Microbiological analysis of epidermal growth factor receptor inhibitor therapy-associated paronychia

Background Paronychia is a well-known, but difficult to treat cutaneous toxicity associated with epidermal growth factor receptor (EGFR) inhibitor therapy. Although bacterial and fungal infections as well as mechanical trauma may play a role as co-pathogens, there is no good basis for an empirical antimicrobial chemotherapy in these patients. Materials and methods We retrospectively analysed the microbiological results and resistance analysis of 42 cases of EGFR inhibitor-associated paronychia induced by cetuximab. Results We identified 20 different species, among these 72% Gram-positive bacteria, 23% Gram-negative bacteria and 5%Candida species. About half of the microbes identified may be considered as residential bacterial flora of the skin, but isolation of microbes from paronychia may indicate a pathogenic relevance for this type of reaction. Eight of our patients were treated with oral antibiotics, whereas two patients received oral antimycotic therapy. All other cases of paronychia were controlled using topical antiseptic, antibiotic and antimycotic agents. Conclusion Empirical oral antibiotic treatment may be performed with oral cephalosporines, ciprofloxacin, levofloxacin or moxifloxacin, as these antimicrobials have high in vitro activity against the majority of the isolated microorganisms and reach high concentrations in the relevant tissue.