Verma Anuragani, Jain Parul, Tripathi Piyush, Kalyan Raj K, Verma Sheetal, Venkatesh Vimala
Microbiology, King George's Medical University, Lucknow, IND.
Clinical Microbiology, King George's Medical University, Lucknow, IND.
Cureus. 2022 Jul 24;14(7):e27197. doi: 10.7759/cureus.27197. eCollection 2022 Jul.
Carbapenemase-producing (CRKP) has become a menace in several intensive care units, which needs to be controlled immediately after being reported by a laboratory. Detection in the laboratory is usually done using phenotypic methods and it is not known whether knowledge of these genes helps in individual patient management. This study aimed to compare the outcomes of oxacillinases β-lactamases (OXA-48) and New Delhi metallo-β-lactamase (NDM-1)-producing CRKP isolates, the two most common carbapenemases reported from India, obtained from patients with bloodstream infections in an ICU in a tertiary care center in North India and to compare the different laboratory methods for their detection.
isolates obtained from the blood culture of patients admitted to various ICUs were subjected to conventional polymerase chain reaction (PCRs) for blaNDM and blaOXA48-like genes. Those positive for any of the genes were tested by the modified carbapenem inactivation method (mCIM) and if found positive were also subjected to ethylenediamine tetraacetic acid (EDTA)-modified carbapenem inactivation method (eCIM). Antibiotic susceptibility tests (AST) were performed and clinical data were recorded.
A total of 49 isolates were positive for one or more carbapenemase genes (30 {61.2%} for blaNDM gene only, 13 {26.5%)} for blaOXA48-like gene only, and six {12.2%} for both). The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of mCIM were found to be 77.6%, 100%, 100%, and 78.9%, respectively. Statistically significant differences were found in the AST pattern between the isolates with two genes. Increased MIC levels of colistin were observed, though they lay in the sensitive range. Mortality occurred in all six patients who were infected with CRKP harboring both the genes though no significant difference was observed in NDM and OXA-48 producing CRKP isolates.
Surveillance of carbapenemase genes in a hospital setting is essential. The possible reasons for the low diagnostic accuracy of mCIM and differences in AST patterns are discussed.
产碳青霉烯酶肺炎克雷伯菌（CRKP）已成为多个重症监护病房的一大威胁，实验室报告后需立即加以控制。实验室检测通常采用表型方法，而这些基因的相关知识是否有助于个体患者的管理尚不清楚。本研究旨在比较产氧碳青霉烯酶β-内酰胺酶（OXA-48）和新德里金属β-内酰胺酶（NDM-1）的CRKP分离株的转归，这两种是印度报告的最常见的碳青霉烯酶，它们来自印度北部一家三级护理中心重症监护病房的血流感染患者，并比较检测它们的不同实验室方法。
从入住各个重症监护病房患者的血培养中获得的分离株，针对blaNDM和blaOXA48样基因进行常规聚合酶链反应（PCR）。对任何一个基因呈阳性的分离株采用改良碳青霉烯灭活法（mCIM）进行检测，若结果为阳性，则进一步采用乙二胺四乙酸（EDTA）改良碳青霉烯灭活法（eCIM）检测。进行抗生素敏感性试验（AST）并记录临床数据。
共有49株分离株一种或多种碳青霉烯酶基因呈阳性（仅blaNDM基因阳性30株{61.2%}，仅blaOXA48样基因阳性13株{26.5%}，两种基因均阳性6株{12.2%}）。发现mCIM的敏感性、特异性、阳性预测值（PPV）和阴性预测值（NPV）分别为77.6%、100%、100%和78.9%。在具有两种基因的分离株之间，AST模式存在统计学显著差异。虽然黏菌素的最低抑菌浓度（MIC）水平仍在敏感范围内，但有所升高。感染同时携带这两种基因的CRKP的所有6例患者均死亡，不过在产NDM和产OXA-48的CRKP分离株之间未观察到显著差异。
在医院环境中监测碳青霉烯酶基因至关重要。讨论了mCIM诊断准确性低和AST模式差异的可能原因。
