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Sequences of small blaTEM-encoding plasmids in Haemophilus influenzae and description of variants falsely negative for blaTEM by PCR

journal contribution
posted on 2023-05-17, 13:49 authored by Stephen TristramStephen Tristram, Franks, LR, Harvey, GL

Objectives: To characterize an unidentified β-lactamase and associated genetic background in a blaTEM and blaROB PCR-negative Haemophilus influenzae isolate, and characterize small blaTEM-encoding plasmids in a collection of H. influenzae.

Methods: The unidentified β-lactamase gene was identified by cloning and sequencing the encoding plasmid. Strains with small blaTEM plasmids were identified using negative PCR for integrative conjugative elements, but positive blaTEM PCR; plasmids from selected isolates were sequenced. PCR for rep and divergent blaTEM were evaluated for detecting small plasmids on selected H. influenzae isolates.

Results: Small plasmids (4.8-5.5 kb) encoding blaTEM appear to be associated with remnants of Tn2 on a conserved plasmid core. The unidentified β-lactamase was actually a TEM-1, with negative blaTEM PCR associated with a previously unrecognized deletion of bp 1-27 of bla(TEM) (Sutcliffe numbering) associated with a larger deletion within Tn2. This deletion was found in other isolates and may be more common than previously thought. PCR for the conserved rep gene appears useful for screening for small blaTEM-encoding plasmids or associated cryptic plasmids in H. influenzae.

Conclusions: Small blaTEM-encoding plasmids in H. influenzae appear relatively conserved, but require further study to confirm this. PCR associated with the rep gene may be useful for studying these small plasmids. A deletion in part of blaTEM in some strains may interfere with some PCRs; therefore, care should be taken with primer selection or design and, preferably, regions within the open reading frame should be targeted.

History

Publication title

Journal of Antimicrobial Chemotherapy

Volume

67

Issue

11

Pagination

2621-2625

ISSN

0305-7453

Department/School

School of Health Sciences

Publisher

Oxford Univ Press

Place of publication

Great Clarendon St, Oxford, England, Ox2 6Dp

Rights statement

Copyright 2012 the authors.

Repository Status

  • Restricted

Socio-economic Objectives

Clinical health not elsewhere classified

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