Bill, Nancy J.

Checkerboard bactericidal studies were performed with two strains each of Streptococcus mitis, S. salivarius , and S. sanguis , and the results were analyzed by the use of isobolograms. Synergy between penicillin and streptomycin or gentamicin was demonstrated with four strains, representing two of S. salivarius , one of S. sanguis , and one of S. mitis ; the remainder were either too susceptible or too resistant to be analyzed. Clindamycin with streptomycin or gentamicin acted synergistically with three strains, representing two of S. sanguis and one of S. salivarius ; the remainder were either too susceptible or too resistant to be analyzed.

Inhibitory activity of cephalexin, cephradine, and cefaclor was compared by the WHO-ICS agar dilution technique. Cefaclor was substantially more active against staphylococci, streptococci, gonococci, meningococci, Haemophilus, Escherichia coli, Klebsiella pneumoniae, Citrobacter diversus, Proteus mirabilis , salmonellae, and shigellae than was cephalexin, which in turn was more active than cephradine. Cefaclor appeared to be less resistant to staphylococcal penicillinase than did the other two agents. None of these cephalosporins was active against Enterobacter, Serratia , indole-positive Proteeae, Pseudomonas , or Bacteroides fragilis .