Quinolone-resistant Streptococcus agalactiae bacteria were recovered from single-patient isolates and found to contain mutations in the gyrase and topoisomerase IV genes. Pulsed-field gel electrophoresis demonstrated that four isolates from the same long-term care facility were closely related; in seven cases, quinolone-resistant Haemophilus influenzae and S. agalactiae bacteria were isolated from the same patient.Although disease caused by Streptococcus agalactiae (group B streptococcus [GBS]) in infants and during pregnancy is well documented, the epidemiology of patients infected with this bacterium is changing to include nonpregnant and elderly adults (1-3, 8, 14, 16). These patients often have significant underlying illness and reside in long-term care facilities (LTCFs) (5). While GBS remains fully susceptible to penicillin, antibiotic susceptibility surveys demonstrate increasing prevalences of resistance to erythromycin and clindamycin (4,8,17). Recently, quinoloneresistant GBS was detected (6). Since LTCFs can also have problems with quinolone-resistant Haemophilus influenzae (7, 9), we have looked for and found coisolation of quinoloneresistant H. influenzae with GBS from the same patients.Antimicrobial susceptibility and clinical sites of all GBS isolates processed by our clinical microbiology laboratory from 1999 to 2002 were recorded. This laboratory receives clinical specimens from patients in our hospital and from those in several affiliated LTCFs. Levofloxacin resistance in GBS was initially identified by disk diffusion methodology. The isolates were further characterized by the infectious disease research laboratory using Etest methodology (AB Biodisk, Piscataway, N.J.) and broth microdilution (STP1 and GPN Sensititre plates; Trek Diagnostic Systems, Inc., Westlake, OH) for susceptibility to erythromycin, clindamycin, ampicillin, penicillin, levofloxacin, moxifloxacin, ciprofloxacin, gatifloxacin, gemifloxacin, and garenoxacin according to manufacturers' recommendations. NCCLS susceptibility breakpoints were used for all antibiotics (10). Since only urinary isolates were routinely tested for levofloxacin susceptibility by our clinical microbiology lab-