Precis Future Med.  2024 Mar;8(1):10-18. 10.23838/pfm.2023.00184.

Development of colistin resistance via heteroresistance modeling in Klebsiella pneumoniae: A diagnostic study

• Seo J
• Ko KS

• KMID: 2553871
• DOI: http://doi.org/10.23838/pfm.2023.00184

Abstract

Purpose
Colistin heteroresistance mediates the failure of antibiotic treatments, is prone to lead to colistin resistance, and has been frequently reported in Klebsiella pneumoniae. This study investigated origins of the increase in colistin resistance following colistin exposure to colistin-heteroresistant K. pneumoniae.
Methods
A modeled colistin-heteroresistant K. pneumoniae strain (i.e., mimicking colistin- heteroresistant [m-CL^HR]) was generated using a susceptible K. pneumoniae strain ATCC 10031 and its resistance-induced mutant. Heteroresistance patterns were investigated through population analysis profiling (PAP), competition assays, and fluctuation and stability tests. An in vitro time-killing assay for colistin was performed for the m-CL^HR to identify the change in susceptible and resistant populations before and after colistin exposure.
Results
The generated m-CL^HR strain showed a typical heteroresistance pattern for colistin in PAP, and its competition assay did not show fitness costs for any population. The ratio of resistant cells to susceptible cells did not deviate significantly from the range of heteroresistance in the fluctuation test, while the ratios of resistant cells preserved their stability. The in vitro time-killing assay thus showed that the resistant cells increased upon colistin exposure; sequencing analyses confirmed that the surviving resistant cells did not originate from susceptible cells by mutation. This study successfully modeled a colistin-heteroresistant K. pneumoniae strain, i.e., m-CL^HR.
Conclusion
In this modeled heteroresistant strain, only the colistin-resistant population survived the colistin treatment—this suggests that the development of colistin resistance from heteroresistant strain is because of the selection of a resistant population and not by the induction of resistance through mutations in susceptible populations.

Keyword

Colistin; Heteroresistance