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The relationship between antibacterial agent usage and prevalence of relevant organisms in hospitals in the West Midlands Introduction: The relative paucity of new antimicrobial drugs and the increasing prevalence of resistant strains of bacteria have focussed attention on ‘antimicrobial stewardship.’ Both the UK Department of Health and the US Centers for Disease Control and Prevention have issued relevant guidelines (1, 2). The UK guidance advises prescribers to take cultures for bacteriology before starting antimicrobial chemotherapy, and to adjust therapy in the light of culture results and local guidelines (1). The Department of Health also requires that NHS hospital trusts report the rates of important infections, including those due to Clostridium difficile (C diff) and meticillin-resistant Staphylococcus aureus (MRSA). Method: We have examined the rate of prescribing for drugs relevant to these diagnoses with reported rates of infection. We used the electronic database Define® (Rx-info Ltd, Exeter, UK), which holds comparative prescribing data for hospitals in the West Midlands from July 2013 to July 2014, and compared these data with Trust reports of infection with C diff and MRSA, recorded by Public Health England (3). We calculated prescribing rates in each Trust by dividing the total number of prescriptions for each antimicrobial by the number of Finished Consultant Episodes (FCEs), a measure of the episodes of care in a hospital. We compared prescribing rates with the declared rates of C diff infection and MRSA bacteraemia, also adjusted for the number of finished consultant episodes using rank correlation. Results: There were 14 acute Trusts with data, accounting for over 1.6 million finished consultant episodes, of which 524 (0.03%) were associated with a reported diagnosis of C diff infection. In total 3794 defined daily doses (DDDs) of oral vancomycin, which is only used for this indication, were prescribed. There was no significant correlation between the number of doses prescribed and the number of infections reported (rho = - 0.037). MRSA can be treated with intravenous infusions of vancomycin or linezolid. There were just 25 cases of MRSA bacteraemia reported in the region. There was no correlation between the number of reports of MRSA and usage of intravenous vancomycin prescribing (41,865 DDDs in total, rho = -0.04) or linezolid (17,490 DDD in total, rho = -0.34), or the sum of the two (rho = -0.1). Comment: We were unable to detect a relationship between the reported prescribing of these important antibacterials and the reported rates of infection with the organisms for which they are most used. The explanations include differences in the completeness of reporting of drug usage or of infection (or bacteraemia) rates from one Trust to another; and differences in usage of the antibiotics we examined—for example, that they are used for the treatment of disorders other than those specifically investigated, or other antibacterials are used for these indications. There remains the important possibility that there is widespread overuse of these important antibacterial agents, with risk that they will lose effectiveness (5). (1) Department of Health's advisory committee on Antimicrobial Resistance and Healthcare Associated Infection. Antimicrobial stewardship: “Start smart - then focus”. 2011 (2) Frieden TR, Bell BP. Core Elements of Hospital Antibiotic Stewardship Programs. 2014 (5) Wise R. J Antimicrob Chemother 2011; 66: 1939–40
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