Published in:
Open Access 01-12-2014 | 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
Published in: BMC Infectious Diseases | Issue 1/2014
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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.