Distribution of ceftazidime-avibactam and colistin MIC values in carbapenem-resistant Klebsiella pneumoniae and its association with carbapenemase genotypes in Can Tho, Vietnam

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Carbapenem-resistant Klebsiella pneumoniae (CRKP) is a World Health Organization critical-priority pathogen, with a bloodstream-infection mortality of 40-70%. Ceftazidime-avibactam (CAZ-AVI) and colistin are key agents against CRKP, yet data on their minimum inhibitory concentrations (MICs) and association with carbapenemase genotypes in the Mekong Delta region of Vietnam are limited. This cross-sectional study on CRKP isolates from clinical specimens at hospitals in Can Tho City (November 2024-July 2025) determined the MICs of CAZ-AVI and colistin and their association with carbapenemase genotypes (blaKPC, blaOXA-48-like, blaNDM, blaIMP, blaVIM). MICs were measured by broth microdilution and interpreted per CLSI M100 (2024) and EUCAST (2024, for colistin); carbapenemases were detected by the modified carbapenem inactivation method (mCIM), the D73C disc, and singleplex polymerase chain reaction (PCR). Among 112 strains, susceptibility was 42.0% for CAZ-AVI (MIC50/MIC90 > 16/4 μg mL-1) and 82.1% for colistin (MIC50 = 1 μg mL-1, MIC90 = 8 μg mL-1). Among 92 PCR-tested strains, co-carriage of ≥2 carbapenemase genes were most common, and blaOXA-48-like was the most prevalent single gene. The CAZ-AVI MIC differed significantly among genotypes (p = 0.002): isolates carrying blaKPC or blaOXA-48-like retained the highest susceptibility, whereas all isolates carrying only a metallo-β-lactamase (blaNDM or blaVIM) were resistant; the colistin MIC did not differ among genotypes (p = 0.376). Carbapenemase genotyping should guide the use of CAZ-AVI in this setting, particularly for distinguishing serine carbapenemase producers from MBL producers, while the elevated colistin MIC90 supports continued surveillance of colistin susceptibility.