Multidrug resistance has been reported in group B streptococcus (GBS) from various
origins but rates among urinary tract infection (UTI) isolates are largely unknown.
Erythromycin, a second-line antibiotic for GBS for which high rates of resistance have
been reported supports the resistance of Staphylococcus to
oxidative stress. Here, we sought to survey multidrug resistant (MDR) GBS from UTI and to investigate
the affect of erythromycin exposure on the bacteria’s ability to resist oxidative stress. We
determined the antibacterial activity of 18 antibiotics against 292 GBS UTI isolates by
disk diffusion; and used in vitro growth assays of MDR GBS exposed to
erythromycin to examine relative resistance to oxidative stress, in the form of H2O2. A
high proportion of all 292 GBS isolates (33.6%) were MDR reflecting high rates of
resistance to four antibiotics: azithromycin (44.5%), clindamycin (26%), erythromycin
(36.3%), and tetracycline (81.5%); however, no resistance was detected for any other
antibiotics tested. Rates of resistance were not significantly different when analysed
according to clinical origins of (acute, recurrent UTI, asymptomatic bacteriuria). The
growth of MDR GBS was attenuated and severely inhibited by exposure to
erythromycin and H2O2, respectively. Surprisingly, exposure of MDR GBS to
erythromycin significantly relieved the severe growth inhibitory effect of H2O2
signifying a partial rescue affect of the antibiotic. The GBS isolates in this study exhibit
high levels of multidrug resistance without an association between resistance and
clinical origin. Exposure of MDR GBS to erythromycin can partially counteract the
severe growth inhibitory effect from H2O2.