Questions on causality and responsibility arising from an outbreak of Pseudomonas aeruginosa infections in Norway

In 2002, Norway experienced a large outbreak of Pseudomonas aeruginosa infections in hospitals with 231 confirmed cases. This fuelled intense public and professional debates on what were the causes and who were responsible. In epidemiology, other sciences, in philosophy and in law there is a long tradition of discussing the concept of causality. We use this outbreak as a case; apply various theories of causality from different disciplines to discuss the roles and responsibilities of some of the parties involved. Mackie's concept of INUS conditions, Hill's nine viewpoints to study association for claiming causation, deterministic and probabilistic ways of reasoning, all shed light on the issues of causality in this outbreak. Moreover, applying legal theories of causation (counterfactual reasoning and the "but-for" test and the NESS test) proved especially useful, but the case also illustrated the weaknesses of the various theories of causation

Reference isotherms for water vapor sorption on nanoporous carbon: results of an interlaboratory study

This paper reports the results of an international interlaboratory study sponsored by the Versailles Project on Advanced Materials and Standards (VAMAS) and led by the National Institute of Standards and Technology (NIST) on the measurement of water vapor sorption isotherms at 25 °C on a pelletized nanoporous carbon (BAM-P109, a certified reference material). Thirteen laboratories participated in the study and contributed nine pure water vapor isotherms and four relative humidity isotherms, using nitrogen as the carrier gas. From these data, reference isotherms, along with the 95% uncertainty interval (Uk=2), were determined and are reported in a tabular format

Evaluation of new monoclonal antibody-based latex agglutination test for detection of cryptococcal polysaccharide antigen in serum and cerebrospinal fluid.

We evaluated the performance of CRYPTO-LEX (Trinity Laboratories, Inc., Raleigh, N. C.), a new mouse immunoglobulin M monoclonal antibody latex agglutination reagent which reacts with the capsular polysaccharide of the four serogroups of Cryptococcus neoformans. This test was compared with CALAS (Meridian Diagnostics, Cincinnati, Ohio) for the ability to detect cryptococcal antigen in serum and cerebrospinal fluid (CSF). A total of 580 clinical specimens (327 serum and 253 CSF samples), primarily from human immunodeficiency virus-infected patients, were tested in this study. Sixty-seven specimens (44 serum and 23 CSF samples) were positive for cryptococcal antigen with both tests, and 511 (282 serum and 229 CSF samples) were negative. The two latex reagents agreed for 326 of 327 serum specimens (44 positives and 282 negatives). One serum specimen with a titer of 1:2 was CALAS positive but CRYPTO-LEX negative. The titer correlation coefficient for the two tests was 0.884 when two highly discordant serum specimens were eliminated from analysis of the data. The two latex tests agreed for 252 of 253 CSF specimens (23 positives and 229 negatives). One specimen with a titer of 1:2 was positive with CALAS and negative by CRYPTO-LEX. The correlation coefficient of the two tests for CSF titers was 0.886. The sensitivity and specificity of CRYPTO-LEX were 97 and 100%, respectively, with a 99.6% correlation with CALAS. These data show that the performance of CRYPTO-LEX is comparable to that of CALAS for detection of cryptococcal antigen in serum and CSF

Comparison of mycobacteria growth indicator tube with BACTEC 460 for detection and recovery of mycobacteria from clinical specimens.

We compared the Mycobacteria Growth Indicator Tube (MGIT) system with the BACTEC 460 (B460) and Lowenstein Jensen (LJ) systems for the recovery of mycobacteria (acid-fast bacteria [AFB]) from 1,441 clinical specimens. Excluding 13 isolates of Mycobacterium gordonae, 178 significant AFB isolates were recovered from 113 patients. Isolates (119) of the Mycobacterium avium complex (MAC) accounted for 67% of all isolates, while isolates (30) of the Mycobacterium tuberculosis complex (MTB) accounted for 17% of isolates. The MGIT system recovered 98 (82%) MAC and 27 (90%) MTB isolates, while the B460 system recovered 101 (85%) MAC and 28 (93%) MTB isolates and the LJ system recovered 91 (76%) MAC and 25 (83%) MTB isolates. Overall, the MGIT system recovered 152 isolates of AFB (85.4% sensitivity), and the B460 and LJ systems recovered 151 (84.8% sensitivity) and 137 (76.9% sensitivity) AFB isolates, respectively. The recoveries of AFB with combinations of media were as follows: MGIT + LJ, 93.2%; B460 + LJ, 92.1%; and MGIT + B460, 96.6%. Although the sensitivity of MGIT was equivalent to that of B460, MGIT required a longer incubation (median, 11 days) than did B460 (median, 8 days) to become positive (P < 0.05)

Confirmation of the presence of Mycobacterium tuberculosis and other mycobacteria in mycobacterial growth indicator tubes (MGIT) by multiplex strand displacement amplification.

Multiplex strand displacement amplification (mSDA) is capable of amplifying three distinct DNA sequences simultaneously. These include sequences present in most genera of mycobacteria, a sequence specific for Mycobacterium tuberculosis, and an internal control. mSDA was used to detect the presence of these target sequences in 154 (72 positive, 76 negative, and 6 failed) clinical specimens cultured in the mycobacterial growth indicator tube (MGIT) system. A wide variety of specimen types were processed and cultured. Once these cultures were deemed positive by MGIT fluorescence or were deemed negative after 8 weeks of incubation, MGIT culture aliquots were processed for mSDA analyses. A chemiluminescent microwell assay was used to detect the amplified products. The procedure was relatively simple and took less than 6 h to complete. The sensitivity of mSDA for detecting acid-fast bacilli was 96.4% compared to that of MGIT culture. Sensitivity and specificity were 97.2 and 96.1%, respectively, when all clinical criteria were considered. mSDA was shown to be a rapid and effective method for confirming the presence of M. tuberculosis and other mycobacteria in positive MGIT cultures