Device-independent, real-time identification of bacterial pathogens with a metal oxide-based olfactory sensor.

A novel olfactory method for bacterial species identification using an electronic nose device called the MonoNose was developed. Differential speciation of micro-organisms present in primary cultures of clinical samples could be performed by real-time identification of volatile organic compounds (VOCs) produced during microbial replication. Kinetic measurements show that the dynamic changes in headspace gas composition are orders of magnitude larger than the static differences at the end of fermentation. Eleven different, clinically relevant bacterial species were included in this study. For each of the species, two to eight different strains were used to take intra-species biodiversity into account. A total of 52 different strains were measured in an incubator at 37 degrees C. The results show that the diagnostic specificities varied from 100% for Clostridium difficile to 67% for Enterobacter cloacae with an overall average of 87%. Pathogen identification with a MonoNose can be achieved within 6-8 h of inoculation of the culture broths. The diagnostic specificity can be improved by broth modification to improve the VOC production of the pathogens involved.

High-throughput amplification fragment length polymorphism (htAFLP) analysis identifies genetic lineage markers but not complement phenotype-specific markers in Moraxella catarrhalis.

Comparative high-throughput amplified fragment length polymorphism (htAFLP) analysis was performed on a set of 25 complement-resistant and 23 complement-sensitive isolates of Moraxella catarrhalis in order to determine whether there were complement phenotype-specific markers within this species. The htAFLP analysis used 21 primer-pair combinations, generating 41 364 individual fragments and 2273 fragment length polymorphisms, with an average of 862 polymorphisms per isolate. Analysis of polymorphism data clearly indicated the presence of two phylogenetic lineages and 40 (2%) lineage-specific polymorphisms. However, despite the presence of 361 (16%) statistically significant complement phenotype-associated polymorphisms, no single marker was 100% complement phenotype-specific. Furthermore, no complement phenotype-specific marker was found within different phylogenetic lineages. These findings agree with previous results indicating that the complement resistance phenotype within M. catarrhalis is probably defined by multiple genes, although not all of these genes may be present within all M. catarrhalis isolates.

Changes in genetic types and population dynamics of Moraxella catarrhalis in hospitalized children are not associated with an exacerbation of existing disease.

Pulsed-field gel electrophoresis typing was performed on a retrospective set of 129 Moraxella catarrhalis isolates obtained over a 20 month period from 70 children admitted to, or presenting at, the Erasmus University Medical Center, Rotterdam, The Netherlands. The mean age of the children (at the end of the study) was 2.5 years, with a range of 6 months to 15 years. Fifty-one different M. catarrhalis types were isolated from the hospitalized children, with 31 % (22/70) being infected with two particularly prevalent M. catarrhalis types. These two prevalent types also exhibited different protein profiles. The majority (72%; 16/22) of the children infected with these two predominant types had spent at least 1 week on two paediatric intensive care wards. No exacerbation of existing disease or new disease was observed in children who experienced M. catarrhalis type changes.

Normative data for a new memory test: the Shum Visual Learning Test.

This study reports normative data and test-retest reliabilities for a visuo-spatial memory test, the Shum Visual Learning Test (SVLT). Participants were 146 Caucasians (70 males and 76 females, age range between 17-83 years). The test was administered to 116 participants once and 30 participants twice (1 month apart). Age (but not gender and education) was found to affect SVLT test performance. The norms, therefore, were presented according to seven age groups (viz., 17-19, 20-29, 30-39, 40-49, 50-59, 60-69, 70+ years). Three indices (learning, retention after interference, and delayed retention) were derived for descriptive and clinical purposes. The test-retest reliabilities for all trials of the SVLT (except Trial 6) were found to be significant (rs ranged from .63 to .82). Normative data reported allow neuropsychologists to compare patient performances with those of appropriate controls and are important for fostering clinical application of this test.

Assessment of visual memory: a comparison of Chinese characters and geometric figures as stimulus materials.

The study compared the suitability of geometric figures and Chinese characters for assessing visual memory. In Study 1, 40 Chinese characters were found to be significantly less verbalisable than were 40 geometric figures from the Biber Figure Learning Test. In Study 2, memory for Chinese characters, for Biber figures, and for items on the Rey Auditory Verbal Learning Test were compared using 14 subjects with left cerebrovascular accident, 15 subjects with right cerebrovascular accident, and 29 matched controls. Subjects in the left hemisphere group showed impairment on the Rey Auditory Verbal Learning Test but not on Chinese characters, whereas subjects in the right hemisphere group showed impairment on Chinese characters but not on the Rey Auditory Verbal Learning Test. This double dissociation was not evident when comparisons involved the Biber Figure Learning Test. The Chinese character set used in this study was thus judged to be more suitable than were geometric figures in the Biber Figure Learning Test for assessing visual memory.