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Effect of changing selection pressures on trimethoprim resistance in Enterobacteriaceae
Abstract:
The incidence of trimethoprim resistance was correlated with changes in prescription behaviour in the Nottingham area from 1978-1985. The prevalence of trimethoprim resistance among Enterobacteriaceae isolated from patients with urinary tract infection rose from 5% to 15% of total strains examined. Strains resistant to trimethoprim but susceptible to sulfamethoxazole appeared from 1980 onward and represented 35% of the total trimethoprim-resistant strains examined in 1985. Co-trimoxazole (trimethoprim + sulfamethoxazole) has been generally available for prescription in the United Kingdom since 1969, whereas trimethoprim alone was released in October 1979. By 1983, prescriptions in the form of trimethoprim alone accounted for approximately 50% (in hospitals) and 15% (in the community) of total trimethoprim usage in the Nottingham area. Although the introduction of trimethoprim alone seems to have had only a minor effect on overall resistance levels, it has greatly increased the proportion of trimethoprim-resistant strains which are susceptible to sulfamethoxazole. This was particularly evident in strains of Proteus spp., in which 52% of the total trimethoprim-resistant strains were sulfamethoxazole-susceptible in 1985.
Insights
The introduction of trimethoprim alone increased trimethoprim resistance in urinary tract infections but also raised susceptibility to sulfamethoxazole. This shift impacted resistance patterns in Enterobacteriaceae, particularly Proteus spp.
Area of Science:
- Medical Microbiology
- Antimicrobial Resistance
- Pharmacology
Background:
- Trimethoprim resistance in Enterobacteriaceae has been a growing concern.
- Co-trimoxazole (trimethoprim + sulfamethoxazole) has been widely prescribed since 1969.
- Trimethoprim monotherapy became available in the UK in 1979.
Purpose of the Study:
- To correlate trimethoprim resistance incidence with prescription behavior changes.
- To analyze the emergence of trimethoprim resistance and its susceptibility to sulfamethoxazole.
- To investigate the impact of trimethoprim monotherapy on resistance patterns.
Main Methods:
- Retrospective analysis of bacterial strains from urinary tract infections in Nottingham (1978-1985).
- Monitoring of trimethoprim resistance prevalence and susceptibility patterns.
- Correlation of resistance data with trimethoprim prescription trends.
Main Results:
- Trimethoprim resistance in Enterobacteriaceae increased from 5% to 15% between 1978 and 1985.
- Trimethoprim-resistant strains susceptible to sulfamethoxazole emerged post-1980, comprising 35% by 1985.
- Trimethoprim monotherapy usage rose significantly, accounting for substantial portions of total trimethoprim use by 1983.
Conclusions:
- The introduction of trimethoprim alone had a minor effect on overall resistance levels.
- Trimethoprim monotherapy significantly increased the proportion of trimethoprim-resistant strains susceptible to sulfamethoxazole.
- This trend was particularly pronounced in Proteus spp. strains.