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Amino acid substitution mutations and mRNA expression levels of the pbp5 gene in clinical Enterococcus faecium isolates conferring high level ampicillin resistance
Author(s) -
Darehkordi Hosein,
Saffari Fereshteh,
Mollaei Hamid Reza,
Ahmadrajabi Roya
Publication year - 2019
Publication title -
apmis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.909
H-Index - 88
eISSN - 1600-0463
pISSN - 0903-4641
DOI - 10.1111/apm.12922
Subject(s) - biology , ampicillin , enterococcus faecium , gene , penicillin binding proteins , allele , penicillin , minimum inhibitory concentration , microbiology and biotechnology , genetics , bacteria , antibiotics , escherichia coli
In this study, clinical ampicillin‐resistant Enterococcus faecium isolates with minimum inhibitory concentrations ( MIC s) for ampicillin in the ranges from 128 to ˃512 μg/mL (n = 17) and two ampicillin‐susceptible isolates ( MIC 1 μg/mL) were investigated. No β‐lactamase production was detected in these isolates. Alterations in the C‐terminal part of pbp 5 and levels of pbp 5 mRNA expression were investigated by sequencing and quantitative real‐time qRT‐PCR , respectively. Sequencing analysis revealed five different pbp 5 alleles (A to E) having differences in 18 amino acid positions spanning from residue 426 to 642. Allele A (V‐462 → A, H‐470 → Q, M‐485 → A, N‐496 → K, A‐499 → T, E‐525 → D, N‐546 → T, A‐558 → T, G‐582 → S, E‐629 → V, K‐632 → Q, and P‐642 → L) was the most frequent allele. The presence of just two susceptible isolates in allele E suggests a possible correlation between amino acid patterns and MIC , even if there is no discernible correlation with specific single amino acid differences. Also, these were the only isolates that showed much lower expression of class B penicillin‐binding protein 5 ( PBP 5) compared to isolates with MIC of 128 or greater. Thus, ampicillin MIC s were correlated with PBP 5 expression.