MI7.1-5 | Respiratory Tract Infections — Glossary

Allergic Bronchopulmonary Aspergillosis; hypersensitivity reaction to Aspergillus antigen in asthmatic patients; central bronchiectasis; elevated IgE

Organism that retains carbol fuchsin dye after acid-alcohol decolourisation due to mycolic acid in cell wall; characteristic of mycobacteria

Accumulation of point mutations in influenza HA or NA genes causing minor antigenic changes; responsible for seasonal influenza epidemics

Major antigenic change in influenza due to reassortment of gene segments between human and animal strains; responsible for influenza pandemics

Fungal ball formed by Aspergillus species growing in a pre-existing pulmonary cavity (e.g., old TB); presents with haemoptysis; not invasive

Pneumonia caused by organisms without a cell wall (Mycoplasma) or intracellular pathogens (Legionella, Chlamydophila); presents with dry cough, bilateral infiltrates; does not respond to beta-lactams

Used to presumptively identify GAS; a zone of inhibition around the A disc indicates sensitivity, differentiating GAS from other streptococci

Bronchoscopic procedure instilling then aspirating saline into distal airways; samples alveolar space; gold standard specimen for PCP, Aspergillus, and atypical pneumonia in immunocompromised

Cartridge-Based Nucleic Acid Amplification Test; detects MTB DNA and rifampicin resistance within 2 hours; WHO-endorsed first-line TB diagnostic

Clinical scoring system (fever, tonsillar exudate, lymphadenopathy, absence of cough) to assess probability of GAS pharyngitis and guide antibiotic use

IgM antibodies that agglutinate RBCs at 4°C; elevated in Mycoplasma pneumoniae infection (>1:64); non-specific but useful bedside test

Pneumonia acquired outside hospital or within 48 hours of admission; S. pneumoniae is the most common bacterial cause

Trehalose dimycolate; surface glycolipid of MTB; causes serpentine cord arrangement on culture; inhibits phagosome-lysosome fusion in macrophages

Equine-derived antitoxin that neutralises circulating diphtheria exotoxin; must be given on clinical suspicion before culture confirmation

Directly Observed Treatment, Short-course; WHO/NI-KSHAY strategy where a health worker observes each dose to ensure adherence; cornerstone of TB control

Atypical lymphocytes (activated CD8+ T cells) seen on peripheral blood smear in EBV infectious mononucleosis; large, irregular nucleus with abundant cytoplasm

In vitro immunodiffusion test to detect diphtheria toxin; a precipitation arc forms between toxigenic strain and antitoxin-impregnated filter paper strip

Polysaccharide cell wall component of Aspergillus; detected in serum or BAL by ELISA as a marker of invasive aspergillosis

Primary TB complex: Ghon focus (subpleural parenchymal lesion) + ipsilateral hilar lymph node calcification; result of primary TB infection

Gomori Methenamine Silver stain; stains fungal cell walls black; used to demonstrate Pneumocystis, Aspergillus, and other fungi in tissue/BAL

CT chest finding in early invasive aspergillosis: area of consolidation surrounded by ground-glass haze (haemorrhagic infarction around angioinvasive fungus)

Pneumonia occurring ≥48 hours after hospital admission; associated with Gram-negative bacilli (Pseudomonas, Acinetobacter) and MRSA

Intercellular adhesion molecule-1; serves as the rhinovirus receptor on upper respiratory epithelial cells

Enriched medium for primary isolation of C. diphtheriae; promotes rapid growth and metachromatic granule formation for early identification

Egg-based solid medium for MTB culture; growth in 3–8 weeks as rough, buff, cauliflower-like colonies

Major virulence factor of GAS; anti-phagocytic; antibodies cross-react with cardiac myosin causing rheumatic fever (molecular mimicry)

Multi-Drug Resistant TB; defined as resistance to at least isoniazid AND rifampicin; requires second-line regimen for ≥18 months

Volutin granules in C. diphtheriae that stain blue-black with Albert stain due to stored polyphosphate; pathognomonic of Corynebacterium on smear

Mycobacteria Growth Indicator Tube; fluorescence-based liquid medium for rapid MTB culture; detects growth in 10–14 days

National Tuberculosis Elimination Programme of India; provides free DOTS therapy, GeneXpert testing, nutritional support (Nikshay Poshan Yojana), and mandates case notification

Serological test detecting heterophile IgM antibodies in EBV infectious mononucleosis; these antibodies agglutinate sheep/horse red blood cells

Atypical fungus causing PCP in immunocompromised hosts; cannot be cultured; diagnosed by GMS stain of BAL showing helmet-shaped cysts

Grayish-white adherent membrane on tonsillar/pharyngeal/laryngeal mucosa in diphtheria; composed of fibrin, dead epithelial cells, bacteria and leucocytes; bleeds on removal

Pyrrolidonyl arylamidase test; positive in GAS (S. pyogenes) and Enterococcus; used to differentiate GAS from other β-haemolytic streptococci

Angioinvasive fungal infection of sinuses extending to orbit and brain, caused by Mucorales; associated with uncontrolled diabetes and immunosuppression

Chronic granulomatous infection of nasal mucosa caused by Rhinosporidium seeberi; endemic in south India; presents as nasal polyps with sporangia on histology

Semi-solid medium used for transport of throat swabs and other specimens; maintains organism viability without allowing multiplication during transit

Microbial protein (e.g., streptococcal pyrogenic exotoxin) that cross-links MHC II on APCs with Vβ region of TCR, causing massive polyclonal T-cell activation and cytokine storm

Selective medium (e.g., Hoyle's or CTBA) for isolation of C. diphtheriae; potassium tellurite inhibits other flora; diphtheria colonies appear grey-black

Acid-fast stain using hot carbol fuchsin, acid-alcohol decolouriser, and methylene blue counterstain; AFB appear red on blue background

Complete lysis of red blood cells around a colony on blood agar, producing a clear zone; characteristic of GAS (S. pyogenes)