Antimicrobial susceptibility of invasive group B streptococcal isolates from south-west Sweden 1988-2001

The antibiotic susceptibility of 297 invasive isolates of group B streptococci (GBS) to a panel of 12 antibiotics was analysed using the E-test. The isolates (from 123 neonates and 174 adults) were collected from south-west Sweden during the 2 periods 1988-1997 and 1998-2001. The breakpoints of the Clinical and Laboratory Standards Institute were used. All isolates were sensitive to cefotaxime, meropenem, linezolid, vancomycin, moxifloxacin and quinupristin-dalfopristin. Two strains displayed a slightly decreased susceptibility to penicillin G (MIC 0.25 microg/ml) also when tested by the broth dilution method. Two per cent were resistant to erythromycin and 1% to clindamycin. Strains with intermediate sensitivity to erythromycin and clindamycin increased over the 2 study periods. 68% were resistant to doxycycline, and the resistance rate for doxycycline increased over the 2 study periods. No strain was resistant to trimethoprim-sulfamethoxazole. Serotype V dominated among strains with intermediate susceptibility to erythromycin and clindamycin. There were no other relationships between serotypes and decreased sensitivity to any agent. There were no significant differences in susceptibility to any agent tested between strains isolated from neonates and adults. In conclusion, penicillins remain the drug of choice in the region but with the increasing rates of intermediate susceptibility to both erythromycin and clindamycin, antibiotic sensitivity analysis should be performed on the GBS isolates from penicillin-allergic patients.