Aeromicrobiology Overview

Aeromicrobiology

• The study of airborne biological particles (microbes and their spores or toxins) and their impact on human, animal, and plant health.
• Focuses on airborne microbes and their impact on human, animal, and plant health.

Types of Aeromicrobiology

• Intramural (indoor): deals with microorganisms present in the air within an indoor environment, including homes and workplaces.
• Extramural (outdoor): studies air in the atmosphere outside buildings.

Key Facts

• Indoor air contains more disease-causing agents than outdoor air.
• Common indoor air fungi genera are Penicillium and Aspergillus.
• Common indoor air bacteria genera are Staphylococci, Bacillus, and Clostridium.

Aeromicrobiological Pathway

• Describes the movement of bioaerosols from launch to deposition.
• Involves four stages: Launching, Transport, Deposition, and Gravitational Settling.

Launching

• The process of releasing bioaerosols into the atmosphere.
• Mainly from terrestrial and aquatic sources.
• Includes wind, water, human and animal movement, and the release of fungal spores during their life cycle.

Transport

• The dispersion of airborne particles through the movement of air.
• Can travel long distances due to wind and air currents.
• Examples: pandemics and the spread of avian influenza.

Deposition

• The process where airborne bioaerosols settle on surfaces.
• Occurs through several mechanisms such as:
  • Gravitational settling: due to gravity; limits the spread of particles.
  • Downward molecular diffusion: caused by natural air currents and eddies.
  • Surface impaction: particles colliding with surfaces like leaves, trees, or walls.
  • Rain deposition and electrostatic deposition: water droplets and electrostatic charges attract and condense bioaerosols.

Microbial Survival in the Air

• Many organisms have mechanisms to survive harsh airborne environments.
• Factors affecting survival in air include:
  • Relative humidity: low humidity can damage cell membranes, while gram-positive bacteria are more tolerant than gram-negative bacteria.
  • Temperature: high temperatures promote inactivation due to desiccation and protein denaturation, while low temperatures allow for longer survival.
  • Radiation: UV radiation causes DNA damage, and ionizing radiation causes DNA breaks; some organisms have protective mechanisms or DNA repair systems.
  • Oxygen, OAFs, and Ions: oxygen toxicity, open air factors (OAFs), and ions can inactivate microorganisms, particularly through the formation of reactive oxygen species (ROS) and ion-mediated damage.

Extramural Aeromicrobiology

• Studies microorganisms in outdoor environments.
• Includes agricultural pathogens and airborne pathogens from waste environments.

Agricultural Aeromicrobiology

• Impacts world food security by affecting crops like rice and wheat.
• Significant economic impact from crop diseases.
• Wheat rust fungi are major pathogens of wheat and other grains.

Waste Disposal Aeromicrobiology

• Hazards associated with wastewater and biosolid treatment and disposal.
• Pathogens include bacteria, viruses, protozoa, and helminths.

Wastewater Treatment and Aerosols

• Wastewater treatment processes, such as activated sludge and trickling filters, produce aerosols containing pathogenic microorganisms
• Composting and land disposal are also sources of aerosols containing pathogens

Intramural Aeromicrobiology

• Intramural environments often have limited air circulation and reduced UV radiation exposure
• Controlled temperature and humidity within indoor environments can support microbial survival
• These factors contribute to the accumulation and survival of microorganisms in enclosed environments such as office buildings, hospitals, and laboratories

Building Factors Influencing Bioaerosols

• Air filtering devices, air circulation systems, occupant hygiene, outdoor air circulation, lighting, temperature, and humidity all impact bioaerosol levels in buildings
• These factors contribute to the health or "sickness" of a building

Public Health Implications of Aeromicrobiology

• The airborne microbe pathway (AMB) can spread pathogens, potentially causing diseases
• The AMB pathway can also be used for disease immunization

Hospitals and Laboratories

• Hospitals and microbiology laboratories are high-risk environments for aerosolization of pathogenic microorganisms
• Hospitals treat patients with diseases, increasing the potential for pathogen spread
• Microbiological laboratories handle pathogens, requiring specific procedures to protect personnel