Tanaka M, Otsuki M, Nishino T, Kobayashi I, Matsumoto T, Kumazawa J. Mutation in DNA gyrase of norfloxacin-resistant clinical isolates of Neisseria gonorrhoeae.
Genitourin Med 1996;
72:295-7. [PMID:
8976839 PMCID:
PMC1195683 DOI:
10.1136/sti.72.4.295]
[Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
BACKGROUND AND OBJECTIVES
Recently a rapid decrease in the susceptibility of Neisseria gonorrhoeae isolates to fluoroquinolones has occurred and gonococcal fluoroquinolone resistance is now a significant problem in the treatment of gonorrhoea in Japan. Thus, in order to investigate the quinolone resistance mechanisms in clinical isolates of N gonorrhoeae we studied an alteration in the DNA gyrase subunit A (GyrA) which is well-known as a common mechanism of bacterial quinolone resistance.
MATERIALS AND METHODS
Four clinical isolates of N gonorrhoeae resistant to norfloxacin and 5 strains susceptible to norfloxacin, including 2 clinical isolates and 3 WHO reference strains, were tested in this study. To identify mutations in the GyrA genes of gonococcal strains, polymerase chain reaction and direct DNA sequencing were performed.
RESULTS
A single base change (serine codon TCC changed to phenylalanine codon TTC), which resulted in an amino acid change in GyrA at position 91, was identified in all 4 norfloxacin-resistant strains for which the MICs of norfloxacin ranged from 1.0 to 8.0 micrograms/ml, while no mutation within GyrA was detected in 5 norfloxacin-susceptible strains for which the MICs of norfloxacin ranged from 0.004 to 0.063 microgram/ml.
CONCLUSIONS
The results from this study suggest that the serine-91 to phenylalanine substitution in GyrA is probably an essential mutation in fluoroquinolone resistance in clinical isolates of N gonorrhoeae.
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