In-vitro activity of synercid and related drugs against Streptococcus oralis isolated from septicaemia and endocarditis cases.

OBJECTIVE

The increase in resistance to gram positive organisms and seriousness of infective endocarditis, makes it necessary to look for an alternate treatment.

METHOD

In-vitro activity of synercid was compared with penicillin, amoxycillin, teicoplanin, vancomycin, clindamycin and erythromycin.

RESULT

Synercid showed minimum inhibitory concentrations (MIC) within the narrow range of 0.06 - 0.5 mg/l. MIC50 and mode values were both 0.25 mg/l. There was just two-fold difference between the MIC50 (0.25 mg/l) and the MIC90, (0.5 mg/l). Although the MICs of synercid for S. oralis were relatively high compared to penicillin, clindamycin, erythromycin and teicoplanin, the in-vitro bactericidal activity of synercid was much greater. Synercid MBC values were < 4 mg/l for most of the isolates, except for one of 16 mg/l and the other >64 mg/l. Killing curve was performed on six isolates of S. oralis from infective endocarditis, two from septicaemia patients and two from the oral flora of normal individuals.

CONCLUSION

Synercid showed superior bactericidal activity when compared to penicillin and vancomycin against all ten isolates of S. oralis tested. Synercid was bactericidal (99.9% kill) against all ten isolates of S. oralis within six hours of contact.