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Increase of beta-Lactam-Resistant Invasive Haemophilus influenzae in Sweden, 1997 to 2010

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Author

Summary, in English

The proportions of Haemophilus influenzae resistant to ampicillin and other beta-lactam antibiotics have been low in Sweden compared to other countries in the Western world. However, a near-doubled proportion of nasopharyngeal Swedish H. influenzae isolates with resistance to beta-lactams has been observed in the last decade. In the present study, the epidemiology and mechanisms of antimicrobial resistance of H. influenzae isolates from blood and cerebrospinal fluid in southern Sweden from 1997 to 2010 (n = 465) were studied. Antimicrobial susceptibility testing was performed using disk diffusion, and isolates with resistance to any tested beta-lactam were further analyzed in detail. We identified a significantly increased (P = 0.03) proportion of beta-lactam-resistant invasive H. influenzae during the study period, which was mainly attributed to a significant recent increase of beta-lactamase-negative beta-lactam-resistant isolates (P = 0.04). Furthermore, invasive beta-lactamase-negative beta-lactam-resistant H. influenzae isolates from 2007 and onwards were found in higher proportions than the corresponding proportions of nasopharyngeal isolates in a national survey. Multiple-locus sequence typing (MIST) of this group of isolates did not completely separate isolates with different resistance phenotypes. However, one cluster of beta-lactamase-negative ampicillin-resistant (BLNAR) isolates was identified, and it included isolates from all geographical areas. A truncated variant of a beta-lactamase gene with a promoter deletion, bla(TEM-1)-P Delta dominated among the beta-lactamase-positive H. influenzae isolates. Our results show that the proportions of beta-lactam-resistant invasive H. influenzae have increased in Sweden in the last decade.

Publishing year

2012

Language

English

Pages

4408-4415

Publication/Series

Antimicrobial Agents and Chemotherapy

Volume

56

Issue

8

Document type

Journal article

Publisher

American Society for Microbiology

Topic

  • Microbiology in the medical area

Status

Published

Research group

  • Infectious Diseases Research Unit
  • Clinical Microbiology, Malmö

ISBN/ISSN/Other

  • ISSN: 1098-6596