Characterizing polymyxin heteroresistance in clinical Klebsiella oxytoca isolates reveals treatment complications, suggesting urgent attention is needed.
Antibiotic heteroresistance presents a growing public health concern since the phenotype is associated with treatment failure and is hard to detect using conventional diagnostic testing. In this study, we characterized polymyxin B heteroresistance in a collection of clinical and environmental isolates of Klebsiella oxytoca , an opportunistic pathogen associated with hospital-acquired infections. All six of the isolates tested exhibited heteroresistance, indicated by a 16-fold difference between the highest non-inhibitory concentration (2 μg/mL) and the minimum inhibitory concentration (32-64 μg/mL) observed in population analysis profile (PAP) assays. Heteroresistance was found to be due to the presence of a stable sub-population of resistant bacteria and was unaffected by growth phase or the presence of host antimicrobial factors present in human serum. MALDI-TOF analysis revealed L-Ara4N modifications of the lipid A of resistant sub-populations. This pilot study identifies polymyxin heteroresistance in K. oxytoca may complicate treatment of infections caused by this organism.
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Ayerakwa et al. (2025) studied this question.
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