Evaluation of colistin susceptibility among Klebsiella pneumoniae isolates by broth microdilution and colistin agar test

IF 1.8 4区医学 Q3 INFECTIOUS DISEASES

Diagnostic microbiology and infectious disease Pub Date : 2025-09-22 DOI:10.1016/j.diagmicrobio.2025.117119

Hitha Haridas , Shweta Raina , Priyanka Das, Shweta Kunwar, Rajni Gaind

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引用次数: 0

Abstract

Background

Colistin is a last-resort antibiotic against multidrug-resistant (MDR) Klebsiella pneumoniae. Reliable susceptibility testing is critical but challenging due to colistin’s complex pharmacodynamics and testing limitations. This study evaluates the performance of the Colistin Agar Test (CAT) against the gold standard Broth Microdilution (BMD) method.

Methods

Study was conducted after confirming stability of colistin in agar plate. A total of 150 non-duplicate clinical isolates of K. pneumoniae (103 colistin intermediate, 47 resistant) were tested using both BMD and CAT. Antimicrobial susceptibility testing (AST) of these isolates was performed using VITEK-2. Quality control was ensured using CLSI-recommended strains. Statistical parameters including Categorical Agreement (CA), Essential Agreement (EA), Major Error (ME), Very Major Error (VME), sensitivity, specificity, predictive values, and Cohen’s Kappa were calculated using BMD as reference.

Results

MICs ranged from 0.125-16 µg/mL (BMD) and 0.125–8 µg/mL (CAT). CA and EA for CAT were 96 % and 87.3 % respectively. ME and VME were 4.8 % and 2.1 %. Sensitivity, specificity, PPV, and NPV of CAT were 97.9 %, 95.1 %, 90.1 %, and 98.9 % respectively. Cohen’s Kappa showed almost perfect agreement (0.91).

Conclusion

CAT demonstrated high agreement with BMD and showed promise as a screening tool for colistin susceptibility in K. pneumoniae. While BMD remains the gold standard, CAT offers a feasible alternative for routine use, particularly in resource-limited settings. However, resistant results by CAT should be confirmed with BMD to avoid false resistance reporting and potential therapeutic exclusion of colistin.

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用肉汤微量稀释法和黏菌素琼脂试验评价肺炎克雷伯菌分离株黏菌素敏感性

背景：粘菌素是抗多药耐药肺炎克雷伯菌的最后手段。可靠的药敏试验至关重要，但由于粘菌素复杂的药效学和试验限制，具有挑战性。本研究对黏菌素琼脂试验（CAT）与金标准微量肉汤稀释法（BMD）的性能进行了评价。方法在琼脂平板上确认黏菌素的稳定性后进行研究。采用BMD和CAT对150株无重复临床分离肺炎克雷伯菌（103株为粘菌素中间体，47株耐药）进行检测。采用VITEK-2进行药敏试验（AST）。采用clsi推荐菌株进行质量控制。以骨密度为参考计算统计参数，包括分类一致性（CA）、基本一致性（EA）、主要误差（ME）、非常主要误差（VME）、敏感性、特异性、预测值和Cohen’s Kappa。结果smics范围为0.125 ~ 16µg/mL （BMD）和0.125 ~ 8µg/mL （CAT）。CAT的CA和EA分别为96%和87.3%。ME和VME分别为4.8%和2.1%。CAT的敏感性、特异性、PPV和NPV分别为97.9%、95.1%、90.1%和98.9%。Cohen’s Kappa几乎完全一致（0.91）。结论cat与BMD具有较高的一致性，有望作为肺炎克雷伯菌粘菌素敏感性的筛查工具。虽然BMD仍然是黄金标准，但CAT为常规使用提供了可行的替代方案，特别是在资源有限的环境中。然而，CAT的耐药结果应与BMD一起确认，以避免错误的耐药报告和可能的治疗排除粘菌素。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Diagnostic microbiology and infectious disease 医学-传染病学

CiteScore

5.30

自引率

3.40%

发文量

149

审稿时长

56 days

期刊介绍： Diagnostic Microbiology and Infectious Disease keeps you informed of the latest developments in clinical microbiology and the diagnosis and treatment of infectious diseases. Packed with rigorously peer-reviewed articles and studies in bacteriology, immunology, immunoserology, infectious diseases, mycology, parasitology, and virology, the journal examines new procedures, unusual cases, controversial issues, and important new literature. Diagnostic Microbiology and Infectious Disease distinguished independent editorial board, consisting of experts from many medical specialties, ensures you extensive and authoritative coverage.