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R factor-mediated resistance to aminoglycoside antibiotics in Pseudomonas aeruginosa
Abstract:
Conjugal transferability of drug resistance was examined, in eleven Pseudomonas aeruginosa strains which were isolated in Frankfurt. Four R factors were demonstrated from three strains using P. aeruginosa as recipients but they were nontransferable to Escherichia coli K12. Two R factors, i.e., Rms146 and Rms147, mediated resistances to tetracycline (TC), streptomycin (SM), sulfanilamide (SA), kanamycin (KM), lividomycin (LV), gentamicin C complex (GM) and 3', 4'-dideoxykanamycin B (DKB). They mediated the formation of aminoglycoside-inactivating enzymes, i.e., SM phosphotransferase, SM adenylyltransferase, KM and LV phosphotransferase l, and GM and DKB 6'-N-acetyltransferase. TC resistance conferred by these R factors was due to impermeability of the drug. P. aeruginosa Ps 142 carried two kinds of R factor in one cell, Rms148 (SM) and Rms149 (SM-SA-GM-CPC) (CPC, carbenicillin). Rms148 (SM) was transferable at a high frequency of 10-1 and mediated the formation of SM phosphotransferase. Rms149 mediated the formation of drug-inactivating enzymes, ie., GM 3-N-acetyltransferase and beta-lactamase, but did not inactivate SM. SM resistance was probably due to impermeability of the drug.
Insights
Drug resistance in Pseudomonas aeruginosa strains was studied. Four R factors were identified, conferring resistance to multiple antibiotics through enzyme inactivation or impermeability, with some transferable between P. aeruginosa but not E. coli.
Area of Science:
- Microbiology
- Genetics
- Molecular Biology
Background:
- Antibiotic resistance is a growing global health concern.
- Understanding the mechanisms of drug resistance transfer in bacteria is crucial for developing effective treatments.
- Pseudomonas aeruginosa is an opportunistic pathogen known for its intrinsic and acquired resistance to antibiotics.
Purpose of the Study:
- To investigate the conjugal transferability of drug resistance in clinical isolates of Pseudomonas aeruginosa.
- To characterize the R factors responsible for antibiotic resistance in these strains.
- To elucidate the mechanisms underlying antibiotic resistance, including enzyme inactivation and drug impermeability.
Main Methods:
- Isolation and characterization of eleven Pseudomonas aeruginosa strains from Frankfurt.
- Conjugation experiments using P. aeruginosa and Escherichia coli K12 as recipients.
- Determination of antibiotic resistance profiles.
- Identification of R factors and analysis of drug-inactivating enzymes (e.g., phosphotransferases, adenylyltransferases, acetyltransferases, beta-lactamases).
Main Results:
- Four R factors were identified in three P. aeruginosa strains, transferable to P. aeruginosa but not E. coli K12.
- Two R factors (Rms146, Rms147) conferred resistance to tetracycline, streptomycin, sulfanilamide, kanamycin, lividomycin, gentamicin C, and dideoxykanamycin B.
- These R factors mediated aminoglycoside-inactivating enzymes and tetracycline resistance via impermeability.
- P. aeruginosa Ps 142 harbored two R factors (Rms148, Rms149) with Rms148 (SM) being highly transferable and mediating SM phosphotransferase.
- Rms149 mediated gentamicin and carbenicillin resistance via enzyme inactivation, with SM resistance likely due to impermeability.
Conclusions:
- Conjugal transfer of drug resistance occurs among P. aeruginosa strains, mediated by specific R factors.
- Mechanisms of resistance include both enzymatic inactivation of antibiotics and reduced drug uptake (impermeability).
- The findings highlight the complex nature of antibiotic resistance in P. aeruginosa and its potential for dissemination.