| dc.description.abstract | Tuberculosis (TB), one of the world's greatest killers, is predominantly spread by the airborne
route. Drug-resistant M. tuberculosis has emerged as a global public health threat despite
effective drugs and disease control strategies. Little is known about M. tuberculosis
transmission and the efficacy of necessary environmental (engineering) interventions for
infection control; particularly in light of the global HIV/Aids epidemic.
This thesis covers the development, validation and calibration of the unique Airborne Infection
Research (AIR) facility (apparatus) that utilises a biological model to sample airborne
M. tuberculosis by transporting infectious air from patient wards to animal exposure chambers
housing guinea pigs. This capability, hitherto a universal limitation due to the unique
characteristics of the tubercle bacili, will now allow a collaboration of researchers horn around
the world to undertake scientific studies to answer fundamental questions about the
infectiousness of drug-resistant M. tuberculosis and the efficacy of various engineering
interventions to minimise the spread of airborne disease. These experiments will provide the
scientific blue-prints for design of safer health care facilities and the development of improved
building and construction standards.
The AIR facility, recently completed as pan of this study, was the culmination of a five year
research project by a collaborative research team From the SA Medical Research Council, the
Council for Scientific and Industrial Research, the Centers for Disease Control, Atlanta, USA;
and Harvard University, Boston, USA; made possible with initial finding provided by the US
Agency for International Development (USAID) and private sector donors which included the
South African National Tuberculosis Association (SANTA).
The author, as the engineering research member of the collaborating research team, was
responsible for all architectural engineering aspects of the research behind the design,
development, operation and, in part, the bioaerosol sampling techniques; and had to develop an
in depth appreciation and understanding of M tuberculosis generation, risk and control in
order to anticipate what was needed from the apparatus to support the various research projects
that are to be undertaken.
The various engineering interventions necessary to curtail transmission of infection, such as
ultraviolet germicidal irradiation (UVGI) and other electro/mechanical interventions can now
be tested and evaluated. The facility, as an apparatus, is capable of supporting the experiments
intended for the study of these interventions in that the effects of varying ventilation rates and
environmental conditions, such as temperature and humidity on the transmission dynamics of
aerosolized infectious particles, are possible.
The thesis discusses the hypothesis, aims, results and conclusions of the apparatus
development, validation and calibration experiments of the unique state-of-the-art facility.
The effectiveness and airtightness (leakage factor) of the air distribution from the wards, the
transporting capacity of gram-positive and negative aerosolized bacteria and the efficacy of the
in-line UVGI units to the animal infection chambers were conclusively proven via validation
experiments. The results presented indicate that from the validated operational parameters of
the apparatus the losses were less than 5% for non-biological substances and less than 12% for
endospores (Serratia marcescens). No significant losses were noted across the transfer axial
fan. A 100% efficacy was achieved across the in-he ultraviolet germicidal irradiation units as
no Serratia marcescens were detected in the animal room.
The calibration experiment, conducted to calibrate the exposure apparatus of the AIR facility
in meeting its purpose to effectively transfer infectious airborne particles from patient wards
(clinical unit) to the animal exposure chambers, concluded from the rate of guinea pig
infections observed that the AIR facility is a highly effective way to quantify the infectiousness
of TB patients. The high rate of observed infections among the guinea pig infections proves
conclusively that the AIR facility will serve its purpose to effectively evaluate infectiousness
of the ward air and to test the efficacy of engineering interventions to minimize the spread of
the disease.
The AIR facility now provides unique opportunity to evaluate the efficacy of novel
engineering interventions for infection control, particularly in light of the global HIV/Aids
epidemic. Future studies that are planned are also discussed. | |
