Luis Eduardo Lucena Baeza. Curs 2012-13
Project summary
Background: OXA-48 carbapenemase is a new molecular class D β-lactamase with activity against penicillins and carbapenems while remaining susceptible to cephalosporins, although it frequently appears to be co-expressed with other antibiotic resistance mechanisms. This carbapenemase was first identified in a Klebsiella pneumoniae isolate from Istanbul, Turkey in 2001. In recent years it has spread worldwide through the same species and other Enterobacteriaceae due to international travel and antibiotic misuse, being responsible for an important number of hospital outbreaks. In addition, routine detection techniques performed in microbiology laboratories usually fail to detect this carbapenemase, which may have contributed to its international dissemination. OXA-48 is encoded in the blaOXA-48 gene, which is transferred through a ~70Kb IncL/M-type plasmid flanked by IS1999 insertion sequences, and this plasmid does not carry other resistance markers.
Hypotheses and aims of this study: given the high number of outbreaks worldwide of OXA-48 β-lactamase in K. pneumoniae isolates and being that carbapenemase the most frequently found in our region, we performed an epidemiological multicenter study to determine the prevalence, clonal relatedness and phylogenetic linkage of all OXA-48-producing K. pneumoniae isolates collected during the year 2012 among 12 regional hospitals in Catalonia.
Material and methods: pulse-field gel electrophoresis (PFGE) and multi-locus sequence typing (MLST) techniques were performed in the 85 positive isolates detected.
Results: PFGE results revealed 5 clusters (A-E) correlating with sequence types ST101, ST17, ST1233 (a new single locus variant of ST540), ST14 and ST405, respectively. The two most prevailing clones were ST405 (66/85; 78%) and ST101 (16/85; 19%), which were associated with β-lactamases of the CTX-M family.
Conclusions: Our results are in agreement with previous reports of ST405 and ST101 detected in Spain and worldwide. Co-expression of OXA-48 carbapenemase with an extended-spectrum beta lactamase (ESBL) phenotype was also very frequent in ST405 and ST101 found in this study.

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