RESUMO
A novel Klebsiella pneumoniae carbapenemase (KPC) variant, KPC-55, produced by a K. pneumoniae ST307 strain was characterized. K. pneumoniae strain BS407 was recovered from an active surveillance rectal swab of a patient newly admitted to a general hospital in Busan, South Korea. Carbapenemase production was confirmed by the modified Hodge test, and the MICs of ß-lactams were determined by the broth microdilution method. The whole genome was sequenced. Cloning and expression of the bla KPC-55 gene in Escherichia coli and MIC determination were performed. The enzyme KPC-55 was used for kinetic assays against ß-lactams and compared with the KPC-2 enzyme. The new allele of the bla KPC gene had a T794A alteration compared to the bla KPC-2 gene, resulting in the amino acid substitution Y264N in the middle of the ß9-sheet. Compared to the KPC-2-producing strain, the KPC-55-producing strain exhibited a lower level of resistance to most ß-lactam drugs tested, however, the KPC-55 enzyme catalyzed aztreonam and meropenem at an increased efficiency compared to the catalytic activity of KPC-2. KPC subtypes could have varied phenotypes due to alterations in amino acid sequences, and such an unexpected resistance phenotype emphasizes the importance of detailed characterizations for the carbapenemase-producing Enterobacterales.
RESUMO
The acquired CTX-M-type extended-spectrum-ß-lactamase (ESBL)-producing Enterobacterales are of great concern in clinical settings because they limit therapeutic options for patients infected by the pathogens. An intriguing clonality of CTX-M ESBL-producing Klebsiella pneumoniae blood isolates was observed from a national cohort study, and comparative genomics were assessed for the 115 K. pneumoniae blood isolates carrying the bla CTX-M gene. The plasmid preference of particular clones of a sequence type (ST) was assessed by liquid mating. A quarter of the bla CTX-M gene-carrying K. pneumoniae blood isolates harbor the gene in their chromosome, and most of those with the built-in bla CTX-M gene belonged either to ST307 or ST48. Notably, all 16 K. pneumoniae ST48 isolates harbored two copies of the bla CTX-M-15 gene in the chromosome. The chromosomal integration of the bla CTX-M-15 gene was mostly derived from the ISEcp1-targeting 5-bp AT-rich locus in the chromosome. The IS26-mediated chromosomal integration occurred when the upstream ISEcp1 from the bla CTX-M gene was truncated, targeting the anchor IS26 copy in the chromosome. Higher transfer efficiency of the bla CTX-M-15 gene-carrying FIA:R plasmid was observed in ST17 than that of the bla CTX-M-14 gene-carrying FIB:FII plasmid. The transfer efficiency of the plasmid differed by isolate among the ST307 members. The K. pneumoniae clones ST307 and ST48 harboring the bla CTX-M-15 gene in the chromosome were able to disseminate stably in clinical settings regardless of the environmental pressure, and the current population of K. pneumoniae blood isolates was constructed. Further follow-up is needed for the epidemiology of this antimicrobial resistance.IMPORTANCE Dominant F-type plasmids harboring the gene have been pointed out to be responsible for the dissemination of the CTX-M extended-spectrum-ß-lactamase (ESBL)-producing K. pneumoniae Recently, the emergence of K. pneumoniae isolates with the bla CTX-M gene in their chromosomes has been reported occasionally worldwide. Such a chromosomal location of the resistance gene could be beneficial for stable propagation, as was the Acinetobacter baumannii ST191 harboring chromosomal bla OXA-23 that is endemic to South Korea. Through the present study, particular clones were identified as having built-in resistance genes in their chromosomes, and the chromosomal integration events were tracked by assessing their genomes. The cefotaxime-resistant K. pneumoniae clones of this study were particularized as results of the fastidiousness for plasmids to acquire the bla CTX-M gene for securing the diversity and of the chromosomal addiction of the bla CTX-M gene for ensuring propagation.
RESUMO
Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by impairments in social communication and restricted and repetitive behaviors and interests. Identifying the genetic background may be one of the key features for the future diagnosis and treatment of ASD. With the tremendous development in genetic diagnosis techniques, next-generation sequencing (NGS) can be used to analyze multiple genes simultaneously with a single test in laboratory and clinical settings and is well suited for investigating autism genetics. According to previous studies, there are two types of genetic variants in ASD, rare variants and common variants, and both are important in explaining pathogenesis. In this study, NGS data from 137 participants with ASD were reviewed retrospectively with consideration for comorbid epilepsy. Diagnostic yield was 17.51% (24/137), and pathogenic/likely pathogenic variants were seen more frequently in female participants. Fourteen participants were diagnosed with comorbid epilepsy, six of them had pathogenic/likely pathogenic variants (43%). Genes with variants of unknown significance (VOUS) which have one or more evidence of pathogenicity following the American College of Medical Genetics (ACMG) criteria were also reviewed in both ASD and ASD with comorbid epilepsy groups. We found that most frequently found VOUS genes have previously been reported as genes related to ASD or other developmental disorders. These results suggest that when interpreting the NGS results in the clinical setting, careful observation of VOUS with some pathological evidence might contribute to the discovery of genetic pathogenesis of neurodevelopmental disorders such as ASD and epilepsy.
