[Susceptibility of Proteus, Morganella and Providencia strains isolated from patients with urinary tract infections on bactericidal activity of normal human serum].

Usefulness of the test determining bactericidal activity of normal human serum was investigated with 50 strains of Proteus, Morganella and Providencia isolated from patients with urinary tract infections (UTI) and with 50 strains isolated from feces. It was found that strains from UTI were more frequently resistant to the action of normal human serum (50% resistant) in comparison with strains isolated from feces (30% resistant). Strains of Proteus belonging to four species were differing greatly in their susceptibility to normal human serum. They can be ranked as followings: P. mirabilis (49% of resistant strains), P. vulgaris (62%), P. morganii (72%) and P. rettgeri (100%). In studies on interaction subinhibitory concentrations of cefotaxime and normal human serum in bactericidal reaction, a synergism was found only with some strains.