Pneumonia

Overlapping Signs and Symptoms of Pneumonia and Acute Bronchitis

Pneumonia and acute bronchitis share similar clinical features:

Common Features:
- Cough, which may be accompanied by purulent or colored sputum (note that this does not specifically indicate a bacterial infection).
Key Indicators Suggestive of Pneumonia:
- Temperature > 37.8°C
- Crepitations (crackles) heard during auscultation
- Oxygen saturation < 95% on room air
- Heart rate > 100 beats per minute
Additional Symptoms of Pneumonia:
- Rigors
- Pleuritic chest pain
- Tachypnea at rest
- Dullness to percussion
Note on Acute Bronchitis: Wheezing may be present, and scattered crackles can occur, but these typically clear with coughing.

Diagnosing Pneumonia in Patients with COPD or Bronchiectasis

The symptoms of pneumonia often overlap with those of COPD and bronchiectasis, making accurate diagnosis crucial, as the treatment for exacerbations differs from pneumonia management.

Pathogens:
- The usual pathogens causing pneumonia (e.g., Streptococcus pneumoniae) remain the most common culprits in patients with COPD or bronchiectasis.
- Frequent infections and prior antibiotic use may result in sputum cultures identifying multidrug-resistant bacteria, though these are often colonizers rather than true pathogens.
Treatment Considerations:
- For patients with low- to moderate-severity pneumonia, standard empirical antibiotic therapy is typically sufficient.
- In cases of high-severity pneumonia, especially in patients colonized with multidrug-resistant Gram-negative organisms (e.g., Pseudomonas aeruginosa), the antibiotic regimen may need adjustment.

Causes

Seasonal	winter- pneumococcus, Respiratory syncytial virus (RSV) June to November – Influenza
potting mix or gardening	Legionella longbeachae
animals/rural	Coxiella burnetii – Q Fever
pregnancy	throughout pregnancy and puerperum, women are at risk from severe influenza
immunocompromised	Fungal Infections: – Aspergillus species: A common cause of invasive pulmonary infections, particularly in patients with severe immunosuppression (e.g., prolonged neutropenia, organ transplantation). – Pneumocystis jirovecii (PJP):A fungal infection that often leads to severe pneumonia in patients with compromised immune function, especially those with HIV/AIDS or on immunosuppressive medications. Bacterial Infections: – Gram-negative bacteria, such as Pseudomonas aeruginosa: Known for causing severe, rapidly progressing pneumonia, particularly in hospitalized or ventilated patients. – Legionella species: Often associated with exposure to contaminated water sources and can lead to severe pneumonia in immunocompromised patients. – Mycobacterium tuberculosis: A concern, especially for individuals from regions with high tuberculosis prevalence. Opportunistic Infections: – Nocardia species: Typically cause localized lung infections, often in patients on chronic immunosuppressive therapy. – Cryptococcus species: Frequently cause focal lung infections and can disseminate in severe cases, particularly in those with HIV/AIDS. Parasitic Infections: – Strongyloides stercoralis: A parasite that can cause severe respiratory symptoms, particularly in immunocompromised individuals living in areas with poor sanitation or inadequate public health infrastructure, and those with regular soil exposure. Viral Infections: – Cytomegalovirus (CMV): A significant cause of viral pneumonia in individuals with weakened immune systems, such as transplant recipients or those with HIV/AIDS.
Injection drug use	S. aureus Anaerobes S. pneumoniae
Alcoholism	Streptococcus pneumoniae Anaerobes Gram negatives such as Klebsiella pneumonia Tuberculosis
COPD/ smoker	Streptococcus pneumoniae Haemophilus influenzae Moraxella catarrhalis
nursing home resident	Streptococcus pneumoniae Gram negatives – Haemophilus influenzae S. aureus Chlamydophila pneumoniae consider tuberculosis and anaerobes (but less common)
poor dental hygiene	anaerobes
bat/ cave exposure	Histoplasma capsulatum
bird exposure	Chlamydophila psitacci Cryptococcus neoforms Histoplasma capsulatum
rabbit exposure	Franciscella tularensis
post-infuenza	S. pneumoniae, S. aureus
brochiectasis, fibrosis	Pseudomonas aeruginosa S. pneumoniae
Tropical Australia	Melioidosis Acinetobacter
Travel to Asia	SARS tuberculosis meliodosis Covid19

Lobar vs Bronchial


Lobar Pneumonia	Bronchopneumonia
When the infection is confined to only one or few lobes of lungs	patchy involvement f the lung parenchyma, originating from the airway
Causative Agents
Legionella pneumophila Klebsiella pneumoniae Haemophilus influenzae Mycobacterium tuberculosis	Staphylococcus aureus Klebsiella pneumoniae Haemophilus influenzae Pseudomonas aeruginos aEscherichia coli Anaerobes, such as Proteus speciesauregenosa
Impact of the Inflammation
Inflammation is confined to one or more lobes.	Inflammation is not localized, and there are multiple inflammatory foci.
Differentials
Atelectasis: tends to be associated with more volume loss, and is more enhancing compared to pneumoniapulmonary malignancy: lung adenocarcinoma affecting an entire lobe

Typical vs Atypical Pneumonia

Characteristic	Typical Pneumonia	Atypical Pneumonia
Onset	Sudden	Gradual
Sputum	Productive, purulent, or bloody	Non-productive or scanty mucoid
Fever	High	Low-grade
Muscle Aches and Headache	Uncommon	Common
Leucocytosis	Common	Uncommon
Culturing and Staining	Can be cultured on standard media/visible on Gram stain	Cannot be cultured on standard media/Not seen on Gram stain
Patient Demographics	Typically all ages	More common in younger patients
Local Signs	Prominent	Minimal
Multisystem Involvement	More extensive	Less involvement
Antibiotic Resistance	Variable	Intrinsically resistant to all β-lactam agents due to lack of a bacterial cell wall
Common Organisms	– Streptococcus pneumoniae – Haemophilus influenzae – Moraxella catarrhalis – Staphylococcus aureus – RSV	– Chlamydophila pneumoniae – Legionella pneumophila – Mycoplasma pneumoniae – Chlamydophila psittaci – Coxiella burnetii – Francisella tularensis

Typical Pathogens

Sudden Onset
Productive, purulent or bloody sputum
High Fever
Mylagia and headache uncommon
Leucocytosis in common

Streptococcus pneumoniae (42%)
- Details:
  - Over 100 known serotypes.
  - Vaccine available for common serotypes.
  - Most frequent bacterial cause of CAP, especially severe cases and those in the elderly.
  - Leading cause of death from CAP.
- Clinical Indicators:
  - Sensitivity: 30%, Specificity: 91% for pneumococcal pneumonia.
    - Sudden onset with rigors
    - pleuritic chest pain
    - purulent sputum
    - lobar consolidation
  - Recurrent infections may indicate immune disorders (e.g., HIV).
- Treatment:
  - Amoxicillin: 1 g (children: 25 mg/kg up to 1 g), every 8 hours.
  - Non-severe penicillin allergy: Cefuroxime 500 mg twice daily.
  - Severe penicillin allergy:
    - Doxycycline 100 mg twice daily.
    - Moxifloxacin 400 mg daily.
    - Azithromycin 500 mg daily.
Staphylococcus aureus (3%)
- Details:
  - Common in winter, intravenous drug users, debilitated patients, and those with influenza.
  - Major cause in hospital-acquired pneumonia (HAP) and ventilator-associated pneumonia (VAP).
  - Uncommon in CAP but can cause severe cases or cavitary pneumonia.
- Clinical Indicators:
  - Short clinical course
  - hemoptysis
  - early multilobar involvement
  - progression to cavitation.
  - Possible complications: Disseminated intravascular coagulation.
- Treatment:
  - Flucloxacillin: 2 g (children: 50 mg/kg up to 2 g), intravenously every 6 hours.
  - Severe allergy: Vancomycin as monotherapy.
Haemophilus influenzae
- Details:
  - Six serotypes based on capsular polysaccharide.
  - A significant cause of:
    - Community-Acquired Pneumonia (CAP), particularly in patients with underlying lung conditions.
    - Acute exacerbations of chronic obstructive pulmonary disease (COPD).
    - Other infections such as otitis media, sinusitis, and in severe cases, meningitis (especially type b).
  - Non-encapsulated strains cause most respiratory infections
  - encapsulated type b (Hib) is responsible for more severe invasive diseases.
    - The introduction of the Hib vaccine has significantly reduced serious invasive infections caused by type b.
  - Commonly affects patients with chronic obstructive pulmonary disease (COPD).
Moraxella catarrhalis
- Aerobic bacterium.
- Common cause of pneumonia in children under 5 years
- A significant cause of:
  - Otitis media (middle ear infection) in children.
  - Acute bacterial rhinosinusitis.
  - Exacerbations of chronic obstructive pulmonary disease (COPD).
  - Less commonly, community-acquired pneumonia (CAP).
- Typically sensitive to beta-lactam antibiotics, although resistance is increasing.
Pseudomonas aeruginosa
- Nature: Usually causes necrotizing or destructive pneumonia.
- Incidence: Rare cause of CAP (Community-Acquired Pneumonia) but significant in other contexts.
- Oxygen Requirement: Strictly aerobic.
- Colonization: Can exist as a colonizer in certain individuals.
- Clinical Importance
  - A key pathogen in:
    - Cystic fibrosis patients.
    - Hospital-Acquired Pneumonia (HAP) and Ventilator-Associated Pneumonia (VAP).
    - Chronic suppurative lung diseases like bronchiectasis.
- Treatment Considerations
  - For Pseudomonas-related exacerbations in cystic fibrosis or bronchiectasis, refer to specialized guidelines for antibiotic management.
  - Antibiotic Resistance: Rapid resistance development, so avoid aminoglycosides (e.g., gentamicin) and quinolones (e.g., ciprofloxacin) as first-line monotherapy unless no alternatives exist.
- Treatment Options
  - Azithromycin: 500 mg orally or enterally daily for 3 to 7 days.
  - Ciprofloxacin: 750 mg orally or enterally every 12 hours for 5 to 7 days.
  - Doxycycline: 100 mg orally or enterally every 12 hours for 10 to 14 days.
Klebsiella pneumoniae (Klebsiella pneumoniae, 8%)
- Facultative anaerobe
- Gram-negative bacillus
- commonly causing severe pneumonia.
- Often associated with lobar pneumonia and can cause necrotizing pneumonia.
- Typically produces a thick, mucoid, blood-tinged sputum known as “red currant-jelly” sputum.
- More common in individuals with underlying health conditions such as alcoholism, diabetes, or chronic lung disease.

Atypical Pathogens

Gradual Onset
Non-productive or only scanty mucoid sputum
low-grade fever
minimal local signs
less multisystem involvement
Mylagia and headache common

Mycoplasma pneumoniae (8%)
- Details:
  - Atypical pathogen causing community-acquired pneumonia, especially in young adults.
- Unique Characteristics:
  - Not visible on Gram stain due to the lack of a rigid cell wall.
  - Can alter its shape and size to adapt to various environments.
  - Intrinsically resistant to beta-lactam antibiotics (e.g., penicillins, cephalosporins).
- Epidemiology
  - Often occurs in outbreaks, particularly in settings like schools or military barracks.
  - Incubation period: 2–3 weeks.
  - Rarely seen in residents of aged-care facilities.
- Clinical Presentation
  - Onset: Gradual and subacute, with symptoms slowly intensifying.
  - Common Symptoms:
    - Persistent dry cough.
    - Low to moderate fever.
    - Malaise and headache.
- Chest Examination:
  - Chest X-ray typically shows bilateral lower zone infiltrates.
  - Clinical signs on chest examination may be minimal, despite radiographic evidence of pneumonia.
- Diagnosis
  - Suspected in young adults with prolonged cough and symptoms out of proportion to physical examination findings.
  - Typical imaging findings include diffuse infiltrates on chest X-ray.
- Treatment Options
  - Effective antibiotics for Mycoplasma pneumoniae, as well as other atypical pathogens like Chlamydia pneumoniae and Chlamydia psittaci:
- Treatment:
  - Doxycycline: 100 mg every 12 hours for 7 days.
  - Azithromycin: 500 mg daily for 3 days.
  - Clarithromycin: 500 mg every 12 hours for 7 days.
Chlamydia pneumoniae
- An atypical respiratory pathogen that causes a spectrum of clinical symptoms.
- Incubation Period: 3 to 4 weeks, with a gradual onset of symptoms.
- Clinical Presentation
  - Common Initial Symptoms:
    - Persistent cough.
    - Fever.
    - Headache.
    - Malaise.
  - Potential Progression:
    - Laryngitis (inflammation of the larynx, causing hoarseness).
    - Pharyngitis (sore throat).
    - Coryza (runny nose).
    - Pneumonia.
- Course of Illness
  - Symptoms often develop slowly and can persist for several weeks or even months, even with appropriate antibiotic therapy.
  - Patients may experience:
    - Chronic cough.
    - Ongoing malaise.
- Complications
  - In some cases, Chlamydia pneumoniae infection can lead to more severe outcomes, including:
    - Asthma Exacerbation: May worsen existing asthma symptoms.
    - Encephalitis: Inflammation of the brain, potentially causing neurological symptoms.
    - Myocarditis: Inflammation of the heart muscle, which can impact heart function.
Chlamydia psittaci
- Details:
  - Zoonotic, acquired from infected birds or environmental sources.
  - Nonrespiratory signs and symptoms may be prominent
Legionella (3%)
- Overview
  - More common in younger patients and smokers, particularly those without additional comorbidities.
  - Often requires hospitalization, with a mortality rate of about 10%.
  - Over 60 species exist, but L. pneumophila is the primary cause of disease.
- Etiology
  - Typically found in natural freshwater environments and man-made water systems, such as:
    - Plumbing systems in large buildings.
    - Cooling towers.
    - Medical devices, decorative fountains, and hot tubs.
  - Transmission occurs through inhalation of aerosolized water droplets containing the bacteria or by aspiration of contaminated drinking water.
  - Not transmitted from person to person.
- Risk Factors
  - Age 50 years or older.
  - Current or past history of smoking.
  - Chronic lung diseases (e.g., emphysema, COPD).
  - Immune system disorders (due to disease or medication).
  - Systemic malignancies.
  - Other underlying conditions, such as diabetes, renal failure, or hepatic failure.
- Prevention
  - Regular maintenance of water systems to prevent Legionella growth, focusing on controlling temperature, stagnation, and disinfectant levels.
- Diagnosis
  - Often presents with nonrespiratory symptoms, including:
    - Diarrhea.
    - High fever.
    - Confusion.
    - Hyponatremia.
- Laboratory Indicators:
  - Neutrophilia without visible organisms on Gram stain of respiratory secretions.Signs of multisystem involvement, such as:
    - Abnormal liver function tests.
    - Elevated serum creatinine kinase.
- Treatment:
  - Azithromycin: 500 mg daily for 3–7 days.
  - Ciprofloxacin: 750 mg every 12 hours for 5–7 days.
  - Doxycycline: 100 mg every 12 hours for 10–14 days.
Coxiella burnetii
- Disease: Causes Q fever.
- Transmission: Typically via inhalation of contaminated dust or aerosols from infected animals.
  - Sources include dried placental material, birth fluids, urine, or feces from infected livestock.
  - Contaminated clothing, wool, hides, or straw can also transmit the bacteria.
  - Person-to-person transmission is extremely rare.
- Incubation Period
  - Approximately 3 weeks, ranging from 9 to 40 days.
- Symptoms
- Onset occurs 2–3 weeks after exposure:
  - Flu-like: Fever, malaise, headache.
  - Musculoskeletal: Myalgias, arthralgias.
  - Respiratory: Dry cough, pleuritic chest pain.
  - Gastrointestinal: Nausea, vomiting, diarrhea.
- Complications
  - Atypical pneumonia.
  - Acute Respiratory Distress Syndrome (ARDS).
  - Granulomatous hepatitis.
  - Endocarditis (especially in those with exposure in rural settings or valvular disease).
  - Chronic Q fever:
    - Most severe form.
    - Risk of endocarditis in patients with valvular disease is high (up to 39%).
  - Post-Q fever fatigue syndrome:
    - Affects 10–15% of patients after acute Q fever.
    - Presents with a chronic fatigue-like picture, often including alcohol intolerance.
- Diagnosis Considerations
  - Non-specific symptoms warrant consideration of Q fever in any undiagnosed febrile illness.
  - Lab Findings:
    - Elevated phase 2 complement fixation testing (CFT): Titre ≥1024.
    - Phase 1 CFT: Negative.
    - EIA phase 2 IgG and phase 2 IgM: Positive.
- Treatment
  - Adults: Doxycycline 100 mg orally every 12 hours for 14 days.
  - Children: Doxycycline 2.2 mg/kg up to 100 mg orally every 12 hours for up to 14 days.
  - Pregnant Women: Doxycycline contraindicated; use trimethoprim + sulfamethoxazole (160 + 800 mg) every 12 hours, with folic acid 5 mg daily.
- Prevention
  - Vaccine: Q-VAX available.
  - Risk Factors for Vaccination:
    - Livestock workers (farmers, abattoir workers, shearers, tanners).
    - Veterinarians, veterinary nurses, and students.
    - Wildlife carers, hunters, zookeepers.
    - High-risk area contractors (abattoirs, shearing sheds).
    - Individuals in indirect contact with livestock (e.g., living near processing plants or feedlots).
- Infection Control Measures
  - Thorough hand washing with soap after animal contact.
  - Use of a properly fitted P2 mask.
  - Wearing gloves and dressing wounds with waterproof dressings when handling animal products, waste, or birth materials.
Respiratory Viruses (18%)
- Details:
  - Includes influenza, RSV, hMPV, parainfluenza, and adenovirus.
  - Can occur alone or with bacterial infections.
- Clinical Indicators:
  - Asthma-like symptoms, especially with RSV.
  - Rarely leads to severe bilateral CAP requiring intensive care.

Differentials

Investigations for Community-Acquired Pneumonia (CAP)

Imaging Studies

CT Chest:
- Generally, CT scans are not recommended for routine evaluation of CAP.
Chest X-Ray:
- Key findings that aid in the diagnosis and evaluation of pneumonia:
  - Consolidation:
    - Represents alveolar filling that replaces air within the affected airspaces.
    - Leads to increased pulmonary attenuation, obscuring the margins of nearby airways and blood vessels.
  - Air Bronchogram:
    - Visible air-filled bronchi surrounded by dense, consolidated lung tissue.
    - In normal lungs, bronchi are not visible since they are surrounded by aerated lung parenchyma.
    - Differential Diagnosis: Nonobstructive atelectasis, aspiration, or neoplasms.
  - Silhouette Sign:
    - Loss of the normal interface between lung and soft tissues (e.g., heart, mediastinum, chest wall, diaphragm).
    - Indicates a pathological process replacing or displacing air in the lung parenchyma.
  - Tree-in-Bud Opacity:
    - Small airways or terminal bronchioles filled with mucus, pus, fluid, or cells.
    - Appears as branching nodular opacities resembling a “budding tree.”
  - Split Pleura Sign:
    - Indicates thickening of the visceral and parietal pleura

Lab Investigations

Blood Tests:
- Full Blood Count (FBC):
  - A white cell count >15 x 10⁹/L suggests bacterial pneumonia.
- Urea and Electrolytes:
  - Urea forms part of the CURB-65 severity scoring system.
  - May reveal unsuspected renal failure or hyponatremia.
- C-Reactive Protein (CRP):
  - While not diagnostic, CRP forms a baseline for later comparison.
  - Lack of CRP decline within 72 hours may indicate treatment failure.
- Liver Function Tests (LFTs):
  - Routine LFTs are not clearly beneficial in patients without jaundice or severe disease.
- Arterial Blood Gases (ABG) and Lactate:
  - Indicated if oxygen saturation is <94%.
  - Lactate measurement is essential to identify tissue hypoperfusion, even if blood pressure is normal.
  - A lactate level >4 mmol/L suggests poor prognosis and indicates risk for septic shock.
Microbiological Testing:
- Blood Cultures:
  - Recommended for moderate to severe CAP and for most hospitalized patients.
  - Should be obtained before initiating antibiotics, if possible.
  - Sensitivity is low (<10% in CAP), and they are generally not needed in:
    - Low-severity CAP.
    - Patients with no significant comorbidities.
    - Patients who received antibiotics before hospital admission.
- Sputum Culture:
  - Indicated for:
    - Severe CAP.
    - Moderate CAP in patients who have not received prior antibiotics.
    - Cases where initial treatment fails.
    - Patients with a positive urine Legionella antigen test.
- Serology:
  - Considered for atypical pathogens like
    - Mycoplasma
    - Chlamydia
Urinary Antigens:
- Pneumococcal Urine Antigen:
  - Sensitivity: 86–90%, Specificity: 71–94%.
  - Not recommended for individuals vaccinated against pneumococcus within the past 5 days.
- Legionella Urine Antigen:
  - Recommended for high-severity CAP and patients with risk factors (e.g., chronic lung disease, smoking, diabetes, immune compromise).
  - Can be performed before or after antibiotic initiation.
Serum Procalcitonin:
- Helps differentiate between viral and bacterial pathogens in hospital-acquired pneumonia (HAP) or ventilator-associated pneumonia (VAP).
- Should not replace clinical judgment for starting antibiotics but useful for monitoring treatment.
Specialized Testing:
- Mycobacterial Testing:
  - Acid-Fast Bacilli (AFB) stain and culture for suspected tuberculosis.
  - Indications: Elderly, immunosuppressed, immigrants from high-prevalence countries.
- PCR Testing:
  - Useful for rapid identification of respiratory viruses
    - Mycoplasma pneumoniae
    - Chlamydia
    - Bordetella pertussis
    - Covid19

Assessing Severity of Community-Acquired Pneumonia (CAP)

Severity assessment tools like SMART-COP and CURB-65 are essential for guiding clinical decisions regarding the management of CAP, including the need for intensive care or hospital admission.

SMART-COP Score

Purpose:
- Predicts the need for Intensive Respiratory or Vasopressor Support (IRVS).
- Less validated for general mortality prediction compared to PSI; less suited for outpatient decision-making.
Score Interpretation:
- 0 to 2 points: Low risk of needing IRVS.
- 3 to 4 points: Moderate risk; approximately 1 in 8 patients may need IRVS.
- 5 to 6 points: High risk; approximately 1 in 3 patients may need IRVS.
- 7 or more points: Very high risk; 2 out of 3 patients may need IRVS.
Severe CAP is indicated by a SMART-COP score of 5 or more.

CURB-65 Criteria

Purpose:
- Estimates the severity of CAP and guides decisions on hospitalization
- Widely validated for predicting mortality in CAP patients
- Can underestimate severity in younger patients without comorbid conditions
Criteria (1 point for each criterion met):
Score Interpretation:
- 0 to 1 points: Low risk, with a 1.5% mortality rate. Suitable for outpatient care.
- 2 points: Moderate risk, with a 9.2% mortality rate. Consider inpatient admission or observation.
- ≥ 3 points: High risk, with a 22% mortality rate. Recommend inpatient admission.
- 4 or 5 points: Very high risk; strong consideration for ICU admission.

Pneumonia Severity Index (PSI)

Identifies patients at risk for mortality from CAP, guiding decisions on hospitalization and outpatient management.
Complexity makes it cumbersome for rapid decision-making in acute settings
Components: Uses 20 variables, including demographics (age, nursing home status), comorbidities, physical findings (e.g., altered mental status, tachypnea), and laboratory parameters (e.g., BUN, arterial pH, sodium).
Scoring: Stratifies patients into five risk classes:
- Class I: Lowest risk; outpatient management.
- Class II-III: Low risk; potential outpatient care.
- Class IV-V: Moderate to high risk; hospitalization or intensive care.
Validation: PSI is well-validated and has high sensitivity for identifying low-risk patients who can be safely managed as outpatients.

Treatment Guidance

Treatment plans and patient disposition should be guided by the severity score:
- Low-risk patients (SMART-COP 0–2 or CURB-65 0–1): Typically managed as outpatients with oral antibiotics.
- Moderate-risk patients (SMART-COP 3–4 or CURB-65 2): Consider inpatient admission, possibly in a monitored unit.
- High-risk patients (SMART-COP ≥5 or CURB-65 ≥3): Require hospital admission; consider early intensive care consultation.
- Very high-risk patients (SMART-COP 7+ or CURB-65 4–5): Require close monitoring with a likelihood of ICU care for respiratory or hemodynamic support.

Treatment

need to check with eTG and confirm, local guidelines may differ

	CAP Empirical treatment	Allergic to Penecillin
low-severity CAP	Amoxicillin 1 g orally,8-hourly rural: procaine benzylpenicillin 1.5 g intramuscularly, daily	Doxycycline 100 mg orally, 12-hourlyOR Clarithromycin 500 mg orally, 12-hourly severe allergy: Moxifloxacin 400 mg orally, daily
atypical pathogens	Doxycycline 100 mg orally, 12-hourly OR Clarithromycin 500 mg orally, 12-hourly
moderate-severity CAP in adults	benzylpenicillin 1.2 g intravenously, 6-hourly PLUS EITHER Doxycycline 100 mg orally, 12-hourly; OR Clarithromycin 500 mg orally, 12-hourly	ceftriaxone 1 g intravenously PLUS EITHER – Doxycycline 100 mg orally, 12-hourly; OR – Clarithromycin 500 mg orally, 12-hourly

Reasons for Treatment Failure in Pneumonia

There are several potential reasons why a patient with pneumonia may not respond adequately to initial treatment. These include:

1. Incorrect Diagnosis

Pneumonia-like symptoms may be caused by other conditions, leading to inappropriate therapy:
- Pulmonary Embolism.
- Pulmonary Edema.
- Pulmonary Eosinophilia.
- Wegener’s Granulomatosis.
- Drug Allergy.
- Lung Cancer.

2. Resistant Organism or Infection

Some pathogens may not respond to standard treatment:
- Atypical bacteria:
  - Mycoplasma pneumoniae.
  - Chlamydia psittaci.
  - Coxiella burnetii.
- Resistant strains of typical pathogens:
  - Staphylococcus aureus (methicillin-resistant strains).
  - β-lactamase-producing Haemophilus influenzae (though rare).
- Viral Infections that are not targeted by antibacterial therapy.
- Pulmonary Tuberculosis.
- Pneumocystis jirovecii (formerly Pneumocystis carinii), particularly in immunocompromised patients.

3. Inadequate Drug, Dose, or Route of Administration

Suboptimal antibiotic choices or delivery methods can lead to ineffective treatment:
- Oral Erythromycin for Legionella: Inadequate tissue levels.
- Azithromycin is ineffective against Coxiella burnetii (Q Fever), requiring a different antibiotic choice.

4. Complications

Pneumonia can lead to complications that hinder recovery:
- Empyema (collection of pus in the pleural space).
- Lung Abscess
- Pleural effusion
- Respiratory failure
- Pulmonary Embolism.
- Drug-related fever, which may be mistaken for persistent infection.
- Brain abscess
- Pericarditis/Myocarditis
- Sepsis and Septic shock

5. Underlying Disease

Comorbid conditions can complicate recovery and lead to treatment failure:
- Lung Cancer.
- Cardiac Failure.
- Immunodeficiency (e.g., HIV/AIDS, chronic steroid use, congenital immunodeficiencies).

Prevention

Vaccinations play a key role in preventing pneumonia:

Pneumococcal vaccine (Pneumovax)
Influenza vaccine

Pneumonia

Overlapping Signs and Symptoms of Pneumonia and Acute Bronchitis

Diagnosing Pneumonia in Patients with COPD or Bronchiectasis