Molecular epidemiology of metallo-lactamase-producing Pseudomonas putida in a Spanish hospital

Abstract number: P1490

Juan C., Zamorano L., Albertí S., Pérez J.L., Oliver A.

Objective: To study the prevalence, nature, involved genetic elements, and the molecular epidemiology of metallo-b-lactamase (MBL)-producing P. putida strains isolated in a Spanish hospital between 2005 and 2008.

Methods: Etest and API 20NE were used, respectively, for the susceptibility testing and identification of P. putida clinical isolates. The MBL Etest was used for screening, and was followed by the amplification of blaVIM genes by PCR. The clonal relatedness between the isolates was evaluated by pulsed-field-gel-electrophoresis (PFGE). The plasmids harbouring the MBL genes were characterised and compared through the analysis of the restriction (BamHI-HindIII) fragments length polymorphisms (RFLP) followed by Southern blot hybridisation using blaVIM probes. Additionally, electroporation of the plasmids to P. aeruginosa PAO1 was attempted. The genetic composition of the integrons harbouring the MBLs was investigated by PCR and sequencing, following previously described protocols.

Results: MBL-producing P. putida was detected in clinical samples (1 urine, 1 sputum, 3 blood, 1 vascular catheter, and 2 peritoneal fluid) from 8 patients, representing 14% of all the infections by P. putida/fluorescens group strains during the study period. In contrast, MBL production was detected in only 0.32% of P. aeruginosa infections during the same period. PFGE revealed that the 8 P. putida isolates belonged to 8 different clones, 2 of them harbouring blaVIM-1 and 6 blaVIM-2. All the strains showed resistance or reduced susceptibility to gentamicin and tobramycin, and half of them were additionally resistant to ciprofloxacin. Southern blot revealed that all the MBLs, except 1 VIM-2, were plasmid-located. An important plasmid diversity was also denoted, since RFLP analysis yielded 6 different patterns among the 7 blaVIM-encoding plasmids. On the other hand, all the MBLs were found to be encoded in class 1 integrons, that showed conserved structures among the different isolates for each MBL: intI1-aacA4-blaVIM-2 and intI1-blaVIM-1-aacA4-aadA1, respectively.

Conclusion: The alarmingly high proportion and clonal diversity of MBL-producing P. putida clinical isolates suggest an important environmental reservoir of these highly relevant resistance determinants. Therefore, considering the threat of potential horizontal transfer of these plasmid-located MBL-encoding integrons to other species such as P. aeruginosa, active surveillance is warranted.

Session Details

Date: 16/05/2009
Time: 00:00-00:00
Session name: 19th European Congress of Clinical Microbiology and Infectious Diseases
Location: Helsinki, Finland, 16 - 19 May 2009
Presentation type:
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