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Biomedical subjects

R M Atlas

Publications and source records attributed to R M Atlas.

At least 19 recordsLinked to original sources
PubMed2002

Responding to the threat of bioterrorism: a microbial ecology perspective--the case of anthrax.

Anthrax is a disease of herbivores caused by the gram-positive bacterium Bacillus anthracis. It can affect cattle, sheep, swine, horses and various species of wildlife. The routes for the spread among wildlife are reviewed. There are three kinds of human anthrax--inhalation, cutaneous, and intestinal anthrax--which differ in their routes of infection and outcomes. In the United States, confirmation of cases is made by the isolation of B. anthracis and by biochemical tests. Vaccination is not recommended for the general public; civilians who should be vaccinated include those who, in their work places, come in contact with products potentially contaminated with B. anthracis spores, and people engaged in research or diagnostic activities. After September 11, 2001, there were bioterrorism anthrax attacks in the United States: anthrax-laced letters sent to multiple locations were the source of infectious B. anthracis. The US Postal Service issued recommendations to prevent the danger of hazardous exposure to the bacterium. B. anthracis spores can spread easily and persist for very long times, which makes decontamination of buildings very difficult. Early detection, rapid diagnosis, and well-coordinated public health response are the key to minimizing casualties. The US Government is seeking new ways to deter bioterrorism, including a tighter control of research on infectious agents, even though pathogens such as B. anthracis are widely spread in nature and easy to grow. It is necessary to define the boundary between defensive and offensive biological weapons research. Deterring bioterrorism should not restrict critical scientific research.

Anthrax↗
PubMed1999

Legionella: from environmental habitats to disease pathology, detection and control.

Studies on Legionella show a continuum from environment to human disease. Legionellosis is caused by Legionella species acquired from environmental sources, principally water sources such as cooling towers, where Legionella grows intracellularly in protozoa within biofilms. Aquatic biofilms, which are widespread not only in nature, but also in medical and dental devices, are ecological niches in which Legionella survives and proliferates and the ultimate sources to which outbreaks of legionellosis can be traced. Invasion and intracellular replication of L. pneumophila within protozoa in the environment play a major role in the transmission of Legionnaires' disease. Protozoa provide the habitats for the environmental survival and reproduction of Legionella species. L. pneumophila proliferates intracellularly in various species of protozoa within vacuoles studded with ribosomes, as it also does within macrophages. Growth within protozoa enhances the environmental survival capability and the pathogenicity (virulence) of Legionella. The growth requirements of Legionella, the ability of Legionella to enter a viable non-culturable state, the association of Legionella with protozoa and the occurrence of Legionella within biofilms complicates the detection of Legionella and epidemiological investigations of legionellosis. Polymerase chain reaction (PCR) methods have been developed for the molecular detection of Legionella and used in environmental and epidemiological studies. Various physical and chemical disinfection methods have been developed to eliminate Legionella from environmental sources, but gaining control of Legionella in environmental waters, where they are protected from disinfection by growing within protozoa and biofilms, remains a challenge, and one that must be overcome in order to eliminate sporadic outbreaks of legionellosis.

Animals↗
PubMed1998

Biocatalytic sulfur removal from fuels: applicability for producing low sulfur gasoline.

Environmental regulations are driving R&D efforts to produce low sulfur fuels, including diesel fuel and gasoline for motor vehicles. Biocatalytic sulfur removal from fuels has potential applicability for producing low sulfur gasoline. Microbial biocatalysts have been identified that can biotransform sulfur compounds found in fuels, including ones that selectively remove sulfur from dibenzothiophene heterocyclic compounds. Most attention is give to the 4S pathway of Rhodococcus, which can remove sulfur from substituted and unsubstituted dibenzothiophenes, including sulfur compounds that hinder chemical catalysis and that resist removal by mild hydrotreatment. Various bioreactor and bioprocess designs are being tested for use with biocatalysts, including recombinant biocatalysts, for use in removing sulfur from fuels and feedstocks within the petroleum refinery stream. With bioprocess improvements that enhance biocatalyst stability, achieve faster kinetics, improve mass transfer limitations, temperature and solvent tolerance, as well as broaden substrate specificity to attack a greater range of heterocyclic compounds, biocatalysis may be a cost-effective approach to achieve the production of low sulfur gasoline. The challenge will be to accomplish these improvements by the time the regulations for low sulfur gasoline and other vehicle fuels go into effect in order to be competitive with emerging nonbiological desulfurization technologies.

Fossil Fuels↗
PubMed1998

Preventing the misuse of microorganisms: the role of the American Society for Microbiology in protecting against biological weapons.

The American Society for Microbiology's (ASM) involvement with issues surrounding biological weapons began during World War II and continues to the present time. The Public and Scientific Affairs Board (PSAB) of the ASM has played an important role in monitoring and responding to legislative and regulatory issues involving biological weapons. As this review makes apparent, there is no consensus of opinion among scientists on their role in biological defense research, or is it likely that there will ever be complete agreement. There is consensus that steps should be taken to prevent biological warfare and that openness of scientific research and global surveillance of disease outbreaks can significantly increase transparency for detecting development of biological weapons. The ASM recommends increased attention to and efforts directed toward global surveillance of disease outbreaks, not only to aid public health organizations in improving human health, but also to establish baseline data against which unusual disease outbreaks can be assessed. Issues of how best to increase global security and to achieve a scientifically based verification protocol of the Biological Weapons Convention are important and continue to be addressed by the ASM.

Biological Warfare↗
PubMed1998

The medical threat of biological weapons.

There is a heightened threat of biological weapons being used for biological warfare or bioterrorism. Many of the microorganisms and toxins that may be used as such biological weapons can easily be acquired and mass produced. Dissemination of aerosols of these biological agents can produce mass casualties. If used by a terrorist they may overwhelm our current public health system. Some biological agents, such as Bacillus anthracis (anthrax) and botulinum toxin, are considered far more likely than others to be used as biological weapons; smallpox virus was apparently produced in mass quantities by the former Soviet Union and may also be a serious threat. The release of such agents could go undetected for several hours or days and would be followed by mass illnesses and a first line of response by the public health community. Rapid epidemiological investigation to identify the nature of the disease outbreak would be critical for limiting casualties. For many, but not all, biological agents there are medical treatments that can greatly lower the mortality rate. There currently are, however, insufficient supplies of medicinals and trained personnel to cope with a massive bioterrorist or biological warfare use of biological weapons. Increasing our preparedness is critical.

Bacterial Infections↗
PubMed1996

Legionella contamination of dental-unit waters.

Volume 61, no. 4, p. 1211, column 2, line 40: this sentence should read as follows. "The viable-culture methods for Legionella sp. detection, however, often fail, and the Centers for Disease Control and Prevention has turned, when necessary, to PCR for epidemiological investigations of Legionnaires' disease and Pontiac fever (19)." Line 46: "(6)" should read "(11)." [This corrects the article on p. 1208 in vol. 61.].

Journal Article↗
PubMed1995

Legionella contamination of dental-unit waters.

Water samples collected from 28 dental facilities in six U.S. states were examined for the presence of Legionella pneumophila and other Legionella spp. by the PCR-gene probe, fluorescent-antibody microscopic, and viable-plate-count detection methods. The PCR and fluorescent-antibody detection methods, which detect both viable and viable nonculturable Legionella spp., gave higher counts and rates of detection than the plate count method. By the PCR-gene probe detection method, Legionella spp. were detected in 68% of the dental-unit water samples and L. pneumophila was detected in 8%. Concentrations of Legionella spp. in dental-unit water reached 1,000 organisms per ml or more in 36% of the samples, and 19% of the samples were in the category of 10,000/ml or above. L. pneumophila, when present in dental-unit water, never reached concentrations of 1,000/ml or more. Microscopic examination with fluorescent-antibody staining indicated that the contamination was in the dental-unit water lines rather than in the handpieces. Legionella spp. were present in 61% of potable water samples collected for comparative analysis from domestic and institutional faucets and drinking fountains; this percentage was not significantly different from the rate of detection of Legionella spp. in dental-unit water. However, in only 4% of the potable water samples did Legionella spp. reach concentrations of 1,000 organisms per ml, and none was in the 10,000 organisms-per-ml category, and so health-threatening levels of Legionella spp. in potable water were significantly lower than in dental-unit water. L. pneumophila was found in 2% of the potable water samples, but only at the lowest detectable level.(ABSTRACT TRUNCATED AT 250 WORDS)

DNA Probes↗
PubMed1994

Detection of Salmonella spp. in oysters by PCR.

PCR DNA amplification of a region of the himA gene of Salmonella typhimurium specifically detected Salmonella spp. In oysters, 1 to 10 cells of Salmonella spp. were rapidly detected by the PCR following a pre-enrichment step to increase sensitivity and to ensure that detection was based on the presence of viable Salmonella spp.

Animals↗
PubMed1994

Frequency of genes in aromatic and aliphatic hydrocarbon biodegradation pathways within bacterial populations from Alaskan sediments.

A significant proportion of the naturally occurring hydrocarbon-degrading populations within Alaskan sediments affected by the Exxon Valdez oil spill had both the xylE and alkB genes and could convert hexadecane and naphthalene to carbon dioxide; a greater proportion of the population had xylE than had alkB, reflecting the composition of the residual oil at the time of sampling; nearly equal populations with xylE alone, alkB alone, and xylE + alkB genes together were found after exposure to fresh crude oil; populations with xylE lacking alkB increased after enrichment on naphthalene. Thus, the genotypes of hydrocarbon-degrading populations reflected the composition of the hydrocarbons to which they were exposed.

Alaska↗
PubMed1993

Effect of amplicon size on PCR detection of bacteria exposed to chlorine.

The effect of amplicon size on the PCR detection of Legionella pneumophila after chlorine inactivation was investigated. Two amplicons specific to the L. pneumophila mip gene were used for the PCR analyses: a 650-bp amplicon and smaller 168-bp amplicon within the 650-bp amplicon; a 108-bp amplicon specific to species rRNA coding sequence also was used. After exposure to chlorine, viable agar grown cells were not detected by plate counts or direct counts with p-iodonitrotetrazolium (INT) after 1 min for treatment at 10 mg/l, after 2 min for treatment at 5 mg/l, and after 4 min for treatment at 2.5 mg/l; viable water grown cells were present at least 4 min after biocide addition even with a chlorine dose of 5 mg/l. At the 10-mg/l dosage, PCR products from the 168-bp amplicon were detected on agarose gels up to 16 min after chlorination; even after 24 hr of PCR the 168-bp products were detectable using a capture probe hybridization assay. However, the 650-bp target was not detected after 4 min chlorine contact time at the same biocide dosage using agarose gels, and PCR products could not be detected by hybridization after 32 min. At lower chlorine concentrations, a similar pattern was seen with the 168-bp amplicon detectable longer after biocide addition than the 650-bp mip amplification target. On the basis of these data, larger amplicons appear to correlate better with viability of L. pneumophila in water samples.

Bacterial Proteins↗
PubMed1993

Hydroxylation and biodegradation of 6-methylquinoline by pseudomonads in aqueous and nonaqueous immobilized-cell bioreactors.

Selective culturing of pseudomonads that could degrade quinoline led to enrichment cultures and pure cultures with expanded substrate utilization and transformation capabilities for substituted quinolines in immobilized and batch cultures. Immobilized cells of the pseudomonad cultures rapidly transformed quinolines to hydroxyquinolines in bioreactors and were able to tolerate higher substrate concentrations compared with batch cultures. After prolonged incubation on a mixture of quinoline and 6-methylquinoline, a quinoline-degrading culture of Pseudomonas putida developed the ability to biodegrade 6-methylquinoline, which initially was resistant to microbial attack, as a sole source of carbon and energy. 6-Methylquinoline was also degraded in a nonaqueous solution by this strain of P. putida when a solution of 6-methylquinoline in decane was flowed through an immobilized-cell fixed-bed bioreactor.

Bacteriological Techniques↗
PubMed1992

Molecular methods for environmental monitoring and containment of genetically engineered microorganisms.

Plans to introduce genetically engineered microorganisms into the environment has led to concerns over safety and has raised questions about how to detect and to contain such microorganisms. Specific gene sequences, such as lacZ, have been inserted into genetically engineered microorganisms to permit their phenotypic detection. Molecular methods have been developed based upon recovery of DNA from environmental samples and gene probe hybridization to specific diagnostic gene sequences for the specific detection of genetically engineered microorganisms. DNA amplification using the polymerase chain reaction has been applied to enhance detection sensitivity so that single gene targets can be detected. Detection of messenger RNA has permitted the monitoring of gene expression in the environment. The use of reporter genes, such as the lux gene for bioluminescence, likewise has permitted the observation of gene expression. Conditional lethal constructs have been developed as models for containment of genetically engineered microorganisms. Suicide vectors, based upon the hok gene have been developed as model containment systems.

Bacteria↗
PubMed1992

Maintenance and killing efficiency of conditional lethal constructs in Pseudomonas putida.

Conditional lethal (suicidal) genetic constructs were designed and employed in strains of Pseudomonads as models for containment of genetically-engineered microbes that may be deliberately released into the environment. A strain of Pseudomonas putida was formed with a suicide vector designated pBAP24h that was constructed by cloning the host killing gene (hok) into the RSF1010 plasmid pVDtac24 and placing it under the control of the tac promoter. After hok induction in P. putida only 40% of surviving cells continued to bear the hok sequences within 4 h of induction; in contrast, 100% of the cells in uninduced controls bore hok. A few survivors that demonstrated resistance to hok-induced killing developed in P. putida, which may have been due to a mutation or physiological adaptation that rendered the membrane 'resistant' to hok. Conditional lethal strains of P. putida also were formed by inserting gef (a chromosomal homolog of hok) under the control of the tac promoter into the chromosome using a transposon. Constructs with chromosomal gef, as well as an RK2-derived plasmid construct containing gef, were only marginally more stable than the hok constructs; they were effective in killing P. putida when induced and within 2 h post-induction killing from either gef construct resulted in a 10(3)-10(5)-fold reduction in viable cell count compared to uninduced controls.

Cloning, Molecular↗
PubMed1992

Differentiation of Giardia duodenalis from other Giardia spp. by using polymerase chain reaction and gene probes.

Giardia spp. are waterborne organisms that are the most commonly identified pathogenic intestinal protozoans in the United States. Current detection techniques for Giardia species in water include microscopy and immunofluorescence techniques. Species of the genus Giardia are classified on the basis of taxonomic criteria, such as cell morphology, and on host specificity. We have developed a polymerase chain reaction- and gene probe-based detection system specific for Giardia spp., which can discriminate between the relevant species of the G. duodenalis type pathogenic to humans and other Giardia species that are not human pathogens. This method can detect a single Giardia cyst and is therefore sensitive enough for environmental monitoring.

Animals↗