INTRODUCTION: Harboring sensitive strains may prevent acquisition of resistant pathogens by competing for colonization of ecological niches. Competition may be relevant to decolonization strategies that eliminate sensitive strains and may predispose to acquiring resistant strains in high-endemic settings. We evaluated the impact of colonization with methicillin-sensitive Staphylococcus aureus (MSSA) and vancomycin-sensitive enterococci (VSE) on acquisition of methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE), respectively, when controlling for other risk factors. METHODS: We conducted a nested case-control study of patients admitted to eight ICUs performing admission and weekly bilateral nares and rectal screening for MRSA and VRE, respectively. Analyses were identical for both pathogens. For MRSA, patients were identified who had a negative nares screen and no prior history of MRSA. We evaluated predictors of MRSA acquisition, defined as a subsequent MRSA-positive clinical or screening culture, compared to those with a subsequent MRSA-negative nares screen within the same hospitalization. Medical records were reviewed for the presence of MSSA on the initial MRSA-negative nares screen, demographic and comorbidity information, medical devices, procedures, antibiotic utilization, and daily exposure to MRSA-positive patients in the same ward. Generalized linear mixed models were used to assess predictors of acquisition. RESULTS: In multivariate models, MSSA carriage protected against subsequent MRSA acquisition (OR = 0.52, CI: 0.29, 0.95), even when controlling for other risk factors. MRSA predictors included intubation (OR = 4.65, CI: 1.77, 12.26), fluoroquinolone exposure (OR = 1.91, CI: 1.20, 3.04), and increased time from ICU admission to initial negative swab (OR = 15.59, CI: 8.40, 28.94). In contrast, VSE carriage did not protect against VRE acquisition (OR = 1.37, CI: 0.54, 3.48), whereas hemodialysis (OR = 2.60, CI: 1.19, 5.70), low albumin (OR = 2.07, CI: 1.12, 3.83), fluoroquinolones (OR = 1.90, CI: 1.14, 3.17), third-generation cephalosporins (OR = 1.89, CI: 1.15, 3.10), and increased time from ICU admission to initial negative swab (OR = 15.13, CI: 7.86, 29.14) were predictive. CONCLUSIONS: MSSA carriage reduced the odds of MRSA acquisition by 50% in ICUs. In contrast, VSE colonization was not protective against VRE acquisition. Studies are needed to evaluate whether decolonization of MSSA ICU carriers increases the risk of acquiring MRSA when discharging patients to high-endemic MRSA healthcare settings. This may be particularly important for populations in whom MRSA infection may be more frequent and severe than MSSA infections, such as ICU patients.

BACKGROUND: Detection of outbreaks of hospital-acquired infections is often based on simple rules, such as the occurrence of three new cases of a single pathogen in two weeks on the same ward. These rules typically focus on only a few pathogens, and they do not account for the pathogens' underlying prevalence, the normal random variation in rates, and clusters that may occur beyond a single ward, such as those associated with specialty services. Ideally, outbreak detection programs should evaluate many pathogens, using a wide array of data sources. METHODS AND FINDINGS: We applied a space-time permutation scan statistic to microbiology data from patients admitted to a 750-bed academic medical center in 2002-2006, using WHONET-SaTScan laboratory information software from the World Health Organization (WHO) Collaborating Centre for Surveillance of Antimicrobial Resistance. We evaluated patients' first isolates for each potential pathogenic species. In order to evaluate hospital-associated infections, only pathogens first isolated >2 d after admission were included. Clusters were sought daily across the entire hospital, as well as in hospital wards, specialty services, and using similar antimicrobial susceptibility profiles. We assessed clusters that had a likelihood of occurring by chance less than once per year. For methicillin-resistant Staphylococcus aureus (MRSA) or vancomycin-resistant enterococci (VRE), WHONET-SaTScan-generated clusters were compared to those previously identified by the Infection Control program, which were based on a rule-based criterion of three occurrences in two weeks in the same ward. Two hospital epidemiologists independently classified each cluster's importance. From 2002 to 2006, WHONET-SaTScan found 59 clusters involving 2-27 patients (median 4). Clusters were identified by antimicrobial resistance profile (41%), wards (29%), service (13%), and hospital-wide assessments (17%). WHONET-SaTScan rapidly detected the two previously known gram-negative pathogen clusters. Compared to rule-based thresholds, WHONET-SaTScan considered only one of 73 previously designated MRSA clusters and 0 of 87 VRE clusters as episodes statistically unlikely to have occurred by chance. WHONET-SaTScan identified six MRSA and four VRE clusters that were previously unknown. Epidemiologists considered more than 95% of the 59 detected clusters to merit consideration, with 27% warranting active investigation or intervention. CONCLUSIONS: Automated statistical software identified hospital clusters that had escaped routine detection. It also classified many previously identified clusters as events likely to occur because of normal random fluctuations. This automated method has the potential to provide valuable real-time guidance both by identifying otherwise unrecognized outbreaks and by preventing the unnecessary implementation of resource-intensive infection control measures that interfere with regular patient care. Please see later in the article for the Editors' Summary.

OBJECTIVES: Reducing unnecessary antibiotic use, particularly among children, continues to be a public health priority. Previous intervention studies have been limited by size or design and have shown mixed results. The objective of this study was to determine the impact of a multifaceted, community-wide intervention on overall antibiotic use for young children and on use of broad-spectrum agents. In addition, we sought to compare the intervention's impact on commercially and Medicaid-insured children. METHODS: We conducted a controlled, community-level, cluster-randomized trial in 16 nonoverlapping Massachusetts communities, studied from 1998 to 2003. During 3 years, we implemented a physician behavior-change strategy that included guideline dissemination, small-group education, frequent updates and educational materials, and prescribing feedback. Parents received educational materials by mail and in primary care practices, pharmacies, and child care settings. Using health-plan data, we measured changes in antibiotics dispensed per person-year of observation among children who were aged 3 to <72 >months, resided in study communities, and were insured by a participating commercial health plan or Medicaid. RESULTS: The data include 223,135 person-years of observation. Antibiotic-use rates at baseline were 2.8, 1.7, and 1.4 antibiotics per person-year among those aged 3 to <24, 24 to <48, and 48 to <72 months, respectively. We observed a substantial downward trend in antibiotic prescribing, even in the absence of intervention. The intervention had no additional effect among children aged 3 to <24 months but was responsible for a 4.2% decrease among those aged 24 to <48 months and a 6.7% decrease among those aged 48 to <72 months. The intervention effect was greater among Medicaid-insured children and for broad-spectrum agents. CONCLUSIONS: A sustained, multifaceted, community-level intervention was only modestly successful at decreasing overall antibiotic use beyond substantial secular trends. The more robust impact among Medicaid-insured children and for specific medication classes provides an argument for specific targeting of resources for patient and physician behavior change.

OBJECTIVE: The goal was to determine the impact of a community-wide educational intervention on parental misconceptions likely contributing to pediatric antibiotic overprescribing. METHODS: We conducted a cluster-randomized trial of a 3-year, community-wide, educational intervention directed at parents of children < 6 years of age in 16 Massachusetts communities to improve parental antibiotic knowledge and attitudes and to decrease unnecessary prescribing. Parents in 8 intervention communities were mailed educational newsletters and exposed to educational materials during visits to local pediatric providers, pharmacies, and child care centers. We compared responses from mailed surveys in 2000 (before the intervention) and 2003 (after the intervention) for parents in intervention and control communities. Analyses were performed on the individual level, clustered according to community. RESULTS: There were 1106 (46%) and 2071 (40%) respondents to the 2000 and 2003 surveys, respectively. Between 2000 and 2003, the proportion of parents who answered > or = 7 of 10 knowledge questions correctly increased significantly in both intervention (from 52% to 64%) and control (from 54% to 61%) communities. We did not detect a significant intervention impact on knowledge regarding appropriate antibiotic use in the population overall. In a subanalysis, we did observe a significant intervention effect among parents of Medicaid-insured children, who began with lower baseline knowledge scores. CONCLUSIONS: Although knowledge regarding appropriate use of antibiotics is improving without additional targeted intervention among more socially advantaged populations, parents of Medicaid-insured children may benefit from educational interventions to promote judicious antibiotic use. These findings may have implications for other health education campaigns.

BACKGROUND: Widespread use of broad-spectrum antibiotics contributes to increasing rates of bacterial resistance to antibiotics. Second-generation macrolides have become popular for use among children because of their broad spectrum and favorable dosing and side-effect profiles, although experts do not generally recommend them for use as initial treatment of infections among younger children. OBJECTIVE: To assess trends in second-generation macrolide use from 1996 to 2000 among children treated as outpatients in 9 US health plans, including associated diagnoses and use as initial treatment. METHODS: We sampled claims data for 25000 children, 3 months to <18 years of>age, who were enrolled between September 1, 1995, and August 31, 2000, in each of 9 US health plans. Medications dispensed were linked with ambulatory visit claims to assign diagnoses. Dispensings without another antibiotic dispensing recorded in the previous 42 days were analyzed as initial treatment of a new illness episode. We analyzed trends in prescribing overall, for initial therapy, and, within specific diagnoses, for differences among health plans. RESULTS: From 1995-1996 to 1999-2000, although overall antibiotic use decreased from 1.15 to 0.91 dispensings per person-year, second-generation macrolide use increased from 0.022 to 0.063 dispensings per person-year. Use as a proportion of all antibiotic dispensings increased from 1.9% to 6.9%, and use as initial therapy increased from 1.4% to 6%. For children <6 years of>age, second-generation macrolide use as initial therapy increased from 0.9% to 5.0% for otitis media and from 5.2% to 24.0% for pneumonia. There was a wide range of prescribing rates among health plans during the last year of the study, from 0.006 to 0.135 dispensings per person-year. CONCLUSIONS: Despite recent trends toward decreased antibiotic use among children, the use of second-generation macrolides among children has increased dramatically, even among younger children, for whom use for initial treatment of illness is not recommended. Large differences in prescribing rates exist among health plans. Continued efforts to promote the use of narrower-spectrum agents when appropriate are needed.