Rapid identification using pyrolysis mass spectrometry and artificial neural networks of Propionibacterium acnes isolated from dogs.

Curie-point pyrolysis mass spectra were obtained from reference Propionibacterium strains and canine isolates. Artificial neural networks (ANNs) were trained by supervised learning (with the back-propagation algorithm) to recognize these strains from their pyrolysis mass spectra; all the strains isolated from dogs were identified as human wild type P. acnes. This is an important nosological discovery, and demonstrates that the combination of pyrolysis mass spectrometry and ANNs provides an objective, rapid and accurate identification technique. Bacteria isolated from different biopsy specimens from the same dog were found to be separate strains of P. acnes, demonstrating a within-animal variation in microflora. The classification of the canine isolates by Kohonen artificial neural networks (KANNs) was compared with the classical multivariate techniques of canonical variates analysis and hierarchical cluster analysis, and found to give similar results. This is the first demonstration, within microbiology, of KANNs as an unsupervised clustering technique which has the potential to group pyrolysis mass spectra both automatically and relatively objectively.

Interference with the oxidative response of neutrophils by Streptococcus pneumoniae.

BACKGROUND: Pneumococcal infections are still a major clinical problem. Polymorphonuclear leucocytes (neutrophils) are considered to have a key role in the host's defence against Streptococcus pneumoniae but the mechanisms by which they kill the pneumococcus remain unclear. As reactive oxygen species are regarded as a major antimicrobial defence of phagocytes an attempt has been made to establish their role in the response of neutrophils to S pneumoniae. METHODS: S pneumoniae isolated from patients with bacteraemic pneumococcal pneumonia were incubated with neutrophils in suspension and superoxide production was measured by reduction of ferricytochrome c. RESULTS: S pneumoniae did not stimulate superoxide production alone or in the presence of normal human serum. Spontaneous superoxide production by neutrophils was actually abrogated by S pneumoniae, as was the powerful respiratory burst stimulated by phorbol myristate acetate. This phenomenon depended on both the dose and the viability of the bacteria. With S pneumoniae in the logarithmic phase of growth inhibitory activity was confined to the organisms themselves but with organisms undergoing autolysis it was also present in filtered supernatants, suggesting that the inhibitory activity can be attributed to a factor released during autolysis. CONCLUSIONS: S pneumoniae can interfere with the respiratory burst of neutrophils. This property may help to explain the pathogenicity of the organism.

Absence of measles, mumps, and rubella viral genomic sequences from multiple sclerosis brain tissue by polymerase chain reaction.

We tested for measles, mumps, and rubella viruses in multiple sclerosis by polymerase chain reaction (PCR). Using RNA extracted from 19 multiple sclerosis and 8 control brain specimens, nested PCR was performed after reverse transcription (RT) of the RNA to cDNA using primer pairs directed against two regions in the genomes of measles and mumps viruses and one region in the rubella virus genome. Despite enhanced sensitivity of nested RT PCR, measles, mumps, and rubella viral genomic sequences were not found in any brain specimen.

Release of gentamicin from acrylic bone cement. Elution and diffusion studies.

It has been generally assumed that release of antibiotic from methylmethacrylate occurs either from the surface, through pores in the matrix of the cement, or by diffusion through the matrix. In vitro and in vivo studies of the release of antibiotic from cement have produced variable and inconsistent results. In our laboratory, preliminary observations suggested that antibiotic is released from methylmethacrylate by flow through an interconnecting series of voids and cracks in the cement, rather than through diffusion after having been homogeneously distributed throughout the cement. Therefore, experiments were performed to answer the fundamental question of whether the matrix of methylmethacrylate bone cement is permeable to gentamicin. In vivo elution studies were performed on injection-molded rods of methylmethacrylate that had been loaded with two different amounts of gentamicin. The first group of rods contained 0.5 gram of gentamicin for each packet and the second, 1.5 grams for each packet. The rods were embedded subcutaneously in the subcostal region of sheep for three months. Bioassay of sections of the rods, using the tube-diffusion technique of Mitchison and Spicer, showed that the more highly loaded cement had released a significantly greater proportion of gentamicin. This occurred because the more highly loaded cement contained a greater number of defects that contained gentamicin (filled voids and interconnecting cracks). In vitro diffusion studies were also performed, using 0.8-millimeter-thick disks of methylmethacrylate that did not contain antibiotic. Test solutions of either gentamicin or methylene blue were placed in the inner compartments of diffusion chambers. The outer compartments contained tissue-culture medium 199, which was sampled monthly and assayed for gentamicin or methylene blue.(ABSTRACT TRUNCATED AT 250 WORDS)

Detection of DNA transcripts of measles genes in multiple sclerosis brain tissue by transfection.

Transfection studies on DNA obtained from 16 multiple sclerosis (MS) and 13 non-MS brain tissues suggested that 3/16 (19%) MS and 3/13 (23%) non-MS samples contained contaminating measles virus double-stranded RNA, and that 6/16 (38%) MS and 0/13 non-MS samples contained DNA transcripts of measles genes. It is argued that the DNA transcripts most probably originated from dual retrovirus and measles infections in the subjects.

Comparison of survival times of mice inoculated with brain tissue from various neurological diseases.

Mice inoculated intracerebrally before the age of 5 days with homogenates of autopsied brain tissue from patients with Creutzfeldt-Jakob (C-J), Alzheimer's, or Pick's diseases showed highly significant decreases in life span when compared with sham-inoculated control mice. With C-J disease there was strong indication of horizontal transmission of the agent to uninoculated mice caged with the inoculated mice. While the results with C-J disease were not unexpected in view of the known infectious etiology of the disease, the results obtained with Alzheimer's and Pick's diseases suggest that previously undetermined infectious or toxic agents may be associated with these two diseases, which currently have unresolved etiologies. Mice inoculated with autopsied brain tissue from patients with multiple sclerosis or subacute sclerosing panencephalitis had life spans similar to those of the control mice.

Application of potassium thiocyanate as a destaining agent for confirming the specificity of viral immunofluorescence.

A study was made of the destaining effects of various agents on measles-infected monolayers which were stained by the indirect method of immunofluorescence. It was found that KSCN, a chaotropic agent, gave the required destaining but was nonspecific in its action, removing antigen as well as adsorbed immunoglobulins. By using a KSCN-EDTA destaining solution, it was shown that two sequential restainings of infected monolayers were possible, which permitted the demonstration of the specificity of the observed immunofluorescence. The technique may be of particular use with clinical specimens in which relatively few cells give immunofluorescence and when the specificity of this fluorescence is questioned.

Botryomycosis: a complication of extensive follicular mucinosis.

A case of extensive follicular mucinosis, without evidence of lymphoma and present for 9 years, was complicated by cutaneous botryomycosis which initially resembled sporotrichosis. Scanty Staphylococcus aureus was cultured with difficulty. No immunodeficiency could be demonstrated, and the importance of a local factor (namely follicular mucinosis) in the production of the characteristic histological reaction of botryomycosis is emphasized.

Sexing mouse pups.

Data on the early sexing of random-bred albino mice (Mus musculus) is presented. It is shown that accurate sexing of newborn pups cannot be made by anogenital distance measurement unless the proportion of animals falling into the overlap-zones are discarded. However, 8-day-old pups may be sexed by the display of abdominal (inguinal) teats in the females.