Bacterial Infections of the Respiratory System

Bacterial Infections of the Respiratory System

• Microorganisms are prevented from entering the respiratory system by hair in nasal passages, IgA antibodies, normal microbiota of the oropharynx, ciliary escalator, and alveolar macrophages.
• Lower respiratory tract is normally sterile.
• Bacterial respiratory infections occur due to inhalation of fine droplets from the mouth into the lungs.
• Periodontal bacteria can be drawn into the lower respiratory tract, leading to pneumonia and exacerbating conditions like COPD.
• Periodontal disease is linked to pneumonia, COPD, and bronchitis.
• Periodontal pathogens may contribute to the pathology of COPD.
• Smoking damages gingiva and oral health, increasing gum pockets and attachment loss, and contributing to COPD.

Normal Respiratory Tract Flora

• Staphylococcus: gram-positive cocci in clusters
• Corynebacterium: pleomorphic, gram-positive rods
• Moraxella: gram-negative diplococci and diplobacilli
• Haemophilus: small, gram-negative rods
• Bacteroides: small, pleomorphic, gram-negative rods
• Streptococcus: gram-positive cocci in chains

Upper Respiratory Tract Infections (URTI)

• Viral infections are the majority of URTI, often mild and self-limiting.
• Bacteria can cause primary or secondary URTI (superinfection of viral infection).
• Otitis media: infection of the middle ear, often viral or bacterial. Caused by bacteria spreading from throat/sinus infections via the eustachian tube.
• Sinusitis: inflammation of paranasal sinuses (commonly maxillary). Usually viral, but can lead to bacterial superinfection. Sinus obstructions block drainage, leading to mucous accumulation.
• Odontogenic sinusitis: sinusitis caused by dental or dentoalveolar infection affecting the sinus floor.

Pharyngitis (Throat Infections)

• Viruses are the most common cause of pharyngitis.
• Bacterial pharyngitis (strep throat) is less common.
• Strep throat is often caused by Streptococcus pyogenes; diagnosed clinically through Centor Criteria.

Lower Respiratory Tract Infections (LRTI)

• Pneumonia: inflammation of lung alveoli.
• Community-acquired pneumonia: pneumonia developed outside of a healthcare facility.
• Healthcare-associated pneumonia: pneumonia developed in a healthcare facility.
• Predisposing factors include poor oral health (periodontal disease) which increases rates of oral streptococci and anaerobes in pneumonia patients, and a link to pneumonia mortality.
• Symptoms of pneumonia include cough, fever, chest pain, shortness of breath, and sputum.
• Bacterial causes include Streptococcus pneumoniae, Haemophilus influenzae, Klebsiella pneumoniae, and others.

Lung Abscess

• Lung abscess is necrosis of lung tissue and pus-filled cavities.
• Causes include aspiration, trauma, and infections like pneumonia.
• Diagnosis includes pleural fluid culture or blood culture, and CT scans.
• Treatment involves broad-spectrum antibiotics and often surgical drainage.

Opportunistic Infections in Immunocompromised Persons

• Opportunistic infections are infections caused by organisms that don't normally cause illness in healthy people.
• People with weakened immune systems (HIV/AIDS, transplants, cancer, autoimmune conditions, cystic fibrosis, diabetes, etc.) are more susceptible.
• Pseudomonas aeruginosa is an example of an opportunistic infection in the lower respiratory tract, often encountered in cystic fibrosis.

Respiratory Bacteria

• Pseudomonas aeruginosa: Gram-negative bacilli, aerobic, common environmental bacteria.
• Mycobacterium tuberculosis: Obligate aerobic, acid-fast resistant bacteria causing slow-growing tuberculosis, a long-term infection, common in underdeveloped countries. Spread by respiratory aerosols.
• Klebsiella pneumoniae: gram-negative bacilli causing pneumonia.

Microbial Resistance

• Antibiotic resistance: bacteria becoming resistant to antibiotics due to mutations, gene transfer, and other factors.
• Multidrug-resistant organisms (MDROs) pose a threat to patient treatment.