Trends in extendeds-spectrum b-lactamase Klebsiella pneumoniae in a tertiary Spanish hospital (1993–2006)

Abstract number: P623

Ardanuy C., Dominguez M., Calatayud L., Tubau F., Ayats J., Peña C., Pujol M., Martín R., Liñares J.

Objective: The objective of this study was to characterise the ESBL-K. pneumoniae strains isolated in a tertiary hospital during a 14-year period (1993–2006).

Methods: Screening of ESBL was performed by double disk synergy test. All available K. pneumoniae strains were typed by PFGE (XbaI). The ESBL characterisation was performed by isoelectric focusing of betalactamases and by PCR of ESBL family. All ESBLs genes of strains causing nosocomial outbreaks were sequenced.

Results: During the study period, K. pneumoniae was isolated from clinical samples of 4925 patients admitted to our hospital. Three hundred and seventy three (7.6%) K. pneumoniae carried an ESBL, and the majority of them (197/373, 53%) were isolated from ICU patients. Isolates from 290 patients were available for further studies. Sixty-seven different PFGE patterns were found among the 290 isolates studied. Two major outbreaks were observed throughout the study period. The first of them, involving 150 patients, occurred between 1993–1995 and was due to the spread of strains of Kp1 clone. The majority (85%) of Kp1 isolates produced one ESBL and 15% two ESBLs. By sequencing 34% of ESBL-Kp1 were identified as SHV-2 (pI 7.6), 51% as SHV-5 (pI 8.2) and 15% as SHV-2 plus SHV-5 (pIs 7.6 and 8.2 respectively). The second outbreak was due to Kp29 clone and accounted for 53 patients. This epidemic Kp29 strain produced an SHV-2 betalactamase (pI 7.6). The majority (66%) of Kp29 isolates were detected between September 1999 and November 2000. Another eight clusters of ESBL-K. pneumoniae (SHV-family) involving 2 to 7 patients each were detected throughout the study period. During 1999–2006 period, 8 unrelated K. pneumoniae producing CTX-M-9 family were detected. Only 2 unrelated strains harbouring a TEM-family ESBLs were detected in 1995 and 2003, respectively.

Conclusion: Although the global prevalence of ESBL-K. pneumoniae infections in our institution was 7.6%, the annual frequency ranged from 3% to 18%. Two major outbreaks were associated with the dissemination of epidemic strains producing SHV-2 and/or SHV-5 ESBLs. Isolation of strains producing CTX-M-9 or TEM families of ESBLs is infrequent among K. pneumoniae.