Respiratory Tract Infections and Pneumonia

Respiratory Tract Infections

• The respiratory tract is divided into upper and lower parts
• The upper respiratory tract includes sinuses, middle ear, pharynx, epiglottis, and larynx
• The lower respiratory tract includes bronchi, bronchioles, and alveoli

Pneumonia

• Pneumonia is an infection of the lung parenchyma (alveoli, distal airways, and interstitium)
• Alveoli fill with bacteria, inflammatory cells, and fluid, forming a consolidation
• Mild pneumonia can be treated at home
• Moderate to severe pneumonia requires hospitalization

Types of Pneumonia

• Community-acquired pneumonia (CAP):

  • Typical (caused by bacteria like S. pneumoniae, H. influenzae, S. aureus, K. pneumoniae, and P. aeruginosa)
  • Atypical (caused by bacteria like M. pneumoniae, C. pneumoniae, Legionella spp., and viruses)
  • Aspiration (caused by aspiration of material from the oropharynx or other lung pathology)

• Nosocomial or hospital-acquired pneumonia (HAP):

  • Early onset
  • Late onset
  • Ventilator-associated

Etiology of Pneumonia

• Typical: S. pneumoniae, H. Influenzae, S. aureus, K. pneumoniae, P. aeruginosa
• Atypical: M. pneumoniae, C. pneumoniae, Legionella spp., Respiratory viruses

Antibiotic Mechanisms of Action

• Cell wall synthesis inhibitors: Beta-lactams, Vancomycin, Isoniazid, Ethambutol, Cycloserine, Ethionamide, Bacitracin, Polymyxin
• Cell membrane alteration: Polymyxins, Bacitracin, Neomycin
• DNA replication inhibitors: Quinolones, Metronidazole
• Transcription inhibitors: Rifampin, Rifabutin
• Protein synthesis inhibitors: Aminoglycosides (e.g., gentamicin), Macrolides (e.g., clarithromycin), Tetracycline, Linezolid
• Antimetabolites: Sulfonamides, Dapsone, Trimethoprim, Para-aminosalicylic acid
• Others: Fluoroquinolones (e.g., ciprofloxacin, moxifloxacin), inhibiting DNA synthesis; drugs that inhibit folic acid synthesis (e.g., sulfonamides, trimethoprim)

Types of Antibiotics

• Cell wall inhibitors: Penicillins, Cephalosporins, Monobactam antibiotics, Vancomycin

Specific Penicillin Classes and Drugs

• Penicillin G: Procaine penicillin G, Benzathine penicillin G; used for Gram +ve bacteria
• Aminopenicillins: Ampicillin, Amoxicillin; used for Gram negative bacteria (E. Coli)
• Penicillinase-resistant penicillins: Methicillin, Nafcillin; effective against penicillinase-producing Staphylococcus aureus
• Antipseudomonal Penicillins: Piperacillin; effective against Pseudomonas aeruginosa

Cephalosporin Generations

• 1st Generation: Cephalexin (primarily Gram +ve, few Gram -ve)
• 2nd Generation: Cefuroxime (More Gram +ve and -ve)
• 3rd Generation: Cefotaxime, Ceftriaxone (Excellent Gram -ve, including Pseudomonas)
• 4th Generation: Cefipime (Wide Gram +ve and -ve, including Pseudomonas)

Other Antibiotics

• Protein Synthesis Inhibitors: Tetracycline, Aminoglycosides (e.g., gentamicin), Macrolides (e.g., clarithromycin), Linezolid
• Others: Sulfonamides, Trimethoprim, Fluoroquinolones (e.g., ciprofloxacin, moxifloxacin)

Empirical treatment of Community-Acquired Pneumonia

• Mild: Amoxicillin (oral)
• Moderate: Amoxicillin and clarithromycin (IV or oral)
• Severe: Co-amoxiclav (IV until clinical improvement) and clarithromycin (IV or oral), (2nd or 3rd cephalosporin)
• Atypical: Macrolides, Doxycycline, Quinolones

Hospital-Acquired Pneumonia (HAP)

• Treatment: Co-amoxiclav for early HAP, Piperacillin/meropenem for Pseudomonas but not MRSA, Vancomycin or linezolid for MRSA

Pneumonia due to Anaerobic Microorganisms (Aspiration Pneumonia)

• Pathogens: Anaerobic and aerobic streptococci, Bacteroides
• Treatment: Amoxicillin or cefuroxime plus metronidazole, Co-amoxiclav, carbapenems, monobactams

Acute Bronchitis

• Treatment: Analgesia, hydration, and comfort measures.
• Bacterial Infection: Amoxicillin, Doxycycline,
• Chronic Bronchitis: Amoxicillin or co-trimoxazole

Upper Respiratory Tract Infections (URTIs)

• Colds and Flu: Most viral URTIs are mild and self-limiting. Rhinoviruses, coronaviruses, influenza viruses
• Management: Symptomatic (rest, hydration, analgesia, antipyretics)

Sore Throat (Pharyngitis)

• Most serious cases: Caused by group Aß-hemolytic streptococcus (Streptococcus pyogenes)
• Treatment: Sensitive to benzylpenicillin (penicillin G) or erythromycin/clarithromycin (for penicillin allergy) for 10 days

Chemoprophylaxis

• Rheumatic fever: I.M. benzathine penicillin
• Duration: Continued for 5 years or until aged 20, whichever is longer.

Otitis Media

• Causative bacteria: Streptococcus pneumoniae, Haemophilus influenzae, Streptococcus pyogenes (and other bacteria)
• Treatment:
  • Amoxicillin, Clavulanic acid
  • Alternatives: Erythromycin/clarithromycin (for penicillin allergy)

Case Studies (Examples of Patient Presentations and Treatments)

• Several cases are presented, with symptoms, diagnoses, and recommended/appropriate antibiotics