IM3.1-22 | Pneumonia — Glossary

An auscultatory sign in which the patient's spoken 'e' is heard through the stethoscope as 'a' (a nasal, bleating quality); found over a consolidated segment; helps confirm consolidation vs. effusion (over effusion, voice sounds are absent or muffled, not aegophonic).

A radiological sign on CXR or CT in which air-filled bronchi are visible as dark branching lucencies within a dense airspace opacity; indicates that the bronchi are patent and the surrounding alveoli are fluid-filled (consolidation); confirms an alveolar filling process (pneumonia, pulmonary oedema) rather than atelectasis or a mass.

Infection control measures for pathogens transmitted by small droplet nuclei that remain suspended in air (particle size <5 µm); require: N95 (FFP2) respirator for all healthcare staff entering the room, negative-pressure single room, door kept closed; indicated for TB (suspected or confirmed), SARS-CoV-2, MERS, measles, chickenpox.

A coordinated approach to optimising antibiotic use to achieve the best clinical outcomes while minimising unintended consequences of antibiotic use (adverse effects, C. difficile colitis, development of resistance); in pneumonia, key stewardship actions include: cultures before antibiotics, de-escalation at 48–72 hours, IV-to-oral switch when clinical stability criteria are met, and setting a definite antibiotic duration at the time of prescribing.

Bacterial pneumonia resulting from aspiration of oropharyngeal secretions or gastric contents into the lower airways; predominantly caused by oral anaerobes (Bacteroides, Fusobacterium, Peptostreptococcus); right lower lobe most commonly affected in upright aspiration; treated with amoxicillin-clavulanate or clindamycin-based regimen.

Chemical lung injury from aspiration of acidic gastric contents (Mendelson syndrome); a sterile chemical injury, not bacterial infection; usually self-limiting and does not require antibiotics unless secondary bacterial infection develops.

Pathogens causing CAP that cannot be grown on standard bacteriological media and may not be visible on Gram stain; include Mycoplasma pneumoniae, Chlamydophila pneumoniae, and Legionella pneumophila; often associated with subacute onset, dry cough, and extrapulmonary features; require macrolides or fluoroquinolones for treatment.

An abnormal auscultatory finding over a consolidated lung segment; characterised by a harsh, hollow, blowing quality with equal inspiratory and expiratory components and a short pause between them; caused by transmission of laryngeal airway sounds through the solid consolidated parenchyma; indicates consolidation (not effusion, which reduces breath sounds).

A bronchoscopic procedure in which sterile saline is instilled into a distal airway and aspirated to recover alveolar cells and secretions; the gold standard for diagnosing pneumonia in immunocompromised patients with diffuse infiltrates; allows diagnosis of PCP (immunofluorescence or PCR), IPA (galactomannan), CMV (shell vial culture), and TB in non-expectorating patients.

A pattern of pneumonia characterised by patchy, bilateral, peribronchial infiltrates rather than lobar consolidation; occurs in H. influenzae, S. aureus, and aspiration pneumonia; also occurs in VAP with bilateral involvement.

Downward displacement (bowing) of the horizontal fissure on CXR, caused by the large gelatinous and expanding exudate of a lobar pneumonia; a classic radiological sign of Klebsiella pneumoniae pneumonia (occasionally also seen in severe pneumococcal or Staphylococcal lobar pneumonia); indicates a large, dense consolidated lobe with high exudate volume.

IgM antibodies that agglutinate red blood cells at low temperatures (4°C) and disaggregate at 37°C; present in ~50% of Mycoplasma pneumoniae CAP; can cause haemolytic anaemia; bedside test: a few drops of blood on ice in a blue-top tube will agglutinate; when warmed in the hand, the clumps dissolve; a positive result supports Mycoplasma as the CAP aetiology.

Pneumonia acquired outside a hospital setting or within the first 48 hours of hospitalisation in a patient not residing in a long-term care facility for ≥90 days; the most common pneumonia syndrome, predominantly caused by S. pneumoniae, H. influenzae, and atypical pathogens.

A non-infectious inflammatory lung disease presenting as recurrent 'pneumonia' that fails to respond to repeated antibiotic courses; characterised by migratory consolidation on imaging (opacity appears, disappears, reappears in a new location); typically affects women in their 50s; diagnosed by bronchoscopic biopsy; responds to corticosteroids, not antibiotics.

A validated severity scoring tool for community-acquired pneumonia; one point each for: Confusion (new-onset, AMTS ≤8), Urea >7 mmol/L, Respiratory rate ≥30/min, Blood pressure (systolic <90 or diastolic ≤60 mmHg), age ≥65 years; score 0–1 = outpatient; score 2 = consider admission; score ≥3 = hospitalise (≥4–5 = consider ICU); predicts 30-day mortality.

The practice of narrowing the antibiotic spectrum once a specific pathogen is identified and clinical stability is established; reduces C. difficile risk, adverse drug effects, cost, and resistance pressure; the single most important antibiotic stewardship intervention in pneumonia management.

Infection control measures for pathogens transmitted by large respiratory droplets (>5 µm) that fall within 1 metre; require: surgical mask for healthcare staff within 1 metre, gloves, single room preferred; indicated for influenza, Mycoplasma pneumoniae, pneumococcal pneumonia (first 24 hours), meningococcal pneumonia, RSV.

Treatment begun before a specific pathogen is identified, based on the most likely organisms for the clinical syndrome, host, and severity tier; must always be reviewed at 48–72 hours when culture results and clinical response data become available to allow de-escalation or escalation.

The presence of frank pus in the pleural space, either from direct spread of a parapneumonic effusion or from haematogenous seeding; a complication of severe pneumonia; diagnosed by pleural fluid analysis (purulent, pH <7.2, glucose <2.2 mmol/L, LDH >1000 IU/L, positive culture); requires intercostal drainage + antibiotics, occasionally surgical decortication.

A rapid molecular diagnostic test for Mycobacterium tuberculosis that simultaneously detects TB DNA and rifampicin resistance from sputum by PCR; results in 2 hours; the recommended first-line diagnostic test under NTEP (India's National Tuberculosis Elimination Programme); more sensitive than smear microscopy, especially in sputum-scarce and HIV-co-infected patients.

A rapid nucleic acid amplification test (NAAT) for Mycobacterium tuberculosis using PCR on sputum or BAL; simultaneously detects TB DNA and rifampicin resistance mutations; result in 2 hours; the recommended first-line TB diagnostic test under NTEP; sensitivity ~89% (higher than smear microscopy, ~56%); particularly valuable in HIV-co-infected and paucibacillary patients.

An HRCT finding of a soft-tissue nodule surrounded by a 'halo' of ground-glass attenuation representing haemorrhage; pathognomonic of invasive pulmonary aspergillosis (IPA) in the neutropenic patient; the nodule represents the fungal colony, the halo represents haemorrhagic infarction in the adjacent parenchyma; the reverse halo sign (ground-glass surrounded by dense consolidation) is seen in cryptogenic organising pneumonia (COP).

A wedge-shaped, pleural-based opacity with the apex pointing toward the hilum, seen on CXR in pulmonary embolism with pulmonary infarction; an important differential for a focal pulmonary opacity that mimics pneumonia; associated with pleuritic chest pain, haemoptysis, and risk factors for venous thromboembolism.

A device delivering heated, humidified oxygen at flows up to 60 L/min with FiO2 up to 100% via large nasal prongs; generates mild positive airway pressure (~1–2 cmH2O per 10 L/min), reduces nasopharyngeal dead space, improves mucociliary clearance; the current first-line escalation for hypoxaemic respiratory failure (type 1) before intubation; not indicated for type 2 (hypercapnic) failure — NIV is preferred for CO2 retention.

Pneumonia developing ≥48 hours after hospital admission that was not incubating at the time of admission; dominated by Gram-negative bacilli (Pseudomonas, Klebsiella, Acinetobacter) and MRSA; requires broader-spectrum empirical antibiotics than CAP.

Respiratory failure with elevated pCO2 (>6 kPa/45 mmHg) in addition to hypoxaemia; occurs in pneumonia complicating COPD when the respiratory muscles are fatigued or hypoxic drive is suppressed by excessive supplemental oxygen; target SpO2 88–92% in COPD patients to avoid suppressing hypoxic drive and worsening CO2 retention.

Fungal pneumonia caused by Aspergillus fumigatus in severely neutropenic patients; characterised by fever unresponsive to antibiotics, haemoptysis, pleuritic pain, and the HRCT halo sign (nodule surrounded by ground-glass haemorrhage halo); diagnosed by serum galactomannan and HRCT; treated with voriconazole (first-line).

A severe CAP particularly affecting diabetics and alcoholics; characterised by currant-jelly sputum (blood-tinged, viscous), lobar consolidation with bulging fissure, high propensity for abscess and cavitation; associated with bacteraemia; requires third-generation cephalosporin or carbapenem.

The most serious atypical CAP pathogen; causes Legionnaires' disease — severe pneumonia with extrapulmonary features (hyponatraemia, abnormal LFTs, haematuria, altered consciousness); source is contaminated water aerosols; cannot be grown on standard media (requires BCYE agar); diagnosed by urinary antigen test; treated with respiratory fluoroquinolone or macrolide; mortality 5–30%.

A rapid immunochromatographic test that detects Legionella pneumophila serogroup 1 antigen in urine; results in 15 minutes; sensitivity ~74%, specificity >99%; positive even after antibiotic treatment has been started; does not detect non-serogroup-1 strains (responsible for ~20% of Legionella CAP); recommended for all moderate-severe hospitalised CAP.

Criteria for distinguishing pleural exudate from transudate; exudate if any of: pleural fluid protein/serum protein >0.5; OR pleural fluid LDH/serum LDH >0.6; OR pleural fluid LDH >2/3 upper limit of normal serum LDH; parapneumonic effusion is always an exudate; transudate suggests heart failure, cirrhosis, or nephrotic syndrome.

An oxazolidinone antibiotic active against Gram-positive organisms including MRSA and vancomycin-resistant Enterococci; 600 mg twice daily IV or orally; an alternative to vancomycin for MRSA pneumonia, particularly in VAP (achieves higher lung tissue concentrations than vancomycin); main adverse effects: thrombocytopaenia, optic neuropathy, peripheral neuropathy with prolonged use (>2 weeks), serotonin syndrome if combined with serotonergic drugs.

A pattern of pneumonia in which consolidation fills an entire lobe or major segment of the lung; characterised by dense homogeneous opacity on CXR with air bronchogram; classic pattern of pneumococcal CAP; pathological stages are congestion, red hepatisation, grey hepatisation, and resolution.

A localised area of suppurative necrosis within the lung parenchyma, typically with a thick-walled cavity and an air-fluid level visible on CXR or CT; common in aspiration pneumonia (anaerobes) and Klebsiella pneumonia; requires prolonged antibiotics (4–6 weeks), occasionally percutaneous or surgical drainage.

Intradermal injection of 2 TU PPD (purified protein derivative) in the volar forearm, read at 48–72 hours by measuring the transverse diameter of induration (not erythema); positive ≥10 mm in immunocompetent adults in endemic areas; indicates TB sensitisation (prior BCG, latent TB, or active TB); does NOT diagnose active TB alone; false-negative (anergy) in severe immunosuppression.

A bedside test of ulnar collateral circulation performed before radial artery puncture for ABG; compress both radial and ulnar arteries while the patient clenches their fist; release the ulnar artery — if the hand flushes pink within 5–7 seconds, ulnar collateral flow is adequate and radial artery puncture is safe; a negative test (failure to flush) indicates poor collateral circulation and radial artery puncture should be avoided.

Staphylococcus aureus with resistance to all beta-lactam antibiotics due to the mecA gene encoding a modified penicillin-binding protein (PBP2a); a key HAP/VAP pathogen; also causes severe necrotising community-acquired pneumonia; treated with vancomycin (target trough 15–20 mg/L) or linezolid.

Bacteria with acquired resistance to ≥3 classes of antibiotics; key MDR pathogens in HAP/VAP include MRSA, carbapenem-resistant Klebsiella (CRKP), and carbapenem-resistant Acinetobacter; require specialist antibiotics (vancomycin, linezolid, colistin, tigecycline) and infection control measures.

The most common atypical CAP pathogen in young adults; causes 'walking pneumonia' — subacute onset with dry cough, low-grade fever, and mild illness; extrapulmonary features include bullous myringitis, haemolytic anaemia (cold agglutinins), and Stevens-Johnson syndrome; cannot be Gram-stained or cultured on standard media; treated with macrolides or doxycycline.

Positive pressure ventilatory support via a tight-fitting face mask (bilevel — inspiratory positive airway pressure, IPAP, and expiratory positive airway pressure, EPAP); reduces work of breathing and CO2 by augmenting tidal volume; first-line treatment for hypercapnic respiratory failure in COPD exacerbation; also used for immunocompromised patients with respiratory failure to avoid intubation; contraindicated in impaired consciousness preventing mask seal, severe haemodynamic instability, or inability to cooperate.

An exudative pleural effusion forming adjacent to a pneumonic consolidation; occurs in up to 40% of hospitalised CAP; uncomplicated effusion resolves with antibiotics; complicated effusion (pH <7.2, glucose <2.2 mmol/L, LDH >1000 IU/L) or empyema (frank pus) requires drainage.

A protein-conjugate vaccine covering 13 pneumococcal serotypes; induces T-cell-dependent immunity (more robust in immunocompromised patients and children); in the prime-boost strategy for previously unvaccinated adults: PCV13 given first, PPV23 ≥8 weeks later; particularly important for asplenic patients, HIV-positive individuals, and immunocompromised adults.

An anti-pseudomonal beta-lactam/beta-lactamase inhibitor combination (4.5 g three times daily IV); the first-line empirical agent for late-onset HAP/VAP with MDR Gram-negative risk; covers Pseudomonas aeruginosa, many Enterobacteriaceae, and anaerobes; does not cover MRSA or carbapenem-resistant organisms.

Sharp, well-localised chest pain that worsens with deep inspiration, coughing, or sneezing; caused by inflammation of the parietal pleura adjacent to a consolidation or infarction; a classic feature of lobar pneumococcal pneumonia and pulmonary embolism with infarction; distinguished from central ischaemic chest pain (which is dull, pressure-like, and not pleuritic).

A rapid immunochromatographic test detecting Streptococcus pneumoniae C-polysaccharide antigen in urine; sensitivity ~70–80%, specificity ~97%; positive even after antibiotics have been started, and remains positive for several days; useful for confirming pneumococcal aetiology when sputum culture is non-diagnostic due to prior antibiotics.

The most common opportunistic pneumonia in HIV-positive patients with CD4 <200 cells/mm³; characterised by progressive breathlessness, dry cough, bilateral perihilar ground-glass opacity on CXR/HRCT, and hypoxia disproportionate to X-ray findings; elevated LDH; diagnosed by BAL with immunofluorescence or PCR; treated with co-trimoxazole (high-dose) + adjunctive steroids if PaO2 <70 mmHg.

Pneumonia developing distal to a bronchial obstruction (most commonly a bronchogenic carcinoma, endobronchial tumour, or foreign body); characterised by recurrent pneumonia in the same lung segment, associated with collapse-consolidation pattern on CXR; a central hilar mass may be visible; should be suspected in smokers over 40 with recurrent same-segment pneumonia.

A polysaccharide vaccine covering 23 pneumococcal serotypes; induces T-cell-independent immunity; indicated for adults ≥65 years and adults with chronic medical conditions; less immunogenic in immunocompromised patients and children under 2; in the prime-boost sequence, given ≥8 weeks after PCV13; re-vaccination after 5 years for immunocompromised and those vaccinated before age 65.

NACO-recommended practice of offering HIV testing to patients presenting with indicator diseases (pneumonia, TB, STIs, unexplained weight loss) as a standard part of clinical care, with pre-test information and post-test counselling; contrasts with patient-initiated testing; aims to identify HIV-positive patients who are unaware of their status at the time of a clinical presentation.

The second pathological stage of lobar pneumonia (days 2–3) in which the alveoli are filled with a fibrinopurulent exudate containing red blood cells and polymorphonuclear leucocytes, giving the lobe a solid, liver-like (hepatised) texture; the lysis of red blood cells in this stage produces the characteristic rust-coloured sputum.

An acid-base disturbance characterised by elevated pH (>7.45) with reduced PaCO2 (<35 mmHg) due to alveolar hyperventilation; in pneumonia, the most common ABG pattern in early-to-moderate disease — the hypoxia from V/Q mismatch drives hyperventilation, reducing PaCO2; the kidneys compensate by excreting bicarbonate (HCO3 mildly reduced).

A fluoroquinolone with reliable anti-pneumococcal activity in addition to atypical pathogen cover; includes levofloxacin (750 mg once daily) and moxifloxacin (400 mg once daily); contrasted with ciprofloxacin which has poor pneumococcal activity and should NOT be used as empirical CAP monotherapy.

Instructions given to a patient and family at discharge (or at an outpatient visit) specifying the precise circumstances that require immediate medical re-presentation; essential for outpatient CAP management; includes: worsening breathlessness, inability to speak in sentences, cyanosis, inability to take tablets due to vomiting, temperature >39.5°C despite treatment, new confusion or drowsiness.

A subset of sepsis with circulatory failure and cellular/metabolic dysfunction (Sepsis 3 definition); in pneumonia: mean arterial pressure <65 mmHg despite adequate fluid resuscitation plus lactate >2 mmol/L; examination findings include warm flushed peripheries (early vasodilatory phase), tachycardia, altered consciousness, and progressing to cold mottled peripheries in late distributive shock; requires vasopressors (noradrenaline) when fluids fail.

A percussion sign specific to free-flowing pleural fluid; the area of dullness shifts as the patient repositions (the fluid redistributes with gravity); distinguishes free-flowing effusion from fixed consolidation (consolidation dullness does not shift with position).

Microbiological acceptance criteria for a sputum specimen: ≥25 polymorphonuclear leucocytes (PMNs) per low-power field (10×) and <10 squamous epithelial cells per LPF; a specimen with >10 squamous cells per LPF represents oropharyngeal saliva and should be rejected; valid culture and Gram stain results can only be reported from acceptable-quality specimens.

The most common cause of CAP worldwide; produces lobar pneumonia with rust-coloured sputum and pleuritic chest pain; capsular polysaccharide inhibits phagocytosis (basis for pneumococcal vaccine); susceptible to penicillin (unless resistant strain); complications include empyema, bacteraemia, meningitis.

The tactile sensation of vibration felt by the examining hand placed on the chest wall when the patient speaks (e.g., says 'ninety-nine' or 'one-one-one'); increased over consolidation (solid lung conducts vibration better); decreased or absent over pleural effusion (fluid dampens vibration).

Hypoxaemia (PaO2 <60 mmHg) with a normal or low PaCO2; caused by V/Q mismatch (the predominant mechanism in pneumonia), diffusion impairment (PCP), or shunt; the hypoxia drives hyperventilation which reduces PaCO2, producing a respiratory alkalosis; managed with supplemental oxygen.

Hypoxaemia combined with hypercapnia (PaCO2 >50 mmHg); caused by respiratory muscle fatigue, severe airway obstruction (COPD exacerbation), or CNS depression of respiratory drive; produces respiratory acidosis; managed with non-invasive ventilation (NIV/BiPAP) or mechanical ventilation if severe.

Pathogens causing CAP that are visible on Gram stain and culturable on standard media; include S. pneumoniae (most common), H. influenzae, Klebsiella pneumoniae, and S. aureus; often present with acute onset, productive cough, and lobar or segmental consolidation.

The pre-dose serum concentration of vancomycin used to monitor dosing adequacy and nephrotoxicity risk; target trough 15–20 mg/L for serious infections including MRSA pneumonia; below 15 = under-dosed, increased risk of treatment failure; above 20 = increased nephrotoxicity risk; measured just before the fourth dose.

A subset of HAP occurring ≥48–72 hours after endotracheal intubation; the most common ICU-acquired infection; caused by MDR Gram-negative organisms and MRSA; carries 20–50% crude mortality.

An oxygen delivery device that uses the Bernoulli principle (jet entrainment of room air) to deliver a precise, fixed fraction of inspired oxygen (FiO2); colour-coded jets: 24% (blue), 28% (white), 31% (orange), 35% (yellow), 40% (red), 60% (green); essential for COPD patients where precise FiO2 prevents suppression of hypoxic drive and CO2 retention; preferred over nasal cannulae or simple face mask when the exact FiO2 must be controlled.

An informal term for a clinically mild pneumonia where the patient remains ambulatory despite radiological confirmation of lower respiratory tract infection; typically caused by Mycoplasma pneumoniae; characterised by subacute onset, dry cough, low-grade fever, minimal physical signs, and bilateral patchy infiltrates on CXR.

The clear, distinct transmission of whispered words through the stethoscope placed over a consolidated lung segment; indicates increased sound conduction through solid (consolidated) lung tissue; absent or muffled over an effusion; a confirmatory sign of consolidation.