Abstract
Sultamicillin (SBTPC) is a mutual prodrug in which ampicillin (ABPC) and a potent β-lactamase inhibitor sulbactam (SBT) are ester-bound in an equimolar ratio. SBTPC is hydrolyzed during absorption after oral administration to provide ABPC and SBT for systemic circulation.
In the present study, the antimicrobial activities of SBTPC against 50 isolates each of 6 species (Staphylococcus aureus, Klebsiella pneumoniae subsp. pneumoniae, Branhamella catarrhalis, Haemophilus influenzae, Streptococcus pneumoniae and Streptococcus pyogenes) of bacteria freshly obtained from upper respiratory tract infections were examined in relation to their bacterial β-lactamase producing abilities. β-Lactamase producing strains were identified using the acidometry disc method with benzylpenicillin (PCG) of cefazolin (CEZ) as a substrate, and their frequencies of appearance were calculated as follows: S. aureus86%; K. pneumoniae subsp. pneumoniae 100%; B. catarrhalis 68%; H. influenzae 24%. Fourteen per cent of S. aureus strains examined were β-lactamase positive using both PCG and CEZ acidometry discs. SBTPC, however, demonstrated excellent antimicrobial activities even against these β-lactamase producing strains. Good activities were observed especially against those bacterial strains producing penicillinase (PCase). Average MIC80, values of SBTPC were 3.13μg/ml for S. aureus and K. pneumoniae subsp. pneumoniae, 0.39μg/ml for B. catarrhalis and H. influenzae, 0.05μg/ml for S. pneumoniae and 0.025μg/ml for S. pyogenes.
As SBTPC was shown to possess excellent antimicrobial activities against PCase producing strains, the enhancement in activities of SBTPC compared to ABPC alone can be attributed to the inhibition of β-lactamase by SBT which, as noted above, is a component of SBTPC in an equimolar ratio to ABPC.
