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Open Access Research article

Characterisation of bla TEM genes and types of β-lactamase plasmids in Neisseria gonorrhoeae – the prevalent and conserved bla TEM-135 has not recently evolved and existed in the Toronto plasmid from the origin

Ibrahim Muhammad1, Daniel Golparian1, Jo-Anne R Dillon2, Åsa Johansson3, Makoto Ohnishi4, Sunil Sethi5, Shao-chun Chen6, Shu-ichi Nakayama4, Martin Sundqvist1, Manju Bala7 and Magnus Unemo1*

Author Affiliations

1 Department of Laboratory Medicine, WHO Collaborating Centre for Gonorrhoea and other Sexually Transmitted Infections, National Reference Laboratory for Pathogenic Neisseria, Microbiology, Örebro University Hospital, SE-701 85, Örebro, Sweden

2 Department of Microbiology and Immunology, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada

3 Department of Clinical Microbiology, Central Hospital, Växjö, Sweden

4 National Institute of Infectious Diseases, Tokyo, Japan

5 Department of Medical Microbiology, Post Graduate Institute of Medical Education and Research (PGIMER), Chandigarh, India

6 National Center for STD Control, Chinese CDC, Nanjing, China

7 Apex Regional STD Teaching, Training and Research Centre, VMMC and Safdarjang Hospital, New Delhi, India

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BMC Infectious Diseases 2014, 14:454  doi:10.1186/1471-2334-14-454

Published: 22 August 2014

Abstract

Background

Antimicrobial resistance (AMR) in Neisseria gonorrhoeae is a major concern worldwide. It has been recently feared that the blaTEM-1 gene is, via blaTEM-135, evolving into an extended-spectrum β-lactamase (ESBL), which could degrade all cephalosporins including ceftriaxone. The aims of the present study were to characterize the blaTEM genes, types of β-lactamase plasmids, the degradation of ampicillin by TEM-135 compared to TEM-1, and to perform molecular epidemiological typing of β-lactamase-producing N. gonorrhoeae strains internationally.

Methods

β-lactamase producing N. gonorrhoeae isolates (n = 139) cultured from 2000 to 2011 in 15 countries were examined using antibiograms, blaTEM gene sequencing, β-lactamase plasmid typing, and N. gonorrhoeae multiantigen sequence typing (NG-MAST). Furthermore, the blaTEM gene was sequenced in the first described Toronto plasmid (pJD7), one of the first Asian plasmids (pJD4) and African plasmids (pJD5) isolated in Canada. The degradation of ampicillin by TEM-135 compared to TEM-1 was examined using a MALDI-TOF MS hydrolysis assay.

Results

Six different blaTEM sequences were identified (among isolates with 125 different NG-MAST STs), i.e. blaTEM-1 (in 104 isolates), blaTEM-135 (in 30 isolates), and four novel blaTEM sequences (in 5 isolates). The blaTEM-1 allele was only found in the African and Asian plasmids, while all Rio/Toronto plasmids possessed the blaTEM-135 allele. Most interesting, the first described gonococcal Toronto plasmid (pJD7), identified in 1984, also possessed the highly conserved blaTEM-135 allele. The degradation of ampicillin by TEM-135 compared to TEM-1 was indistinguishable in the MALDI-TOF MS hydrolysis assay.

Conclusions

blaTEM-135, encoding TEM-135, is predominantly and originally associated with the Rio/Toronto plasmid and prevalent among the β-lactamase producing gonococcal strains circulating globally. blaTEM-135 does not appear, as previously hypothesized, to have recently evolved due to some evolutionary selective pressure, for example, by the extensive use of extended-spectrum cephalosporins worldwide. On the contrary, the present study shows that blaTEM-135 existed in the Toronto plasmid from its discovery and that blaTEM-135 is highly conserved (not further evolved in the past >30 years). Nevertheless, international studies for monitoring the presence of different blaTEM alleles, the possible evolution of the blaTEM-135 allele, and the types of β-lactamase producing plasmids, remain imperative.

Keywords:
Gonorrhoea; Antimicrobial resistance; blaTEM-1; blaTEM-135; TEM-1; TEM-135; Rio/Toronto plasmid, Extended-spectrum β-lactamase (ESBL)