Is coverage of S. aureus necessary in cellulitis/erysipelas? A literature review

Background Empirical treatment of patients with cellulitis/erysipelas usually targets both streptococci and methicillin-sensitive S. aureus (MSSA). However, the recommendation to empirically cover MSSA is weak and based on low-quality evidence. Methods and objective A systematic review was conducted in PubMed and clinical trial registries to assess the role of S. aureus in cellulitis/erysipelas and the need for empirical MSSA coverage. Results Combined microbiological and serological data, and response to penicillin monotherapy suggest that streptococci are responsible for the vast majority of cases of cellulitis/erysipelas. However, most cases are non-culturable and the specificity of microbiological and serological studies is questionable based on recent studies using molecular techniques. According to epidemiological data and three randomized controlled trials, empirical coverage of methicillin-resistant S. aureus (MRSA) is not recommended for most patients, despite the high prevalence of MRSA in many areas. If MRSA is indeed not an important cause of uncomplicated cellulitis/erysipelas, then the same may apply to MSSA. Based on indirect comparison of data from clinical studies, cure rates with penicillin monotherapy (to which most MSSA are resistant) are comparable to the cure rates reported in many studies using wider-spectrum antibiotics. Conclusion Considering the limitations of microbiological studies in identifying the pathogens responsible for cellulitis/erysipelas, treatment needs to be guided by clinical trials. Trials comparing penicillin or amoxicillin monotherapy to MSSA-covering regimens are needed to definitively answer whether empirical coverage of MSSA is needed and to identify the subset of patients that can be safely treated with penicillin or amoxicillin monotherapy.