RESUMEN
Klebsiella pneumoniae carbapenemase (KPC) actively hydrolyzes carbapenems, antibiotics often used a last-line treatment for multidrug-resistant bacteria. KPC clinical relevance resides in its widespread dissemination. In this work, we report the genomic context of KPC coding genes blaKPC-2, blaKPC-3 and blaKPC-30 in multidrug-resistant Klebsiellapneumoniae isolates from Brazil. Plasmids harboring blaKPC-3 and blaKPC-30 were identified. Fifteen additional carbapenem-resistant K. pneumoniae isolates were selected from the same tertiary hospital, collected over a period of 8 years. Their genomes were sequenced in order to evaluate the prevalence and dissemination of blaKPC-harboring plasmids. We found that blaKPC genes were mostly carried by one of two isoforms of transposon Tn4401 (Tn4401a or Tn4401b) that were predominantly located on plasmids highly similar to the previously described plasmid pKPC_FCF3SP (IncN). The identified pKPC_FCF3SP-like plasmids carried either blaKPC-2 or blaKPC-30. Two K. pneumoniae isolates harbored pKpQIL-like (IncFII) plasmids, only recently identified in Brazil; one of them harbored blaKPC-3 in a Tn4401a transposon. Underlining the risk of horizontal spread of KPC coding genes, this study reports the prevalence of blaKPC-2 and the recent spread of blaKPC-3, and blaKPC-30, in association with different isoforms of Tn4401, together with high synteny of plasmid backbones among isolates studied here and in comparison with previous reports.
RESUMEN
In the present study, we screened a collection of 77 Proteus mirabilis clinical isolates for the presence of mutators, using the frequency of both rifampicin and fosfomycin resistance mutants as markers of spontaneous mutagenesis. We found that none of the strains in our collection are mutators for the rifampicin resistance (RifR) marker. Nevertheless, a significant fraction of the isolates (17%) show high frequencies of fosfomycin resistant mutants (FosR). We show that this increased mutability to FosR correlates with a low level of resistance to Fosfomycin (MICs 8-64µg/ml). These strains also show high frequencies of single step mutants with clinically relevant FosR resistance levels (MIC ≥256µg/ml). Our findings point out to the risk of fosfomycin resistance emergence in P. mirabilis.