Whole-genome sequence analysis of morphological changes in Haemophilus influenzae after beta-lactam exposure

Abstract

This report describes mutations in genes responsible for cell deformities in haemophili under beta-lactam pressure in vitro. Light and transmission electron microscopy confirmed a hypothesis regarding changes in the shape of haemophili that had become more filamentous in the presence of ampicillin (2 mg/L) and cefuroxime (8 mg/L) after 30 days of serial passage. Short-axis size increased by 28% (from 0.767 to 1.06 µm) and long-axis length increased by 54% (from 1 to 2.175 µm). Additionally, whole-genome sequencing analysis (Illumina platform, software PROKKA) revealed a variety of mutations in genes responsible for cell morphology in isolates examined in this study: ftsI (A1576 → C; G1154 → C; T986 → C; G1684 → C), mreB (C476 → T), mreC (A5 → G), mrdA (A1148 → G; C179 → T; G1613 → T), mrdB (T668 → G), mltC (C1016 → T) and rodA (T668 → G). The results of this study indicate that shifts in bacterial shape could play a role in the adaptation of haemophili to a new niche created by beta-lactams as a strategy of antibiotic therapy survival.

Keywords: Beta-lactams; Haemophili; Whole-genome sequencing.