The A to Z of A/C plasmids

Abstract

Plasmids belonging to incompatibility groups A and C (now A/C) were among the earliest to be associated with antibiotic resistance in Gram-negative bacteria. A/C plasmids are large, conjugative plasmids with a broad host range. The prevalence of A/C plasmids in collections of clinical isolates has revealed their importance in the dissemination of extended-spectrum β-lactamases and carbapenemases. They also mobilize SGI1-type resistance islands. Revived interest in the family has yielded many complete A/C plasmid sequences, revealing that RA1, designated A/C1, is different from the remainder, designated A/C2. There are two distinct A/C2 lineages. Backbones of 128-130 kb include over 120 genes or ORFs encoding proteins of at least 100 amino acids, but very few have been characterized. Genes potentially required for replication, stability and transfer have been identified, but only the replication system of RA1 and the regulation of transfer have been studied. There is enormous variety in the antibiotic resistance genes carried by A/C2 plasmids but they are usually clustered in larger regions at various locations in the backbone. The ARI-A and ARI-B resistance islands are always at a specific location but have variable content. ARI-A is only found in type 1 A/C2 plasmids, which disseminate blaCMY-2 and blaNDM-1 genes, whereas ARI-B, carrying the sul2 gene, is found in both type 1 and type 2. This review summarizes current knowledge of A/C plasmids, and highlights areas of research to be considered in the future.

Complete Nucleotide Sequences of Two VIM-1-Encoding Plasmids from Klebsiella pneumoniae and Leclercia adecarboxylata Isolates of Czech Origin

“…However, direct repeats were not found at the boundaries of the Tn1696-like transposon structure, excluding its transposition into pKpn-431cz. Interestingly, resistance islands composed of a class 1 integron and multiple transposons included within a class II transposon structure have been previously identified in IncA/C 2 MDR plasmids (23,24).…”

Initial Assessment of the Molecular Epidemiology of bla NDM-1 in Colombia

“…The bla NDM-1 -bearing plasmid (178 kb) contained an Inc A/C2 replicon, extensively associated with antibiotic resistance in Gram-negative bacteria (22). The plasmid backbone shares similarity with other plasmids carrying bla NDM-1 and other ␤-lactamases in a variety of Gram-negative species (see Table S2 in the supplemental material).…”

Characterization of Two Multidrug-Resistant IncA/C Plasmids from the 1960s by Using the MinION Sequencer Device

“…lasmids belonging to the A/C incompatibility group (IncA/C) are large, low-copy-number, conjugative extrachromosomal elements that often encode resistance genes (1,2,3,4). The efficient conjugation system and broad host range of IncA/C plasmids and their ability to mobilize multidrug-resistant genomic islands (GIs) are presumably responsible for the rapid dissemination of resistance genes among Gram-negative enteric bacteria (5,6).…”