Cluster of multidrug-resistant Neisseria gonorrhoeae with reduced susceptibility to the newer cephalosporins in Northern Greece

Sir, Therapeutic options for gonococcal infection are nowadays limited due to the spread of gonococci resistant to a wide variety of antimicrobials. The dramatic increments in the rates of quinolone-resistant gonococci and the current shortage of spectinomycin leave the newer cephalosporins as the last safe choice among the drugs that are currently recommended as first-line treatment. Therefore, increasing reports of reduced in vitro activities of expanded-spectrum cephalosporins against Neisseria gonorrhoeae are of serious concern.1–5 The aim of this report from the Greek National Reference Centre for Neisseria gonorrhoeae (NRCNG) is to be aware of the presence, in Northern Greece, of a cluster of multiresistant gonococci that exhibit decreased susceptibility to the newer cephalosporins. From December 2006 through January 2008, a total of 195 gonococcal strains were submitted to the NRCNG, and all were characterized by serovar identification with the GC serotyping panel (BACTUS AE, Sweden) and tested for susceptibility to various antimicrobials using the Etest (AB Biodisk, Sweden). By analysing the results, a group of 17 isolates showed cefotaxime MICs 0.25–1 mg/L, as opposed to ≤0.002–0.125 mg/L for the remaining gonococci. By extending susceptibility testing to other cephalosporins, these isolates were found to exhibit raised MICs to cefixime and ceftriaxone also, while being highly resistant to cefuroxime and non-susceptible to cefoxitin, ceftazidime and cefepime. Cefalotin and aztreonam MIC50 values were increased up to 8-fold when compared with the ATCC 49266 strain, which was tested in parallel. This group of cephalosporin decreased susceptibility (CEDS) isolates consisted of non-penicillinase-producing, fluoroquinolone-resistant and multidrug-resistant strains with low-level resistance to penicillin G, tetracycline, erythromycin and chloramphenicol (Table 1). Antimicrobial susceptibility profile of 17 CEDS gonococcia aAntibiotic susceptibility testing was performed on GC agar supplemented with Vitox. MICs of β-lactam antibiotics were determined in triplicate. bSusceptibility breakpoints are those of the CLSI,6 except for norfloxacin, erythromycin, azithromycin and chloramphenicol, for which generally accepted criteria were used. For classification in susceptibility categories according to these criteria, Etest MIC values lying between two marginal concentrations are rounded to the nearest highest concentration. Antimicrobial susceptibility profile of 17 CEDS gonococcia aAntibiotic susceptibility testing was performed on GC agar supplemented with Vitox. MICs of β-lactam antibiotics were determined in triplicate. bSusceptibility breakpoints are those of the CLSI,6 except for norfloxacin, erythromycin, azithromycin and chloramphenicol, for which generally accepted criteria were used. For classification in susceptibility categories according to these criteria, Etest MIC values lying between two marginal concentrations are rounded to the nearest highest concentration. CEDS isolates were allocated to a distinct serovar, Bpyut, not exhibited by any other strain isolated during the study period. Additionally, all shared the same plasmid content, harbouring only the cryptic gonococcal plasmid, and showed highly similar PFGE-generated SpeI restriction patterns, 14 of them being identical. CEDS strains were also of the same origin, all submitted from the Skin and Venereal Disease Hospital located in Thessaloniki. They accounted for 63% of 27 viable gonococci that were received from this setting and represented 39% of all 43 gonorrhoea cases reported from Northern Greece during the 14 month period running from December 2006 through January 2008. We conclude that CEDS gonococci were disseminated in Northern Greece by clonal spread of a single strain. Epidemiological data were obtained through a standard questionnaire answered by the patients, including demographic and sexual behaviour data, previous sexually transmitted disease history and area of acquisition of infection. No relation between the CEDS strains and any particular group of the population was apparent. Data were available for all CEDS strains apart from the first one isolated in December 2006. The second strain was isolated in the same month from a Spanish–English heterosexual contact, while the remaining 15 isolates were obtained after February 2008 from Greek heterosexual men who affirmed contacts with casual female partners in Thessaloniki. Due to only slight reductions in susceptibility to cefotaxime, which is the cephalosporin regularly tested, CEDS strains passed unnoticed. As a consequence, patients were given the standard regimen used for gonorrhoea in the Venereal Hospital of Thessaloniki since 2002, which included cefuroxime sodium (single intramuscular dose of 1.5 g), plus tetracycline (100 mg twice daily for 8 days). Although therapeutic failures were not reported, the fact that the CEDS strains were subsequently found resistant to both agents does not guarantee this treatment's outcome, and this could be a cause for the persistence of these strains. The susceptibility profile of the CEDS cluster of gonococci resembles those of N. gonorrhoeae strains with reduced susceptibility to newer β-lactams reported previously from Japan1–3 and elsewhere.4,5 Cephalosporin susceptibility reductions have been associated with various types of mosaic penicillin-binding protein 2, occurring via homologous recombination between penA genes of N. gonorrhoeae and other Neisseria species.2,5 Most of the strains with decreased susceptibility to the newer cephalosporins reported so far, including CEDS in this study, exhibited multidrug resistance indicating the operation of non-specific mechanisms, such as alterations in penB and mtrR genetic loci. Furthermore, strains with these characteristics are most often resistant to fluoroquinolones.1–5 Apart from its apparent clinical impact, the uniform multiply resistant pattern of cephalosporin non-susceptible strains from distant geographical areas suggests that they may have emerged from a limited number of strains, which were subsequently disseminated worldwide.4 Nevertheless, studies on isolates separated in time and place indicated a considerable degree of heterogeneity among gonococci with these characteristics.5 For Greece, with established high rates of resistance to traditional anti-gonococcal agents and an estimated frequency of quinolone-resistant strains that reached a peak of 56% in 2007 (unpublished data of the NRCNG), the emergence of strains with diminished susceptibility to cephalosporins is threatening. From a global point of view as well, increasing reports of such non-susceptible gonococci since the 1990s is most alarming. Surveillance of N. gonorrhoeae antimicrobial susceptibility continuously contacted in the NRCNG is supported by the Hellenic Pasteur Institute. None to declare. For their contributions to gonorrhoea surveillance, we thank Helen Avgerinou (Microbiology Laboratory of the ‘Andreas Sygros’ Hospital, Athens), Olga Paniara and Athena Argyropoulou (Microbiology Laboratory of the ‘Evangelismos’ General Hospital, Athens), Evangelos Papafrangas and Maria Martsoukou (‘Sismanogleion’ General Hospital, Athens) and Alkiviadis Vatopoulos (National School for Public Health). We also thank Prof. Leonidas Tzouvelekis (Athens University Medical School) for helpful comments on the manuscript.