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- Title
Characterization of extended-spectrum {beta}-lactamase-producing isolates of Haemophilus parainfluenzae.
- Authors
Stephen G. Tristram; Marthinus J. Pitout; Karen Forward; Sarah Campbell; Scott Nichols; Ross J. Davidson
- Abstract
: Objectives To characterize the β-lactam resistance mechanisms of two clinical isolates of cefotaxime-resistant Haemophilus parainfluenzae recovered from patients in South Africa. : Methods The relatedness of isolates and plasmids was assessed using PFGE and restriction enzyme analysis, respectively. Plasmid-mediated and chromosomally integrated blaTEM genes and ftsI genes were sequenced, and the plasmid-mediated blaTEM-15 was used to transform a range of control organisms. : Results The two isolates were found to be unique according to PFGE, but had an identical 3.7 kb plasmid encoding a TEM-15 β-lactamase. Both isolates also had substitutions in penicillin binding protein 3 (PBP3) consistent with substitutions known to exist in β-lactamase-negative ampicillin-resistant (BLNAR) strains of Haemophilus influenzae. The cefotaxime MICs for control strains of H. influenzae, H. parainfluenzae and BLNAR H. influenzae transformed with the plasmid-mediated blaTEM-15 were 1.0, 1.0 and 4.0 mg/L, respectively, compared with 16.0 and 8.0 mg/L, respectively, for the two parent H. parainfluenzae. : Conclusions The high-level cefotaxime resistance in the H. parainfluenzae isolates was due to a combination of a plasmid-mediated TEM-15 extended-spectrum β-lactamase with altered PBP3 probably contributing. Other contributing resistance mechanisms could not be excluded.
- Subjects
SOUTH Africa; LACTAMS; HAEMOPHILUS parainfluenzae; CEFOTAXIME
- Publication
Journal of Antimicrobial Chemotherapy (JAC), 2008, Vol 61, Issue 3, p509
- ISSN
0305-7453
- Publication type
Article
- DOI
10.1093/jac/dkm523