Tuberculosis

🌍 Tuberculosis (TB) remains a major global infectious disease. 🧪 Offer HIV testing to people with suspected or confirmed TB (UK practice) and consider other immunosuppression risks. 💉 BCG protects mainly against severe childhood TB (TB meningitis, miliary TB) rather than reliably preventing adult pulmonary TB. 📋 TB is a notifiable disease in the UK.

🔬 Microbiology

• Mycobacterium tuberculosis = obligate aerobe, acid-fast bacillus (Ziehl–Neelsen stain → 🔴 red rods).
• Cell wall: lipid-rich (mycolic acids) → acid-fastness + survival in macrophages.
• ⏱️ Slow-growing: generation time ~12–18 h.
• 🧪 Cord factor: associated with granuloma formation and virulence.
• Lab ID (classical): niacin & nitrate reduction positive (now often superseded by NAAT/culture workflows).

🌍 Epidemiology & Risk (UK focus)

• UK risk is higher with: recent exposure, birth/residence in high-incidence settings, homelessness, imprisonment, alcohol/drug misuse, and immunosuppression (including HIV).
• 📈 HIV increases risk of reactivation and extrapulmonary disease; imaging can be atypical when CD4 is low.
• 💊 Drug resistance is defined by resistance patterns (at least isoniazid + rifampicin for MDR-TB); manage with specialist TB services.

🫁 Clinical Types

• Primary TB: Ghon focus + regional LN = Ghon complex. Often asymptomatic.
• Latent TB: Dormant infection: no symptoms, no active disease; detected via immunological testing (IGRA ± TST depending on pathway).
• Post-primary (reactivation): classically apical disease ± cavitation, haemoptysis, weight loss, night sweats.
• Miliary TB: haematogenous spread → diffuse millet-seed lesions 🌾.
• Extrapulmonary TB: – 🧠 CNS: meningitis, tuberculoma, spinal TB (Pott’s). – 🚻 GU: sterile pyuria, infertility. – 🍽️ GI: ileocaecal disease/obstruction. – ❤️ Pericarditis → constrictive risk. – 🧂 Adrenal: Addison’s.

📋 Clinical Features

• 🗣️ Persistent cough (often >3 weeks) ± haemoptysis.
• 🌡️ Fever, night sweats, weight loss.
• 😮 Chest pain, breathlessness if pleural involvement.
• ⚠️ Extrapulmonary clues: meningism, back pain, sterile pyuria, lymphadenopathy.

🔎 Investigations (UK/NICE approach)

• 🩻 CXR as initial imaging; CT/MRI for CNS/spine/disseminated disease when indicated.
• 🧪 Microbiology: sputum (or induced sputum/BAL) for AFB smear + culture + NAAT (rapid ID and resistance signals e.g. rifampicin).
• 🧫 Culture remains reference standard (also enables full susceptibility testing).
• 🧬 IGRA/TST: primarily for latent TB assessment (interpret in context; IGRA not affected by BCG).
• 🔬 Histology from tissue when extrapulmonary TB suspected: caseating granulomas (micro confirmation preferred where possible).
• 🧪 Baseline bloods before treatment: LFTs, renal function; document visual acuity/colour vision if ethambutol used.

💊 Management (Drug-Sensitive TB)

• Standard 6-month regimen:
  • 2 months: Isoniazid + Rifampicin + Pyrazinamide + Ethambutol (HRZE).
  • 4 months: Isoniazid + Rifampicin (HR).
• Adherence support: offer enhanced case management; DOT is offered particularly for people from under-served groups / at high risk of poor adherence.
• Steroids: consider adjunct corticosteroids in TB meningitis and often TB pericarditis (specialist guidance).

💊 Drug Toxicities (High-Yield)

• 💊 Isoniazid → hepatitis, neuropathy (give pyridoxine).
• 🟠 Rifampicin → hepatitis, orange secretions, potent enzyme inducer (drug interactions).
• 🔥 Pyrazinamide → hepatitis, hyperuricaemia/gout.
• 👁️ Ethambutol → optic neuritis (reduced visual acuity/red–green impairment).
• 👂 Aminoglycosides (historical regimens) → ototoxicity + nephrotoxicity (specialist DR-TB care).

🤝 TB & HIV (UK – BHIVA principles)

• 📷 Imaging can be atypical when CD4 is low; extrapulmonary disease is more common.
• 🧪 Start ART promptly: CD4 <50 usually within 2 weeks; otherwise often within ~8–12 weeks (specialist decision; avoid very early ART in CNS TB).
• ⚠️ Rifampicin has major drug–drug interactions with ART → check interaction resources and involve HIV/TB specialists.