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Abstract:
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.
Insights
Most clinical Proteus strains exhibit chloramphenicol resistance, often transmissible and linked to an inactivating enzyme. This resistance is unstable, decreasing over time in laboratory conditions.
Area of Science:
- Microbiology
- Antibiotic Resistance
- Molecular Biology
Background:
- Investigating antibiotic resistance mechanisms in clinical bacterial isolates is crucial for public health.
- Proteus species are common causes of various infections, and their resistance patterns impact treatment efficacy.
- Chloramphenicol, though older, remains relevant in certain clinical contexts, necessitating understanding of resistance.
Purpose of the Study:
- To determine the prevalence of chloramphenicol resistance in clinical Proteus strains isolated between 1970-1975.
- To elucidate the mechanisms underlying Proteus resistance to chloramphenicol, focusing on enzyme activity and transmissibility.
- To examine the stability of chloramphenicol resistance in Proteus cultures under laboratory conditions.
Main Methods:
- Phenotypic characterization of chloramphenicol sensitivity in clinical Proteus isolates.
- Assessment of resistance transmissibility (e.g., via conjugation or plasmid analysis).
- Enzyme assays to detect chloramphenicol-inactivating activity and analysis of enzyme synthesis rates.
- Monitoring resistance stability during prolonged storage of bacterial cultures.
Main Results:
- A high percentage (62.82%) of clinical Proteus strains were resistant to chloramphenicol.
- Seventy-five percent of resistant isolates exhibited transmissible resistance, primarily due to a highly active chloramphenicol-inactivating enzyme.
- Resistance was unstable, decreasing during laboratory storage, with a direct correlation between stability, resistance level, and storage duration.
Conclusions:
- Transmissible chloramphenicol resistance in Proteus is mediated by a constitutive enzyme, with synthesis rate correlating to resistance level.
- Even phenotypically sensitive strains may possess low-activity inactivating enzymes; resistance acquisition in mutants depends on initial enzyme presence.
- The instability of chloramphenicol resistance in Proteus highlights the dynamic nature of antibiotic resistance mechanisms.