[Mechanisms of Proteus resistance to chloramphenicol].

Data on chloramphenicol sensitivity of clinical Proteus strains isolated within 1970--1975 and some mechanisms of their resistance to this antibiotic are presented. It was found that most of the Proteus strains (62.82 +/- 2.15 per cent) were resistant to chloramphenicol. 75 per cent of the isolates had resistance of transmissive character. Resistance of the Proteus cultures to chloramphenicol was not a stable feature and was lost during storage under laboratory conditions. Direct correlation between stability of the antibiotic resistance in the Proteus, the resistance level and the period of the culture storage was found. It was shown that the transmissive resistance to chloramphenicol in the Proteus cultures was due to synthesis of a highly active constituitive chloramphenicol-inactivating enzyme. Direct relation between the Proteus resistance level to chloramphenicol and the rate of the enzyme synthesis was noted. A number of the Proteus strains phenotypically sensitive to this antibiotic was capable of its inactivation. Still, the activity of the enzyme was low. The rate of the enzyme synthesis and the level of the acquired resistance in the chloramphenicol resistant mutants depended on the presence or absence of the enzyme in the cells of the initial sensitive strain. The capacity for chloramphenicol accumulation in a number of the chloramphenicol resistant mutants of the Proteus was decreased.