Chemical and Biological Threats to Public Safety
Frank A. Barile in Barile’s Clinical Toxicology, 2019
Anthrax is an infectious disease caused by the spore-forming bacterium Bacillus anthracis. The organism is an obligate aerobe and facultative anaerobe. The highly resistant, prominent polypeptide capsule of the endospore renders B. anthracis immune to most methods of disinfection or natural processes of inactivation.† Thus the organism may be present in the soil for decades, occasionally infecting grazing goats, sheep, and cattle. When ingested, the hibernating, dehydrated, protected spores release viable bacteria on contact with gastrointestinal (GI) fluids. Human infection occurs by three routes of exposure to anthrax spores: cutaneous, GI, and inhalation. Although human cases of anthrax are infrequent in North America, the U.S. military views anthrax as a potential biological terrorist threat because of its high resistance and ease of communicability through the air.
Histopathology
Peter D O Davies, Stephen B Gordon, Geraint Davies in Clinical Tuberculosis, 2014
Mycobacterium tuberculosis (MTB) is a tough, resistant bacterium protected by a lipid coat. It is an obligate pathogen and an obligate aerobe. It is an extremely efficient pathogen with an amazing capacity to survive adverse conditions. The most common route of infection is by inhalation of droplets from an infected person coughing. Droplets measure 2–10 microns in diameter and contain several TB bacilli. Their small size enables them to reach the alveoli without being trapped by the mucociliary escalator. Patients with smear-positive sputum with tuberculosis will infect individuals coming in close contact with them. The duration of contact, ventilation and pattern of cough will affect transmission. If the community has many infected individuals, there will be significant numbers of bacteria present in crowding situations – in homes, on buses, on trains and on various means of transport; in schools; and at sports events. Overcrowding of sleeping quarters will exacerbate the problem. The pathology that develops depends on whether the individual has had previous exposure to the bacterium, their state of health at the time and the virulence of the bacterium.
Biology of microbes
Philip A. Geis in Cosmetic Microbiology, 2006
One of the key reasons for these differences in oxygen tolerance among organisms is the effect of toxic oxygen by-products of metabolism. Oxygen accepts electrons and then becomes reduced into superoxide radical, hydrogen peroxide, and hydroxyl radical prior to its breakdown into water. Obligate aerobe organisms need enzymes that protect against these toxic O2 products. Such organisms evolved the superoxide dismutase and catalase enzymes as they developed the more efficient mechanisms of energy generation using oxygen-based metabolisms. The relationship between these enzymes and oxygen tolerance is also shown in Table 2.5.
Phase variation of Clostridium difficile virulence factors
Published in Gut Microbes, 2018
Brandon R. Anjuwon-Foster, Rita Tamayo
Phase variable expression of cwpV occurs through a post-transcriptional mechanism.17 In one orientation of the cwpV switch, the leader mRNA adopts a structure allowing transcriptional elongation into the cwpV coding sequence. In the opposite orientation, the leader mRNA forms an intrinsic terminator that causes premature termination of transcription, precluding transcription of the cwpV coding sequence and CwpV biosynthesis. To determine whether a similar cis-acting mechanism occurs via the flagellar switch, we evaluated the same transcriptional reporters in Bacillus subtilis, a spore-forming obligate aerobe, where we postulated that C. difficile-specific trans-acting regulatory factors would be absent. In contrast with results from C. difficile, we found that the flg ON and OFF reporters yielded equivalent activity in B. subtilis, indicating that no intrinsic transcription terminator is present in the flagellar switch. Northern blotting failed to detect evidence of premature transcript termination, suggesting that factor-dependent termination also does not occur.15 However, the low sensitivity of northern blotting using a Digoxigenin-labeled probe does not eliminate the possibility of factor-dependent termination.15
Targeting pulmonary tuberculosis using nanocarrier-based dry powder inhalation: current status and futuristic need
Published in Journal of Drug Targeting, 2019
Tulshidas S. Patil, Ashwini S. Deshpande, Shirish Deshpande, Pravin Shende
M Tb is considered as an acid-fast, obligate aerobe and intracellular pathogen. Due to their acid-fasting nature, they cannot be decolonised in an acid environment. Also, being an obligate aerobe and intracellular pathogen, bacilli find their sanctuary inside the alveolus where oxygen-rich environment is present. The clever bacilli are able to keep themselves intact after ingestion by the AMs and subsequent granuloma formation. This granuloma was referred as tubercle for the first time by Robert Koch, the founder of M Tb. In latent TB infection, the patient does not show any symptoms and feel sick. But the reactivation of the latent TB infection may occur in immune-compromised conditions like HIV infection, diabetes mellitus, corticosteroids therapy, etc.
Innovative strategies in the diagnosis and treatment of tuberculosis: a patent review (2014–2017)
Published in Expert Opinion on Therapeutic Patents, 2018
Tulshidas S. Patil, Ashwini S. Deshpande
In nearly 98% of the cases, M TB bacilli are transmitted through the air when the M TB diseased person coughs. being an acid-fast, obligate aerobe, and intracellular pathogen, M TB resides within the oxygen-rich and acidic environment of alveolar macrophages. Infected individuals with strong immunity are able to clear M TB infection without any treatment. In remaining ones, bacilli overcome the degradation mechanisms of AMs and survive inside them by forming a granuloma. Bacilli may spread through blood in different parts of the body such as lung apices, liver, spleen, lymph nodes, meninges, genitourinary tract, etc. During this period, the infected individual may not show any radiological piece of evidences but may start developing T-cell mediated immune response (i.e. start releasing IFN-γ). Thus, the tuberculin skin test and IFN-γ release assay become positive in this latent TB infection. In a maximum number of cases, pathogenesis ceases here. Whereas, in some cases, this TB infection may turn into TB disease. This development of infection into disease may be accelerated in immunocompromised conditions such as HIV infection, diabetes mellitus, TNF-α inhibitors, etc. [36]. If this TB infection is undetected or lately detected, it may enhance the risk of transmitting the infection to other individuals. Very few diagnostic methods have emerged until the end of 2017. The rapid and accurate diagnosis in the earliest period is of utmost importance in global TB control, especially in the case of smear-negative and drug-resistant TB. Also, the development of diagnostic tools that can accurately detect the LTBI and can monitor the treatment responses is an essential prerequisite.
Related Knowledge Centers
- Anaerobic Respiration
- Bacteria
- Cellular Respiration
- Electron Transport Chain
- Fermentation
- Oxidative Stress
- Oxygen
- Mycobacterium Tuberculosis
- Adenosine Triphosphate
- Acid-Fastness