Early administration of GP therapy should concern emerging resistance due to widespread use of GPs [8
], possible suboptimal therapies for MSSA infections [19
], the rising incidence of MRSA infection [21
], and potential additional morbidity associated with delaying appropriate treatment [3
]. The relationship between timing of effective antibiotics administration and outcomes has resulted in conflicting conclusions between numerous studies exploring mortality predictors for MRSAB [6
]. These discrepancies may be due to different definitions of the timing for appropriate antibiotic therapy, dosing of GP administration, analysis methods, adjustment difficulties, and diverse patient populations. Among which, some of patients started GP treatment, and others switched to GPs after receiving β
-lactams, while many received other antibiotic therapy. This study indicated that discordant therapy (initial no GP therapy for MRSA infection) is not the only factor determining mortality. Consistent with previous reports [9
], our results also illustrated that initiating GP therapy earlier, after a positive preliminary BC, did not reduce the 14-day mortality of patients with MRSAB.
The guidelines for the prophylaxis and treatment of MRSA infections in the UK suggested that when the strain is oxacillin susceptible, step-down therapy, shifting from an agent encompassing MRSA to oxacillin, is safer than its alternative, the escalation therapy [23
]. However, this suggestion was not supported by definitive clinical studies, epidemiological studies, or a theoretical rationale. GPs, rather than β
-lactam therapy, might have resulted in higher rates of relapse and mortality in patients with MSSA bacteremia [19
]. Emerging vancomycin resistance among Gram-positive organisms is a major threat to patient's safety in hospitals, and overusing GPs could promote the selection and spread of these resistant organisms [24
]. Clinicians should prudently prescribe GPs, and the decision for empirical GP therapy requires additional data, such as a rapid polymerase-chain-reaction BC test for MRSA [25
Except severity of MRSAB represented by high APACHE II score, concurrent pneumonia was an independent risk factor for our MRSA bacteremic patients with regard to 14-day all-cause and attributed mortalities. As is known, GPs have poor penetration into lung tissues [26
], and standard vancomycin doses may be subtherapeutic in critically ill patients [27
]. Linezolid, which has a greater lung penetration rate and better pharmacokinetic properties [28
], might be the therapeutic choice for these particular patients.
This study was performed at a single center, and the results may not be generalized to the outside of this population, especially to areas with a high prevalence of MRSAB. The nature of this observational study was a limitation; a randomized controlled trial assessing the effects of appropriate therapy is neither ethical nor feasible. The result lacks of dosing regimens of GP administration and lacks of GP target attainment. While the efficiency of GP therapy on the isolates was not assessed with minimum inhibitory concentration (MIC) or serum concentration data for vancomycin or teicoplanin. Patients with MRSAB who were treated with vancomycin had a higher risk of treatment failure and mortality when the isolate MIC was >1
]. No data existed regarding to the serum concentration of teicoplanin, and general infections may have required >10
mg/L and endovascular infections >20
]. We did not take into account susceptibility/resistance to non-GP drugs (particularly fluoroquinolones and aminoglycosides). Nevertheless, the fluoroquinolones and aminoglycosides are suboptimal therapies for MRSA infection [31
]. Finally, we excluded MRSA bacteremic patients with endocarditis due to endocarditis that is different from other MRSAB in terms of severity of infection and needed for aggressive surgical intervention. However, measuring 14-day mortality may be well-represented therapeutic effect for nonendocarditis bloodstream infection.