Mixed flora: indication for therapy or early warning sign?

"Mixed flora" is a commonly returned result yielding not in either indication for therapy or identification of potential causative organisms. We sought to determine whether mixed flora (MF) was in fact a harbinger of impending pneumonia or a benign result that could be therapeutically ignored. Bronchoalveolar lavage (BAL) results of injured adults undergoing mechanical ventilation in a trauma intensive care unit were stratified by identified organisms and by colony counts. The incidence of mixed flora as a component of the specimen report was compared for diagnostic (greater than 10(5) colony forming units/mL) versus nondiagnostic results using chi2 accepting P < 0.05 as significant. Nondiagnostic specimens were then stratified as MF only or MF and other identified pathogenic organisms. This group was further evaluated to determine the use of antibiotic therapy and development of pneumonia. Finally, patients with nondiagnostic reports and subsequent BAL were analyzed to determine specific species if subsequent BAL were required or if later pneumonia occurred. During 2007, 159 BALs were performed on injured patients of which 93 were diagnostic for pneumonia, whereas 66 were nondiagnostic. Of the diagnostic specimens, 15 (16%) included mixed flora. Of the 66 nondiagnostic specimens, 39 (59%) contained mixed flora. Nine (60%) of the 15 with diagnostic mixed flora were started on antibiotic therapy for an average of 6.2 days. The remaining 39 (82%) patients with mixed flora received no antibiotic therapy and never developed pneumonia. These data demonstrate that in the absence of diagnostic threshold of an identifiable pathogenic organism, therapy for pneumonia should not be instituted or continued.

Explaining Differences in Crash and Injury Crash Outcomes in Red Light Camera Studies.

Evaluations of red light camera (RLC) traffic safety programs have produced mixed results. Some conclude RLCs were associated with significant increases in motor vehicle crashes and injury crashes, whereas other research reports safety benefits. To understand the difference in findings, the present analysis assessed whether standards required for internal validity in quasi-experimental public health program evaluations were adhered to in frequently cited RLC analyses. Four evaluation standards were identified and used to assess the RLC analyses: lack of bias in the selection of both (a) treated sites and (b) comparison sites, (c) integration of relevant control variables in the analysis, and (d) full disclosure of results of the statistical analysis. Six leading RLC studies were then critiqued. Only two of the six studies adhered to the four standards and both concluded RLCs were associated with significant increases in crashes and injury or possible injury crashes. A third study reported an increase in fatal/injury crashes but did not test for statistical significance. Three studies reported equivocal findings; however, each failed to adhere to most standards. Differences in findings were attributed to the evaluation methods used. If implementing an RLC program, communities should use sound public health evaluation methods to assess effectiveness.