High rate of Multidrug-Resistant Organisms (MDROs) among COVID-19 patients presenting with bacteremia upon hospital admission.

We investigated the clinical implications of bacteremia among hospitalized COVID-19 patients. Higher rates (52.1%) of multidrug resistant organisms (MDRO) were noted on hospital admission compared to nosocomial acquisition (25%). Methicillin resistant Staphylococcus aureus was the predominant pathogen. Bacteremia with MDRO should be considered in the differential diagnosis among at risk populations especially those admitted from nursing facilities.

Risk Factors for In-hospital Mortality from Coronavirus Disease 2019 Infection Among Black Patients-An Urban Center Experience.

BACKGROUND: Racial disparities are central in the national conversation about coronavirus disease 2019 (COVID-19) , with Black/African Americans being disproportionately affected. We assessed risk factors for death from COVID-19 among Black inpatients at an urban hospital in Detroit, Michigan. METHODS: This was a retrospective, single-center cohort study. We reviewed the electronic medical records of patients positive for severe acute respiratory syndrome coronavirus 2 (the COVID-19 virus) on qualitative polymerase chain reaction assay who were admitted between 8 March 2020 and 6 May 2020. The primary outcome was in-hospital mortality. RESULTS: The case fatality rate was 29.1% (122/419). The mean duration of symptoms prior to hospitalization was 5.3 (3.9) days. The incidence of altered mental status on presentation was higher among patients who died than those who survived, 43% vs 20.0%, respectively (P < .0001). From multivariable analysis, the odds of death increased with age (≥60 years), admission from a nursing facility, Charlson score, altered mental status, higher C-reactive protein on admission, need for mechanical ventilation, presence of shock, and acute respiratory distress syndrome. CONCLUSIONS: These demographic, clinical, and laboratory factors may help healthcare providers identify Black patients at highest risk for severe COVID-19-associated outcomes. Early and aggressive interventions among this at-risk population may help mitigate adverse outcomes.

Classification of bloodstream infections in patients recently discharged from acute-care facilities: Hospital acquired or healthcare-associated community onset?

Laboratory-identified bloodstream infections (LAB-ID BSIs) in recently discharged patients are likely to be classified as healthcare-associated community-onset (HCA-CO) infections, even though they may represent hospital-onset (HO) infections. A review of LAB-ID BSIs among patients discharged within 14 days revealed that 109 of 756 cases (14.4%) were HO infections. The BSI risk being misclassified as HCA CO may underestimate the hospital infection risk.

Low Frequency of Staphylococcus Aureus in Lower Extremity Skin and Soft Tissue Infections.

BACKGROUND: Staphylococcus aureus is often implicated in skin/soft tissue infections (SSTI). However, SSTI at sites of pressure necrosis and peripheral vascular disease (PVD) are often polymicrobial. The frequency of S aureus in these infections is uncertain. METHODS: We retrospectively reviewed culture results from adults (January 1, 2015-March 31, 2017), evaluated their records and selected SSTI in lower extremities. The patient demographics, comorbidities, characteristics and culture results were recorded. The results were stratified by S aureus status and a composite risk score (RS) was developed (2 points for each difference in S aureus frequency with P < 0.05 [chi-square test] and 1 point for P = 0.06-0.1). The predictors of S aureus were determined by regression analysis using SSPS software. RESULTS: We encountered 356 lower extremity-SSTI (243 foot/ankle, 56 tibia/calf, 30 thigh, 12 hip and 15 groin). S aureus was detected in 173 (48.6%) cases, 59.6% were methicillin-resistant isolates. S aureus was more common in lesions without necrosis (56.3% vs. 42.9%; P = 0.01), with drainage (59.6% vs. 44.7%; P = 0.02), in male sex (53.2% vs. 40.0%; P = 0.02) and was less common in patients with PVD (38.1% vs. 50.9%; P = 0.07), and paraplegia (39.6% vs. 50.0%; P = 0.2). S aureus was less common in polymicrobial SSTI (45.0% vs. 58.5%; P = 0.03). RS of 0-8 correlated with increasing S aureus prevalence from 23.1% (RS = 0-1) to 78.6% (RS = 8; P<0.001). The predictors of S aureus were drainage (odds ratio [OR] = 1.83; 95% confidence intervals [CI]: 1.11, 3.02), lack of PVD (OR = 1.59; CI: 1.03, 2.46) and absence of necrosis (OR = 1.91; CI: 1.08, 3.40). CONCLUSIONS: Patients with suspected polymicrobial lower extremity-SSTI and low RS may not need empirical antistaphylococcal therapy.

Polymicrobial Staphylococcus aureus bacteremia: Frequency, distinguishing characteristics and outcome.

Staphylococcus aureus bacteremia (SAB) is usually monomicrobial (M-SAB). We reviewed SAB in adults (≥18years old) over a 13year-period and compared polymicrobial (P-SAB) and M-SAB. We encountered 93 P-SAB among 1537 SAB cases (6.1%). The source distribution was comparable; however, source-specified differences were apparent. P-SAB was noted in 12/58 (20.7%) necrotizing soft tissue infections/sacral decubiti and foot gangrene vs. 1/122 (0.8%) cellulitis/abscesses (P<0.001), in 7/64 (10.9%) femoral intravascular catheters (IVC) vs.16/376 (4.3%) IVC in other sites (P=0.03) and 15/134 (11.2%) healthcare-associated pneumonia (HAP) vs. 1/33 (3.0%) community-associated cases (P=0.1). Methicillin-resistance frequency was similar but community-associated SCCmec types (IV/V) were infrequent (17.9% vs. 34.2%; P=0.04). P-SAB was associated with higher mortality (50.5% vs. 24.2%; P<0.001) across nearly all sources. In summary, P-SAB is infrequent, usually encountered in necrotizing soft tissue infections/decubiti, femoral IVC and possibly HAP. The actual incidence of S. aureus in these infections should be defined.

Current trends in candidemia and species distribution among adults: Candida glabrata surpasses C. albicans in diabetic patients and abdominal sources.

Candidemia rate and species distribution vary according to the type of patients, country of origin and antifungal prophylaxis use. To present current candidemia epidemiological trends. A retrospective examination of candidemia in adults (≥18 years-old) hospitalised from 2007 to 2015. Cases were identified through the microbiology laboratory. Candida species were distinguished based on colony morphology and VITEK-2 YBC cards, (bioMerieux, Durham, NC, USA). Patient characteristics, species distribution, source and outcome were assessed. We encountered 275 patients (294 episodes) with candidemia. The rate of candidemia dropped in 2010 (P = 0.003) without further decline. Nearly all cases (97.5%) were healthcare-associated. C. albicans (n = 118) and C. glabrata (n = 77) proportions varied without a discernable trend. C. glabrata was more common in diabetics [52.9% vs. 32.0% (non-diabetics); P = 0.004] and abdominal sources [53.3% vs. 35.5% (other sources); P = 0.03], especially gastric/duodenal foci [88.9% vs. 44.1% (other abdominal foci); P = 0.02]. All-cause 30-day mortality rate was 43.3% without changes over time or differences between C. albicans and C. glabrata. In conclusion, the candidemia rate remains stable after a decline in 2010. C. albicans remains the most common species but C. glabrata predominates in diabetics and abdominal sources. These findings suggest possible species-related differences in colonisation dynamics or pathogenicity.

Screening for Intermediately Vancomycin-Susceptible and Vancomycin-Heteroresistant Staphylococcus aureus by Use of Vancomycin-Supplemented Brain Heart Infusion Agar Biplates: Defining Growth Interpretation Criteria Based on Gold Standard Confirmation.

BHI agars supplemented with vancomycin 4 (BHI-V4) and 3 (BHI-V3) mg/liter have been proposed for screening vancomycin intermediately susceptible Staphylococcus aureus (VISA) and heteroresistant (hVISA) phenotypes, respectively, but growth interpretation criteria have not been established. We reviewed the growth results (CFU) during population analysis profile-area under the curve (PAP-AUC) of consecutive methicillin-resistant Staphylococcus aureus (MRSA) blood isolates, which were saved intermittently between 1996 and 2012. CFU counts on BHI-V4 and BHI-V3 plates were stratified according to PAP-AUC interpretive criteria: <0.90 (susceptible [S-MRSA]), 0.90 to 1.3 (hVISA), and >1.3 (VISA). CFU cutoffs that best predict VISA and hVISA were determined with the use of receiver operating characteristic (ROC) curves. Mu3, Mu50, and methicillin-susceptible S. aureus (MSSA) controls were included. We also prospectively evaluated manufacturer-made BHI-V3/BHI-V4 biplates for screening of 2010-2012 isolates. The PAP-AUC of 616 clinical samples was consistent with S-MRSA, hVISA, and VISA in 550 (89.3%), 48 (7.8%), and 18 (2.9%) instances, respectively. For VISA screening on BHI-V4, a cutoff of 2 CFU/droplet provided 100% sensitivity and 97.7% specificity. To distinguish VISA from hVISA, a cutoff of 16 CFU provided 83.3% sensitivity and 94.7% specificity; the specificity was lowered to 89.5% with a 12-CFU cutoff. For detecting hVISA/VISA on BHI-V3, a 2-CFU/droplet cutoff provided 98.5% sensitivity and 93.8% specificity. These results suggest that 2-CFU/droplet cutoffs on BHI-V4 and BHI-V3 best approximate VISA and hVISA gold standard confirmation, respectively, with minimal overlap in samples with borderline PAP-AUC. Simultaneous screening for VISA/hVISA on manufacturer-made BHI-V4/BHI-V3 biplates is easy to standardize and may reduce the requirement for PAP-AUC confirmation.

Decreasing prevalence of isolates with vancomycin heteroresistance and vancomycin minimum inhibitory concentrations ≥2 mg/L in methicillin-resistant Staphylococcus aureus over 11 years: potential impact of vancomycin treatment guidelines.

We evaluated vancomycin MIC (V-MIC) and the prevalence of intermediately susceptible (VISA) and heteroresistant (hVISA) isolates trends in methicillin-resistant Staphylococcus aureus bacteremia among 720 adults (≥ 18 years) inpatients over 4 study periods (2002-2003, 2005-2006, 2008-2009, and 2010-2012). V-MIC (Etest) and the prevalence of hVISA and VISA (determined by population analysis profile-area under the curve) were stratified according to the study period. Mean vancomycin MIC was 1.78 ± 0.39, 1.81 ± 0.47, 1.68 ± 0.26, and 1.54 ± 0.28 mg/L in 2002-2003, 2005-2006, 2008-2009, and 2010-2012, respectively (P < 0.0001). We noted a steadily decreasing prevalence of isolates with V-MIC ≥ 2 mg/L (50.0%, 45.2%, 35.4%, and 18.7%; P < 0.0001) and hVISA (9.7%, 6.6%, 3.0%, and 2.1%; P=0.0003). VISA prevalence remained low (0-2%). These changes coincided with steadily increasing vancomycin trough levels (9.9 ± 7.8, 11.1 ± 8.4, 16.6 ± 7.8, and 19.7 ± 5.9 mg/L in 2002-2003, 2005-2006, 2008-2009, and 2010-2012, respectively; P < 0.0001). These changes imply that adherence to vancomycin treatment guidelines may suppress the development of less susceptible isolates.

MALDI-TOF identification of Gram-negative bacteria directly from blood culture bottles containing charcoal: Sepsityper® kits versus centrifugation-filtration method.

Matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry has dramatically altered the way microbiology laboratories identify clinical isolates. Direct blood culture (BC) detection may be hampered, however, by the presence of charcoal in BC bottles currently in clinical use. This study evaluates an in-house process for extraction and MALDI-TOF identification of Gram-negative bacteria directly from BC bottles containing charcoal. Three hundred BC aliquots were extracted by a centrifugation-filtration method developed in our research laboratory with the first 96 samples processed in parallel using Sepsityper® kits. Controls were colonies from solid media with standard phenotypic and MALDI-TOF identification. The identification of Gram-negative bacteria was successful more often via the in-house method compared to Sepsityper® kits (94.7% versus 78.1%, P≤0.0001). Our in-house centrifugation-filtration method was further validated for isolation and identification of Gram-negative bacteria (95%; n=300) directly from BC bottles containing charcoal.

Use of portable electronic devices in a hospital setting and their potential for bacterial colonization.

Portable electronic devices are increasingly being used in the hospital setting. As with other fomites, these devices represent a potential reservoir for the transmission of pathogens. We conducted a convenience sampling of devices in 2 large medical centers to identify bacterial colonization rates and potential risk factors.

Invasive Bordetella holmesii infections.

Bordetella holmesii is a rare cause of invasive human disease. The fastidious and unusual nature of this organism makes routine isolation and identification challenging. We report two cases of B. holmesii bacteremia that were rapidly identified by matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF MS) when standard techniques failed to provide speciation. There are no current standards for susceptibility testing or treatment recommendations. The rare occurrence and challenges in identifying this pathogen led us to perform a comprehensive review of the epidemiology, clinical presentations, and treatment options for this potentially invasive pathogen.

Decreasing incidence of Staphylococcus aureus bacteremia over 9 years: greatest decline in community-associated methicillin-susceptible and hospital-acquired methicillin-resistant isolates.

BACKGROUND: The impact of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) emergence on the epidemiology of S aureus bacteremia (SAB) is not well documented. METHODS: This was an observational study of adult (aged ≥18 years) inpatients with SAB in a single 808-bed teaching hospital during 2002-2003, 2005-2006, 2008-2009, and 2010 with period-stratified SAB rate, onset mode, patient characteristics, and outcome. RESULTS: We encountered a total of 1,098 cases over the entire study period. The rate decreased steadily over time (from 6.64/10(3) discharges in 2002-2003 to 6.49/10(3) in 2005-2006, 5.24/10(3) in 2008-2009, and 5.00/10(3) in 2010; P = .0001), with a greater decline in community-associated cases (0.99/10(3), 0.77/10(3), 0.58/10(3), and 0.40/10(3), respectively; P = .0005) compared with health care-associated cases (5.65/10(3), 5.72/10(3), 4.66/10(3), and 4.60/10(3), respectively; P = .005). The decline was principally in MSSA (3.11/10(3), 2.21/10(3), 2.24/10(3), and 1.75/10(3), respectively; P = .00006), including both community-associated (P = .0002) and health care-associated cases (P = .006). Although overall rate changes in MRSA were not significant (P = .09), hospital-onset MRSA decreased markedly (P < .00001), whereas CA-MRSA increased (P = .03). The all-cause 100-day mortality rate did not change significantly (25.6% for 2002-2003, 25.2% for 2005-2006, 28.1% for 2008-2009, and 32.2% for 2010; P = .10). Differences in MSSA/MRSA-associated mortality decreased (20.1% vs 30.6%, P = .03 for 2002-2003; 18.1% vs 28.9%, P = .05 for 2005-2006; 21.7% vs 32.9%, P = .05 for 2008-2009; and 29.3% vs 34.9, P = .5 for 2010). CONCLUSIONS: SAB incidence is decreasing, with the greatest decline in community-associated MSSA and hospital-onset MRSA cases. Most health care-associated cases currently are community-onset. MRSA/MSSA-related mortality is comparable. These changes are likely related to the emergence of CA-MRSA and the inpatient-to-outpatient shift in health care.

Detection of extended-spectrum ß-lactamase and Klebsiella pneumoniae Carbapenemase genes directly from blood cultures by use of a nucleic acid microarray.

The growing crisis of multidrug-resistant (MDR) Gram-negative bacteria requires that current technologies permit the rapid detection of extended-spectrum ß-lactamase (bla(ESBL)) and Klebsiella pneumoniae carbapenemase (bla(KPC)) genes. In the present study, we assessed the performance characteristics of a commercially available nucleic acid microarray system for the detection of bla(ESBL) and bla(KPC) genes directly from positive blood cultures. Using blood cultures (BCs) that contained Gram-negative bacilli identified by Gram staining, we isolated bacterial DNA using spin columns (BC-C) and rapid water lysis (BC-W). Twenty ESBL/KPC-positive and 20 ESBL/KPC-negative blood culture samples, as well as 20 non-lactose-fermenting organisms, were tested. The 20 isolates that were ESBL positive by phenotypic testing were also evaluated on solid medium (SM), and the DNA was extracted by use of a spin column (SM-C). The resulting 140 DNA extractions were assessed for DNA quantity and quality using 260/280-nm absorbance ratios, and DNA microarray analysis was performed in a blinded fashion. Microarray and phenotypic results were concordant for 98.3% of BC-W, 90% of BC-C, and 95% of SM-C samples. Compared to phenotypic testing, the sensitivity and specificity for BC-C samples were 88.9% and 100%, respectively, and for BC-W samples, the sensitivity and specificity were 94.4% and 100%, respectively. BC-W samples yielded the highest concordance with phenotypic results. Nucleic acid microarrays offer promise in the identification of bla(ESBL) and bla(KPC) genes directly from blood cultures, thereby reducing the time to identification of these important pathogens.

Lack of association of outcomes with treatment duration and microbiologic susceptibility data in Clostridium difficile infections in a non-NAP1/BI/027 setting.

BACKGROUND: Concerns regarding the poor response of severe Clostridium difficile infection (CDI) treated with metronidazole have arisen over the last 5 y. METHODS: We conducted a prospective, non-interventional study of CDI cases at our institution to evaluate the role of drug resistance, co-morbidities, and the emergence of hypervirulent strains on patient outcomes. A total of 118 adult inpatients with diarrhea and a positive stool for C. difficile toxin immunoassay had positive stool cultures and were included in the study. All 118 isolates had vancomycin and metronidazole susceptibility testing via the E-test method; rep-PCR was performed on 47 isolates. Of the 118 study patients, 107 were treated with either metronidazole or vancomycin. RESULTS: Initial therapy was metronidazole in 98.1% (n = 105) and vancomycin in 1.9% (n = 2) patients. Evaluable clinical response within 5 days of treatment was noted in 52.5% (52/99) of cases. The mean duration of treatment was 11.7 ± 7.2 days. The 30-day all-cause mortality rate was 24.6% (29/118). Recurrence occurred in 23.6% (21/89). A recent stay in the intensive care unit was associated with increased 30-day mortality (odds ratio 3.58, p = 0.012). There were no isolates resistant to metronidazole or vancomycin. Only 1 isolate was possibly related to the NAP1/BI/027 reference strain. No strain-related differences in deaths or recurrence were noted. CONCLUSIONS: Deaths related to CDI in our study appear to be related to multiple factors and did not appear to be independently related to antibiotic susceptibility, strain type, or treatment duration.

Relevance of vancomycin-intermediate susceptibility and heteroresistance in methicillin-resistant Staphylococcus aureus bacteraemia.

OBJECTIVES: To assess the relevance of vancomycin-intermediate susceptibility (VISA) and heteroresistance (hVISA) in methicillin-resistant Staphylococcus aureus (MRSA) bacteraemia. METHODS: We determined vancomycin MICs for 371 saved MRSA blood isolates (2002-03; 2005-06) by Etest and broth microdilution (BMD), screened for hVISA (Etest methods), determined the population analysis profile (PAP)/AUC for isolates with suspected reduced susceptibility (MICs >2 mg/L and/or hVISA-screen-positive versus Mu3 (hVISA control), and stratified patient characteristics and outcome according to susceptibility phenotype: VISA (PAP/AUC >1.3), hVISA (PAP/AUC 0.9-1.3), and susceptible (S-MRSA; PAP/AUC <0.9). RESULTS: PAP/AUC revealed 6 (1.6%) VISA and 30 (8.1%) hVISA phenotypes. The Etest MIC was above the susceptibility cut-off (2 mg/L) for all VISA isolates, whereas the BMD MIC was within the susceptibility range in two (33.3%) instances. Eight hVISA isolates (26.7%) with MICs of 2 mg/L were hVISA-screen negative. SCCmec typing revealed SCCmec II in 100% of VISA, 86.7% of hVISA and 75.5% of S-MRSA isolates (P = 0.04). Prior vancomycin use was documented in 100% of VISA, 73.3% of hVISA and 52.2% of S-MRSA cases (P = 0.002). Outcome (compared in 243 vancomycin-treated patients with MICs of 2 mg/L) revealed longer time to clearance in VISA cases [12.1 ±â€Š13.1 days versus 3.3 ±â€Š3.9 (hVISA) and 3.7 ±â€Š5.1 (S-MRSA); P = 0.001], more frequent endocarditis [33.3% versus 9.1% (hVISA; P = 0.1) and 4.2% (S-MRSA; P = 0.001)] and attributable mortality [33.3% versus 9.1% (hVISA; P = 0.1) and 8.4% (S-MRSA); P = 0.08]. CONCLUSIONS: No adverse outcome was documented with hVISA phenotype, whereas VISA contributed to vancomycin treatment failure. VISA and hVISA appear to emerge in SCCmec II isolates among vancomycin-exposed patients and are better detected by Etest.

Molecular analysis of 2 cases of methicillin-resistant Staphylococcus aureus cholecystitis and a review of the literature.

We present 2 cases of methicillin-resistant Staphylococcus aureus (MRSA) acalculous cholecystitis and review the literature. We performed pulsed field gel electrophoresis, typing of the staphylococcal cassette chromosome mec element, and Panton-Valentine leukocidin testing on the isolates. One each was closely related to USA100 and USA300, indicating that both healthcare- and community-associated strains may cause MRSA cholecystitis.

Vancomycin MIC plus heteroresistance and outcome of methicillin-resistant Staphylococcus aureus bacteremia: trends over 11 years.

Vancomycin MICs (V-MIC) and the frequency of heteroresistant vancomycin-intermediate Staphylococcus aureus (hVISA) isolates are increasing among methicillin (meticillin)-resistant Staphylococcus aureus (MRSA) isolates, but their relevance remains uncertain. We compared the V-MIC (Etest) and the frequency of hVISA (Etest macromethod) for all MRSA blood isolates saved over an 11-year span and correlated the results with the clinical outcome. We tested 489 isolates: 61, 55, 187, and 186 isolates recovered in 1996-1997, 2000, 2002-2003, and 2005-2006, respectively. The V-MICs were < or = 1, 1.5, 2, and 3 microg/ml for 74 (15.1%), 355 (72.6%), 50 (10.2%), and 10 (2.1%) isolates, respectively. We detected hVISA in 0/74, 48/355 (13.5%), 15/50 (30.0%), and 8/10 (80.0%) isolates with V-MICs of < or = 1, 1.5, 2, and 3 microg/ml, respectively (P < 0.001). The V-MIC distribution and the hVISA frequency were stable over the 11-year period. Most patients (89.0%) received vancomycin. The mortality rate (evaluated with 285 patients for whose isolates the trough V-MIC was > or = 10 microg/ml) was comparable for patients whose isolates had V-MICs of < or = 1 and 1.5 microg/ml (19.4% and 27.0%, respectively; P = 0.2) but higher for patients whose isolates had V-MICs of > or = 2 microg/ml (47.6%; P = 0.03). However, the impact of V-MIC and hVISA status on mortality or persistent (> or = 7 days) bacteremia was not substantiated by multivariate analysis. Staphylococcal chromosome cassette mec (SCCmec) typing of 261 isolates (including all hVISA isolates) revealed that 93.0% of the hVISA isolates were SCCmec type II. These findings demonstrate that the V-MIC distribution and hVISA frequencies were stable over an 11-year span. A V-MIC of > or = 2 microg/ml was associated with a higher rate of mortality by univariate analysis, but the relevance of the V-MIC and the presence of hVISA remain uncertain. A multicenter prospective randomized study by the use of standardized methods is needed to evaluate the relevance of hVISA and determine the optimal treatment of patients whose isolates have V-MICs of > or = 2.0 microg/ml.

Role of SCCmec type in outcome of Staphylococcus aureus bacteremia in a single medical center.

Staphylococcus aureus virulence factors may determine infection presentation. Whether SCCmec type-associated factors play a role in S. aureus bacteremia is unclear. We conducted a prospective observation of adult inpatients with S. aureus bacteremia (1 November 2005 to 31 December 2006), performed SCCmec typing of methicillin-resistant S. aureus (MRSA) isolates, and stratified the results according to SCCmec type. We studied 253 patients. MRSA accounted for 163 (64.4%) cases. The illness severity index was similar in MRSA and methicillin-sensitive S. aureus (MSSA) cases. MRSA caused higher in-hospital mortality (23.9% versus 8.9%; P=0.003), longer bacteremia (4.7+/-6.5 days versus 2.7+/-2.9 days; P=0.01), but similar metastatic infection (14.7% versus 15.6%). Stratifying the results according to SCCmec type revealed significant differences. SCCmec type II caused highest mortality (33.3%) versus type IVa (13.5%), other MRSA (12.5%), and MSSA (8.9%). SCCmec IVa produced the highest metastatic infection (26.9% versus 9.1% [SCCmec II], 8.3% [other MRSA], and 15.6% [MSSA]). Persistent bacteremia (>or= 7 days) was similar in all SCCmec types (16.7 to 20.7%); each exceeded MSSA (6.7%; P=0.05). In multivariate analysis, SCCmec II was a predictor of mortality (odds ratio [OR]=3.73; 95% confidence interval [CI] = 1.81 to 7.66; P=0.009), SCCmec IVa was a predictor of metastatic infection (OR=3.52; CI=1.50 to 8.23; P=0.004), and MRSA (independent of SCCmec type) was a predictor of persistent bacteremia (OR=4.16; CI=1.47 to 11.73; P=0.007). These findings suggest that SCCmec-associated virulence factors play a role in the outcome of S. aureus bacteremia. Additional studies are needed to identify which virulence factors are the determinants of increased mortality with SCCmec type II and metastatic infection with SCCmec type IVa.