Supplemental Antibiotics to Enhance the Action of Gentamicin in Pseudomonas and Mixed Infections

A survey of 66 patients treated with gentamicin alone indicated that 14 patients showed persistence of Pseudomonas or a mixed flora, and they required additional treatment. A study of a mixed infection (peritonitis) in mice and of an experimental infection of mice with Pseudomonas aeruginosa was made with gentamicin treatment alone or in combination with other antibiotics. The challenge organisms were given ip, and the treatment sc 1 hr later. Gentamicin was significantly beneficial in the treatment of peritonitis. Ampicillin, chloramphenicol, penicillin G, or streptomycin could be added without any loss of benefit, but only kanamycin-gentamicin treatment was better than gentamicin alone. Gentamicin was also effective in treating the challenge with Pseudomonas. Ampicillin or carbenicillin in addition to gentamicin did not produce any less benefit, but no clear-cut gain was produced by adding one of a variety of antibiotics to the basic gentamicin regimen.