoculum was controlled by performing a colony count for each test. We determined MBC values and MBC/MIC ratios to study tolerance to vancomycin. Vancomycin tolerance was defined as a high MBC value and an MBC/MIC ratio > or =32.
Fifty-six and 44 of the Enterococcus strains were identified as E. faecium and E. faecalis, respectively. Thirty-one E. faecium and 48 E. faecalis were found to be susceptible to vancomycin and these susceptible strains were included in this study. The MICs of susceptible strains ranged from < or =1 to 4 mg/l, the MBCs were > or =512 mg/l. Tolerance was detected in all E. faecalis and E. faecium strains. The standard E. faecalis 21913 strain also exhibited tolerance according to the high MBC value and the MBC/MIC ratio. We defined the tolerant strains as having no bactericidal effect and MBC/MIC > or =32. We found that a 100% tolerance was present in susceptible strains.
One of the hypotheses for tolerance is that tolerant cells fail to mobilize or create the autolysins needed for enlargement and division. Our data suggests that tolerance may compromise glycopeptide therapy of serious enterococci infections. To add an aminoglycoside to the glycopeptide therapy unless MBCs are unavailable can be useful in the effective treatment of serious Enterococcus infections.
耐受性可定义为细菌在高浓度杀菌剂存在的情况下生长的能力，这样可避免药物的杀菌作用，但最低抑菌浓度（MIC）保持不变。我们研究了从不同临床标本中分离出的粪肠球菌和屎肠球菌菌株对万古霉素的耐受性。
万古霉素购自西格玛化学公司。我们研究了100株肠球菌菌株。其中56株和44株肠球菌菌株分别被鉴定为粪肠球菌和屎肠球菌。为了确定MIC和最低杀菌浓度（MBC），我们将过夜琼脂培养的菌株接种到Muller-Hinton肉汤中，并在37℃下振荡培养4 - 6小时以获得对数期培养物。通过对每个测试进行菌落计数来控制接种量。我们确定MBC值和MBC/MIC比值以研究对万古霉素的耐受性。万古霉素耐受性定义为高MBC值且MBC/MIC比值≥32。
56株和44株肠球菌菌株分别被鉴定为屎肠球菌和粪肠球菌。发现31株屎肠球菌和48株粪肠球菌对万古霉素敏感，这些敏感菌株被纳入本研究。敏感菌株的MIC范围为≤1至4mg/L，MBC≥512mg/L。在所有粪肠球菌和屎肠球菌菌株中均检测到耐受性。标准粪肠球菌21913菌株根据高MBC值和MBC/MIC比值也表现出耐受性。我们将耐受菌株定义为无杀菌作用且MBC/MIC≥32。我们发现敏感菌株中存在100%的耐受性。
耐受性的一种假说是耐受细胞无法动员或产生扩大和分裂所需的自溶素。我们的数据表明，耐受性可能会影响严重肠球菌感染的糖肽类治疗。除非无法获得MBC，否则在糖肽类治疗中添加氨基糖苷类药物可能有助于有效治疗严重的肠球菌感染。
