title: Distribution and expression of the Ade multidrug efflux systems in Acinetobacter baumannii clinical isolates.
abstract: One hundred Acinetobacter baumannii clinical isolates were examined for inhibitory effect of reserpine and carbonyl cyanide m-chlorophenylhydrazone (CCCP) on the antimicrobial susceptibility and expression of 4 resistant-nodulation-cell division (RND)-type multidrug efflux systems, including AdeABC, AdeDE, AdeIJK, and AdeFGH, using RT-PCR. Ten A. baumannii isolates expressing AdeABC, AdeIJK, or AdeFGH were randomly selected for determination of transcription level and regulatory mutations. While all the isolates were resistant to multiple drugs, the reserpine and CCCP experiment showed that the multidrug resistance phenotype in most A. baumannii isolates was associated with efflux pumps. Most isolates expressed at least one of the RND-type efflux pumps tested (97%). AdeIJK expression was most common (97%), but none of the isolates produced AdeDE. Fifty-two percent of the A. baumannii isolates simultaneously produced up to 3 RND-type efflux systems (i.e., AdeABC, AdeFGH, and AdeIJK). No good correlation between the expression of RND-type efflux pumps and the type of antimicrobial resistance was observed. Overexpression of AdeABC, AdeIJK, and AdeFGH was not always related to the presence of mutations in their corresponding regulatory genes. This study highlights (i) the universal presence of the RND-type efflux pumps with variable levels of expression level among the A. baumannii in this collection and (ii) the complexity of their regulation of expression.
authors.affiliation: a Research Unit in Microbial Food Safety and Antimicrobial Resistance, Department of Veterinary Public Health, Faculty of Veterinary Science, Chulalongkorn University, Bangkok 10330, Thailand.
authors.forename: Sirawit
authors.initials: S
authors.lastname: Pagdepanichkit
authors.affiliation: b Department of Microbiology, Faculty of Medicine, Mahidol University, Bangkok, Thailand.
authors.forename: Chanwit
authors.initials: C
authors.lastname: Tribuddharat
authors.affiliation: a Research Unit in Microbial Food Safety and Antimicrobial Resistance, Department of Veterinary Public Health, Faculty of Veterinary Science, Chulalongkorn University, Bangkok 10330, Thailand.
authors.forename: Rungtip
authors.initials: R
authors.lastname: Chuanchuen
mesh_terms: D040981:Acinetobacter baumannii / Q000187:drug effects / Q000302:isolation & purification / Q000378:metabolism*; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics*; D006801:Humans; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D026901:Membrane Transport Proteins
keywords: Acinetobacter baumannii; RND-type efflux systems; multidrug resistance; résistance multimédicamenteuse; systèmes d’efflux de type RND