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Antimicrobial Monotherapy versus Combination Therapy for the Treatment of Complicated Intra-Abdominal Infections
Petite SE, Bauer SR, Bollinger JE, et al. Pharmacotherapy. 2016;36:1138-1144.
Study Question: Is there a difference in the clinical cure rates between piperacillin/ tazobactam (PIP/TAZ) and the combination of vancomycin with PIP/TAZ for complicated intra-abdominal infections (cIAIs)?
Study Description: This study was retrospective cohort analysis conducted from September 2010 to July 2014 that identified adult patients an ICD-9 code of cIAI, treated with PIP/TAZ for at least 72 hours, and had an abnormal white blood cell count or temperature. Excluded were those without source control within 48 hours of starting antimicrobials, pancreatitis, primary peritonitis, or immunocompromised. Combination therapy included patients that received vancomycin within 48 hours after initiating PIP/TAZ. The primary endpoint was the clinical cure rate at day 28 or at hospital discharge if sooner. Secondary endpoints included clinical cure rate at day 7, microbiology results, incidence of
nephrotoxicity, hospital and ICU length of stay (LOS) and mortality.
Results: A total of 228 patients in the monotherapy group (PIP/TAZ) and 189 patients in the combination group were included. Immunosuppression (n = 116) was the major reason for exclusion, and more patients in the combination group required vasopressors on day one. There was no difference in the clinical cure rate at day 28 (33.9% vs. 25.5%; p = 0.064) or at day 7, or 28-day mortality between groups. ICU LOS was shorter in the monotherapy group (6 vs. 7 days, p = 0.04); however, hospital LOS was not significantly different. Risk factors associated with the isolation of MRSA or enterococci were MRSA or enterococcal infection in the previous year or positive MRSA in the nares. The multivariable logistic regression found no significant factors associated with clinical cure at day 28.
Conclusion: There was no difference in clinical cure rates between monotherapy and combination therapy for cIAIs. The monotherapy group had a significantly shorter ICU LOS.
Perspective: Combination therapy did not affect the clinical cure rates for cIAIs, although the cure rates were low. Patients with a previous MRSA or enterococcal infection in the past year, or MRSA colonization were more likely to have these organisms isolated. Due to the high rate of vancomycin-resistant enterococci (>50%) in this study, individual institutional antibiograms should be used to tailor therapy decisions.