RESUMEN
A recent study indicated that Neisseria subflava, one of the commensal Neisseria species, may play an important role in the emergence of Neisseria gonorrhoeae strains with chromosomally mediated resistance to penicillin or cephalosporin by the horizontal genetic exchange of penA genes encoding the target site for penicillin or cephalosporin. The present investigation examined the antimicrobial susceptibility of 45 isolates of N. subflava from the oral cavities of Japanese men and women to various agents used for the treatment of gonococcal infections. Of the 45 isolates, 40 (88.9%) and 4 (8.8%) were intermediately resistant and resistant to penicillin, respectively, with the minimal inhibitory concentration (MIC)(50) and MIC(90) of penicillin being 0.5 mg/l and 1 mg/l, respectively. Of the 45 isolates, 13 (28.9%) and 14 (31.1%) were resistant to tetracycline and ciprofloxacin, respectively, and 3 (6.7%) showed reduced susceptibility to cefixime (although the susceptibility category was not determined). These results indicate that several isolates of N. subflava have acquired resistance or intermediate resistance to various antimicrobial agents, including penicillin, cephalosporin, tetracycline, and ciprofloxacin. The present study may thus confirm that N. subflava may be involved in the emergence of N. gonorrhoeae strains with either intermediate or total resistance to penicillin or cephalosporin by the horizontal genetic exchange of the penA gene.
Asunto(s)
Antibacterianos/farmacología , Infecciones por Bacterias Gramnegativas/microbiología , Boca/microbiología , Neisseria/efectos de los fármacos , Cefixima/farmacología , Ceftriaxona/farmacología , Ciprofloxacina/farmacología , Farmacorresistencia Bacteriana Múltiple , Femenino , Humanos , Japón , Masculino , Pruebas de Sensibilidad Microbiana , Neisseria/aislamiento & purificación , Penicilinas/farmacología , Tetraciclina/farmacologíaRESUMEN
In Japan, Neisseria gonorrhoeae, a sexually transmitted pathogen, has recently shown significant resistance to various antimicrobial agents. In this study, a checkerboard method was utilized to investigate the in vitro activities of cefixime (CFIX), cefteram (CFTM), or amoxicillin (AMPC) in combination with azithromycin (AZM) against 25 clinical isolates of N. gonorrhoeae. Synergy, defined as a fractional inhibitory concentration (FIC) index of less than or equal to 0.50, was observed in 32% of isolates with CFIX+AZM, 12% of isolates with CFTM+AZM, and 4% of isolates with AMPC+AZM. Moreover, partial synergy, defined as an FIC index of greater than 0.50 and less than 1, was observed in 44% of isolates with CFIX+AZM, 68% of isolates with CFTM+AZM, and 52% of isolates with AMPC+AZM. In particular, as a result of the combination of CFIX and AZM, for all isolates, significant reductions were observed in the median CFIX minimum inhibitory concentration (MIC; from 0.25 to 0.008 microg/ml; P < 0.0001) and the median AZM MIC (from 0.12 to 0.03 microg/ml; P < 0.0001). However, antagonism, defined as an FIC index of greater than 1, was observed in only 4% of the isolates with both CFIX+AZM and CFTM+AZM, while it was seen in 12% of the isolates with AMPC+AZM. To our knowledge, this is the first study to demonstrate that the in vitro activity of CFIX against N. gonorrhoeae can be significantly enhanced in combination with AZM.