Pneumonia Dewasa

01Pathophysiology

Pneumonia is an acute inflammation of the lung parenchyma caused by infectious pathogens including bacteria, viruses, fungi, and parasites, but excluding Mycobacterium tuberculosis. The PNPK Pneumonia Dewasa 2023 focuses on bacterial pneumonia in adults.

The pathogenic mechanism begins when microorganisms breach the host's respiratory defense barriers. Under normal conditions, the upper airway filters, warms, and humidifies inspired air, while mucociliary clearance and cough reflexes remove pathogens. Alveolar macrophages serve as the last line of innate defense. When these mechanisms are overwhelmed or impaired, whether by high pathogen inocula, virulent organisms, or compromised host defenses, bacteria colonize the lower respiratory tract and trigger an inflammatory cascade.

Bacterial adherence to the alveolar epithelium activates resident macrophages, which release cytokines (IL-1, IL-6, TNF-alpha). This recruits neutrophils into the alveolar space, causing the hallmark exudative process: protein-rich fluid, inflammatory cells, and fibrin fill the alveoli. This explains why you see consolidation on imaging: the air-filled alveoli become fluid-filled, producing opacity on chest radiograph and bronchial breath sounds on auscultation. The air bronchogram sign occurs because the airways remain patent while the surrounding parenchyma is consolidated.

The systemic inflammatory response accounts for fever, leukocytosis, and elevated inflammatory markers such as CRP and procalcitonin. The ventilation-perfusion mismatch caused by fluid-filled, non-ventilated alveoli that continue to be perfused explains the hypoxemia and dyspnea seen clinically.

Pneumonia is classified based on where infection is acquired:

• Community-Acquired Pneumonia (CAP) is acquired outside the hospital setting. The dominant pathogen globally is S. pneumoniae, though Indonesian data from 2015 show K. pneumoniae (14%) and S. pneumoniae (13%) as the leading isolates from sputum cultures.

• Hospital-Acquired Pneumonia (HAP) develops >48 hours after hospital admission, not in incubation at the time of admission. Ventilator-Associated Pneumonia (VAP) develops >48 hours after endotracheal intubation. Both carry a higher burden of Gram-negative and drug-resistant organisms. Data from RSUPN Dr. Cipto Mangunkusumo (2018) showed K. pneumoniae (27.1%), A. baumannii (23.4%), A. lwoffii (7.4%), and P. aeruginosa (6.1%) as the predominant HAP/VAP pathogens.

The concept of aspiration is central to HAP pathogenesis. Over 45% of healthy individuals aspirate oropharyngeal secretions during sleep. In debilitated hospitalized patients, impaired consciousness, suppressed cough reflex, and reduced ciliary function allow colonizing bacteria from the oropharynx to reach the lower airways.

The PNPK Pneumonia Dewasa 2023 notes that the former category of Healthcare-Associated Pneumonia (HCAP) has been removed from guidelines. Prospective studies found that contact with healthcare settings alone does not independently predict multidrug-resistant (MDR) pathogens, so HCAP is no longer a separate clinical entity.

02Classification and Clinical Manifestation

Typical vs. Atypical

Atypical pathogens include Mycoplasma pneumoniae, Chlamydia pneumoniae, Legionella spp., Chlamydia psittaci, and Coxiella burnetii. These organisms are intracellular or lack a cell wall, making them inherently resistant to beta-lactams and requiring treatment with macrolides or fluoroquinolones.

By Site of Acquisition

Severity Classification: CURB-65

CURB-65 is interpreted as follows:

Severity Classification: PSI (Pneumonia Severity Index)

The PSI incorporates 20 variables including age, sex, nursing home residence, comorbidities (malignancy +30, liver disease +20, heart failure +10, cerebrovascular disease +10, renal disease +10), physical exam findings, and laboratory values. The PNPK recommends using CURB-65 as the standard, with PSI available for hospitals with more complete facilities.

IDSA/ATS 2007 Criteria for Severe CAP

Severe pneumonia is defined by at least one major criterion or three or more minor criteria.

Minor criteria: respiratory rate 30/min or more, $Pa{O}_2\mathrm{/}Fi{O}_{2}PaO\_2/FiO\_2$ ratio 250 or below, multilobar infiltrates, confusion/disorientation, uremia (BUN 20 mg/dL or more), leukopenia (<4,000), thrombocytopenia (<100,000), hypothermia (core temperature <36 degrees C), hypotension requiring aggressive fluid resuscitation.

Major criteria: need for mechanical ventilation, septic shock requiring vasopressors.

03Diagnostic Workup

Chest radiograph is the cornerstone of pneumonia diagnosis. The PNPK Pneumonia Dewasa 2023 states that clinical signs and symptoms alone have low diagnostic accuracy. The diagnosis of pneumonia is confirmed when imaging demonstrates infiltrate, opacity, consolidation, or air bronchogram in combination with acute onset of supportive clinical features: cough, chest pain, dyspnea, purulent sputum, fever >38 degrees C, signs of consolidation on exam, and leukocytosis (>10,000) or leukopenia (<4,500) with a left shift.

If a patient shows clinical improvement within 5 to 7 days, a repeat chest radiograph is not necessary. This is an important testing principle: imaging should be repeated only when clinical improvement is not achieved or when clinical deterioration occurs.

CT scan of the chest (with or without contrast) is the most accurate radiologic test. Indications include: clinical suspicion with non-diagnostic CXR, severe/complex/recurrent pneumonia, immunocompromised patients, failure to respond to adequate therapy, suspicion of an underlying condition (malignancy, TB, interstitial lung disease, lung abscess). Contrast is added when malignancy is suspected.

Sputum culture remains the microbiologic gold standard, but sputum quality must be verified first. A valid specimen contains fewer than 10 epithelial cells and more than 25 leukocytes per low-power field. Invalid specimens include saliva and samples delivered to the laboratory beyond 2 hours without cold chain (2 to 8 degrees C). For outpatients, routine sputum and blood cultures are not recommended. For inpatients, Gram stain and culture should be obtained before starting empiric antibiotics, particularly in severe CAP (especially intubated patients), patients receiving empiric MRSA or Pseudomonas coverage, those with a prior respiratory isolate of MRSA or P. aeruginosa, and those hospitalized and given parenteral antibiotics within the preceding 90 days.

Procalcitonin is not ordered routinely. A normal PCT does not exclude bacterial pneumonia, and antibiotics should not be withheld pending the result. PCT is useful in follow-up: to assess response to treatment and to guide antibiotic discontinuation when clinical signs of systemic inflammation persist. This is a commonly tested concept: the role of PCT is in de-escalation, not in initial decision-making.

CRP above 100 mg/L can help determine prognosis and the need for mechanical ventilation but has low specificity for infection.

For HAP/VAP, the diagnostic criteria (per CDC-Atlanta) require a new or progressive opacity/consolidation/infiltrate on imaging plus at least two of the following: temperature >38 degrees C, purulent secretions, crackles or bronchial breath sounds, leukocytosis (>12,000) or leukopenia (<4,000), worsening oxygenation (SpO2 <94%, increased oxygen requirement, increased ventilator demand) or ABG showing decreased PaO2 ($Pa{O}_2\mathrm{/}Fi{O}_{2}PaO\_2/FiO\_2$ <240).

04Management and Treatment

CAP Outpatient

CAP Inpatient (Nonsevere)

CAP Inpatient (Severe, per IDSA/ATS 2007 criteria)

HAP Empiric Therapy

VAP Empiric Therapy

For VAP, antibiotics must cover S. aureus, P. aeruginosa, and other Gram-negative bacilli. The regimen is built by selecting one agent from each column:

Aminoglycosides should be avoided when alternative agents provide adequate Gram-negative coverage, because of poor pulmonary tissue penetration, nephrotoxicity, ototoxicity, and lower clinical response rates shown in meta-analyses.

Timing of Antibiotics

This is a high-yield testing point. For nonsevere pneumonia, antibiotics should be administered within 4 to 8 hours of diagnosis. For severe pneumonia with sepsis, antibiotics must be given within 1 hour of diagnosis.

Switch Therapy (Terapi Sulih)

Parenteral antibiotics can be switched to oral after a minimum of 2 to 3 days (safest at day 3, switching on day 4) if the patient meets all of the following stability criteria: hemodynamically stable, clinical improvement, able to tolerate oral medication, normal gastrointestinal function, temperature <37.8 degrees C, heart rate <100/min, respiratory rate <24/min, systolic BP >90 mmHg, oxygen saturation >90% or PaO2 >60 mmHg.

Switch options include sequential (same drug IV to oral, e.g., Levofloxacin IV to Levofloxacin oral), switch-over (different drug with equivalent potency, e.g., Ceftazidime IV to Ciprofloxacin oral), and step-down (same or different drug with lower potency, e.g., Cefotaxime IV to Amoxicillin oral).

Duration of Therapy

For CAP, antibiotics (IV/oral combined) are generally given for 3 to 5 days if clinical improvement is achieved. Prolongation is considered when: initial therapy is ineffective, extrapulmonary infection exists (meningitis, endocarditis), MDRO is the causative agent, or necrotizing pneumonia/empyema/lung abscess develops.

For HAP/VAP, the standard duration is 7 days. This may be shortened or extended based on clinical response and laboratory parameters. For non-fermenting Gram-negatives (Pseudomonas spp., Acinetobacter spp.) with high relapse rates, up to 14 days may be considered.

MDRO Pneumonia

Non-Pharmacologic Management

Outpatient: bed rest, adequate hydration, antipyretics for high fever, mucolytics/expectorants as needed.

Inpatient (general ward): supplemental oxygen, IV fluids for rehydration and electrolyte correction, symptomatic medications.

Inpatient (ICU): oxygen therapy, IV fluids, consider non-invasive ventilation (NIV) first, escalate to invasive mechanical ventilation if NIV fails. For septic shock: fluid resuscitation, vasopressors to maintain MAP of 65 mmHg or above, manage per sepsis protocols.

Rehabilitation

The PNPK includes rehabilitation medicine recommendations: airway clearance techniques (chest physiotherapy, vibration, cough assist devices when peak cough flow <270 L/min), breathing exercises (diaphragmatic breathing, pursed-lip breathing), range-of-motion and postural exercises, early mobilization and ambulation, outpatient aerobic training (3-5 times/week, 30 minutes, moderate intensity), and extremity strengthening.

Prevention

Vaccination is the primary preventive strategy. Influenza vaccine: annual, especially for adults over 50, nursing home residents, those with chronic diseases, immunosuppression, and healthcare workers; given IM, effectiveness 38-65% in healthy adults and 34-73% in elderly. Pneumococcal vaccine: indicated for adults 65 and older, those with chronic diseases, asplenia, or immunosuppression; one dose for adults, effectiveness 43-76%. Additional prevention includes smoking cessation, hand hygiene, masking, standard precautions, effective cough training, and aerobic fitness.

For HAP/VAP prevention: hand hygiene, proper sterilization/disinfection of reusable respiratory equipment, use of sterile water for rinsing respiratory devices, avoid routine ventilator circuit changes (change only when visibly soiled), oral hygiene with tooth brushing, head-of-bed elevation to 30-45 degrees, subglottic secretion drainage, ETT cuff pressure maintained at 20-30 cm H2O, check nasogastric tube position before each feeding, assess gastric residual volume, minimize duration of mechanical ventilation (daily extubation readiness assessment, sedation optimization, early mobilization, early tracheostomy in selected cases, use NIV when possible), and judicious antibiotic use to reduce MDRO emergence.

05Differential Diagnosis and Distractors

06Traps and High-Yield Pearls

The most common way students lose points on adult pneumonia questions involves three areas.

First, confusing severity scoring with treatment selection. CURB-65 and PSI determine where the patient is treated (outpatient, ward, ICU), not which antibiotic class to use. A student might see a CURB-65 of 1 and correctly identify outpatient management, but then erroneously select an inpatient IV regimen. Conversely, a CURB-65 of 4 should prompt ICU-level care, not just ward admission.

Second, the timing of antibiotics. The PNPK draws a clear line: nonsevere pneumonia must receive antibiotics within 4 to 8 hours, while severe pneumonia with sepsis demands antibiotics within 1 hour. Vignettes that describe a patient with septic shock and pneumonia are testing whether you will delay antibiotics to wait for culture results (wrong) or start empiric therapy immediately and collect cultures beforehand if possible (correct). Notably, the PNPK also states that procalcitonin should not delay antibiotic initiation. A normal initial PCT does not rule out bacterial pneumonia, and antibiotics should never be withheld pending the result.

Third, the approach to treatment failure. The PNPK emphasizes that the most common cause of treatment failure is host factors, not incorrect antibiotic selection. When a patient does not improve within 72 hours, the framework for evaluation is threefold: patient factors (local obstruction by foreign body or malignancy, empyema, superinfection, fluid overload), drug factors (wrong agent, wrong dose, malabsorption, drug interactions, drug fever), and pathogen factors (resistant organism, atypical pathogen, TB, fungal infection). The reflexive answer of "change the antibiotic" is often the distractor. The correct next step is to reassess the diagnosis, broaden the workup (CT scan, bronchoscopy, repeat cultures), and consider referral to a higher-level facility.

Additional pearls to remember: For HAP/VAP, always avoid aminoglycosides if an alternative beta-lactam or fluoroquinolone provides adequate Gram-negative coverage, due to poor lung penetration and toxicity. The concept of de-escalation is repeatedly emphasized: once culture and sensitivity results are available, narrow the antibiotic spectrum. And the former HCAP category no longer exists in current guidelines; healthcare contact alone does not predict MDR organisms. What does predict MDR risk is IV antibiotic use within the preceding 90 days.