Early identification of carbapenemase-producing Enterobacteriaceae (CPE) is essential to prevent their dissemination within health care settings. Our objective was to evaluate the accuracy of 11 phenotypic assays for the detection of CPE. Two collections of carbapenem-resistant Enterobacteriaceae (CRE) isolates were evaluated, including 191 retrospective isolates (122 CP-CRE and 69 non-CP isolates) as well as 45 prospective clinical isolates (15 CP-CRE and 30 non-CP-CRE) obtained over a 3-month period. The sensitivity and specificity of each test was determined, with molecular genotype serving as the gold standard. Among the retrospective cohort, sensitivities ranged from 72% for the boronic acid synergy test for the detection of KPC producers to Ն98% for the modified Carba NP, the Rapidec Carba NP, the manual Blue Carba, and the modified carbapenem inactivation method for the detection of any CPE. Sensitivity differed among tests across enzyme classes. All assays had excellent specificity exceeding 95%, with the exception of the boronic acid synergy test (88%) and modified Hodge test (91%). Prospectively, 45 CRE isolates were encountered over a 3-month period, including 15 CPE (33%) and 30 non-CP-CRE (67%). Results from the prospective cohort were similar. However, a decrease in specificity was observed across most tests, likely due to restricted inclusion of non-CP-CRE to assess the specificity of the assays. Overall, accuracy of CPE detection varied across phenotypic tests. Local epidemiology of CP genotypes, turnaround time, and ease of incorporation into the laboratory workflow should be considered when selecting a phenotypic assay for clinical use.KEYWORDS carbapenem-resistant organisms, carbapenemase-producing organisms, prevalence C arbapenemase-producing carbapenem-resistant Enterobacteriaceae (CP-CRE) are associated with significant morbidity and mortality (1, 2). A variety of carbapenemase genes have been described that are either plasmid or chromosomally encoded, including bla KPC , bla SME , bla IMI , bla NDM , bla VIM , bla IMP , and bla OXA-48-type (2). Early and accurate identification of CP-CRE is essential to prevent their dissemination within health care settings.Detection of CP-CRE in clinical laboratories is challenging, as isolates may only have moderate reductions in susceptibilities to carbapenems (3), and resistance may be mediated by other mechanisms, such as extended-spectrum-␤-lactamase (ESBL) and/or AmpC ␤-lactamase producers with decreased membrane permeability. Molecular methods for the detection of carbapenemase genes are costly, may require significant expertise, and are limited by the targets included. Thus, rapid and affordable phenotypic assays to broadly classify CRE into CP-CRE versus non-CP-CRE have been developed.

This article critically examines some of the claims of chaos theory from the perspective of the philosophy of science. Chaos theory uses scientific terminology, but it is possibly better described as a metaphysical belief or value orientation. Some of the concepts developed by chaos theory are of great interest and may be useful in counseling. These concepts, however, are not always clear and consistent, and the theory could become the repository of all kinds of untestable and even antiscientific notions.

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