Trends in antimicrobial resistance in Neisseria gonorrhoeae isolated in Canada: 2000-2009.
ABSTRACT Canada conducts surveillance of penicillin, tetracycline, erythromycin, spectinomycin, ciprofloxacin, cefixime, and ceftriaxone susceptibilities in Neisseria gonorrhoeae isolates to support development of national treatment guidelines for sexually transmitted infections.
N. gonorrhoeae isolates were collected by Canadian provincial public health laboratories and included isolates from males and females ranging in age from 1 to 86 years. Minimum inhibitory concentrations (MICs) were determined by agar dilution at the National Microbiology Laboratory, Public Health Agency of Canada, and MIC interpretations were based on the criteria of the Clinical Laboratory Standards Institute.
From 2000 to 2009, 40,875 isolates of N. gonorrhoeae were tested by provincial laboratories and 10,993 of these were characterized by the Public Health Agency of Canada. There was an increasing incidence of N. gonorrhoeae isolates that were chromosomally resistant to penicillin, tetracycline, and erythromycin while the plasmid-mediated resistance strains (penicillinase-producing N. gonorrhoeae, tetracycline-resistant N. gonorrhoeae, and PP/tetracycline-resistant N. gonorrhoeae strain all had a declining trend. The percentage of isolates resistant to ciprofloxacin significantly increased from 1.3% in 2000 to 25.5% in 2009. Only 0.17% of isolates tested were azithromycin resistant. Between 2000 and 2009, the modal MICs for ceftriaxone increased from 0.016 μg/mL to 0.063 μg/mL.
Ciprofloxacin resistance in N. gonorrhoeae within Canada has increased to a level where quinolones are no longer the preferred drugs for the treatment of gonococcal infections and the modal MICs for the third-generation cephalosporins have increased over time. Close monitoring of antibiotic susceptibilities are required to inform treatment options.
- SourceAvailable from: Sinisa Vidovic[show abstract] [hide abstract]
ABSTRACT: A longitudinal study combining multilocus sequence typing with molecular evolutionary analysis determined the distribution, population structure and evolution of antibiotic resistance in Neisseria gonorrhoeae isolates in Saskatchewan collected between 2005 and 2008. Of 195 gonococcal isolates examined, 29 sequence types (STs) were identified with 3 major circulating strains (STs 1-3) comprising 52% of all gonococcal isolates studied. The prevalence, persistence, distribution pattern and clonality of these isolates strongly suggest that gonorrhea endemicity within this broad geographic region was driven by these 3 circulating strains. ST-1 exhibited a significantly (P=0.001) higher prevalence throughout the study, accounting for ∼25 % of tested isolates each year. The spatial distribution of the gonococcal strains indicated that ST-1 in 2007 entered a linear component of sexual network reaching the remote north, resulting in the further spread and maintenance of infection. Ciprofloxacin and azithromycin resistances were observed in distantly related gonococcal lineages, clearly indicating the convergent acquisition of these antibiotic resistant phenotypes. In addition, all ciprofloxacin and azithromycin resistant lineages were found at the edges of the minimum spanning tree, far from the major lineages, suggesting that these antibiotic phenotypes were most likely introduced into the province. In contrast, resistance to penicillin was mostly found in the endemic gonococcal lineages, suggesting that penicillin resistance was probably acquired in Saskatchewan as a result of spontaneous mutations in already established lineages. Tetracycline resistance was present in all STs except one, indicating its ubiquitous nature in the gonococcal population studied.Journal of clinical microbiology 09/2012; · 4.16 Impact Factor