Investigation of Chlorhexidine Tolerance and its Association with Antibiotic Resistance in Clinical Gram-Negative Bacilli Isolates

Clin Lab. 2021 Sep 1;67(9). doi: 10.7754/Clin.Lab.2021.210123.

ABSTRACT

BACKGROUND: Chlorhexidine (CHX) is one of the most frequently used antiseptic agents in challenging multidrug-resistant (MDR) isolates. There is an increasing number of reports on reduced susceptibility (tolerance) to CHX in MDR isolates. We aimed to investigate CHX tolerance in Gram-negative bacilli (GNB) and its possible association with antibiotic resistance.

METHODS: A total of 84 enteric GNB (ENT) and 40 non-fermentative GNB (NFGNB) isolates were collected from different clinical specimens. Disk diffusion method was performed to differentiate between MDR and non-MDR isolates and tolerance to CHX was determined by a modified agar dilution method. In GNB isolates, CHX tolerance was defined as a minimum inhibitory concentration (MIC) ≥ 4 mg/L.

RESULTS: We detected that 26.2% (22/84) of ENT and 50.0% (20/40) of NFGNB were MDR and the rest were non-MDR isolates. The CHX tolerance rate was detected as 50.0% (10/20) in MDR-NFGNB and 15.0% (3/20) in non-MDR-NFGNB, and this difference was statistically significant (p < 0.05). Conversely, the tolerance rate was observed as 4.5% (1/22) in MDR-ENT and 1.6% (1/62) in non-ENT, and this difference was not statistically significant (p ˃ 0.05).

CONCLUSIONS: NFGNB isolates had a higher tendency to CHX tolerance than ENT, and antibiotic resistance facili-tates the selection of CHX tolerance in NFGNB but not in ENT isolates.

PMID:34542983 | DOI:10.7754/Clin.Lab.2021.210123