Mutation in 23S rRNA associated with macrolide resistance in Neisseria gonorrhoeae.
Fifty-six azithromycin-resistant (MICs, 2.0 to 4.0 micro g/ml) Neisseria gonorrhoeae strains with cross-resistance to erythromycin (MICs, 2.0 to 64.0 micro g/ml), isolated in Canada between 1997 and 1999, were characterized, and their mechanisms of azithromycin resistance were determined. Most (58.9%) of them belonged to auxotype-serotype class NR/IB-03, with a 2.6-mDa plasmid. Based on resistance to crystal violet (MICs >or= 1 micro g/ml), 96.4% of these macrolide-resistant strains appeared to have increased efflux. Nine of the eleven strains selected for further characterization were found to have a promoter region mtrR mutation, a single-base-pair (A) deletion in the 13-bp inverted repeat, which is believed to cause overexpression of the mtrCDE-encoded efflux pump. The two remaining macrolide-resistant strains (erythromycin MIC, 64.0 micro g/ml; azithromycin MIC, 4.0 micro g/ml), which did not have the mutation in the mtrR promoter region, were found to have a C2611T mutation (Escherichia coli numbering) in the peptidyltransferase loop in domain V of the 23S rRNA alleles. Although mutations in domain V of 23S rRNA alleles had been reported in other bacteria, including E. coli, Streptococcus pneumoniae, and Helicobacter pylori, this is the first observation of these mutations associated with macrolide resistance in N. gonorrhoeae.
National Laboratory for Sexually Transmitted Diseases, National Microbiology Laboratory, Population and Public Health Branch, Health Canada, Winnipeg, Manitoba, Canada. Lai_King_Ng@hc-sc.gc.ca
Lai-King
LK
Ng
Irene
I
Martin
Gary
G
Liu
Louis
L
Bryden
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D017963:Azithromycin / Q000494:pharmacology; D002170:Canada / Q000453:epidemiology; D004269:DNA, Bacterial / Q000187:drug effects / Q000235:genetics; D004351:Drug Resistance; D004917:Erythromycin / Q000494:pharmacology; D006069:Gonorrhea / Q000453:epidemiology / Q000382:microbiology; D006801:Humans; D008826:Microbial Sensitivity Tests; D009154:Mutation / Q000235:genetics; D009344:Neisseria gonorrhoeae / Q000187:drug effects*; D009690:Nucleic Acid Conformation; D015345:Oligonucleotide Probes; D010458:Peptidyl Transferases / Q000235:genetics; D012338:RNA, Ribosomal, 23S / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014169:Transformation, Bacterial
D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D015345:Oligonucleotide Probes; D012338:RNA, Ribosomal, 23S; D004917:Erythromycin; D017963:Azithromycin; D010458:Peptidyl Transferases