Background: This study was performed to evaluate the interaction of erythromycin or rifampin with vancomycin against Staphylococcus epidermidis biofilms. Methods: Biofilm-forming S. epidermidis strains (ATCC 35983, 35984) and polyurethane (PU) sheets were incubated for the formation of bacterial biofilms. Biofilms on PU sheets were treated with various antibiotic regimens. The number of viable bacteria on the sheets was counted. Results: While erythromycin or vancomycin alone did not significantly reduce the biofilm bacterial concentration, the combination of vancomycin and erythromycin resulted in a clear reduction in bacterial concentration compared with the single agents. Rifampin was the most active single agent against biofilm-forming S. epidermidis, while the combination of rifampin and vancomycin showed further reduction in bacterial concentration. Conclusions: These data suggest that the combination of erythromycin or rifampin and vancomycin is more effective than vancomycin alone in the treatment of biofilm infections caused by biofilm-forming S. epidermidis.

With the widespread emergence of antimicrobial resistance, combination regimens of ceftriaxone and vancomycin (C+V) or ceftriaxone and rifampin (C+R) are recommended for empirical treatment of pneumococcal meningitis. To evaluate the therapeutic efficacy of meropenem (M), we compared various treatment regimens in arabbit model of meningitis caused by penicillin-resistant Streptococcus pneumoniae (PRSP). Therapeutic efficacy was also evaluated by the final bacterial concentration in the cerebrospinal fluid (CSF) at 24 hr. Each group consisted of six rabbits. C+V cleared the CSF at 10 hr, but regrowth was noted in 3 rabbits at 24 hr. Meropenem monotherapy resulted in sterilization at 10 hr, but regrowth was observed in all 6 rabbits at 24 hr. M+V also resulted in sterilization at 10 hr, but regrowth was observed in 2 rabbits at 24 hr. M+V was superior to the meropenem monotherapy at 24 hr (reduction of 4.8 vs. 1.8 log10 cfu/mL, respectively; p=0.003). The therapeutic efficacy of M+V was comparable to that of C+V (reduction of 4.8 vs. 4.0 log10 cfu/mL, respectively; p=0.054). The meropenem monotherapy may not be a suitable choice for PRSP meningitis, while combination of meropenem and vancomycin could be a possible alternative in the treatment of PRSP meningitis.

Pulsed-field gel electrophoresis, ribotyping, and fingerprinting analysis of 22 invasive isolates of multidrug-resistant (MDR) pneumococci from Korea showed that 59 to 82% were genetically related. DNA sequencing of the PBP 2B gene showed relatively uniform alterations in nucleotides (5.4 to 7.8%) and amino acids (3.0 to 4.3%), while Asn-276→Lys, Arg-285→Cys and Ser-305→Phe substitutions were unique to Korean MDR strains, suggesting the spread of a few epidemic clones of resistant pneumococci within Korea.