1 Eijkman-Winkler Institute for Microbiology, Infectious Diseases & Inflammation, University Medical Centre, Utrecht, The Netherlands; 2 Analytical Diagnostic Centre, Department of Microbiology, Curaçao, The Netherlands Antilles
Keywords: beta-lactamase, multidrug resistance, spread
Sir,
In recent years, the growing incidence of extended-spectrum ß-lactamases (ESBLs), in particular produced by Klebsiella pneumoniae isolates in nosocomial infections, has also become evident in Curaçao (Netherlands Antilles). Because of the islands location, the occurrence of ESBLs may be a consequence of local emergence or import from other countries.1 To identify a possible source for the increase in these multidrug-resistant isolates, 65 non-duplicate clinical isolates of ESBL-producing K. pneumoniae were investigated having been collected in the St Elisabeth Hospital from November 1999 to June 2002.
Identification and susceptibility testing were carried out using an automated system (Vitek, bioMérieux Vitek Inc., Hazelwood, USA). When MICs indicated the potential presence of an ESBL, a double-disc synergy test (DDST) was used to confirm ESBL production.2 Ribotyping using EcoRI was carried out with an automated riboprinter (Qualicon Europe Ltd., Warwick, UK) as described previously.3 Fourteen isolates collected during 2001 from an outbreak in the neonatal intensive care unit (NICU) were considered separately, because of the isolated character of this event. Twelve isolates were collected from November 1999 to December 2000 (group A). Thirteen isolates were collected outside the NICU, during 2001 (group B). Twenty-six isolates were collected in the first 6 months of 2002 (group C). There was a significant increase in the isolation of ESBL-producing K. pneumoniae isolates in Curaçao, from less than one per month in 1999/2000 to approximately five per month in the first half of 2002, which was only partly explained by better screening methods.
Twenty-two distinct ribotype patterns were identified (Figure 1) and were compared to an international database containing more than 1800 ribotype patterns that was constructed during the framework of the Genetic Epidemiology Network for Europe (GENE) project (www.ewi.med.uu.nl/gene). Ten of the 22 patterns, found in 42 Curaçao isolates, were identical to patterns in the GENE database and most were found in different countries. Interestingly, ribotype 77 was the most represented type (26 isolates) in Curaçao and was also the ribotype with the largest number of isolates (98 isolates) of the 10 matching patterns from the GENE database. This ribotype was mainly found in the Americas, but also in Europe. Other geographically widespread ribotypes, found both in the Americas and in Europe, were ribotypes 122 (44 isolates in the GENE database), 438 (38 isolates) and 38 (22 isolates). These results indicate that most Curaçao klebsiellae in our study (42 out of 65 isolates) do not represent endemic strains but are exchanged between the island and other parts of the world, and also many of these imported strains have a wide geographical distribution.
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Our data indicate that there is an ongoing outbreak of ESBL-producing K. pneumoniae in Curaçao. Most of the ESBL-producing isolates (83%) appear to carry plasmid-encoded SHV-type ß-lactamases and this plasmid is not easily transferable from the majority of isolates. Isoelectric focusing indicated that most of the isolates harbour a diversity of ß-lactamase genes, with an AmpC-type present in 12%. There is a prevalent clone, whose ribotype pattern indicated that it is was probably imported from the Americas or Europe.
Acknowledgements
We would like to thank George A. Jacoby, Lahey Clinic, Burlington and Fred C. Tenover, CDC Atlanta for the use of their reference strains and also thanks to Richard J. Hollis, University of Iowa City, Iowa and Vivian Fussing, Statens Serum Institute, Copenhagen, Denmark for the use of their ribotype data. This work was supported in part by the European Union Fifth Framework Programme, under grant QLK2-2000-01404 (Genetic Epidemiology Network for Europe).
Footnotes
* Corresponding author. Tel: +31-30-2507625; Fax: +31-302541770; E-mail: mvanwestreenen{at}hotmail.com
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