Study objectives: Mycobacterium tuberculosis (MTb)
bacilli are carried on airborne droplet nuclei produced by
aerosolization that can occur from coughing, talking, or even singing.
Because of their prolonged period of suspension, they can be filtered
from the air onto a porous medium and readily detected using polymerase
chain reaction (PCR).
Design: Prospective cohort
Setting: Samples of circulating air were
collected over a 12-month period from within the rooms of 10
hospitalized patients who were under respiratory isolation to rule out
MTb infection. A small laboratory pump was used to draw ambient air at
a rate of 2 L/min over a 6-h period through a 0.2-μm polycarbonate
membrane filter placed near the patient’s bed. Analysis of the
membrane filters was conducted using PCR. Sputum cultures for MTb were
performed simultaneously, and the results of smears stained for
acid-fast bacilli (AFB) were noted.
results: MTb complex was successfully detected by PCR in six of
seven patients in whom sputum MTb cultures were subsequently positive,
and in zero of three with subsequently negative sputum cultures.
Sampling in one patient with a positive culture, in whom PCR results
were negative, was only carried out for 2 h due to pump
malfunction. One of the six PCR-positive patients was AFB-smear
negative at the time of air sampling.
preliminary findings indicate that the technique of Micropore membrane
air sampling with PCR analysis has important applications in the
epidemiology and diagnosis of MTb.
Abbreviations: AFB = acid-fast bacilli;
MAS/PCR = membrane air sampling with polymerase chain reaction
analysis; MTb = Mycobacterium tuberculosis;
PCR = polymerase chain reaction