8.1.3. Evidence summary and rationale for the recommendationA study randomising patients treated empirically with anantibiotic regimen including or not an antibiotic active againstmethicillin-resistant Staphylococcus aureus (MRSA) did not showany difference between the two strategies in terms of length-ofstay and mortality [113]. An observational and prospective studyfound a decrease in mortality in patients who had received anempirical antibiotic therapy including vancomycin [114]. Theprevalence of MRSA VAP (15%) supports this result. The literaturesuggests that inappropriate empirical antibiotic therapy plays amajor part in the mortality of patients with MRSA HAP[115]. However, a study found an increase in ICU length-of-stayin patients with MRSA HAP, independently from the adequacy ofthe empirical treatment [116]. The adequacy of the empiricalantibiotic therapy is a critical factor for survival and the length-ofstay [113,117]. A randomized controlled study highlighted anincrease in MRSA emergence in patients treated empirically withvancomycin [113]. This encourages highly selecting patients to betreated empirically with an antibiotic directed against MRSA.In conclusion, only one study conducted in an environment inwhich the prevalence of MRSA was high (15% of VAP episodes)showed an association between the empirical use of an antibioticagainst MRSA and an improvement in HAP outcomes. There istherefore no rationale for the systematic empirical use of anantibiotic against MRSA in France, the prevalence being lower than3% [118]. However, the consideration of the local ecology isimportant. Some risk factors encourage including an antibioticactive against MRSA in the empirical antibiotic therapy of HAP,without the possibility to establish an exhaustive list (experts’