Changes in
taxonomy may clarify each species contribution for recruitment and dissemination of their relevant β-lactamases. The CTX-M-2 subgroup is linked to Kluyvera ascorbata, KLUC to Kluyvera ...cryocrescens, and CTX-M-25 to Kluyvera georgiana. The CTX-M-8 subgroup can be linked to
genomospecies 3 and CTX-M-9 to
genomospecies 2. Kluyvera sichuanensis and
genomospecies 1 harbor new subgroups. The CTX-M-1 subgroup has a direct counterpart in an isolate proposed as a new genomospecies 5.
A clinical isolate of C. freundii with reduced susceptibility to extended-spectrum β-lactams from a woman with cystocele associated with recurrent urinary tract infection was analyzed. Susceptibility ...tests, double disk synergy tests (DDST) and enzymatic activity by the agar iodometric method suggested the presence of ESBLs. Conjugation experiments revealed the presence of a large conjugative plasmid (pLM07/20) with an exclusive FrepB replicon type (IncF/FIB). PCR analysis and sequencing confirmed the presence of the blaCTX-M-14 gene in the pLM07/20 from C. freundii.LM07/10. Although this is the first report of CTX-M-14 in Venezuela, we alert the medical community that future increase of these β-lactamases in our city could be due to dissemination of plasmids into bacterial populations.
KPC-2 is one of the most relevant serine-carbapenemases among the carbapenem-resistant
We previously isolated from the environmental species Chromobacterium haemolyticum a class A CRH-1 β-lactamase ...displaying 69% amino acid sequence identity with KPC-2. The objective of this study was to analyze the kinetic behavior and crystallographic structure of this β-lactamase. Our results showed that CRH-1 can hydrolyze penicillins, cephalosporins (except ceftazidime), and carbapenems with similar efficacy compared to KPC-2. Inhibition kinetics showed that CRH-1 is not well inhibited by clavulanic acid, in contrast to efficient inhibition by avibactam (AVI). The high-resolution crystal of the apoenzyme showed that CRH-1 has a similar folding compared to other class A β-lactamases. The CRH-1/AVI complex showed that AVI adopts a chair conformation, stabilized by hydrogen bonds to Ser70, Ser237, Asn132, and Thr235. Our findings highlight the biochemical and structural similarities of CRH-1 and KPC-2 and the potential clinical impact of this carbapenemase in the event of recruitment by pathogenic bacterial species.
Objectives: We analysed the architecture and probable origin of a class 1 integron from cefotaxime-resistant Morganella morganii isolates. Methods: bla genes and class 1 integron elements were ...detected by PCR and DNA–DNA hybridization in a M. morganii strain isolated in 1996. PCR-mapping and sequencing of different fragments were carried out to determine the integron's architecture. Results and conclusions: A class 1 integron (In116), strongly related to the In6/In7 family, was detected in a plasmid from an oxyimino-cephalosporin-resistant M. morganii strain, producing CTX-M-2 β-lactamase. The variable region of In116 contains aacA4, blaOXA-2 and orfD cassettes. Downstream of the 3′-conserved-segment (3′-CS), an orf513-containing common region is followed by blaCTX-M-2 and flanking regions, having 96–99% nucleotide identity with Kluyvera ascorbata's kluA-1 and neighbouring sequences. Some of the evidence supporting the incorporation of foreign DNA is as follows: a partial deletion in a second 3′-CS (3′-CS2), and the absence of 59-base element or IS-like structures upstream of blaCTX-M-2.
To the best of our knowledge, no genomic descriptions of bla
-harbouring plasmids are available in literature so far. The aim of this study was to describe the genomic features of three bla
...-harbouring plasmids recovered from Pseudomonas aeruginosa isolated in Argentina in different periods.
bla
-harbouring plasmids from three clinical P. aeruginosa isolates were transferred by transformation into P. aeruginosa PAO-1. Then, genomic DNA of these transformants was extracted and sequenced using NovaSeq 6000 System-Illumina. De novo assemblies were generated using Unicycler program and reads were mapped against a reference genome of P. aeruginosa PAO-1. Plasmids sequences were predicted identifying the reads that did not map the reference sequence of PAO-1. These reads were recovered and assembled de novo. In silico predictions were carried out using bioinformatics tools.
One Plasmid (pP6VIM-11) was distributed in 2 contigs, a second plasmid (pPOta2VIM-11) was found in a single contig, and the last one (pP936401VIM-11) was fragmented into 4 contigs. pP6VIM-11 and pPOta2VIM-11 belonged to the IncP-1β group, displaying 64% of coverage and 83.9% of identity among them. pP936401VIM-1 plasmid corresponded to the IncN group. The bioinformatic analysis revealed that bla
was located in a class 1 integron, flanked by insertion sequences, exhibiting potential for its dissemination. However, none of the plasmids were conjugative.
This study corresponded to the first description and deposit of bla
-harbouring plasmids in P. aeruginosa, which expands the limited knowledge about their molecular epidemiology.
PDF
