Inhibition of Pseudomonas aeruginosa by 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 aeruginosa 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 aeruginosa in vitro. Experiments in mice with erythromycin-ascorbic acid 
combination show that the curvative 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. 