Comparative epidemiology of bacteremia due to methicillin-resistant Staphylococcus aureus between older and younger adults: a propensity score analysis

Methicillin-sensitive Staphylococcus aureus bacteremia in aged patients: the importance of formal infectious specialist consultation

Background

Infectious specialist consultations (ISC) provide ever more evidence for improved outcome in Staphylococcus aureus bacteremia (SAB). Most ISC are formal (bedside). However, the impact of ISC on clinical management and prognosis lacks evaluation in aged patients with SAB.

Methods

Multicenter retrospective analysis of methicillin-sensitive (MS) SAB. Patients were stratified according to age ≥ 60 years (sub-analyses for ≥ 75 years and females) and formal (bedside) ISC given within 7 days of SAB diagnosis. The impact on management and outcome of formal ISC was explored. Statistics were performed with univariate analysis, Cox proportional hazards regression model analysis, including propensity-score adjustment, and graphic Kaplan–Meier interpretation.

Results

Altogether 617 patients were identified and 520 (84%) had formal ISC. Presence of formal ISC resulted in equivalent clinical management regardless of age over or under 60 years: localization and eradication of infection foci (80 vs. 82% and 34 vs. 36%) and use of anti-staphylococcal antibiotics (65 vs. 61%). Patients aged ≥ 60 years managed without formal ISC, compared to those with formal ISC, had less infection foci diagnosed (53 vs. 80%, p < 0.001). Lack of formal ISC in patients aged ≥ 60 years resulted in no infection eradication and absence of first-line anti-staphylococcal antibiotics. Formal ISC, compared to absence of formal ISC, lowered mortality at 90 days in patients aged ≥ 60 years (24 vs. 47%, p = 0.004). In Cox proportional regression, before and after propensity-score adjustment, formal ISC was a strong positive prognostic parameter in patients aged ≥ 60 years (HR 0.45; p = 0.004 and HR 0.44; p = 0.021), in patients aged ≥ 75 years (HR 0.18; p = 0.001 and HR 0.11; p = 0.003) and in female patients aged ≥ 75 years (HR 0.13; p = 0.005).

Conclusion

Formal ISC ensures proper active clinical management irrespective of age and improve prognosis in aged patients with MS-SAB.

Disease Burden, Characteristics, and Outcomes of Methicillin-Resistant Staphylococcus aureus Bloodstream Infection in Hong Kong

We aimed to describe disease burden, characteristics, and outcomes of methicillin-resistant Staphylococcus aureus (MRSA) bloodstream infection (BSI) in Hong Kong. A retrospective, observational study was conducted in 26 Hong Kong public hospitals between January 2010 and December 2012. The primary outcome measures were 30-day mortality rate and infection-related hospital cost. Of 1133 patients reviewed, 727 (64.17%) were male, 1075 (94.88%) had health care-associated community-onset and 44 (3.88%) had hospital-onset MRSA infection. The mean age of patients was 76 (SD = 15) years, including 172 (15.18%) aged 20 to 59 years and 961 (84.8%) aged ≥60 years. The annual incidence rates in age groups of 20 to 59 years and ≥60 years were 0.96 to 1.148 per 100 000 and 22.7 to 24.8 per 100 000, respectively. The 30-day mortality was 367 (32.39%). Older patients (>79 years), chronic lung disease, and prior hospitalization were associated with increased mortality. The mean cost was US$10 565 (SD = 11 649; US$1 = HK$7.8). MRSA BSI was a significant burden in Hong Kong.

Clinical presentation, management and outcomes of Staph aureus bacteremia (SAB) in older adults

AIM

The incidence of Staphylococcus aureus bacteremia (SAB) increases with advancing age with higher mortality reported in older adults. We aimed to describe the clinical presentation, management and outcomes of older patients with SAB.

METHODS

We analyzed data from a retrospectively collected database including 1692 patients with SAB, and compared 1158 older patients (≥65 years) with 534 younger patients (<65 years) in terms of clinical features, management of infection, and outcomes.

RESULTS

Older patients were significantly less likely to be febrile on presentation, with 37.5 % (415/1106) of older patients presenting with normal body temperature [versus 29.2 % (152/520) of younger patients]. Older patients were however, more likely to have leukocytosis, septic shock, lower heart rate and lower diastolic blood pressure compared with younger patients. Management of older patients included significantly less imaging studies, performance of transesophageal echocardiogram (TEE) and infectious diseases consultation. TEE was performed less in older patients [124/726 (17.1 %) versus 72/285 (25.3 %)]. Mortality was significantly higher in older patients [550/1158 (47.5 %) versus 124/534 (23.2 %)], with predictors for mortality for the entire cohort in multivariate analysis including older age, higher Charlson comorbidity index, female sex, impaired functional capacity, pneumonia or primary bacteremia, and non-performance of TEE.

CONCLUSIONS

Mortality rates in older patients with SAB are higher compared with younger patients. Several diagnostic and therapeutic procedures in the management of SAB were less likely to be performed in older patients in our cohort. These may have implications on outcome and should not be dismissed on the basis of age alone.

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.

Comparison of commercial antimicrobial susceptibility test methods for testing of Staphylococcus aureus and Enterococci against vancomycin, daptomycin, and linezolid

Three commercial antimicrobial susceptibility testing (AST) methods were compared to broth microdilution for testing of Staphylococcus aureus and enterococci against vancomycin, daptomycin, and linezolid. Despite high levels of categorical agreement and essential agreement, vancomycin MICs determined by MicroScan were often 1 log2 concentration higher and MICs determined by Phoenix 1 log2 concentration lower. Daptomycin MICs were 1 to 2 log2 concentrations higher by all AST methods, except Etest, potentially impacting definitive antimicrobial therapy for bloodstream infections due to these organisms.

Intensive care unit-acquired bacteremia in mechanically ventilated patients: clinical features and outcomes

Intensive care unit (ICU)-acquired bacteremia (IAB) is associated with high medical expenditure and mortality. Mechanically ventilated patients represent one third of all patients admitted to ICU, but the clinical features and outcomes in mechanically ventilated patients who develop IAB remain unknown. We conducted a 3-year retrospective observational cohort study, and 1,453 patients who received mechanical ventilation on ICU admission were enrolled. Among patients enrolled, 126 patients who had developed IAB ≧48 hours after ICU admission were identified. The study patients were divided into IAB and no IAB groups, and clinical characteristics of IAB based on specific bacterial species were further analyzed. The multivariate Cox regression analysis showed that ventilator support for chronic obstructive pulmonary disease and congestive heart failure, and patients admitted from nursing home were the independent risk factors for developing IAB. Patients with IAB were significantly associated with longer length of ICU stay, prolonged ventilator use, lower rate of successful weaning, and higher rate of ventilator dependence and ICU mortality as compared to those without IAB. IAB was the independent risk factor for ICU mortality (HR, 1.510, 95% CI 1.054–1.123; p = 0.010). The clinical characteristics of IAB related to specific bacterial species included IAB due to Pseudomonas aeruginosa being likely polymicrobial, lung source and prior antibiotic use; Escherichia coli developing earlier and from urinary tract source; methicillin-resistant Staphylococcus aureus related to central venous catheter and multiple sets of positive hemoculture; and Elizabethkingia meningoseptica significantly associated with delayed/inappropriate antibiotic treatment. In summary, IAB was significantly associated with poor patient outcomes in mechanically ventilated ICU patients. The clinical features related to IAB and clinical characteristics of IAB based on specific bacterial species identified in our study may be utilized to refine the management of IAB.

Hospital- and community-associated methicillin-resistant Staphylococcus aureus: a 6-year surveillance study of invasive infections in Chinese children

AIM

To investigate and compare the characteristics of invasive hospital-associated (HA) and community-associated (CA) methicillin-resistant Staphylococcus aureus (MRSA) infections in Chinese children.

METHODS

Clinical data on 59 paediatric patients with invasive MRSA isolated from the normally sterile sites between 2006 and 2011 were obtained from the clinical MRSA surveillance database of Beijing Children's Hospital. The molecular characteristics of the invasive MRSA strains were then analysed.

RESULTS

Invasive MRSA infections rose from 0.89 per 10 000 admissions in 2006 to 3.75 in 2011, with a notable increase in invasive CA-MRSA infections from 0 to 2.43 over the same period. The median age of the CA patients (n = 29) was 0.33 years, compared with 1.17 years for the HA patients (n = 30). Multisite infection, severe pneumonia and empyema were found in 55.2%, 73.1% and 61.5% of CA children and in 30%, 32% and 24% of HA patients, respectively. ST59-MRSA-IVa accounted for 40.7% of all isolates and the Panton-Valentine leukocidin (PVL) gene carriage rate was significantly higher in patients with necrotizing pneumonia and osteoarthritis than in those with other diseases.

CONCLUSION

The incidence of paediatric invasive MRSA infection, particularly CA-MRSA infection, increased in Chinese children between 2006 and 2011. The invasive infections caused by CA-MRSA occurred more frequently in younger children with more severe pneumonia or empyema.