Prakash Vittal P, Rao Sambasiva R, Parija Subash C
Department of Microbiology, Jawaharlal Institute of Postgraduate Medical Education and Research (JIPMER), Pondicherry, India.
BMC Infect Dis. 2005 Mar 17;5:14. doi: 10.1186/1471-2334-5-14.
Enterococci tend to be one of the leading causes of nosocomial infections, with E. faecalis and E. faecium accounting up to 90% of the clinical isolates. Nevertheless, the incidence of other species of enterococci from clinical sources shows an alarming increase with the properties of intrinsic resistance to several antibiotics including beta-lactams and glycopeptides. Thus proper identification of enterococci to species level is quintessential for management and prevention of these bacteria in any healthcare facility. Hence this work was undertaken to study the prevalence of unusual species of enterococci causing human infections, in a tertiary care hospital in South India.
The study was conducted in a tertiary care hospital in South India from July 2001 to June 2003. Isolates of enterococci were collected from various clinical specimens and speciated using extensive phenotypic and physiological tests. Antimicrobial susceptibility testing were performed and interpreted as per NCCLS guidelines. Whole cell protein (WCP) fingerprinting of enterococci were done for species validation by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and analyzed computationally.
Our study showed the prevalence of unusual (non-faecalis and non-faecium enterococci) and atypical (biochemical variant) species of enterococci as 19% (46 isolates) and 5% (12 isolates) respectively. The 7 unusual species (46 isolates) isolated and confirmed by phenotypic characterization includes: 15 E. gallinarum (6.2%), 10 E. avium (4.1%), 6 E. raffinosus (2.5%), 6 E. hirae (2.5%), 4 E. mundtii (1.7%), 3 E. casseliflavus-including the two atypical isolates (1.2%) and 2 E. durans (0.8%). The 12 atypical enterococcal species (5%) that showed aberrant sugar reactions in conventional phenotyping were confirmed as E. faecalis, E. faecium and E. casseliflavus respectively by WCP fingerprinting. The antimicrobial susceptibility testing depicted the emergence of high-level aminoglycoside and beta-lactam resistance among different species apart from intrinsic vancomycin resistance by some species, while all the species tested were susceptible for linezolid and teicoplanin.
Our study reveals the emergence of multi-drug resistance among unusual species of enterococci posing a serious therapeutic challenge. Precise identification of enterococci to species level enables us to access the species-specific antimicrobial resistance characteristics, apart from knowing the epidemiological pattern and their clinical significance in human infections.
肠球菌往往是医院感染的主要原因之一，粪肠球菌和屎肠球菌占临床分离株的90%。然而，来自临床来源的其他肠球菌物种的发病率呈现出惊人的增长，这些肠球菌具有对包括β-内酰胺类和糖肽类在内的多种抗生素的固有耐药特性。因此，在任何医疗机构中，将肠球菌准确鉴定到种水平对于管理和预防这些细菌至关重要。因此，开展这项工作以研究印度南部一家三级护理医院中引起人类感染的不常见肠球菌物种的流行情况。
该研究于2001年7月至2003年6月在印度南部的一家三级护理医院进行。从各种临床标本中收集肠球菌分离株，并使用广泛的表型和生理测试进行分类。按照美国国家临床实验室标准委员会（NCCLS）指南进行抗菌药物敏感性测试并进行解释。通过十二烷基硫酸钠-聚丙烯酰胺凝胶电泳（SDS-PAGE）对肠球菌进行全细胞蛋白（WCP）指纹图谱分析以进行种属验证，并进行计算机分析。
我们的研究表明，不常见（非粪肠球菌和非屎肠球菌）和非典型（生化变异型）肠球菌物种的流行率分别为19%（46株分离株）和5%（12株分离株）。通过表型特征分离并确认的7种不常见物种（46株分离株）包括：15株鹑鸡肠球菌（6.2%）、10株鸟肠球菌（4.1%）、6株棉子糖肠球菌（2.5%）、6株海氏肠球菌（2.5%）、4株蒙氏肠球菌（1.7%）、3株卡氏黄色肠球菌——包括2株非典型分离株（1.2%）和2株耐久肠球菌（0.8%）。在传统表型分析中显示异常糖反应的12株非典型肠球菌物种（5%）通过WCP指纹图谱分别确认为粪肠球菌、屎肠球菌和卡氏黄色肠球菌。抗菌药物敏感性测试表明，除了一些物种具有固有的万古霉素耐药性外，不同物种中还出现了高水平的氨基糖苷类和β-内酰胺类耐药性，而所有测试物种对利奈唑胺和替考拉宁敏感。
我们的研究揭示了不常见肠球菌物种中多重耐药性的出现，这带来了严重的治疗挑战。将肠球菌准确鉴定到种水平使我们能够了解物种特异性的抗菌耐药特征，同时了解其流行病学模式及其在人类感染中的临床意义。
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