HOW IS TB TRANSMITTED The TB bacilli are

HOW IS TB TRANSMITTED ? • The TB bacilli are almost always transmitted by patients with active pulmonary disease. • A patient expels TB bacilli in small droplets of respiratory secretions, which quickly evaporate leaving “droplet nuclei”, less than 5 μm in diameter. • Droplet nuclei of this size, containing 1– 3 bacilli, can remain suspended in the air indefinitely and, following inhalation, are able to reach deep into the lungs to produce infection. Larger particles do not remain airborne for as long and do not transmit TB as efficiently.

THE RISK OF INFECTION DEPENDS ON: • the infectiousness of the source; • the environment (e. g. overcrowding and inadequate ventilation promote transmission of droplet nuclei); • the duration and intensity of exposure; and • the susceptibility of the recipient. • Smear-positive patients who expel tubercle bacilli into the air, especially when they cough (also when they sneeze, speak or sing), are the most infectious sources

PROPER COLLECTION OF SPUTUM • Exposure to patients collecting sputum is one of the greatest hazards to a laboratory technician – if the patient is an undiagnosed smear-positive case, he or she will produce infectious aerosols during cough. • Any coughing patient who has to come to the laboratory should be asked to cover his or her mouth with hand or tissue. • Always collect sputum specimens outdoors, where the movement of the air will rapidly dilute infectious droplets and UV rays will inactivate TB bacilli. NEVER collect sputum specimens in laboratories, toilets, waiting rooms,

CONTAINERS OF TB SAMPLES : Containers are: leakproof clean 50 -ml capacity made of clear or translucent material screw-capped with a watertight seal. Containers are labelled on the sides. 6

WHAT’S WRONG? • Containers are labelled only on the cap, not on the side! • One specimen container is not made of clear-view plastic. 7

WHAT’S WRONG? • Some containers are not properly labelled. • Identification can not rely on request forms. Containers should always be labelled (forms have been placed under the containers and could easily become mixed up!) • Viability of AFB on paper ? 8

TRANSPORTATION

WHAT’S WRONG? Box container is open and is not leakproof. Specimen containers are not packed vertically. Some containers appear to be open. Specimen containers are not made of clear-view plastic The box is not fitted with a locking mechanism. How do you handle the containers/specimens? 12

REFERENCES Ø Laboratory biosafety manual, 3 rd edition Ø TUBERCULOSIS LABORATORY BIOSAFETY MANUAL Ø ﺍیﻤﻨی ﻭ ﺑﻬﺪﺍﺷﺖ ﺩﺭ آﺰﻣﺎیﺸگﺎﻫﻬﺎی ﺩیﺪ ﻣﺴﺘﻘیﻢ ﻭ کﺸﺖ ﺳﻞ ﻣﻨﺎﺑﻊ