The treatment of invasive NTHi infection can be seriously affected by antibiotic resistance.
NTHi is able to persist in the respiratory tract and also to be responsible of recurrent infections ( Leach et al., 1994). The asymptomatic colonization of the human nasopharynx is considered as the first step in the pathogenesis. The non-invasive infections usually affect the upper respiratory tract, whereas the invasive infections include bacteremia, and meningitis ( Tristram et al., 2007 Murphy et al., 2009 Langereis and de Jonge, 2015). Non-typeable Haemophilus influenzae (NTHi) commonly resides in the human nasopharynx, from which it can disseminate to other organs and cause two types of infections, differing in their epidemiology and severity. In contrast, the transcript levels of ompP2 (encoding the outer membrane protein P2) and acrB gene (encoding AcrB) were significantly lower under heat stress condition.Ĭonclusion: This study shows that the transcriptional modulation of ponB, ompP2, acrR, and acrB in the heat stress response is correlated to enhanced antimicrobial effects of imipenem on non-typeable H. The expression levels of ponB (encoding PBP1b) and acrR (regulator of AcrAB-TolC efflux pump) were significantly increased at 42☌. Transcriptome analysis showed that under heat stress conditions, there were 141 differentially expressed genes with a | log2(fold change)| > 1, including 67 up-regulated and 74 down-regulated genes. Results: Quantitation of NTHi viable cells after incubation with 0.25 μg/mL of imipenem for 3 h revealed more than a twofold decrease in GE47 and GE88 viable cells at 42☌ as compared to 37☌.
Global transcriptional changes were monitored by RNA-seq after pre-incubation of bacterial cells at either 37 or 42☌, and the expression levels of relevant target genes were confirmed by qRT-PCR. The detection of PBPs was carried out by Bocillin-FL. The imipenem killing activity was assessed after incubation of the NTHi strains at either 37 or 42☌ for 3 h with increasing concentrations of imipenem. Methods: The two NTHi clinical isolates (GE47 and GE88, imipenem MICs by E-test > 32 μg/mL) examined in this study were collected at Geneva University Hospitals. Objective: The purpose of the present study was to investigate the penicillin binding proteins (PBPs), drug influx and efflux modulations during heat stress and their effects on the bactericidal action of imipenem on non-typeable Haemophilus influenzae (NTHi).
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