Inhibition Ofpseudomonas Æruginosaby Ascorbic Acid Acting Singly and in Combination With Antimicrobials: In‐vitro and In‐vivo Studies

Ascorbic acid, acting on its own, is found to exert a bacteriostatic action in vitro on 16 strains of Pseudomonas æruginosa tested. This action, attributable to the oxidation of ascorbic acid, is dependent on individual strains and the inoculum size. In combination with sulphamethoxazole, trimethoprim, Septrin, ampicillin, erythromycin, chloramphenicol or colistin sulphate, ascorbic acid acts synergistically on Pseudomonas æruginosa in vitro. Experiments in mice with erythromycin-ascorbic acid combination show that the curative dose 50 of ascorbic acid acting alone is 11·22 milligrammes per kilogram body weight. This was significantly lowered (P = < 0·001) to 6·91 mg/kg if administered in combination with erythromycin (10 mg/kg). In human patients with cystic fibrosis, by the combined administration of ascorbic acid sulphamethoxazole and trimethoprim (Bactrim, Roche) the pseudomonas infection could be controlled, as the viable number of organisms significantly diminished during the therapy.