Rout Bidyutprava, Dash Sumesh Kumar, Sahu Kundan Kumar, Behera Birasen, Praharaj Ira, Otta Sarita
Department of Microbiology, IMS and SUM Hospital, SOA University, Kalinga Nagar, Bhubaneswar, India.
Scientist-E, RMRC (ICMR), Bhubaneswar, Odisha, India.
Access Microbiol. 2023 Oct 16;5(10). doi: 10.1099/acmi.0.000595.v3. eCollection 2023.
The increasing antibiotic resistance like the advent of carbapenem resistant Enterobactarales (CRE), Carbapenem Resistant (CRAB), and Carbapenem Resistant (CRPA) has led to to the use of toxic and older drugs like colistin for these organisms. But worldwide there is an increase in resistance even to colistin mediated both by chromosomes and plasmids. This necessitates accurate detection of resistance. This is impeded by the unavailability of a user-friendly phenotypic methods for use in routine clinical microbiology practice. The present study attempts to evaluate two different methods - colistin broth disc elution and MIC detection by Vitek two in comparison to CLSI approved broth microdilution (BMD) for colistin for Enterobactarales, , and clinical isolates.
Colistin susceptibility of 6013 carbapenem resistant isolates was determined by BMD, Colistin Broth Disc Elution (CBDE), and Vitek two methods and was interpreted as per CLSI guidelines. The MIC results of CBDE, Vitek two were compared with that of BMD and essential agreement (EA), categorical agreement (CA), sensitivity, specificity, very major error (VME), major error (ME) and Cohen's kappa (CK) was calculated. The presence of any plasmid-mediated colistin resistance (mcr-1, 2, 3, 4 and 5) was evaluated in all colistin-resistant isolates by conventional polymerase chain reaction.
Colistin resistance was found in 778 (12.9 %) strains among the carbapenem resistant isolates. had the highest (18.9 %) colistin resistance by the BMD method. MIC of Vitek two had sensitivity ranging from 78.2-84.8% and specificity of >92 %. There were 171 VMEs and 323 MEs by Vitek two method, much more than CLSI acceptable range. The highest percentage of errors was committed for (27.8 % of VME and 7.9 % ME). On the other hand, the CBDE method performed well with EA, CA, VME and ME within acceptable range for all the organisms. The sensitivity of the CBDE method compared to gold standard BMD varied from 97.5-98.8 % for different strains with a specificity of more than 97.6 %. None of the isolated colistin resistant organisms harboured plasmids.
As BMD has many technical complexities, CBDE is the best viable alternative available for countries like India. A sensitive MIC reported by Vitek two needs to be carefully considered due high propensity for VMEs particularly for spp.
随着碳青霉烯类耐药肠杆菌科细菌（CRE）、耐碳青霉烯类鲍曼不动杆菌（CRAB）和耐碳青霉烯类铜绿假单胞菌（CRPA）等抗生素耐药性的不断增加，导致人们开始使用如多粘菌素等毒性较大且较老的药物来对付这些微生物。但在全球范围内，即使对多粘菌素的耐药性也在增加，这是由染色体和质粒介导的。这就需要准确检测耐药性。而在常规临床微生物学实践中，缺乏一种用户友好的表型方法阻碍了这一检测。本研究试图评估两种不同的方法——多粘菌素肉汤纸片洗脱法和Vitek 2检测最低抑菌浓度（MIC），并与美国临床和实验室标准协会（CLSI）批准的用于肠杆菌科细菌、鲍曼不动杆菌和铜绿假单胞菌临床分离株的多粘菌素肉汤微量稀释法（BMD）进行比较。
采用BMD、多粘菌素肉汤纸片洗脱法（CBDE）和Vitek 2方法测定6013株碳青霉烯类耐药分离株对多粘菌素的敏感性，并按照CLSI指南进行解释。将CBDE、Vitek 2的MIC结果与BMD的结果进行比较，并计算基本一致性（EA）、分类一致性（CA）、敏感性、特异性、非常重大错误（VME）、重大错误（ME）和科恩kappa系数（CK）。通过常规聚合酶链反应评估所有耐多粘菌素分离株中是否存在任何质粒介导的多粘菌素耐药性（mcr-1、2、3、4和5）。
在碳青霉烯类耐药分离株中，发现778株（12.9%）菌株对多粘菌素耐药。鲍曼不动杆菌通过BMD方法检测出的多粘菌素耐药率最高（18.9%）。Vitek 2的MIC敏感性范围为78.2 - 84.8%，特异性>92%。Vitek 2方法存在171个VME和323个ME，远远超出CLSI可接受范围。鲍曼不动杆菌出现的错误百分比最高（占VME的27.8%和ME的7.9%）。另一方面，CBDE方法表现良好，其EA、CA、VME和ME均在所有生物体的可接受范围内。与金标准BMD相比，CBDE方法对不同菌株的敏感性在97.5 - 98.8%之间，特异性超过97.6%。所有分离出的耐多粘菌素生物体均未携带mcr质粒。
由于BMD存在许多技术复杂性，对于像印度这样的国家，CBDE是最佳的可行替代方法。由于VME的高发生率，特别是对于鲍曼不动杆菌属，Vitek 2报告的敏感MIC需要谨慎考虑。
