Background: This study aimed to investigate the prevalence of penicillinase-producing Neisseria gonorrhoeae (PPNG) and their blaTEM-135 gene variant in 2007 and 2012 in Nanjing, China. In addition, molecular epidemiological typing of all isolates was performed to elucidate the genetic relationships of the PPNG strains.
Methods: A total of 199 and 77 N. gonorrhoeae isolates were collected at the National Center for STD Control in 2007 and 2012, respectively. Nitrocefin tests were performed to identify PPNG. Mismatch amplification mutation assay was used to identify blaTEM-135. All isolates were genotyped using N. gonorrhoeae multiantigen sequence typing (NG-MAST), and additionally, porB-based phylogenetic analysis was performed for the PPNG isolates.
Results: The total prevalence of PPNG isolates was 41% (114/276) and 58% (66/114) of these PPNG isolates possessed blaTEM-135. In 2007, 45% (90/199) produced β-lactamase, and of those PPNG, 58% (52/90) possessed blaTEM-135. In 2012, 31% (24/77) were PPNG, and 58% (14/24) of those isolates contained blaTEM-135. There were 162 NG-MAST STs among the 276 isolates, and 89 of those were novel STs. A strong association between specific NG-MAST STs and blaTEM-135 was found, and the porB-based phylogenetic analysis showed a distant evolutionary relationship between isolates in 2007 and isolates in 2012.
Conclusions: A high prevalence of PPNG and blaTEM-135 was found in Nanjing, China. blaTEM-135 might be a precursor in the evolution into an extended-spectrum β-lactamase that can degrade ceftriaxone, which stresses the need to continuously monitor PPNG, blaTEM-135, and additional evolving blaTEM gene variants.