Department of Microbiology, Assam University, Assam, India.
Department of Microbiology, Silchar Medical College and Hospital, Assam, India.
Indian J Med Res. 2024 Jul;160(1):109-117. doi: 10.25259/ijmr_2224_22.
Background & objectives The global prevalence of vancomycin-resistant Staphylococcus aureus (VRSA) has increased two fold since 2010, accounting for 2.4 per cent of S. aureus infections. The emerging hVISA isolates and their increasing trends pose a serious therapeutic challenge. The present study investigated in vitro vancomycin and teicoplanin minimum inhibitory concentration (MIC) creep in S. aureus and assessed their revertants. Methods A total of 845 isolates were collected for this study, and 246 were confirmed as S. aureus. Molecular characterization of vancomycin resistance was carried out by PCR assay targeting genes types viz: vanA, vanB, vanC, vanC2/C3, vanD, vanE, and vanG. MIC was determined for vancomycin and teicoplanin by agar dilution method. MIC creep and revertant analysis were done by broth dilution method in the presence and absence of antibiotics. Results PCR assay confirmed 12 isolates were harboured vanA, followed by vanD (n=8) and vanB (n=7). The study showed 69 isolates were screened positive for glycopeptide non-susceptibility. While analyzing vancomycin MIC creep, four isolates showed a significant increase in MIC, whereas no creep phenomenon was observed for the rest. In the case of teicoplanin, seven isolates showed the MIC creep phenomenon. Revertant analysis of all the isolates that showed MIC creep phenomenon for vancomycin and teicoplanin reverted to their original MIC when the antibiotic pressure was withdrawn. Interpretation & conclusions In the present study setting, glycopeptide non-susceptibility was found in eight per cent of the isolates, and the present study found the occurrence of multiple van genes from isolates calculated from a single study center will impose a serious challenge in infection control and antibiotic policy. This study also underscores that heterogenic resistant isolates, upon exposure to vancomycin and teicoplanin at a minimum level, exhibited an increase in MIC, which will impact individuals receiving glycopeptide therapy.
自 2010 年以来，耐万古霉素金黄色葡萄球菌（VRSA）的全球流行率增加了两倍，占金黄色葡萄球菌感染的 2.4%。新兴的高万古霉素中介金黄色葡萄球菌（hVISA）分离株及其增加趋势对治疗构成严重挑战。本研究调查了金黄色葡萄球菌中外源万古霉素和替考拉宁最低抑菌浓度（MIC）的逐渐增加，并评估了其回复突变株。
本研究共收集了 845 株分离株，其中 246 株被确认为金黄色葡萄球菌。通过 PCR 检测针对基因类型（vanA、vanB、vanC、vanC2/C3、vanD、vanE 和 vanG）的万古霉素耐药性进行分子特征分析。通过琼脂稀释法测定万古霉素和替考拉宁的 MIC。在存在和不存在抗生素的情况下，通过肉汤稀释法进行 MIC 逐渐增加和回复突变分析。
PCR 检测证实 12 株分离株携带 vanA，其次是 vanD（n=8）和 vanB（n=7）。该研究显示 69 株分离株对糖肽类药物的敏感性降低。在分析万古霉素 MIC 逐渐增加时，4 株分离株的 MIC 显著增加，而其余分离株则未观察到 MIC 逐渐增加现象。对于替考拉宁，7 株分离株出现 MIC 逐渐增加现象。当抗生素压力解除时，所有显示万古霉素和替考拉宁 MIC 逐渐增加的分离株的回复突变分析均恢复到原始 MIC。
在本研究环境中，8%的分离株对糖肽类药物的敏感性降低，本研究从单个研究中心计算出的分离株中发现了多种 van 基因，这将对感染控制和抗生素政策构成严重挑战。本研究还强调，异质性耐药分离株在接触万古霉素和替考拉宁的最低水平时，MIC 增加，这将影响接受糖肽类药物治疗的个体。
