Synergism of antibiotic combinations against treponemes.

The use of combinations of drugs in the treatment of syphilis was reviewed by Willcox (1954). He appraised trends in the use of pencillin alone and in combination with arsenic, bismuth, and mercury compounds. Of the participating clinics in the study, 65-3 per cent. used penicillin alone and 28-9 per cent. used penicillin in combination with other drugs, while the remaining 5-8 per cent. used arsenic and bismuth compounds alone. All clinics in North America relied solely upon penicillin. Most investigations of the effect of combinations of antimicrobial agents have concerned bacteria other than treponemes. Purcell, Wright, and Finland (1953) concluded from their studies in vitro with seven strains of Staphylococcus aureus that the development of resistance to penicillin, streptomycin, and erythromycin may have been delayed by use of combinations of erythromycin with either penicillin or streptomycin. Bulger and Nielson (1968) reported that evaluations in vitro of antibiotic combinations should be correlated with effectiveness in vivo. They tested strains of Staphylococcus aureus, Escherichia coli, Proteus mirabilis, Aerobacter spp., and Klebsiella spp. against seven antibiotic combinations. Synergism was observed with ampicillin-kanamycin against Streptococcus faecalis and Proteus mirabilis 17121, with cephalothin-kanamycin against Staphylococcus aureus 970, and with dicloxacillin-hetacillin against Aerobacter spp. 6160 A. Stottmeier, Woodley, and Kubica (1969) reported that 5 ,Lg./ml. erythromycin in combination with oxacillin-methenamine, and with isoniazid, was bacteriostatic to strains of Mycobacterium intracellulare when the antimicrobial agents were kept in contact with bacteria for 12 hrs in concentrations attainable in man. Eickhoff, Bennett, Hayes, and Feeley (1970) examined the effects of antibiotic combinations against Pseudomonas pseudomallei. Synergism was observed with dicloxacillin and ampicillin and evidence of synergism with sulphadiazine-kanamycin, novobiocin-kanamycin, and