In Marsha's clinical case, the doctor suspected tuberculosis due to her symptoms and potential exposure to *Mycobacterium tuberculosis* in a Nigerian medical lab. To prevent transmission, she was ordered to isolate at home in a single room, wear a respiratory mask, and take a semester off school. She was prescribed a drug cocktail of isoniazid and rifampin to be taken three times daily for at least three months.

Clinical Focus: Tuberculosis Treatment and Quarantine

In a clinical case, a $${}20$$-year-old student returning to the United States after interning for a tuberculosis testing organization in Nigeria experienced persistent fatigue, coughing, loss of appetite, night sweats, and a low-grade fever of $${}37.4$$ °C ($${}99.3$$ °F). These symptoms subsequently worsened over $${}2$$ weeks to sharp chest pains when breathing, a fever of $${}38.2$$ °C ($${}100.8$$ °F), and sputum containing blood and white clumps.

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Tuberculosis (TB) is one of the deadliest infectious diseases in human history. Although tuberculosis infection rates in the United States are extremely low, the CDC estimates that about one-third of the world’s population is infected with *Mycobacterium tuberculosis*, the causal organism of TB,

Tuberculosis

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Microbiology covers the scope and sequence requirements for a single-semester microbiology course for non-majors. The book presents the core concepts of microbiology with a focus on applications for careers in allied health. The pedagogical features of the text make the material interesting and accessible while maintaining the career-application focus and scientific rigor inherent in the subject matter. Microbiology’s art program enhances students’ understanding of concepts through clear and effective illustrations, diagrams, and photographs.

Microbiology is produced through a collaborative publishing agreement between OpenStax and the American Society for Microbiology Press. The book aligns with the curriculum guidelines of the American Society for Microbiology.

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*M. tuberculosis* is an acid-fast, high G + C, gram-positive, nonspore-forming rod. Its cell wall is rich in waxy mycolic acids, which make the cells impervious to polar molecules. After inhalation, the bacteria enter the alveoli. The cells are phagocytized by macrophages but can survive and multiply within these phagocytes because of the protection by the waxy mycolic acid in their cell walls. If not eliminated by macrophages, the infection can progress, causing an inflammatory response and an accumulation of neutrophils and macrophages in the area. Several weeks or months may pass before an immunological response is mounted by T cells and B cells. Eventually, the lesions in the alveoli become walled off, forming small round lesions called tubercles. Bacteria continue to be released into the center of the tubercles and the chronic immune response results in tissue damage and induction of apoptosis (programmed host-cell death) in a process called liquefaction. This creates a caseous center, or air pocket, where the aerobic M. tuberculosis can grow and multiply. Tubercles may eventually rupture and bacterial cells can invade pulmonary capillaries; from there, bacteria can spread through the bloodstream to other organs, a condition known as miliary tuberculosis. The rupture of tubercles also facilitates transmission of the bacteria to other individuals via droplet aerosols that exit the body in coughs.

Pathogenicity of *Mycobacterium tuberculosis*

Ruth Ella Moore was a prominent researcher known for her work on blood typing, dental cavities, and the gut microbiome, as well as for being the first Black woman to earn a natural science Ph.D. She wrote her dissertation on new methods of isolating Mycobacterium tuberculosis to better study the disease and develop a cure, producing isolates that became critical for diagnosis and other medical procedures.

Ruth Ella Moore

Clinical Focus: Tuberculosis Symptoms and Travel History

Microscopic examination to detect the presence of acid-fast bacilli in clinical specimens is a key method for identifying *Mycobacterium tuberculosis*. Additionally, the pathogen can be identified by its slow growth in culture, which produces colorless granulated colonies after $${}4$$ weeks, or by molecular methods such as immunofluorescence, nucleic acid hybridization, direct nucleic acid amplification (NAA) testing, and DNA sequencing.

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