*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*

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,

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The respiratory tract can be infected by many different types of bacteria, which cause many different diseases. The diseases that can be caused by bacteria include: 
- Streptococcal Pharyngitis (strep throat)
 - Scarlet fever
- Acute Rheumatic Fever
- Acute Glomerulonephritis
- Acute Otitis Media (AOM)
- Otitis Media with Effusion (OME)
- Bacterial Rhinosinusitis
- Diphtheria
- Tuberculosis
- Haemophilus Pneumonia
- Mycoplasma Pneumonia
- Chlamydial Pneumonias
- Health Care-Associated Pneumonia
- Pseudomonas Pneumonia
- Pertussis (Whooping Cough)
- Legionnaires Disease
- Q Fever
- Psittacosis

The Different Bacterial Infections of the Respiratory System

https://openstax.org/details/books/microbiology/

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.

OpenStax Microbiology Textbook

*Streptococcus pyogenes* causes several infections, including: 
 - Streptococcal Pharyngitis (strep throat)
 - Scarlet fever
 - Acute Rheumatic Fever
 - Acute Glomerulonephritis

Streptococcal Infections of the Respiratory System

Acute Otitis Media (AOM) is characterized by the formation and accumulation of pus in the middle ear. The pus builds up, resulting in moderate to severe bulging of the tympanic membrane and otalgia (ear pain). Inflammation resulting from the infection leads to swelling of the eustachian tubes, and may also lead to fever, nausea, vomiting, and diarrhea, particularly in infants.

Acute Otitis Media (AOM)

Otitis Media with Effusion (OME) can be caused by any blockage of the eustachian tubes, with or without infection, this can cause fluid to become trapped and accumulate in the middle ear. The accumulated fluid offers an excellent reservoir for microbial growth and, consequently, secondary bacterial infections often ensue. This can lead to recurring and chronic earaches, which are especially common in young children. 

Otitis Media with Effusion (OME)

Bacterial Rhinosinusitis often occurs as a secondary infection after a viral infection. Bacterial sinusitis involves infection and inflammation within the paranasal sinuses. The most common causes of bacterial rhinosinusitis include *S. pneumoniae,* *H. influenzae,* and *M. catarrhalis*

Bacterial Rhinosinusitis

Diphtheria is caused by *Corynebacterium diphtheriae* and is a respiratory infection of the oropharynx but can also cause impetigo-like lesions on the skin. Although the disease can affect people of all ages, it tends to be most severe in those younger than 5 years or older than 40 years.

Diphtheria

Tuberculosis

Pertussis is commonly called whooping cough, and is caused by *Bordetella pertussis* The disease is characterized by mucus accumulation in the lungs that leads to a long period of severe coughing. Sometimes, following a bout of coughing, a sound resembling a “whoop” is produced as air is inhaled through the inflamed and restricted airway hence the name whooping cough.

Pertussis (Whooping Cough)

Legionnaires disease (also known as legionellosis) is an atypical pneumonia and is caused by an aerobic gram-negative bacillus *Legionella pneumophila.* infections typically occur from human-made reservoirs such as air-conditioning cooling towers, humidifiers, misting systems, and fountains.

Legionnaires Disease

Q fever is caused by a rickettsia, *Coxiella burnetii.* The primary reservoirs for this bacterium are domesticated livestock such as cattle, sheep, and goats. The bacterium may be transmitted by ticks or through exposure to the urine, feces, milk, or amniotic fluid of an infected animal. In humans, the primary route of infection is through inhalation of contaminated farmyard aerosols.

Q Fever

Psittacosis is a rare infection and is typically found in people who work with birds. *Chlamydia trachomatis,* the causative agent of the sexually transmitted disease chlamydia, can cause pneumonia in infants when the infection is passed from a person giving birth to a baby.

Psittacosis

Bacterial pneumonia is a prevalent, potentially serious infection; it caused more 50,000 deaths in the United States in 2014. There are several types, including: 
 - Haemophilus Pneumonia
 - Mycoplasma Pneumonia
 - Chlamydial Pneumonias
 - Health Care-Associated Pneumonia
 - Pseudomonas Pneumonia

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