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

ABSTRACT

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/I. MIC50 and mode values were both 0.25 mg/I. There was just two-fold difference between the MIC50 [0.25 mg/I] and the MIC90, [0.5 mg/I]. 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/I for most of the isolates, except for one of 16 mg/I and the other >64 mg/I. 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