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Characterization of extended-spectrum beta-lactamase-producing isolates of Haemophilus parainfluenzae


Tristram, SG and Pitout, MJ and Forward, K and Campbell, S and Nichols, S and Davidson, RJ, Characterization of extended-spectrum beta-lactamase-producing isolates of Haemophilus parainfluenzae, Journal of Antimicrobial Chemotherapy, 61, (3) pp. 509-514. ISSN 0305-7453 (2008) [Refereed Article]

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DOI: doi:10.1093/jac/dkm523


Objectives: To characterize the -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 -lactamase. Both isolates also had substitutions in penicillin binding protein 3 (PBP3) consistent with substitutions known to exist in -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 -lactamase with altered PBP3 probably contributing. Other contributing resistance mechanisms could not be excluded.

Item Details

Item Type:Refereed Article
Research Division:Biomedical and Clinical Sciences
Research Group:Medical microbiology
Research Field:Medical bacteriology
Objective Division:Health
Objective Group:Clinical health
Objective Field:Clinical health not elsewhere classified
UTAS Author:Tristram, SG (Dr Stephen Tristram)
UTAS Author:Nichols, S (Mr Scott Nichols)
ID Code:51675
Year Published:2008
Web of Science® Times Cited:27
Deposited By:Health Sciences A
Deposited On:2008-04-17
Last Modified:2014-11-25
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