Pneumonia & Respiratory Tract Infection: Antibiotic risk for Clostridium difficile Kieran Hand*, Adil Ahmed †, Adriana Basarab ¶, Whitney Chow †, Nick Cortes ¶ & Sally Pearce* *Pharmacy Department, † Department of General Medicine, ¶ Microbiology Department Southampton University Hospitals NHS Trust Introduction  Respiratory tract infections (RTI), including community-acquired pneumonia (CAP), acute exacerbation of chronic obstructive pulmonary disease (AECOPD) and aspiration pneumonia are a leading cause of hospital admission and result in considerable morbidity and mortality.  Antibiotics generally recommended for treatment of RTI are however, also implicated in the development of Clostridium difficile infection (CDI) 1,2.  In response to a comparatively high incidence of CDI in a large university teaching hospital, antibiotic treatment guidelines were revised in November 2007 to promote prescribing of antibiotics considered low-risk for predisposing patients to CDI.Objectives  Evaluate clinical outcomes in patients treated with low-risk antibiotics compared to patients treated with high-risk antibiotics.Method  The new RTI guidelines (Table 1) were published on the hospital intranet and printed algorithms were distributed to the relevant clinical areas. Junior doctors in the admissions unit and ward pharmacists received training and pharmacists promoted guideline compliance. Table 1. Antibiotic prescribing for respiratory tract infection (RTI)  Data were collected from consecutive RTI admissions to the hospital’s acute medical unit over a 2-week period in December Ethics approval was not required. The diagnosis on the post-take ward round (PTWR) was considered the definitive diagnosis.  During the weeks following the audit, case notes were reviewed to establish outcome data. If inflammatory markers had not normalised on discharge, for the purposes of this analysis they were assumed to have normalised on the day following discharge.  Treatment failure was defined as a change in PTWR antibiotic therapy other than a switch from intravenous to oral agents.Results  Sixty-four consecutive patients admitted with RTI were included in the study.  Severity assessments were documented on admission for two of 33 suspected CAP cases.  Retrospective severity scoring indicated that 24 had non-severe CAP but 13 of these were treated with antibiotic regimens recommended for severe pneumonia.  Of the 24 patients treated with antibiotics for AECOPD, only 7 had documented evidence of increased sputum purulence, the pre- requisite for antibiotic therapy as recommended by the UK National Institute for Health and Clinical Excellence (NICE) 3.  Table 2 summarises the results for 58 patients for whom clinical outcome data were available.  First-line low-risk antibiotic regimens were used for two-thirds of patients (38/58) following the PTWR. No cases of Clostridium difficile infection presented within a 30-day follow-up.  Treatment failure rates for low-risk regimens appeared lower than for high-risk regimens for all RTI combined and all other outcome measures appeared broadly comparable for low-risk and high-risk regimens.  Median Charlson co-morbidity index score was 1.0 for both groups of patients - those who received high-risk antibiotics and those who received low-risk antibiotics. Table 2. Outcomes by PTWR diagnosis and risk group of PTWR antibiotic regimen Discussion and Conclusion  The results suggest a tendency amongst doctors to over-prescribe antibiotics for patients with AECOPD and to overprescribe broad-spectrum antibiotic regimens for non-severe pneumonia.  This may reflect a lack of awareness of current guidelines and severity assessment algorithms or may indicate defensive prescribing by inexperienced junior doctors.  The study has suggested a trend towards non-inferiority with regard to clinical outcomes in the treatment of RTI for antibiotic regimens considered ‘low-risk’ for predisposing patients to Clostridium difficile infection compared to ‘high- risk’ regimens.  This study is exploratory and hypothesis-generating and a randomised controlled trial is required to confirm these findings.  Treatment with ‘low-risk’ antibiotics appears to be comparable to standard treatment regimens in patients with respiratory tract infection admitted to a large teaching hospital and may result in reduced incidence of Clostridium difficile infection. References 1.British Thoracic Society. BTS Guidelines for the management of community-acquired pneumonia in adults. Thorax 2001;56 (suppl IV): Fowler S, Webber A, Cooper BS et al. Successful use of feedback to improve antibiotic prescribing and reduce Clostridium difficile infection: a controlled interrupted time series. J Antimicrob Chemother 2007; 59(5): NICE. Management of exacerbations of COPD. Thorax 2004; 59: