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Demonstration of R factors from Pseudomonas aeruginosa
Abstract:
Sixty strains of Pseudomonas aeruginosa were selected from our clinical stock cultures and used as donors of drug resistance to examine the presence of R factors. They were highly resistant to one or more of six drugs including tetracycline (TC), chloramphenicol (CM), streptomycin (SM), sulfanilamide (SA), carbenicillin (CPC), and kanamycin (KM). Three FP(-), auxotrophic mutants of P. aeruginosa were used as recipients, which had been made resistant to either rifampin (RMP) or KM by in vitro mutation. Each donor was mated with each of the three recipients, and 45 strains were found to transfer their resistance to one or more recipients. A second series of conjugation experiments using 45 exconjugants as donors showed that 23 could transfer their resistance. We conclude that these strains carry R factors that are transmissible to one or more recipients. Eleven carried resistance to (TC.CM.SM.SA.CPC), nine to (TC.CM.SM.SA), one to (TC.CM.SA.CPC), one to (TC.CM.SA), and one to (SM). All of these R factors could not be transmitted to other species belonging to the family Enterobacteriaceae.
Insights
This study investigated R factors in Pseudomonas aeruginosa, finding that many clinical strains can transfer drug resistance. These transferable R factors confer resistance to multiple antibiotics but are not transmitted to other bacterial families.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Antibiotic resistance is a growing global health concern.
- R factors, or resistance plasmids, are key mechanisms of antibiotic resistance spread.
- Pseudomonas aeruginosa is an opportunistic pathogen frequently associated with hospital-acquired infections.
Purpose of the Study:
- To investigate the presence and transmissibility of R factors in clinical isolates of Pseudomonas aeruginosa.
- To determine the spectrum of antibiotic resistance conferred by these R factors.
- To assess the potential for inter-species transfer of these R factors.
Main Methods:
- Conjugation experiments were performed using sixty clinical strains of Pseudomonas aeruginosa as donors and three auxotrophic mutants of P. aeruginosa as recipients.
- Donors exhibited high resistance to tetracycline (TC), chloramphenicol (CM), streptomycin (SM), sulfanilamide (SA), carbenicillin (CPC), and kanamycin (KM).
- Exconjugants were subsequently used as donors in a second round of conjugation experiments to confirm resistance transfer.
Main Results:
- Forty-five of the sixty donor strains successfully transferred drug resistance to at least one recipient.
- Twenty-three of the exconjugants, acting as secondary donors, could transfer their acquired resistance.
- Specific resistance profiles identified included TC.CM.SM.SA.CPC (11 strains), TC.CM.SM.SA (9 strains), TC.CM.SA.CPC (1 strain), TC.CM.SA (1 strain), and SM (1 strain).
Conclusions:
- Clinical isolates of Pseudomonas aeruginosa harbor transmissible R factors.
- These R factors confer resistance to a range of clinically relevant antibiotics.
- The studied R factors demonstrated limited transmissibility, being confined within the Pseudomonas species and not transferred to Enterobacteriaceae.
