Molecular characterization of fluoroquinolones, macrolides, and imipenem resistance in Haemophilus influenzae: analysis of the mutations in QRDRs and assessment of the extent of the AcrAB-TolC-mediated resistance

Collection Location Koleksi E-book & E-Journal Perpustakaan Pusat Unila
Edition Vol. 37, Issue. 10
Call Number
ISBN/ISSN 1435-4373
Subject(s) Biomedicine
Classification NONE
Series Title
GMD E-Journal
Language English
Publisher Springer
Publishing Year 2018
Publishing Place Switzerland
Abstract/Notes Abstract
The aims of the present study were to characterize the mechanisms of resistance to fluoroquinolones, macrolides, and imipenem
in Haemophilus influenzae, to assess the extent of the AcrAB-TolC-mediated resistance, and to define a core genome multilocus
sequence typing (cgMLST) scheme for H. influenzae by using whole-genome sequencing. Four amino acid substitutions in GyrA
(at Ser84 and Asp88), ParC (at Ser84), and ParE (at Asp420) were found to be closely associated to the MICs.We did not find any
amino acid substitution surrounding the three highly conserved amino acid motifs in PBP3 related to imipenem resistance. All the
isolates possessed the ermB gene. Carbonyl cyanide m-chlorophenylhydrazone (CCCP) decreased the MIC of imipenem by
twofold for FQR-6 and fourfold for GE47 and GE88 strains. For erythromycin, the MICs were decreased by twofold.We found
that the six FQR isolates were clustered in two groups. The number of different loci within FQR-1_FQR-3_FQR-5 cluster was 6,
while FQR-2 and FQR-4 differed for 21 loci. FQR-1_FQR-3_FQR-5 and FQR-2_FQR-4 clusters were distant among each other
and compared to 19 genomes downloaded from NCBI, to 8 strains heteroresistant to imipenem, and to 4 strains monoresistant to
ciprofloxacin isolated in Denmark.We confirmed that specific amino acid substitutions in GyrA, ParC, and ParE are implicated
in quinolone resistance. Additionally, the degree of resistance is related to the number of these amino acid substitutions. We
provide robust evidence that drug efflux is one of the substantial mechanisms of imipenem and erythromycin resistance in H.
Keywords Imipenem . Fluoroquinolone . Macrolide .H. influenzae . CCCP .Whole-genome sequencing . cgMLST . Antibiotic
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