# Rapid colistin susceptibility determination by a novel fluorogenic method in Klebsiella pneumoniae strains

## TL;DR

A new fast method can detect colistin resistance in Klebsiella pneumoniae within 2 hours, helping treat critically ill patients more effectively.

## Contribution

A novel fluorogenic method for rapid colistin susceptibility testing in K. pneumoniae strains is introduced and validated.

## Key findings

- The fluorometric method determined colistin MIC in K. pneumoniae within 2 hours.
- The new method showed high agreement with standard methods for most tested strains.
- The fluorometric method can help guide timely treatment decisions in critical care settings.

## Abstract

Klebsiella pneumoniae is a causative agent that can lead to fatal infections, especially in intensive care patients. Colistin treatment is employed as a last resort in K. pneumoniae infections caused by strains resistant to almost all antibiotics from different groups. However, in recent years, colistin resistance has also become widespread in K. pneumoniae strains. Therefore, before starting treatment with this relatively toxic drug, it is essential to know its susceptibility to colistin. A standard colistin susceptibility test typically takes 24–48 h. In this study, we investigated the accuracy of our novel fluorometric method, which enables the determination of colistin minimal inhibitory concentration (MIC) within 2 h for K. pneumoniae.

For this purpose, we determined and compared the MIC values of 24 colistin-resistant and 18 colistin-susceptible K. pneumoniae strains using the standard broth microdilution method and the new fluorometric method.

In the comparison of MIC values determined by standard and fluorometric methods, it was observed that the MIC values of 22 strains were identical, there was a 1-dilution (1/2) difference in 14 strains, and a 2-dilution (1/4) difference in six strains.

We believe that the new fluorometric antibiotic susceptibility testing method will be a valuable tool in the rapid detection of colistin resistance in K. pneumoniae and thus for guiding appropriate treatment in critically ill patients.