title: Prevalence of Ambler class A β-lactamases and ampC expression in cephalosporin-resistant isolates of Acinetobacter baumannii.
abstract: We examined the prevalence of various cephalosporins' resistance mechanisms in Acinetobacter baumannii clinical isolates. Phenotypic and molecular detection of Ambler classes A, B and D β-lactamases was performed on 75 isolates. Clonal relatedness was defined using Repetitive Extragenic Palindromic PCR. PCR mapping was used to examine the linkage of insertion sequences and the ampC gene, and ampC expression was analyzed by TaqMan reverse transcriptase-PCR. Twenty-six (37%) isolates carried at least one of the blaPER-1 or blaTEM-1. Sixty-nine (98.5%) out of 70 cephalosporin-resistant isolates had insertions upstream of the ampC gene, of which 48 (69%) and 6 (8%) were identified as ISAba1and ISAba125, respectively. Higher level of expression was obtained in resistant isolates lacking ISAba1/ampC combination in comparison with that in positive ones. The ability to up-regulate the expression of ampC gene in association with different insertion elements has become an important factor in A. baumannii resistance to cephalosporins.
authors.affiliation: Tabriz Research Center of Infectious and Tropical Diseases, Tabriz University of Medical Sciences, Tabriz 5163639888, Iran.
authors.forename: Mohammad Ahangarzadeh
authors.initials: MA
authors.lastname: Rezaee
authors.forename: Omid
authors.initials: O
authors.lastname: Pajand
authors.forename: Mohammad Reza
authors.initials: MR
authors.lastname: Nahaei
authors.forename: Reza
authors.initials: R
authors.lastname: Mahdian
authors.forename: Mohammad
authors.initials: M
authors.lastname: Aghazadeh
authors.forename: Morteza
authors.initials: M
authors.lastname: Ghojazadeh
authors.forename: Zoya
authors.initials: Z
authors.lastname: Hojabri
mesh_terms: D000151:Acinetobacter Infections / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology*; D040981:Acinetobacter baumannii / Q000201:enzymology* / Q000235:genetics; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D018550:Cephalosporin Resistance; D002510:Cephalosporinase / Q000235:genetics* / Q000378:metabolism; D002511:Cephalosporins / Q000494:pharmacology*; D002874:Chromosome Mapping; D004252:DNA Mutational Analysis; D052978:Disk Diffusion Antimicrobial Tests; D006801:Humans; D058889:Molecular Typing; D016254:Mutagenesis, Insertional; D015995:Prevalence; D060888:Real-Time Polymerase Chain Reaction; D012141:Respiratory Tract Infections / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology; D001618:beta-Lactamases / Q000235:genetics / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D002511:Cephalosporins; D002510:Cephalosporinase; C048795:AmpC beta-lactamases; D001618:beta-Lactamases; C063912:carbapenemase