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Infect Genet Evol. 2019 Jan 14;69:61-67. doi: 10.1016/j.meegid.2019.01.013. [Epub ahead of print]

Multicentre investigation of carbapenemase-producing Klebsiella pneumoniae and Escherichia coli in Bulgarian hospitals - Interregional spread of ST11 NDM-1-producing K. pneumoniae.

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Medical University of Sofia, Medical Faculty, Department of Medical Microbiology, Bulgaria. Electronic address:
Medical University of Varna, Department of Microbiology and Virology, University Multiprofile Hospital for Active Treatment (UMHAT), St Marina, Varna, Bulgaria.
Medical University of Sofia, Medical Faculty, Department of Medical Microbiology, Bulgaria.
MICOER-Institute, Munich, Germany.
Department of Clinical Microbiology, Medical Institute - Ministry of the Interior, Sofia, Bulgaria.
Molecular Medicine Center, Medical University of Sofia, Sofia, Bulgaria.
Medical University of Plovdiv, Department of Microbiology and Immunology, UMHAT, "St George", Plovdiv, Bulgaria.
Medical University of Pleven, Department of Microbiology and Virology, UMHAT "Georgi Stranski", Pleven, Bulgaria.
Emergency Medical Institute "Pirogov", Sofia, Bulgaria.
Second Multiprofile Hospital for Active Treatment, Sofia, Bulgaria.
UMHAT "Prof. dr St Kirkovich" Stara Zagora, Thracian University, Stara Zagora, Bulgaria.



The aim of this study was to investigate the mechanisms of beta-lactam-resistance and the clonal relatedness of carbapenem-nonsusceptible Klebsiella pneumoniae and Escherichia coli isolates, collected consecutively in eight centers in five Bulgarian cities from November 2014 to March 2018. Carbapenemase-producing enterobacteria were detected in all but one centers. Overall, 104 K. pneumoniae and one E. coli were analysed.


Antimicrobial susceptibility and beta-lactamases were analysed. Conjugation experiments, plasmid fingerprinting and replicon typing, as well as MLST and ERIC-PCR were carried out.


KPC-2 (51%) and NDM-1 (47%) were the main carbapenemases identified. KPC-2 producing K. pneumoniae were classified into 10 MLST-types. The four dominating MLST-types ST29, ST15, ST336 and ST902 comprised 79% of the KPC-2 producers. All but one of the NDM-1 producing isolates belonged to the MLST-type ST11 and were found in seven centers. Furthermore, single K. pneumoniae isolates producing VIM-1 (ST147) and OXA-48 (ST15) were identified. In addition to the carbapenemases, the ESBLs CTX-M-15, CTX-M-3, and SHV-12 as well as AmpC enzyme CMY-4 were found. The FIIAs-replicon-type was found in all KPC-2 producers while the A/C-replicons dominated in NDM-1 producing isolates. The single NDM-1 producing E. coli was determined as MLST-Type ST10 (Warwick scheme).


The interregional clonal expansion of NDM-1 producing ST11 K. pneumoniae and the dissemination of blaKPC-2 carrying plasmids were responsible for the spread of carbapenemase-producing K. pneumoniae in Bulgaria. Our findings highlight the urgency to prevent dissemination of these highly transmissible and dangerous lineages.


Bulgaria; Carbapenemases; E. coli; K. pneumoniae; KPC; NDM

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