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Objective To understand the impact of methicillin-resistant Staphylococcus aureus (MRSA)blood-stream infection on the length of hospital stay,hospital mortality,and poor prognosis of patients.Methods 357 patients with Staphylococcus aureus (S .aureus)bacteremia in a hospital between January 1 ,2009 and December 31 , 2013 were surveyed and analyzed retrospectively.Results Of 357 patients,91 were infected with MRSA and 266 with methicillin-susceptible S .aureus (MSSA).The length of hospital stay was statistically different between MR-SA and MSSA group(29 d vs 23 d,P <0.01);before infection,length of hospital stay of MRSA group was longer than MSSA group(P <0.01 );after infection,length of hospital stay was not statistically different between two groups(17 d vs 16.5 d,P = 0.92 ).Mortality of MRSA group and MSSA group was not statistically different (13.19% vs 9.02%,χ2 =1 .28,P =0.26).The incidence of poor prognosis of MRSA group was higher than MSSA group(29.67% vs 16.92%,χ2 =6.85,P =0.01 ).Multivariate analysis results showed that MRSA infection was independent risk factor for poor prognosis (P <0.01).Conclusion MRSA infection doesn’t contribute to the pro-longation of hospital stay,but MRSA bloodstream infection is a risk factor for poor prognosis of patients.
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There have been conflicting data about the interactions between vancomycin and beta-lactam agents against Staphylococcus aureus strains with heterogeneous resistance to vancomycin. We evaluated the efficacy of these combinations against Mu 3 and heterogeneously vancomycin-resistant S. aureus (hetero-VRSA) strains which were isolated from Korean patients using a population analysis method. Antagonistic effects were observed when less than 1 g/mL of beta-lactam antibiotics was combined with vancomycin, whereas synergistic effects were noticed with more than 4 microgram/mL of beta-lactam antibiotics. The antagonistic effects at low concentrations of beta-lactams were most prominent at 2 microgram/mL of vancomycin, which were the vancomycin MICs of tested hetero-VRSA strains. This study showed the variable effects of vancomycin- beta-lactam combinations depending on the concentrations of beta-lactam antibiotics and this property could be used to develop screening methods for hetero-VRSA strains.