Bacterial Infections of the Respiratory System

Bacterial Agents Causing Lower Respiratory Tract Infections and Mycoplasma Pneumonia

• Mycobacterium tuberculosis, Mycoplasma pneumonia, Legionella pneumophilia, Chlamydia psittaci, and Coxiella burnetti are bacterial agents that can cause lower respiratory tract infections (LRTIs).
• Legionella pneumophilia is naturally found in freshwater environments and can be acquired through air-borne transmission or aerosolized droplets.
• Chlamydia psittaci is a type of bacteria that often infects birds and can cause psittacosis, which can progress to pneumonia.
• Macrolide antibiotics such as erythromycin, azithromycin, and clarithromycin are the first line of treatment for Chlamydia psittaci, and tetracyclines are the second line of treatment.
• Chlamydia pneumoniae is a common cause of community-acquired pneumonia, and macrolides, particularly azithromycin, are the first line of therapy.
• Coxiella burnetti, which primarily infects animals, can be transmitted from animals to humans and is treated with doxycycline.
• Mycoplasma pneumoniae is the smallest bacteria and does not have a cell wall, making it insensitive to penicillin and cephalosporin.
• Mycoplasma pneumoniae colonies can be visualized using Diene's stain, which imparts a "fried egg" appearance to the colony.
• Mycoplasma pneumoniae may take up to 3 weeks to produce detectable colonies and its antigenic determinants are membrane glycolipids and proteins.
• M. pneumoniae adheres tightly to and fuses with the membranes of respiratory epithelial cells, inhibiting cilia and disrupting the epithelial cells over time.
• Atypical pneumonia caused by Mycoplasma pneumoniae is characterized by ciliostasis and damage to respiratory epithelial cells, resulting in flu-like symptoms at the onset.
• Complications of Mycoplasma pneumoniae include pneumothorax, intravascular coagulopathy, arthritis, myocarditis, erythema multiforme, Guillain-Barre syndrome, and meningoencephalitis.