Comparative genomic analysis of Pseudomonas aeruginosa strains susceptible and resistant to carbapenems and aztreonam isolated from patients with healthcare-associated infections in a Mexican hospital.

Pseudomonas aeruginosa (PA) is an important opportunistic pathogen that causes different infections on immunocompromised patients. Within PA accessory genome, differences in virulence, antibiotic resistance and biofilm formation have been described between strains, leading to the emergence of multidrug-resistant strains. The genome sequences of 17 strains isolated from patients with healthcare-associated infections in a Mexican hospital were genomically and phylogenetically analyzed and antibiotic resistance genes, virulence genes, and biofilm formation genes were detected. Fifteen of the 17 strains were resistant to at least two of the carbapenems meropenem, imipenem, and the monobactam aztreonam. The antibiotic resistance (mexA, mexB, and oprM) and the biofilm formation (pslA and pslD) genes were detected in all strains. Differences were found between strains in accessory genome size. The strains had different sequence types, and seven strains had sequence types associated with global high risk epidemic PA clones. All strains were represented in two groups among PA global strains. In the 17 strains, horizontally acquired resistance genes to aminoglycosides and beta-lactams were found, mainly, and between 230 and 240 genes that encode virulence factors. The strains under study were variable in terms of their accessory genome, antibiotic resistance, and virulence genes. With these characteristics, we provide information about the genomic diversity of clinically relevant PA strains.

Commensal and virulent Escherichia coli strains of vaginal origin are reservoirs of resistance cassettes in class 1 integrons.

INTRODUCTION: Antimicrobial resistance in Escherichia coli, one of the causal agents of aerobic vaginitis, leads to the persistence of the infection. The investigation of integrons acquires relevance, since they are elements that are responsible for the acquisition of resistance to antibiotics. The aim of this work was to describe the structural diversity of class 1 integrons in virulent and commensal strains of E. coli isolated from patients with vaginal infection. METHODOLOGY: Ninety-two strains of E. coli were isolated from patients with aerobic vaginitis. Resistance profile against 19 antibiotics and class 1 integrons were detected by PCR. The identity and arrangement of cassettes was determined by sequencing. ERIC-PCR assays were carried out in strains with identical arrays. Finally, genotyping by Clermont algorithm and serotyping were performed. Seventeen strains showed integrons located in plasmids. RESULTS: Ten different gene cassette arrays were identified in 30 strains of E. coli. Cassettes corresponding to genes coding for adenylyltransferases (aadA), dihydrofolate reductases (dfrA), and oxacillinases (blaOXA) were detected. Array dfrA17-aadA5 was predominantly prevalent over the other arrays identified. Phylogenetic group A was the most predominant, followed by group B2 and D. CONCLUSIONS: This study demonstrates the presence of E. coli of vaginal origin carrying class 1 integrons, which are main genetic elements of capture of resistance genes, with the possibility of capturing new resistance cassettes. These evidences should serve for the modification of protocols in the diagnosis and treatment of aerobic vaginitis, and the development of policies for the rational use of antimicrobials.

Characteristics of KPC-2-producing Klebsiella pneumoniae (ST258) clinical isolates from outbreaks in 2 Mexican medical centers.

The KPC-producing Klebsiella pneumoniae sequence type 258 (ST258) is an important pathogen widely spread in nosocomial infections. In this study, we identified the KPC-2-producing K. pneumoniae clinical isolates of 2 unrelated outbreaks that corresponded to pandemic strain ST258. The isolates showed high resistance to cephalosporins, carbapenems, quinolones, and colistin. The KPC-2-producing K. pneumoniae isolates were compared to the previously studied KPC-3-producing K. pneumoniae isolates from an outbreak in Mexico; they showed an unrelated pulsed-field gel electrophoresis fingerprinting pattern and a different plasmid profile. The KPC-2 carbapenemase gene was identified in two 230- and 270-kb non-conjugative plasmids; however, 1 isolate transferred the KPC-2 gene onto an 80-kb plasmid. These findings endorse the need of carrying out a continuous molecular epidemiological surveillance of carbapenem-resistant isolates in hospitals in Mexico.