Michele Cheung

Methicillin-Resistant Staphylococcus aureus (MRSA) Carriage in 10 Nursing Homes in Orange County, California

County, California • Author(s): Courtney Reynolds, MS; Victor Quan, BA; Diane Kim, BS; Ellena Peterson, PhD; Julie Dunn, MPH; Matthew Whealon, BS; Leah Terpstra, BA; Hildy Meyers, MD, MPH; Michele Cheung, MD, MPH; Bruce Lee, MD, MBA; Susan S. Huang, MD, MPH Source: Infection Control and Hospital Epidemiology, Vol. 32, No. 1 (January 2011), pp. 91-93 Published by: The University of Chicago Press on behalf of The Society for Healthcare Epidemiology of America Stable URL: http://www.jstor.org/stable/10.1086/657637 . Accessed: 20/05/2014 22:28

Nursing home characteristics associated with methicillin-resistant Staphylococcus aureus (MRSA) Burden and Transmission.

BackgroundMRSA prevalence in nursing homes often exceeds that in hospitals, but reasons for this are not well understood. We sought to measure MRSA burden in a large number of nursing homes and identify facility characteristics associated with high MRSA burden.MethodsWe performed nasal swabs of residents from 26 nursing homes to measure MRSA importation and point prevalence, and estimate transmission. Using nursing home administrative data, we identified facility characteristics associated with MRSA point prevalence and estimated transmission risk in multivariate models.ResultsWe obtained 1,649 admission and 2,111 point prevalence swabs. Mean MRSA point prevalence was 24%, significantly higher than mean MRSA admission prevalence, 16%, (paired t-test, p<0.001), with a mean estimated MRSA transmission risk of 16%.In multivariate models, higher MRSA point prevalence was associated with higher admission prevalence (p=0.005) and higher proportions of residents with indwelling devices (p=0.01). Higher estimated MRSA transmission risk was associated with higher proportions of residents with diabetes (p=0.01) and lower levels of social engagement (p=0.03).ConclusionsMRSA importation was a strong predictor of MRSA prevalence, but MRSA burden and transmission were also associated with nursing homes caring for more residents with chronic illnesses or indwelling devices. Frequent social interaction among residents appeared to be protective of MRSA transmission, suggesting that residents healthy enough to engage in group activities do not incur substantial risks of MRSA from social contact. Identifying characteristics of nursing homes at risk for high MRSA burden and transmission may allow facilities to tailor infection control policies and interventions to mitigate MRSA spread.

Predicting High Prevalence of Community Methicillin-Resistant Staphylococcus aureus Strains in Nursing Homes

We assessed characteristics associated with community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) carriage among residents of 22 nursing homes. Of MRSA-positive swabs, 25% (208/824) were positive for CA-MRSA. Median facility CA-MRSA percentage was 22% (range, 0%-44%). In multivariate models, carriage was associated with age less than 65 years (odds ratio, 1.2; P<.001) and Hispanic ethnicity (odds ratio, 1.2; P=.006). Interventions are needed to target CA-MRSA.

2004 California pediatric West Nile virus case series.

Relatively few pediatric West Nile virus cases have been recognized in the United States since the virus was first identified in 1999. We reviewed the clinical characteristics of 23 cases in pediatric patients that occurred in California in 2004 to better understand the infection in this population.

Successful strategies for high participation in three regional healthcare surveys: an observational study

BackgroundRegional healthcare facility surveys to quantitatively assess nosocomial infection rates are important for confirming standardized data collection and assessing health outcomes in the era of mandatory reporting. This is particularly important for the assessment of infection control policies and healthcare associated infection rates among hospitals. However, the success of such surveys depends upon high participation and representativeness of respondents.MethodsThis descriptive paper provides methodologies that may have contributed to high participation in a series of administrative, infection control, and microbiology laboratory surveys of all 31 hospitals in a large southern California county. We also report 85% (N = 72) countywide participation in an administrative survey among nursing homes in this same area.ResultsUsing in-person recruitment, 48% of hospitals and nursing homes were recruited within one quarter, with 75% recruited within three quarters.ConclusionsPotentially useful strategies for successful recruitment included in-person recruitment, partnership with the local public health department, assurance of anonymity when presenting survey results, and provision of staff labor for the completion of detailed survey tables on the rates of healthcare associated pathogens. Data collection assistance was provided for three-fourths of surveys. High compliance quantitative regional surveys require substantial recruitment time and study staff support for high participation.

Evaluation of indirect fluorescent antibody assays compared to rapid influenza diagnostic tests for the detection of pandemic influenza A (H1N1) pdm09.

Performance of indirect fluorescent antibody (IFA) assays and rapid influenza diagnostic tests (RIDT) during the 2009 H1N1 pandemic was evaluated, along with the relative effects of age and illness severity on test accuracy. Clinicians and laboratories submitted specimens on patients with respiratory illness to public health from April to mid October 2009 for polymerase chain reaction (PCR) testing as part of pandemic H1N1 surveillance efforts in Orange County, CA; IFA and RIDT were performed in clinical settings. Sensitivity and specificity for detection of the 2009 pandemic H1N1 strain, now officially named influenza A(H1N1)pdm09, were calculated for 638 specimens. Overall, approximately 30% of IFA tests and RIDTs tested by PCR were falsely negative (sensitivity 71% and 69%, respectively). Sensitivity of RIDT ranged from 45% to 84% depending on severity and age of patients. In hospitalized children, sensitivity of IFA (75%) was similar to RIDT (84%). Specificity of tests performed on hospitalized children was 94% for IFA and 80% for RIDT. Overall sensitivity of RIDT in this study was comparable to previously published studies on pandemic H1N1 influenza and sensitivity of IFA was similar to what has been reported in children for seasonal influenza. Both diagnostic tests produced a high number of false negatives and should not be used to rule out influenza infection.

What Is Nosocomial? Large Variation in Hospital Choice of Numerators and Denominators Affects Rates of Hospital-Onset Methicillin-Resistant Staphylococcus aureus

We calculated hospital-onset methicillin-resistant Staphylococcus aureus (HO-MRSA) rates for Orange County, California, hospitals using survey and state data. Numerators were variably defined as HO-MRSA occurring more than 48 hours (37%), more than 2 days (30%), and more than 3 days (33%) postadmission. Survey-reported denominators differed from state-reported patient-days. Numerator and denominator choices substantially impacted HO-MRSA rates.

Differences in hospital-associated multidrug-resistant organisms and Clostridium difficile rates using 2-day versus 3-day definitions.

We surveyed infection prevention programs in 16 hospitals for hospital-associated methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci, extended-spectrum β-lactamase, and multidrug-resistant Acinetobacter acquisition, as well as hospital-associated MRSA bacteremia and Clostridium difficile infection based on defining events as occurring >2 days versus >3 days after admission. The former resulted in significantly higher median rates, ranging from 6.76% to 45.07% higher.

Protective effect of methicillin-susceptible Staphylococcus aureus carriage against methicillin-resistant S. aureus acquisition in nursing homes: A prospective cross-sectional study

OBJECTIVE To evaluate whether an ecologic inverse association exists between methicillin-susceptible Staphylococcus aureus (MSSA) prevalence and methicillin-resistant S. aureus (MRSA) prevalence in nursing homes. METHODS We conducted a secondary analysis of a prospective cross-sectional study of S. aureus prevalence in 26 nursing homes across Orange County, California, from 2008-2011. Admission prevalence was assessed using bilateral nares swabs collected from all new residents within 3 days of admission until 100 swabs were obtained. Point prevalence was assessed from a representative sample of 100 residents. Swab samples were plated on 5% sheep blood agar and Spectra MRSA chromogenic agar. If MRSA was detected, no further tests were performed. If MRSA was not detected, blood agar was evaluated for MSSA growth. We evaluated the association between MRSA and MSSA admission and point prevalence using correlation and linear regression testing. RESULTS We collected 3,806 total swabs. MRSA and MSSA admission prevalence were not correlated (r = -0.40, P = .09). However, MRSA and MSSA point prevalence were negatively correlated regardless of whether MSSA prevalence was measured among all residents sampled (r = -0.67, P = .0002) or among those who did not harbor MRSA (r = -0.41, P = .04). This effect persisted in regression models adjusted for the percentage of residents with diabetes (β = -0.73, P = .04), skin lesions (β = -1.17, P = .002), or invasive devices (β = -1.4, P = .0006). CONCLUSIONS The inverse association between MRSA and MSSA point prevalence and minimal association on admission prevalence suggest MSSA carriage may protect against MRSA acquisition in nursing homes. The minimal association on admission prevalence further suggests competition may occur during nursing home stays.