Evaluation of the Staph-Zym system with staphylococci isolated from bovine intramammary infections

A total of 148 staphylococci isolated from bovine intramammary infections were used to evaluate the Staph-Zym system (ROSCO, Taastrup, Denmark). The overall accuracy of the system was 91.9%. The system correctly identified all strains of Staphylococcus aureus, Staphylococcus simulans, and Staphylococcus xylosus and 95% of Staphylococcus intermedius strains. Of 33 Staphylococcus hyicus strains, 31 (93.9%) were classified correctly by the Staph-Zym system, as well as 8 (80%) of 10 Staphylococcus chromogenes strains. All 11 Staphylococcus epidermidis strains and the 1 Staphylococcus haemolyticus strain included in the study were identified, but the Staph-Zym system had difficulty distinguishing strains of Staphylococcus warneri and Staphylococcus hominis from other species in the S. epidermidis group. The Staph-Zym system correctly identified all six S. xylosus strains and two of three Staphyloccus sciuri strains. The Staph-Zym system was considered an acceptable alternative to conventional methods for identification of bovine mammary gland isolates.     

Identification of veterinary pathogens by use of commercial identification systems and new trends in antimicrobial susceptibility testing of veterinary pathogens.

Veterinary diagnostic microbiology is a unique specialty within microbiology. Although isolation and identification techniques are similar to those used for human pathogens, many veterinary pathogens require unique cultivation or identification procedures. Commercial identification systems provide rapid, accurate identification of human pathogens. However, the accuracy of these systems with veterinary pathogens varies widely depending on the bacterial species and the host animal from which it was isolated. Increased numbers of veterinary strains or species in the data bases of the various systems would improve their accuracy. Current procedures and interpretive criteria used for antimicrobial susceptibility testing of veterinary pathogens are based on guidelines used for human pathogens. The validity of these guidelines for use with veterinary pathogens has not been established. As with fastidious human pathogens, standardized methodologies and quality control isolates are needed for tests of organisms such as Actinobacillus pleuropneumoniae and Haemophilus somnus. Furthermore, interpretive criteria for veterinary antimicrobial agents based on the MIC for veterinary pathogens, the pharmacokinetics of the antimicrobial agent in the host animal, and in vivo efficacy of the antimicrobial agent are needed. This article reviews both the commercial identification systems evaluated with veterinary pathogens and current methods for performing and interpreting antimicrobial susceptibility tests with veterinary pathogens. Recommendations for future improvements in both areas are discussed.     

Haemodynamic model of a unilateral iliac stenosis with an aortoiliac bypass

A hydrodynamic model for the part of the human arterial network below the renal arteries has been constructed using specially fabricated distensible tubes and a pulsatile pump to simulate an aortoiliac bypass. The experiments and the computer model indicated that no ‘steal’ occurred due to the insertion of the bypass graft. Also, the results showed that the length of the stenosis had a non-systematic apparent effect on the physiological significance of the obstruction and that the kinetic power represented only a small percentage of the total power. The total power efficiency of the bypass graft was unaffected by its elastic properties. The experimental investigation also indicated that the pressure drop across the stenosis was considerably larger than the drop calculated using the Poiseuille flow relationship when the stenosis was severe. Therefore, a critical arterial stenosis value cannot be defined as an obstruction of a constant percentage reduction of luminal area. It varies directly with the effective cross-sectional area and inversely with the flow rate. The value of angiography in assessing the functional significance of any arterial stenosis is there-fore limited. A better method for evaluation requires quantitative measurements of local blood pressure and blood flow, not only at rest, but also under conditions creating augmented flows due to exercise.     

Disseminated cryptococcosis presenting as cellulitis with necrotizing vasculitis.

Patients with disseminated cryptococcosis infrequently present with cutaneous involvement. Skin lesions, when present, are usually multiple and polymorphous in appearance. Cellulitis caused by Cryptococcus neoformans is rare, and necrotizing vasculitis associated with cryptococcal vascular invasion has not to our knowledge been reported. We report here a case of disseminated cryptococcosis in a renal transplant recipient who had cellulitis and necrotizing vasculitis and in whom a diagnostic skin biopsy allowed for early therapy with cure and salvage of the renal allograft.     

Temporal pattern of herpes simplex virus type 1 infection and cell death in the mouse brain stem: influence of guanosine nucleoside analogues

Levels of bystander death occurring in herpes simplex virus type 1 (HSV-1)-infected mouse brain stems were studied, as well as the extent to which bystander death is influenced by guanosine nucleoside analogue treatment. Consecutive sections from brain stems of HSV-1-infected mice were stained alternately for (i) viral infection and (ii) cell death (TUNEL assay). Virus antigen was detectable in brain stems on day 3 of infection, while TUNEL staining was comparatively lower. An increase in the extent of TUNEL staining was observed on day 4 of infection. Despite this increase, however, the ratio of TUNEL-stained to infection marker-stained tissue still indicated that the amount of TUNEL staining remained lower than infection staining at this time point. On days 5 and 6 of infection, TUNEL staining continued to increase and the TUNEL/infection marker ratio switched on day 6 in favour of excess TUNEL staining, which was observed in and around the foci of infection, suggesting bystander death. The excess TUNEL staining on day 6 of infection was further increased on treatment with antivirals. The significance and implications of these results are discussed with respect to the nature and mechanism of action of the TUNEL assay, dynamics of primary HSV-1 infection, immunological influences and potential effects of antiviral treatment. The potential problems of the TUNEL assay are considered in the context of viral infection and the TUNEL assay, in combination with infection marker staining, may potentially provide a model system for quantitative analysis of true bystander death during HSV infection in vivo.     

Finger opening in an overarm throw is not triggered by proprioceptive feedback from elbow extension or wrist flexion

 Accuracy in an overarm throw requires great precision in the timing of finger opening. We tested the hypothesis that finger opening in an overarm throw is triggered by proprioceptive feedback from elbow extension or wrist flexion. The hypothesis was tested in two ways: first, by unexpectedly perturbing elbow extension or slowing wrist flexion and determining whether changes occurred in finger opening, and second, by measuring the latency from the start of these joint rotations to the start of finger opening. Subjects threw balls fast and accurately from a sitting or standing position while joint rotations were recorded with the search-coil technique. Elbow extension was unexpectedly blocked near the start of forward motion of the hand by a rope attached to the wrist that passed through a catch mechanism located behind the subject. In spite of a slowing or complete block of elbow extension, and in some cases a replacement of elbow extension by elbow flexion, finger opening always occurred and at the same latency as for normal throws. Wrist flexion was slowed in seven of eight subjects when subjects changed from throwing with a light ball (14 g, 70 mm diam.) to a heavy ball (210 g, 65 mm diam.). For the first throw with the heavy ball, this slowing was neither fully anticipated by the subject nor compensated for by the changed proprioceptive feedback associated with the slowing. Consequently, the timing of finger opening was unchanged and (to the surprise of the thrower) the ball went high. Furthermore, in unperturbed throws with tennis balls, the latency from onset of wrist flexion or elbow extension to onset of finger opening was too short for either to have triggered finger opening (across subjects means were 4 ms for wrist flexion and 21 ms for elbow extension). In additional analysis, no relation was found between the time of onset of earlier occurring rotations at the shoulder and the time of onset of finger opening. We concluded that, although a role for all proprioceptive feedback in triggering finger opening cannot be disproved by these experiments, it can be ruled out for feedback arising from elbow extension and wrist flexion, and it seems unlikely for feedback arising from events occurring very early in the throw. The more likely possibility is that finger opening in an overarm throw is triggered by a central command based on an internal model of hand trajectory. Received: 6 July 1998 / Accepted: 16 October 1998     

APOE is a potential modifier gene in an autosomal dominant form of frontotemporal dementia (IBMPFD).

PURPOSE: Inclusion-body myopathy, Paget's disease of bone and frontotemporal dementia is an adult-onset autosomal dominant illness (IBMPFD) caused by mutations in the valosin-containing protein (VCP) on chromosome 9p21.1-p12. The penetrance of the gene is 82% for myopathy, 49% for Paget's disease, but may be as low as 30% for frontotemporal dementia. Modifier genes could account for decreased frontotemporal dementia penetrance. In this study apolipoprotein-E (APOE) was evaluated for this role in IBMPFD families based on its known modifier effect in Alzheimer's disease. METHODS: From a database of 231 members of 15 families, 174 had APOE genotype available for analysis. Logistic regressions on APOE genotype and frontotemporal dementia were performed, using appropriate covariates. RESULTS AND CONCLUSION: FTD was associated with APOE 4 genotype (P=0.0002), myopathy (P=0.0006), and age (P=0.01), but not microtubule associated protein tau (MAPT) H2 haplotype (P=0.5) or gender (0.09) after adjustment for membership in pedigrees with at least one APOE 4 genotype. These data suggest a potential link between APOE 4 genotype and the specific form of frontotemporal dementia found in IBMPFD. The molecular basis of this link bears further investigation. We did not observe an association of frontotemporal dementia and H2 MAPT haplotype.     

Positional cloning of the gene for X-linked retinitis pigmentosa 3: homology with the guanine-nucleotide-exchange factor RCC1

The gene for retinitis pigmentosa 3 (RP3), the most frequent form of X- linked RP (XLRP), has been mapped previously to a chromosome interval of less than 1000 kbp between the DXS1110 marker and the OTC locus at Xp21.1-p11.4. Employing a novel technique, YAC Representation Hybridization (YRH)', we have recently identified a small XLRP associated microdeletion in this interval, as well as several putative exons including the 3' end of a gene that was truncated by the deletion. cDNA library screening and sequencing of a cosmid centromeric to the deletion has now enabled us to identify numerous additional exons and to detect several point mutations in patients with XLRP. The predicted gene product shows homology to RCC1, the guanine-nucleotide- exchange factor (GEF) of the Ras-like GTPase Ran. Our findings suggest that we have cloned the long-sought RP3 gene, and that it may encode the GEF of a retina-specific GTP-binding protein.      

High throughput parallel analysis of hundreds of patient samples for more than 100 mutations in multiple disease genes

As more mutations are identified in genes of known sequence, there is a crucial need in the areas of medical genetics and genome analysis for rapid, accurate and cost-effective methods of mutation detection. We have developed a multiplex allele-specific diagnostic assay (MASDA) for analysis of large numbers of samples (> 500) simultaneously for a large number of known mutations (> 100) in a single assay. MASDA utilizes oligonucleotide hybridization to interrogate DNA sequences. Multiplex DNA samples are immobilized on a solid support and a single hybridization is performed with a pool of allele-specific oligonucleotide (ASO) probes. Any probes complementary to specific mutations present in a given sample are in effect affinity purified from the pool by the target DNA. Sequence-specific band patterns (fingerprints), generated by chemical or enzymatic sequencing of the bound ASO(s), easily identify the specific mutation(s). Using this design, in a single diagnostic assay, we tested samples for 66 cystic fibrosis (CF) mutations, 14 beta-thalassemia mutations, two sickle cell anemia (SCA) mutations, three Tay-Sachs mutations, eight Gaucher mutations, four mutations in Canavan disease, four mutations in Fanconi anemia, and five mutations in BRCA1. Each mutation was correctly identified. Finally, in a blinded study of 106 of these mutations in > 500 patients, all mutations were properly identified. There were no false positives or false negatives. The MASDA assay is capable of detecting point mutations as well as small insertion or deletion mutations. This technology is amenable to automation and is suitable for immediate utilization for high-throughput genetic diagnostics in clinical and research laboratories.