Dawn M. Sievert

Severe community-acquired pneumonia due to Staphylococcus aureus, 2003-04 influenza season

S. aureus community-acquired pneumonia has been reported from 9 states.

Public Health Surveillance for Methicillin-Resistant Staphylococcus aureus: Comparison of Methods for Classifying Health Care– and Community-Associated Infections

OBJECTIVES We compared 3 methods for classifying methicillin-resistant Staphylococcus aureus (MRSA) infections as health care associated or community associated for use in public health surveillance. METHODS We analyzed data on MRSA infections reported to the Michigan Department of Community Health from October 1, 2004, to December 31, 2005. Patient demographics, risk factors, infection information, and susceptibility were collected for 2151 cases. We classified each case by the health care risk factor, infection-type, and susceptibility pattern methods and compared the results of the 3 methods. RESULTS Demographic, clinical, and microbiological variables yielded similar health care-associated and community-associated distributions when classified by risk factor and infection type. When 2 methods yielded the same classifications, the overall distribution was similar to classification by 3 methods. No specific combination of 2 methods was superior. CONCLUSIONS MRSA categorization by 2 methods is more accurate than it is by a single method. The health care risk factor and infection-type methods yield comparable classification results. Accuracy is increased by using more variables; however, further research is needed to identify the optimal combination.

A multivariable model to classify methicillin-resistant staphylococcus aureus infections as health care or community associated

Background Methicillin-resistant Staphylococcus aureus (MRSA) infections are often defined as health care (HA) or community-associated (CA) using common classification schemes involving health care risk factor, infection type, susceptibility pattern, or molecular typing. This investigation compared pulsed-field gel electrophoresis (PFGE) molecular typing results (dichotomized as HA or CA) with our new MRSA infection classification method. The goal was to develop an improved predictive model for PFGE-type based primarily on the other 3 classification variables. Methods Methicillin-resistant S. aureus infections reported to the Michigan Department of Community Health from October 2004 to December 2005 were analyzed. Patients’ demographics, risk factors, infection information, and susceptibility results were collected for 2151 cases. A subset of 244 MRSA infections with available PFGE results was analyzed. Results of logistic regression are presented using a receiver operating characteristic curve analysis. Results The multivariable models predicted the PFGE classification as HA or CA (Max-rescaled R 2 = 61%) better than health care risk factor, infection type, or susceptibility pattern alone (max-rescaled R 2 = 21%, 34%, and 46%, respectively). The best model included infection type, susceptibility pattern, age, and hospitalized during infection. Conclusions This model provides a simpler, more accurate prediction of HA or CA status, thus enhancing efforts to control MRSA infections.

Effective State-Based Surveillance for Multidrug-Resistant Organisms Related to Health Care-Associated Infections

In September 2008, the Council of State and Territorial Epidemiologists and the Centers for Disease Control and Prevention sponsored a meeting of public health and infection-control professionals to address the implementation of surveillance for multidrug-resistant organisms (MDROs)—particularly those related to health care-associated infections. The group discussed the role of health departments and defined goals for future surveillance activities. Participants identified the following main points: (7) surveillance should guide prevention and infection-control activities, (2) an MDRO surveillance system should be adaptable and not organism specific, (3) new systems should utilize and link existing systems, and (4) automated electronic laboratory reporting will be an important component of surveillance but will take time to develop. Current MDRO reporting mandates and surveillance methods vary across states and localities. Health departments that have not already done so should be proactive in determining what type of system, if any, will fit their needs.

Characterization of Hospitalized Community-Onset Staphylococcus aureus Lower Respiratory Tract Infections Among Generally Healthy Persons 50 Years of Age or Younger

BackgroundCase series have described severe lower respiratory tract infection (LRI) in healthy, community-dwelling persons caused by methicillin-resistant Staphylococcus aureus (MRSA). Evaluating populations at risk is needed. MethodsSurveillance for patients aged 50 years or younger hospitalized with LRI who had S aureus isolated from blood or respiratory specimen during September 2008 to August 2010 was performed at 25 hospitals in 5 US metropolitan areas. Persons with recent health care exposure were excluded. Lower respiratory tract infection diagnosis required supporting radiographic or clinical evidence. Clinical characteristics of LRI were compared by methicillin resistance phenotype. ResultsIn total, 94 hospitalized community-onset S aureus LRI cases were identified. Lower respiratory tract infection cases were identified in both young adults and children (60%, 35–50 years; and 19%, younger than 17 years), without any seasonality or association with influenza circulation. Among the 94 case patients with LRI, 34 patients (36%) had bacteremia, 36 patients (40%) required ICU admission, and 6 patients (6%) died; proportions were similar between cases with methicillin-susceptible S aureus and MRSA. Lower respiratory tract infection cases with MRSA had longer median length of stay compared with those with methicillin-susceptible S aureus (9 vs. 6 days; P = 0.04). Lower respiratory tract infection cases with evidence of influenza infection had higher mortality compared with LRI cases without influenza infection (31% vs. 2%; P = 0.003). During influenza circulation, 35 (55%) of 64 case patients with LRI were tested for influenza, and 9 (26%) of the 35 case patients tested positive. ConclusionsS aureus LRI occurred in both adults and children, without any seasonality or association with MRSA and with and without evidence of influenza infection, although case fatality was higher among those with evidence of influenza infection.