Antibacterial prescribing and antibacterial resistance in English general practice: cross sectional study Commentary: antibiotic resistance is a dynamic process

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Abstract
Objective: To quantify the relation between community based antibacterial prescribing and antibacterial resistance in community acquired disease. Design: Cross sectional study of antibacterial prescribing and antibacterial resistance of routine isolates within individual practices and primary care groups. Setting: 405 general practices (38 groups) in south west and north west England. Main outcome measures: Correlation between antibacterial prescribing and resistance for urinary coliforms and Streptococcus pneumoniae. Results: Antibacterial resistance in urinary coliform isolates is common but the correlation with prescribing rates was relatively low for individual practices (ampicillin and amoxicillin rs=0.20, P=0.001; trimethoprim rs=0.24, P=0.0001) and primary care groups (ampicillin and amoxicillin rs=0.44, P=0.05; trimethoprim rs=0.31, P=0.09). Regression coefficients were also low; a practice prescribing 20% less ampicillin and amoxicillin than average would have about 1% fewer resistant isolates (0.94/100; 95% confidence interval 0.02 to 1.85). Resistance of S pneumoniae to both penicillin and erythromycin remains uncommon, and no clear relation with prescribing was found. Conclusions: Routine microbiological isolates should not be used for surveillance of antibacterial resistance in the community or for monitoring the outcome of any change in antibacterial prescribing by general practitioners. Trying to reduce the overall level of antibiotic prescribing in UK general practice may not be the most effective strategy for reducing resistance in the community. What is already known on this topic The probability of an individual hosting a resistant organism is increased by recent use of an antibacterial drug Correlation between antibacterial prescribing and coliform resistance in routine microbiological samples from the community has been reported in one study What this study adds In English general practice, there are significant but low correlations between antibacterial prescribing and resistance in routine isolates of urinary coliforms Substantial differences in prescribing between high and low prescribing practices are associated with only small differences in resistance Improved methods of assessing national antimicrobial resistance are required Objective: To quantify the relation between community based antibacterial prescribing and antibacterial resistance in community acquired disease. Design: Cross sectional study of antibacterial prescribing and antibacterial resistance of routine isolates within individual practices and primary care groups. Setting: 405 general practices (38 groups) in south west and north west England. Main outcome measures: Correlation between antibacterial prescribing and resistance for urinary coliforms and Streptococcus pneumoniae. Results: Antibacterial resistance in urinary coliform isolates is common but the correlation with prescribing rates was relatively low for individual practices (ampicillin and amoxicillin rs=0.20, P=0.001; trimethoprim rs=0.24, P=0.0001) and primary care groups (ampicillin and amoxicillin rs=0.44, P=0.05; trimethoprim rs=0.31, P=0.09). Regression coefficients were also low; a practice prescribing 20% less ampicillin and amoxicillin than average would have about 1% fewer resistant isolates (0.94/100; 95% confidence interval 0.02 to 1.85). Resistance of S pneumoniae to both penicillin and erythromycin remains uncommon, and no clear relation with prescribing was found. Conclusions: Routine microbiological isolates should not be used for surveillance of antibacterial resistance in the community or for monitoring the outcome of any change in antibacterial prescribing by general practitioners. Trying to reduce the overall level of antibiotic prescribing in UK general practice may not be the most effective strategy for reducing resistance in the community. What is already known on this topic The probability of an individual hosting a resistant organism is increased by recent use of an antibacterial drug Correlation between antibacterial prescribing and coliform resistance in routine microbiological samples from the community has been reported in one study What this study adds In English general practice, there are significant but low correlations between antibacterial prescribing and resistance in routine isolates of urinary coliforms Substantial differences in prescribing between high and low prescribing practices are associated with only small differences in resistance Improved methods of assessing national antimicrobial resistance are required