Journal Article

Occurrence and molecular analysis of extended-spectrum β-lactamase-producing <i>Proteus mirabilis</i> in Hong Kong, 1999–2002

P. L. Ho, Alex Y. M. Ho, K. H. Chow, River C. W. Wong, R. S. Duan, W. L. Ho, Gannon C. Mak, Kenneth W. Tsang, W. C. Yam and K. Y. Yuen

in Journal of Antimicrobial Chemotherapy

Published on behalf of British Society for Antimicrobial Chemotherapy

Volume 55, issue 6, pages 840-845
Published in print June 2005 | ISSN: 0305-7453
Published online April 2005 | e-ISSN: 1460-2091 | DOI:
Occurrence and molecular analysis of extended-spectrum β-lactamase-producing Proteus mirabilis in Hong Kong, 1999–2002

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Objectives: A study was conducted to evaluate the occurrence and characterization of extended-spectrum β-lactamases (ESBLs) among blood isolates of Proteus mirabilis collected over a 4 year period in Hong Kong.

Methods: Production of ESBLs among 99 consecutive and non-duplicate isolates was evaluated by the double-disc synergy test. The ESBLs were characterized by isoelectric focusing and PCR sequencing using specific primers. The epidemiological relationship of the isolates was studied by the Dienes test and PFGE.

Results: ESBLs were identified in 13 isolates, from none in 1999–2000 and up to 18.5% (5/27) in 2001 and 25.8% (8/31) in 2002. The ESBL-producing isolates were more resistant to ceftriaxone than to ceftazidime, and were more likely than non-ESBL-producers to have resistance to ciprofloxacin (76.9% versus 14%) and gentamicin (38.5% versus 9.3%). The ESBL content included CTX-M-13 (n=8), CTX-M-14 (n=3), SHV-5 (n=2), TEM-11 (n=1), and an unidentified ESBL with a pI of 7.5. The Dienes test revealed that the genetic background in the 99 isolates was highly heterogeneous, with 54 distinct types among 92 isolates and seven were non-typeable. Among the 13 ESBL-producing isolates, five different backgrounds, including one cluster (Dienes-pulsotype A) with nine isolates, were identified by both Dienes test and PFGE, thus suggesting both clonal and multi-clonal spread of the CTX-M enzymes.

Conclusions: Our findings indicate the emergence of CTX-M enzymes among P. mirabilis in Hong Kong. More ESBL screening of this species is required to improve their recognition.

Keywords: antimicrobial resistance; epidemiology; cephalosporin resistance

Journal Article.  4858 words. 

Subjects: Medical Oncology ; Critical Care

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