Journal Article

Acquisition and transfer of antibiotic resistance genes in association with conjugative plasmid or class 1 integrons of Acinetobacter baumannii

Leungtongkam, Udomluk, Tasanapak, Kannipa, Sitthisak, Sutthirat, Thummeepak, Rapee

2018

Overview

Conjugation is a type of horizontal gene transfer (HGT) that serves as the primary mechanism responsible for accelerating the spread of antibiotic resistance genes in Gram-negative bacteria. The present study aimed to elucidate the mechanisms underlying the conjugation-mediated gene transfer from the extensively drug-resistant Acinetobacter baumannii (XDR-AB) and New Delhi Metallo-beta-lactamase-1-producing Acinetobacter baumannii (NDM-AB) to environmental isolates of Acinetobacter spp. Conjugation experiments demonstrated that resistance to ticarcillin and kanamycin could be transferred from four donors to two sodium azide-resistant A. baumannii strains, namely, NU013R and NU015R. No transconjugants were detected on Mueller-Hinton Agar (MHA) plates containing tetracycline. Plasmids obtained from donors as well as successful transconjugants were characterized by PCR-based replicon typing and S1-nuclease pulsed-field gel electrophoresis (S1-PFGE). Detection of antibiotic resistance genes and integrase genes (int) was performed using PCR. Results revealed that the donor AB364 strain can transfer the blaOXA-23 and blaPER-1 genes to both recipients in association with int1. A 240-kb plasmid was successfully transferred from the donor AB364 to recipients. In addition, the aphA6 and blaPER-1 genes were co-transferred with the int1 gene from the donor strains AB352 and AB405. The transfer of a 220-kb plasmid from the donors to recipient was detected. The GR6 plasmid containing the kanamycin resistance gene (aphA6) was successfully transferred from the donor strain AB140 to both recipient strains. However, the blaNDM-1 and tet(B) genes were not detected in all transconjugants. Our study is the first to demonstrate successful in vitro conjugation, which indicated that XDR-AB contained combination mechanisms of the co-transfer of antimicrobial resistance elements with integron cassettes or with the plasmid group GR6. Thus, conjugation could be responsible for the emergence of new types of antibiotic-resistant strains.

• Publisher: Public Library of Science,Public Library of Science (PLoS)
• Subject: Acinetobacter / Acinetobacter baumannii / Acinetobacter baumannii - genetics / Acinetobacter baumannii - growth & development / Antibiotic resistance / Antibiotics / Antimicrobial agents / Antimicrobial resistance / Bacteria / Bacterial Proteins - genetics / Biology and Life Sciences / Cassettes / Chromosomes / Conjugation / Conjugation, Genetic / Dosage and administration / Drug resistance / Drug Resistance, Multiple, Bacterial / Electrophoresis / Enzymes / Gel electrophoresis / Gene transfer / Genes / Genomics / Gram-negative bacteria / Identification / INT1 gene / Integrase / Integrons / Kanamycin / Kanamycin - pharmacology / Laboratories / Medicine and Health Sciences / Metallography / Microbial drug resistance / Microbial Sensitivity Tests / Microbial Viability / Nosocomial infections / Nuclease / Parasitology / Physical Sciences / Plasmids / Plasmids - genetics / Public health / Pulsed-field gel electrophoresis / Research and Analysis Methods / Sodium / Sodium azide / Sodium Azide - pharmacology / Sodium azides / Strains (organisms) / Streptococcus infections / Studies / Tetracycline - pharmacology / Ticarcillin / Ticarcillin - pharmacology / Typing / β Lactamase