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Thermosensitive replication of a kanamycin resistance factor
Abstract:
A strain of Proteus vulgaris isolated from the urinary tract of a patient with postoperative pyelonephritis and resistant to sulfonamide, streptomycin, tetracycline, and kanamycin (KM) was found to transfer only KM resistance by cell-to-cell conjugation. The genetic determinant controlling the transferable KM resistance was considered to be an R factor and was designated R (KM). Successive transfer of KM resistance was demonstrated also from Escherichia coli 20S0, which received the R (KM) factor, to other substrains of E. coli K-12 or Salmonella typhimurium LT-2. The transfer of the R (KM) factor was strongly affected by the temperature at which the mating culture was kept. The transfer frequency of R (KM) at 25 C was about 10(5) times higher than at 37 C. The R (KM) factor was spontaneously eliminated from the host bacterial cells when P. vulgaris was cultured at 42 C, but no elimination occurred at 25 C. This elimination of the R (KM) factor at elevated temperature was also observed when the R (KM) factor infected E. coli and S. typhimurium. On the other hand, a normal R factor could not be eliminated from the same E. coli host strain by cultivation at the higher temperature. We consider the thermosensitive transfer and the spontaneous elimination of the R (KM) factor at higher temperature to depend upon thermosensitive replication of the R (KM) factor.
Insights
A novel R factor (R(KM)) conferring kanamycin resistance was identified in Proteus vulgaris. This R factor exhibits temperature-sensitive transfer and elimination, suggesting thermosensitive replication.
Area of Science:
- Microbiology
- Genetics
- Molecular Biology
Background:
- Antibiotic resistance is a growing global health concern.
- R factors are genetic elements that confer antibiotic resistance.
- Understanding R factor transfer and stability is crucial for combating resistance.
Purpose of the Study:
- To characterize a novel R factor (R(KM)) from a clinical isolate of Proteus vulgaris.
- To investigate the transfer dynamics and stability of the R(KM) factor.
- To elucidate the genetic basis for the observed temperature sensitivity.
Main Methods:
- Bacterial conjugation experiments were performed using Proteus vulgaris, Escherichia coli, and Salmonella typhimurium.
- Kanamycin resistance transfer frequencies were measured at different temperatures (25°C and 37°C).
- Spontaneous elimination of the R factor was assessed by culturing bacteria at elevated temperatures (42°C).
Main Results:
- A transferable kanamycin resistance determinant, designated R(KM), was identified in Proteus vulgaris.
- The R(KM) factor showed significantly higher transfer frequency at 25°C compared to 37°C (approx. 10^5-fold difference).
- The R(KM) factor was spontaneously eliminated from host cells at 42°C, a phenomenon not observed with a normal R factor.
Conclusions:
- The R(KM) factor possesses temperature-sensitive replication, leading to thermosensitive transfer and spontaneous elimination at higher temperatures.
- This thermosensitive nature offers a potential mechanism for controlling the spread of specific antibiotic resistance genes.
- Further research into thermosensitive R factors could lead to novel strategies for managing antibiotic resistance.