Is Methicillin-Resistant Staphylococcus aureus More Virulent than Methicillin-Susceptible S. aureus? A Comparative Cohort Study of British Patients with Nosocomial Infection and Bacteremia

Abstract

Staphylococcus aureus is the most common cause of hospital-acquired bacteremia. From 1995 through 2000, data on age, sex, patient specialty at time of first bacteremia, primary and secondary sites of infection, delay in initiating antimicrobial therapy, and patient outcome were prospectively recorded for 815 patients with nosocomial S. aureus bacteremia. The proportion of patients whose death was attributable to methicillin-resistant S. aureus (MRSA) was significantly higher than that for methicillin-susceptible S. aureus (MSSA) (11.8% vs. 5.1%; odds ratio [OR], 2.49; 95% confidence interval [CI], 1.46-4.24; P<.001). After adjustment for host variables, the OR decreased to 1.72 (95% CI, 0.92-3.20; P=.09). There was no significant difference between rates of disseminated infection (7.1% vs. 6.2% for MRSA-infected patients and MSSA-infected patients, respectively; P=.63), though the rate of death due to disseminated infection was significantly higher than death due to uncomplicated infection (37% vs. 10% for MRSA-infected patients [P<.001] and 37% vs. 3% for MSSA-infected patients [P<.001]). There was a strong statistical trend toward death due to nosocomial MRSA infection and bacteremia, compared with MSSA.

Rapid detection of meticillin-resistant Staphylococcus aureus bacteraemia using combined three-hour short-incubation matrix-assisted laser desorption/ionization time-of-flight MS identification and Alere Culture Colony PBP2a detection test

“…In another meta-analysis, Whitby et al (2001) observed that bacteraemia caused by MRSA was associated with significantly higher mortality rates than bacteraemia caused by MSSA (29 % vs 12 %). The associated proportion of patients whose death was attributable to MRSA was significantly higher than that for MSSA [11.8 % vs 5.1 %; odds ratio (OR) 2.49] (Melzer et al, 2003). Bacteraemia due to MRSA is associated with both an increase in median hospital length of stay (9 days compared with 7 days) and consequently higher median hospital charges (US$ 26 424 vs US$ 19 212) (Melzer et al, 2003).…”

“…The associated proportion of patients whose death was attributable to MRSA was significantly higher than that for MSSA [11.8 % vs 5.1 %; odds ratio (OR) 2.49] (Melzer et al, 2003). Bacteraemia due to MRSA is associated with both an increase in median hospital length of stay (9 days compared with 7 days) and consequently higher median hospital charges (US$ 26 424 vs US$ 19 212) (Melzer et al, 2003).The treatment of MSSA bacteraemia with vancomycin is associated with treatment failure and higher mortality rates compared with treatment with b-lactam antibiotics In patients with MSSA-associated bacteraemia, Kim et al (2008) showed in a retrospective cohort study a mortality rate of 37 % in patients treated with vancomycin versus a mortality rate of 18 % in patients treated with b-lactam antibiotics. In a patient population with MSSA-associated infective endocarditis, Lodise et al (2007) showed that the mortality rate in patients who received empirical vancomycin was signifcantly higher (39.4 %) than he mortality rate of 11.4 % in patients who received empirical b-lactam therapy.…”

Does Insurance Type, Private Versus Public, Have a Correlation with MRSA Carrier Status In a Population Undergoing Orthopedic Surgery?

“…MRSA SSI are disastrous and lead to adverse health outcomes and higher rates of complications in orthopaedic patients [7,8]. SSI with MRSA increases post-operative hospital stay by two weeks, doubles hospitalization rates, and triples overall care costs [7,8,17].…”

“…Preoperative nasal colonization with SA has been shown to be a strong risk factor for SSI, with carriers being two to nine times more likely than non-carriers to acquire SSI [1,[3][4][5][6]. Methicillin-resistant SA (MRSA) infection provides particularly difficult complications following surgical procedures and has been documented to be twice as deadly as methicillin-sensitive SA (MSSA) in SSI [7,8]. MRSA follows similar trends of SSI as Methicillin-sensitive SA, with preoperative MRSA positive carriers being at higher risk of SSI as opposed to MRSA negative patients [2].…”

“…Ellis et al reported SSI rates three times higher in nosocomial MRSA carriers than non-carriers [9]. SSI with MRSA has been linked to many adverse health outcomes and higher rates of complications in orthopaedic patients [7,8]. Given the seriousness of MRSA SSI complications, it is crucial to know patient colonization status preoperatively in order to provide appropriate perioperative treatment [1,8].…”