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

BACKGROUND: Antimicrobial resistance (AMR) in Neisseria gonorrhoeae is a major concern worldwide. It has been recently feared that the bla(TEM-1) gene is, via bla(TEM-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 bla(TEM) 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, bla(TEM) gene sequencing, β-lactamase plasmid typing, and N. gonorrhoeae multiantigen sequence typing (NG-MAST). Furthermore, the bla(TEM) 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 bla(TEM) sequences were identified (among isolates with 125 different NG-MAST STs), i.e. bla(TEM-1) (in 104 isolates), bla(TEM-135) (in 30 isolates), and four novel bla(TEM) sequences (in 5 isolates). The bla(TEM-1) allele was only found in the African and Asian plasmids, while all Rio/Toronto plasmids possessed the bla(TEM-135) allele. Most interesting, the first described gonococcal Toronto plasmid (pJD7), identified in 1984, also possessed the highly conserved bla(TEM-135) allele. The degradation of ampicillin by TEM-135 compared to TEM-1 was indistinguishable in the MALDI-TOF MS hydrolysis assay. CONCLUSIONS: bla(TEM-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. bla(TEM-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 bla(TEM-135) existed in the Toronto plasmid from its discovery and that bla(TEM-135) is highly conserved (not further evolved in the past >30 years). Nevertheless, international studies for monitoring the presence of different bla(TEM) alleles, the possible evolution of the bla(TEM-135) allele, and the types of β-lactamase producing plasmids, remain imperative. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/1471-2334-14-454) contains supplementary material, which is available to authorized users.