Klebsiella pneumoniae FFUL 22K was isolated in April 1999 from the urine of an intensive care unit patient in Portugal. The strain showed an extended-spectrum cephalosporin resistance profile. A typical synergistic effect between cefotaxime or cefepime and clavulanic acid was observed. An Escherichia coli transformant displayed a similar resistance phenotype and harbored a ca. 9.4-kb plasmid (p22K9). Cloning experiments revealed that the extended-spectrum β-lactamase was encoded by bla _GES-1 , previously described in class 1 integrons from K. pneumoniae ORI-1 and Pseudomonas aeruginosa Pa695. Further sequence analysis demonstrated that the bla _GES-1 gene cassette was located on a new class 3 integron. The integron was 2,863 bp long and consisted of an intI3 integrase gene, an attI3 recombination site, two promoter regions, and two gene cassettes. The IntI3 integrase was 98.8% identical to that of Serratia marcescens AK9373. The bla _GES-1 gene cassette was inserted at the attI3 site. The second gene cassette was the result of a fusion event between bla _OXA-10 -type and aac(6′)-Ib gene cassettes and conferred resistance to kanamycin. This is the second class 3 integron reported and the first time that the bla _GES-1 gene cassette has been found on an integron belonging to this class, highlighting the considerable heterogeneity of their genetic environment and the spread of gene cassettes among different classes of integrons.

This study focused on the population structure of OXA-23-producing Acinetobacter baumannii clinical isolates from Rio de Janeiro, Brazil. The analysis included several genomic typing methods, including PFGE, two multilocus sequence typing (MLST) schemes, sequence group (SG) determination and bla_OXA-51-like sequencing. The genomic context of the bla_OXA-23 gene was also evaluated using I-CeuI hybridizations and PCR assays. Congruent clustering was obtained revealing four lineages. In accordance, four new sequence types (STs) (ST131, ST132, ST133 and ST134) were obtained with the MLST-OD scheme (associated with the Oxford Database) and four (ST79, ST15 and two new allelic profiles) with the MLST-IP scheme (developed by the Institute Pasteur). Four SGs (SG1, SG4 and two new profiles) were identified, allowing the association of 70% of the isolates with European clone II. bla_OXA-51-like sequencing revealed the presence of bla_OXA-66, bla_OXA-69, bla_OXA-95 and bla_OXA-132. Identification of new STs together with new SG profiles are findings suggestive of a local diversity hotspot that is worth exploring.

The evolution and spread of antibiotic resistance is often mediated by mobile genetic elements. Integrative and conjugative elements (ICEs) are the most abundant conjugative elements among prokaryotes. However, the contribution of ICEs to horizontal gene transfer of antibiotic resistance has been largely unexplored. Here we report that ICEs belonging to mating-pair formation (MPF) classes G and T are highly prevalent among the opportunistic pathogen Pseudomonas aeruginosa, contributing to the spread of carbapenemase-encoding genes (CEGs). Most CEGs of the MPF_G class were encoded within class I integrons, which co-harbour genes conferring resistance to other antibiotics. The majority of the integrons were located within Tn3-like and composite transposons. Conserved attachment site could be predicted for the MPF_G class ICEs. MPF_T class ICEs carried the CEGs within composite transposons which were not associated with integrons. The data presented here provides a global snapshot of the different CEG-harbouring ICEs and sheds light on the underappreciated contribution of these elements to the evolution and dissemination of antibiotic resistance on P. aeruginosa.