RESUMEN
BACKGROUND: OXA-48 is a highly prevalent carbapenemase and has been isolated worldwide. Here, we investigate the in vivo horizontal gene transfer (HGT) of blaOXA-48 from Klebsiella pneumoniae to Escherichia coli in an infected patient. METHODS: Bacterial isolates were characterized by susceptibility testing, multilocus sequence typing, DiversiLab, and plasmid analyses. Transferability of blaOXA-48 was evaluated by in vitro transconjugation using the outbreak strain and E. coli J53. In vivo transconjugation was investigated using the larvae of the greater wax moth (Galleria mellonella) and low-complexity-microbiota mice. RESULTS: OXA-48-harboring K. pneumoniae isolates belonging to ST14 were isolated during a nosocomial outbreak from 6 patients. Molecular and epidemiological analyses revealed the HGT of an approximately 60-kb OXA-48-containing IncL/M-type plasmid from K. pneumoniae to E. coli belonging to the novel ST666 in a patient. In vitro conjugation experiments revealed a transconjugation frequency of 8.7 × 10(-7). HGT of OXA-48 in a newly developed in vivo model using G. mellonella larvae revealed a higher transconjugation frequency of 1.3 × 10(-4). The conjugation frequency of OXA-48 from K. pneumoniae and E. coli in the gut of low-complexity-microbiota mice was determined to be 2.9 × 10(-5). CONCLUSIONS: The in vivo intergenus gene transfer of OXA-48 in the gut of an infected patient was verified in vitro and in 2 in vivo models, which both showed even higher transmission frequencies vs in vitro conditions. This implies that the current in vitro protocols might not correctly reflect the HGT of carbapenemase genes in vivo.
Asunto(s)
Infección Hospitalaria/microbiología , Transferencia de Gen Horizontal/genética , Infecciones por Klebsiella/microbiología , Resistencia betalactámica/genética , beta-Lactamasas/genética , Anciano , Animales , ADN Bacteriano/análisis , ADN Bacteriano/genética , Escherichia coli/efectos de los fármacos , Escherichia coli/genética , Femenino , Humanos , Klebsiella pneumoniae/efectos de los fármacos , Klebsiella pneumoniae/genética , Masculino , Ratones , Persona de Mediana Edad , Tipificación de Secuencias Multilocus , Plásmidos/genéticaRESUMEN
OBJECTIVES: To characterize a pan-drug-resistant Serratia marcescens clinical isolate carrying the New Delhi metallo-ß-lactamase (NDM)-1. METHODS: The presence of ß-lactamase genes was examined by PCR and sequencing. Antibiotic susceptibility was determined by antibiotic gradient test. Transformation assays, transconjugation assays, PFGE and PCR-based replicon typing were used for plasmid analysis. Horizontal gene transfer was evaluated by liquid mating using Escherichia coli J53 as a recipient. Pathogenicity of NDM-1 expressing S. marcescens was analysed using the Galleria mellonella infection model. RESULTS: S. marcescens isolate SM1890 was non-susceptible to all tested antibiotics, with minocycline retaining intermediate activity. blaNDM-1 was located on a 140 kb IncA/C-type plasmid which was transferable to E. coli and Klebsiella pneumoniae by conjugation. The LD50 of the NDM-positive, SM1890 isolate was higher than that of other, NDM-1 negative, S. marcescens strains. CONCLUSIONS: The presence of a blaNDM-1-harbouring IncA/C plasmid resulted in marked resistance to ß-lactam antibiotics, but had no significant effect on virulence of isogenic strains. Because of the intrinsic resistance of S. marcescens to colistin and reduced susceptibility to tigecycline, treatment options for infections by NDM-1-positive isolates are extremely limited in this species.
