Molecular epidemiology of carbapenemase-producing Klebsiella pneumoniae in a hospital in Madrid: Successful establishment of an OXA-48 ST11 clone

• The emergence of carbapenemase-producing Klebsiella pneumoniae (CPKp) is a major concern.
• The percentage of CPKp isolates ranged from 0.8% in 2009 to 4.3% in 2013.
• 97 CPKp isolates were identified (59 OXA-48, 37 VIM-1 and 1 KPC-2).
• A major OXA-48-producing ST11 clone emerged and displaced the pre-existing strains.
• Whole-genome sequencing of OXA-48 ST11 detected 121 genes related to antibiotic and antiseptic resistance.

Here we report a retrospective clinical and molecular study conducted in a tertiary care facility in southern Madrid, Spain, from January 2009 to February 2014 to investigate the epidemiology of carbapenemase-producing Klebsiella pneumoniae (CPKp). Carbapenemase genes were identified in 97 non-duplicate K. pneumoniae isolates, including 59 harbouring blaOXA-48, 37 harbouring blaVIM-1 and 1 harbouring blaKPC-2. Pulsed-field gel electrophoresis (PFGE) analysis verified the presence of 20 different clonal types, whilst multilocus sequence typing (MLST) assigned the isolates to eight sequence types (STs). A gradual increase was noted in the number of CPKp isolated, ranging from 0.8% in 2009 to 4.3% in 2013. A large outbreak was also identified, initiated in 2013 owing to a blaOXA-48 and blaCTX-M-15 co-producing ST11 clone and involving a total of 44 patients. Whole-genome sequencing was used to characterise the resistome of a representative isolate from this outbreak. Bioinformatics analysis revealed the presence of 121 genes related to antibiotic and antiseptic resistance, mutations in the ompk35 and ompk36 genes, and the presence of the blaOXA-48 gene on a 62 811 bp IncL/M-type plasmid as part of a Tn1999.2 composite transposon. These results portray the increasing trend in carbapenemase-producing isolates in this hospital and highlight the successful establishment of a blaOXA-48 and blaCTX-M-15 co-producing ST11 clone that has led to the displacement of previous circulating clones.