K. pneumoniae (Kp) constitutes nowadays one of the most challenging to control bacterial pathogen, as it have evolved toward high level antimicrobial resistance. Carbapenems are one of the most reliable last-resort treatment for multidrug resistant enterobacteria. For these reason, worldwide emergence and rapid spread of carbapenem resistance through all continents, constitutes a major global publichealthcare problem. By far, the production of KPC enzymes is the most clinically relevant carbapenem resistant mechanism in Kp. Since 2010, almost all KPC
producing Kp (KPC-Kp) nosocomial outbreaks have been associated to the pandemic distributed clone, ST258. More recently the emergence and dissemination of new epidemic lineages have been described in Italy and Colombia. The aim of this study was to assess the epidemiological features of KPC-Kp isolates recovered in Buenos Aires hospitals in order to understand the ongoing evolution of carbapenem resistance. A total of 60 Kp isolates recovered from clinical samples or surveillance cultures of inpatients at 2 Hospitals, during 2016-2017, were included. Antibiotic susceptibility was determined according to CLSI. Phenotypic screening for KPC was conducted by agar diffusion synergy test, using phenyl boronic acid, and the presence of the blaKPC was confirmed by PCR and sequencing. blaKPC genetic context was achieved by PCR mapping and plasmid replicon typing was performed according Carattoli et al. The clonal relationship among KPC-Kp isolates was evaluated by XbaI-PFGE and Multilocus Sequence Typing (MLST). The presence of pilV-1, specific for Kp ST258, was conducted according to Adler et al. All the isolates were resistant to ampicillin and cephalosporins, and not susceptible to imipenem and /or meropenem. Fifty five/60, 52/60, 49/60 and 21/60 were resistant to ciprofloxacin, trimethoprim-sulfamethoxazole, gentamicin and amikacin, respectively. The presence of KPC-2 was detected in all isolates by phenotypic and genotypic methods. Thirteen/69 isolates belonged to ST258 and the remaining 47 mainly corresponded to the hypermucoviscous ST25 and to a lesser extent to ST11 and to the recently reported hypervirulent epidemic clone ST307. blaKPC-2 was mainly located in Inc FIA and L/M plasmids. In those KPC-Kp belonging to epidemic clones ST258 and ST307 blaKPC-2 was located in the mobile element Tn4401, while the upstream region of this element was variable in Kp-KPC belonging to ST25, be ing detected ISKpn8 instead of ISKpn7. Conclusions: The absolute prevalence of ST258 KPC-Kp previously observed in our region is being replaced by the emergence more virulent clones such as ST25 and ST307. KPC-Kp ST307 has been postulated as candidate to become a prevalent high-risk clone in the near future. In addition, KPC-Kp ST25 have been related to a hypermucoviscous hypervirulent clone associated with severe infections. Dissemination of
simultaneously carbapenem-resistant and hypervirulent clones could mark an evolutionary step toward the establishment of these clones as major nosocomial pathogens.