Molecular characterization of penicillinase-producing neisseria gonorrhoeae isolated in two time periods, 2003-2004 and 2014-2015, in Italy

The emergence of antibiotic resistant strains poses a great concern for gonorrhea treatment. The aim of this study was to characterize penicillinase-producing Neisseria gonorrhoeae (PPNG) isolates collected in Italy in two time frames, 2003-2004 and 2014-2015. A total of 80 PPNG were characterized for the blaTEM gene variant and the plasmid type. Furthermore, gonococci were typed using Neisseria gonorrhoeae multiantigen sequence typing. Antibiotic susceptibility assay was performed for penicillin, ciprofloxacin, ceftriaxone, and spectinomycin by Etest and minimum inhibitory concentration (MIC) test strip methods. The β-lactamase production was detected using nitrocefin test. Among PPNG isolates, four blaTEM alleles were identified as follows: blaTEM-1, blaTEM-228, blaTEMP14S, and blaTEM-135. The African plasmid possessed the blaTEM-1, blaTEM-228, and blaTEMP14S, whereas blaTEM-135 was identified in Toronto/Rio and Asian plasmids. The percentage of isolates with the blaTEM-1-carrying African plasmid increased from 42.5% in 2003-2004 to 55% in 2014-2015; conversely, the isolates with blaTEM-135-carrying Toronto/Rio plasmid decreased from 57.5% to 35%. Among the isolates carrying the Toronto/Rio plasmids possessing blaTEM-135, sequence type (ST)661 and ST5624 were found to be the predominant STs in both periods 2003-2004 and 2014-2015, respectively. More than half of the PPNG isolates were resistant to ciprofloxacin. Increase in the isolates carrying the African plasmid possessing blaTEM-1 and a parallel decrease of the blaTEM-135-carrying Toronto/Rio plasmid was observed. Moreover, PPNG isolate harbored Toronto/Rio plasmid with blaTEM-135 belonged mainly to two major STs (ST661 and ST5624). Given the possible role of a mutated blaTEM gene as an additional mechanism to extended spectrum β-lactamase resistance, it is crucial to monitor gonococci carrying these resistance genes.