The infectiousness of tuberculosis (TB) is directly related to the number of Mycobacterium tuberculosis organisms expelled into the air by an infected patient.
Step-by-Step Justification:
* TB Transmission Mechanism:
* TB spreads through airborne droplet nuclei, which remain suspended for long periods.
* Factors Affecting Infectiousness:
* High bacterial load in sputum: Smear-positive patients are much more infectious.
* Coughing and sneezing frequency: More expelled droplets increase exposure risk.
* Environmental factors: Poor ventilation increases transmission.
Why Other Options Are Incorrect:
* A. Hand hygiene habits: TB is airborne, not transmitted via hands.
* B. Presence of acid-fast bacilli (AFB) in blood: TB is not typically hematogenous, and blood AFB does not correlate with infectiousness.
* C. Tuberculin skin test (TST) >20 mm: TST indicates prior exposure, not infectiousness.
CBIC Infection Control References:
* APIC Text, "Tuberculosis Transmission and Control Measures".