Emergence and spread of azithromycin-resistant Neisseria gonorrhoeae in Scotland.
OBJECTIVE
The aim of this study was to analyse the trend in azithromycin susceptibility (AzDS) of Neisseria gonorrhoeae in Scotland between April 2004 and December 2007, and to characterize isolates exhibiting decreased AzDS or high-level azithromycin resistance (AzHLR).


METHODS
Antibiotic susceptibility testing and N. gonorrhoeae multiantigen sequence typing (NG-MAST) were performed on all gonococcal isolates received by the Scottish Bacterial Sexually Transmitted Infections Reference Laboratory (SBSTIRL) during the study period.


RESULTS
AzHLR isolates were observed for the first time in 2004 and increased from 0.3% to 3.9% in 2007. AzDS declined from 2.1% to 1.3% in the same period. Taken together, AzDS and AzHLR isolates accounted for 5.2% of the gonococcal infections in Scotland in 2007. NG-MAST revealed that only a small number of sequence types (STs) contained AzHLR and AzDS isolates; these STs also included azithromycin-susceptible isolates. Most STs containing AzHLR isolates were genetically related on the basis of their por and tbpB alleles; however, demographic data suggested that they formed discrete sexual networks.


CONCLUSIONS
AzHLR strains of N. gonorrhoeae are increasing in Scotland. A 1 g dose of azithromycin should not be considered as an alternative antibiotic therapy for gonococcal infections. The use of azithromycin to treat chlamydia in patients co-infected with N. gonorrhoeae results in a level of azithromycin in vivo that is sublethal for N. gonorrhoeae, which may lead to resistance.
Scottish Bacterial Sexually Transmitted Infections Reference Laboratory (SBSTIRL), Department of Medical Microbiology, Royal Infirmary of Edinburgh, UK. helen.palmer@luht.scot.nhs.uk
Helen M
HM
Palmer
Hugh
H
Young
Andrew
A
Winter
Jayshree
J
Dave
D000328:Adult; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D017963:Azithromycin / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics; D015373:Bacterial Typing Techniques; D004269:DNA, Bacterial / Q000235:genetics; D024881:Drug Resistance, Bacterial; D005260:Female; D005838:Genotype; D006069:Gonorrhea / Q000382:microbiology*; D006801:Humans; D008297:Male; D008826:Microbial Sensitivity Tests; D009344:Neisseria gonorrhoeae / Q000145:classification / Q000187:drug effects* / Q000302:isolation & purification*; D012606:Scotland; D017422:Sequence Analysis, DNA
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D017963:Azithromycin