Diagnosing infections--current and anticipated technologies for point-of-care diagnostics and home-based testing

In recent years, we have witnessed many transitions in healthcare systems around the globe. For example, population expansion and ageing, and the human immunodeficiency virus (HIV)-AIDS epidemics, have exerted pressure to decentralize the practice of healthcare outside of traditional settings to bring care to those in need. Upstream of patient management, diagnosis is aimed at adequately orienting medical decisions, and considerable efforts have been made to make this process faster and more efficient. However, there are several diseases and medical conditions that may/will benefit from technologies and tests that can be performed closer to the patient, at the point of care or even in the home. In this review, and in light of the paradox that technology and assay developers and healthcare officials must take into consideration for advancing human health in developed and developing countries, we present an overview of rapid diagnosis of infectious diseases at the point of care and of technologies that may contribute to enhancement of the worldwide point-of-care testing market.

Assessment of microbiological quality of drinking water from household tanks in Bermuda

Bermuda residents collect rainwater from rooftops to fulfil their freshwater needs. The objective of this study was to assess the microbiological quality of drinking water in household tanks throughout Bermuda. The tanks surveyed were selected randomly from the electoral register. Governmental officers visited the selected household (n = 102) to collect water samples and administer a short questionnaire about the tank characteristics, the residents' habits in terms of water use, and general information on the water collecting system and its maintenance. At the same time, water samples were collected for analysis and total coliforms and Escherichia coli were determined by 2 methods (membrane filtration and culture on chromogenic media, Colilert kit). Results from the 2 methods were highly correlated and showed that approximately 90% of the samples analysed were contaminated with total coliforms in concentrations exceeding 10 CFU/100 mL, and approximately 66% of samples showed contamination with E. coli. Tank cleaning in the year prior to sampling seems to protect against water contamination. If rainwater collection from roofs is the most efficient mean for providing freshwater to Bermudians, it must not be considered a source of high quality drinking water because of the high levels of microbial contamination.

A search for specific and common susceptibility loci for schizophrenia and bipolar disorder: a linkage study in 13 target chromosomes

We report the first stage of a genome scan of schizophrenia (SZ) and bipolar disorder (BP) covering 18 candidate chromosomal areas. In addition to testing susceptibility loci that are specific to each disorder, we tested the hypothesis that some susceptibility loci might be common to both disorders. A total of 480 individuals from 21 multigenerational pedigrees of Eastern Québec were evaluated by means of a consensus best-estimate diagnosis made blind to diagnoses in relatives and were genotyped with 220 microsatellite markers. Two-point and multipoint model-based linkage analyses were performed and mod scores (Z, for max Z(max)) are reported. The strongest linkage signals were detected at D18S1145 (in 18q12; Z = 4.03) for BP, and at D6S334 (in 6p 22-24; Z(het) = 3.47; alpha = 0.66) for SZ. Three other chromosomal areas (3q, 10p, and 21q) yielded linkage signals. Chromosomes 3p, 4p, 5p, 5q, 6q, 8p, 9q, 11q, 11p, 12q, 13q, 18p and 22q showed no evidence of linkage. The 18q12 results met the Lander and Kruglyak (1995) criterion for a genome-wide significant linkage and suggested that this susceptibility region may be shared by SZ and BP. The 6p finding provided confirmatory evidence of linkage for SZ. Our results suggest that both specific and common susceptibility loci must be searched for SZ and BP.

The contribution of arginine residues within the P6-P1 region of alpha 1-antitrypsin to its reaction with furin

A series of mutants incorporating furin recognition sequences within the P6-P1 region of the reactive site loop of alpha(1)-antitrypsin were constructed. Variants containing different combinations of basic residues in the P1, P2, P4, and P6 positions replacing the wild type (P6)LEAIPM(P1) sequence were evaluated for their capacity to establish SDS-resistant complexes with furin, to affect association rate constants (k(ass) and k'(ass)), or to inhibit furin-dependent proteolysis of a model precursor in vivo. Each variant abolished processing of pro-von Willebrand factor in transfected hEK293 cells. The k(ass) of all variants were found to be similar (1.1-1.7 x 10(6) m(-1) s(-1)) except for one mutant, RERIRR, which had a k(ass) of 3.3 x 10(5) m(-1) s(-1). However, the stoichiometry of inhibition varied with values ranging from 2.9 to >24, indicating rapid formation of the acyl-enzyme intermediate (high k'(ass)). Moreover, those variants having high stoichiometry of inhibition values were accompanied by the rapid formation of cleaved forms of the inhibitors. The data suggest that the rate of conversion of the acyl-enzyme (EI') into the highly stable complex (EI*) was affected by replacement of specific residues within the reactive site loop. Taken together, the results reveal how furin recognition sequences within the context of the biochemical properties of serpins will play a role in the capacity of the protein to follow either the inhibitory or the substrate pathway.

Significant linkage for Tourette syndrome in a large French Canadian family

Family and twin studies provide strong evidence that genetic factors are involved in the transmission of Gilles de la Tourette syndrome (TS) and related psychiatric disorders. To detect the underlying susceptibility gene(s) for TS, we performed linkage analysis in one large French Canadian family (127 members) from the Charlevoix region, in which 20 family members were definitely affected by TS and 20 others showed related tic disorders. Using model-based linkage analysis, we observed a LOD score of 3.24 on chromosome 11 (11q23). This result was obtained in a multipoint approach involving marker D11S1377, the marker for which significant linkage disequilibrium with TS recently has been detected in an Afrikaner population. Altogether, 25 markers were studied, and, for level of significance, we derived a criterion that took into account the multiple testing arising from the use of three phenotype definitions and three modes of inheritance, a procedure that yielded a LOD score of 3.18. Hence, even after adjustment for multiple testing, the present study shows statistically significant evidence for genetic linkage with TS.

Retrieval of droplet-size density distribution from multiple-field-of-view cross-polarized lidar signals: theory and experimental validation

Multiple-field-of-view (MFOV) secondary-polarization lidar signals are used to calculate the particle-size density distribution (PSD) at the base of a cloud. At the cloud base, multiple scattering is weak and single backscattering is predominant by many orders of magnitude. Because secondary polarization is a direct measure of multiple scattering, it is therefore advantageous to use secondary polarization. A mathematical relation among the PSD, the lidar fields of view, the scattering angles, and the angular depolarization is derived to facilitate use of secondary polarization. The model is supported by experimental MFOV lidar measurements carried out in a controlled environment, and its limitations and restrictions are discussed.

6p24-22 region and major psychoses in the Eastern Quebec population. Le Groupe IREP

Recent reports of a linkage trend in 6p24-22 for schizophrenia (SZ), in different samples, were tempered by the concurrent evidence of negative reports in other samples. In the studies showing positive results, different definitions of affection and a wide spectrum of diagnoses were used. Our objectives were not only to test for linkage at 6p24-22 in the Eastern Quebec population, but also to test whether this putative vulnerability locus was either selectively linked to schizophrenia (SZ), or to bipolar disorder (BP), or to both major psychoses. Parametric and nonparametric linkage analyses with 12 microsatellite markers in 6p24-p22 were performed on a sample of 18 large multigenerational pedigrees (N = 354) either affected by SZ, or by BP, or equally affected by both major psychoses (i.e., mixed pedigrees). Three affection definitions were usually tested in our program: one on schizophrenia (SZ), one on bipolar disorder (BP), and one that comprised SZ and BP under the hypothesis of a susceptibility locus common to both in major psychoses (common locus, CL). The results of parametric analyses did not support a major gene hypothesis. However, in one large mixed pedigree (#151), we observed with the common locus phenotype (CL) lod scores of 2.49 and 2.15, respectively, at the D6S296 and D6S277 loci under a dominant model. Our data suggest the presence of a potential vulnerability locus at 6p24-22 that could be related to both schizophrenia and bipolar affective disorder. These results may be seen as congruent with former studies that used schizoaffective as well as schizophrenia diagnoses as entry criteria for the affected families, and used an affection definition that comprised affective psychoses as well as schizophrenia.

Negative outcomes: what is the evidence on self-administered treatments?

D.C. Mohr (1995) suggested that high deterioration rates may occur in self-directed treatments. The investigators examined data from 5 studies of self-administered treatment for depression and found in contrast much lower rates (9% vs. 19%) than those cited in Mohr's review. The negative response rates for the self-administered treatments compared favorably with the negative response rates in the therapist-administered treatments provided in the National Institute of Mental Health Treatment of Depression Collaborative Research Program. The findings indicate that it may be the manner in which participants are prepared for self-administered treatment that is critical.

Childhood/early adolescence-onset and adult-onset schizophrenia. Heterogeneity at the dopamine D3 receptor gene

BACKGROUND

The dopamine D3 receptor gene (DRD3) is a meaningful candidate gene because it unifies the dopamine and the limbic hypotheses for schizophrenia. We tested for an allelic association between schizophrenia and the DRD3 Mscl alleles, hypothesising heterogeneity between childhood/early adolescence-onset schizophrenia (CO-SZ) and adult-onset schizophrenia (A-SZ).

METHOD

The frequencies of the DRD3 alleles were compared between 70 DSM-III-R schizophrenics (35 CO-SZ and 35 A-SZ) and 79 controls.

RESULTS

Compared with the controls, the subsample of A-SZ, but not CO-SZ, showed an over-proportion (P = 0.025) of allele 1. The association was not found in the total sample, combining the two subsamples.

CONCLUSIONS

Consistently with former studies, our data suggest an aetiological heterogeneity between CO-SZ and A-SZ and a possible specificity of the excess of allele 1 to the familial form of schizophrenia and to schizophrenia with a better outcome.

Negative outcomes: what is the evidence on self-administered treatments?

D.C. Mohr (1995) suggested that high deterioration rates may occur in self-directed treatments. The investigators examined data from 5 studies of self-administered treatment for depression and found in contrast much lower rates (9% vs. 19%) than those cited in Mohr's review. The negative response rates for the self-administered treatments compared favorably with the negative response rates in the therapist-administered treatments provided in the National Institute of Mental Health Treatment of Depression Collaborative Research Program. The findings indicate that it may be the manner in which participants are prepared for self-administered treatment that is critical.

Characterization of In0 of Pseudomonas aeruginosa plasmid pVS1, an ancestor of integrons of multiresistance plasmids and transposons of gram-negative bacteria

Many multiresistance plasmids and transposons of gram-negative bacteria carry related DNA elements that appear to have evolved from a common ancestor by site-specific integration of discrete cassettes containing antibiotic resistance genes or sequences of unknown function. The site of integration is flanked by conserved segments coding for an integraselike protein and for sulfonamide resistance, respectively. These segments, together with the antibiotic resistance genes between them, have been termed integrons (H. W. Stokes and R. M. Hall, Mol. Microbiol. 3:1669-1683, 1989). We report here the characterization of an integron, In0, from Pseudomonas aeruginosa plasmid pVS1, which has an unoccupied integration site and hence may be an ancestor of more complex integrons. Codon usage of the integrase (int) and sulfonamide resistance (sul1) genes carried by this integron suggests a common origin. This contrasts with the codon usage of other antibiotic resistance genes that were presumably integrated later as cassettes during the evolution and spread of these DNA elements. We propose evolutionary schemes for (i) the genesis of the integrons by the site-specific integration of antibiotic resistance genes and (ii) the evolution of the integrons of multiresistance plasmids and transposons, in relation to the evolution of transposons related to Tn21.

Characterization of the nonenzymatic chloramphenicol resistance (cmlA) gene of the In4 integron of Tn1696: similarity of the product to transmembrane transport proteins

Integrons constitute a novel family of DNA elements which evolved by site-specific integration of discrete units between two conserved segments. On the In4 integron of Tn1696, a precisely inserted gene cassette of 1,549 bp conferring nonenzymatic chloramphenicol resistance (cmlA) is present between the streptomycin-spectinomycin resistance (aadA2) gene cassette and the 3'-conserved segment of the integron. In this study, we present the nucleotide sequence of the cmlA gene cassette of Tn1696, show its similarity to bacterial efflux systems and other transport proteins, and present evidence for alterations that its expression exerts on bacterial membranes. The cmlA gene cassette apparently carries its own promoter(s), a situation that has not heretofore been observed in the integrons of multiresistance plasmids and transposons of gram-negative bacteria. One or more of these promoters were shown to be functionally active in expressing a cat marker gene from promoter-probe vectors. The putative CmlA polypeptide appears to provoke a reduction of the content of the major porins OmpA and OmpC.

Characterization and expression of the prostatic arginine esterase gene, a canine glandular kallikrein

The prostatic arginine esterase gene was isolated from a genomic library prepared with dog liver DNA in lambda EMBL3. The selected clone contained an insert of approximately 17 kb which included the whole coding portion of arginine esterase mRNA (5 exons plus 4 introns), 2 kb upstream from the initiation site and 12 kb downstream from the polyadenylation site. The intron-exon boundaries were identical to all known mammalian kallikrein genes. The deduced amino acid sequence indicated a high degree of identity (51-61%) with other kallikreins expressed not only in the prostate but also in the pancreas of various animal species. The 5'-flanking sequences contained potential regulatory elements such as a variant TATA box (TTTAAA), a CCAAT box, a SP1 transcriptional factor binding site (GGGCGG), and two TGTCCT motifs resembling glucocorticoid response elements. Southern blot analysis with an amplified cDNA fragment of 487 bp corresponding to the 5' portion of the mRNA and with a DNA probe from a different portion of the arginine esterase gene indicated the presence of two to three homologous genes in the canine genome while in a previous study a single band was detected using a 400-bp arginine esterase cDNA corresponding to the 3' portion of the mRNA. These results suggest that the arginine esterase gene belongs to a small kallikrein gene family. Arginine esterase mRNA is expressed primarily in the prostate but also at an extremely low level (approximately a thousandfold less) in several other tissues including the liver, the gracilis thigh muscle, the kidney, and the pancreas.

On the evolution of Tn21-like multiresistance transposons: sequence analysis of the gene (aacC1) for gentamicin acetyltransferase-3-I(AAC(3)-I), another member of the Tn21-based expression cassette

The aminoglycoside-3-O-acetyltransferase-I gene (aacC1) from R plasmids of two incompatibility groups (R1033 [Tn1696], and R135) was cloned and sequenced. In the case of R1033, it was shown that the aacC gene is coded by a precise insertion of 833 bp between the aadA promoter and its structural gene in a Tn21 related transposon (Tn1696). This insertion occurs at the same target sequence as that of the OXA-1 beta-lactamase gene insertion in Tn2603. Upstream of the aacC gene, we found an open reading frame (ORF) which is probably implicated in the site-specific recombinational events involved in the evolution of this family of genetic elements. These results provide additional confirmation of the role of Tn21 elements as naturally occurring interspecific transposition and expression cassettes.

Precise insertion of antibiotic resistance determinants into Tn21-like transposons: nucleotide sequence of the OXA-1 beta-lactamase gene

Several plasmid-encoded beta-lactamases are on multiresistance transposable elements. The OXA-1 beta-lactamase gene is part of Tn2603, which is borne on the R plasmid RGN238. We report here the complete nucleotide sequence of the OXA-1 beta-lactamase gene and flanking sequences. The OXA-1 gene shows a greater than 50% sequence divergence from the OXA-2 gene, yet there is significant functional similarity at the peptide level. Analysis of 5' and 3' flanking sequences shows that Tn2603 differs from its probable precursor, Tn21, by a precise 1004-base-pair insertion, containing the OXA-1 structural gene, at the target sequence AAAGTT, which is located between the Tn21 streptomycin/spectinomycin (aadA) promoter and its structural gene. A 5- for 6-base repeat of the target sequence is found at the end of the insertion. The same precise insertion and repeat of the target sequence are found for the OXA-2 gene from R46. The 5' flanking regions of two other genes, the trimethoprim-resistance gene from R388 and the gentamicin resistance (aadB) gene from pDGO100, are greater than 98% homologous to the 5' flanking sequences of the OXA-1, OXA-2, and aadA genes until they diverge at the target sequence. From the available sequence data a recombinational hot spot is defined at the nucleotide level 5' of the aadA gene of Tn21, and a second potential hot spot is proposed 3' of this gene.