Lecture 5 - Aeromicrobiology PDF

 Lecture 5 Aeromicrobiology Prepared by: Dr. Abeer Aloufi Assistant professor in Molecular Bacteriology Lecture 5: Aeromicrobiology What is the meaning of Aeromicrobiology? Aerobiology: t...

 Lecture 5 Aeromicrobiology Prepared by: Dr. Abeer Aloufi Assistant professor in Molecular Bacteriology Lecture 5: Aeromicrobiology What is the meaning of Aeromicrobiology? Aerobiology: to Aerobiology: the describe a project field of aero- that involved the microbiology is study of life in important as it the air involves, the formation of aerosols ? 1969 1986 √ Aerobiology: is Aerobiology: the Aerobiology: is the study of study of the study of airborne diseases that may microorganisms biological particles be transmitted via and their spores (microbes and their spores or toxins), the respiratory invisible to the and their movement route naked eye and impact on suspended in air human, animal, and plant health Lecture 5: Aeromicrobiology Intramural (indoor) Extramural (outdoor) ▪ It deals with microorganisms present in the air in an indoor environment ▪ The study of air in the atmosphere, which is ▪ Microbes can survive for extended periods found outside the buildings, is referred to as indoors as they have relatively less radiation outside air outdoor aero microbiology exposure Aeromicrobiology ▪ In outdoor or extramural environments, the involves various aspects ▪ It involves home and workplace environments expanse of space and the presence of air in which airborne microbes create major public of intramural (indoor) turbulence are the two controlling factors in the health concerns and extramural movement of bioaerosols (outdoor) aerobiology as ▪ Indoor air contains more disease-causing agents they relate to the airborne ▪ Outdoor air microbes The number and kind of that have higher chances of infections than transmission of microorganisms may vary from place to place, outdoor air, especially in large gatherings like environmentally relevant depending upon the human population densities schools and theaters microorganisms ▪ Some microbes include; Algae, Protozoa, ▪ The commonest genera of fungi in indoor air Yeasts, Molds, Bacterial species (spore-forming are Penicillium, Aspergillus or non-spore-forming) ▪ The commonest genera of bacteria found in indoor air are Staphylococci, Bacillus, and Clostridium Lecture 5: Aeromicrobiology Important Airborne Pathogens: Aeromicrobiological (AMB) pathway ▪ Numerous plant pathogens are spread by the aeromicrobiological pathway ▪ Up to 70% of all plant diseases are caused by fungi ▪ Aerial transmission is capable of transporting these phytopathogens many thousands of kilometers ▪ The impact of airborne plant pathogens, especially fungi, on the economy of the agricultural industry costs billions of dollars each year Lecture 5: Aeromicrobiology Important Airborne Pathogens: Aeromicrobiological (AMB) pathway ▪ There are also numerous airborne pathogenic microorganisms that infect animals ▪ For example, the foot-and-mouth disease (FMD) virus is known to be transmitted by the aeromicrobiological pathway Lecture 5: Aeromicrobiology Important Airborne Pathogens: Aeromicrobiological (AMB) pathway ▪ Humans can also be infected by airborne transmission of many pathogens Lecture 5: Aeromicrobiology Important Airborne Toxins: Botulinal toxin is a neurotoxin that is normally associated with ingestion of Botulinal A contaminated food, secreted by Clostridium botulinum Enterotoxins Enterotoxin produced by bacteria is staphylococcal, the symptoms include cramping, vomiting, and diarrhea, which occur within one hour of exposure by aerosolization Endotoxins Lipopolysaccharide (LPS) is an important airborne toxin derived from the outer membrane of gram-negative bacteria, also referred to as Endotoxin Lecture 5: Aeromicrobiology Aerosols: ▪ Particles suspended in air are called aerosols ▪ These pose a threat to human health mainly through respiratory intake and deposition in nasal and bronchial airways ▪ In addition, soil or dust particles can act as a “ raft ” for biological entities ▪ Smaller aerosols travel further into the respiratory system and generally cause more health problems than larger particles ▪ Symptoms of particulate matter inhalation include decreased pulmonary function, chronic coughs, bronchitis, and asthmatic attacks Lecture 5: Aeromicrobiology Nature of Bioaerosols: ▪ A bioaerosol is an airborne collection of biological material ▪ Biological contaminants include whole entities such as bacterial and viral human pathogens ▪ They also include airborne toxins, which can be parts or components of whole cells ▪ In either case, biological airborne contaminants are known as bioaerosols, which can be ingested or inhaled by humans ▪ Bioaerosols vary considerably in size and composition depending on a variety of factors including the type of microorganism or toxin, the types of particles they are associated with such as mist or dust, and the gases in which the bioaerosol is suspended Lecture 5: Aeromicrobiology Nature of Bioaerosols: ▪ Bioaerosols in general range from 0.02 to 100 µm in diameter and are classified on the basis of their size: ▪ The composition of bioaerosols can be liquid or solid, or a mixture of the two, and should be thought of as microorganisms associated with airborne particles, or as airborne particles containing microorganisms ▪ This is because it is rare to have microorganisms (or toxins) that are not associated with other airborne particles such as dust or water Lecture 5: Aeromicrobiology Aeromicrobiological Pathway: Launching Transport Deposition Gravitational settling Downward molecular diffusion Surface impaction Rain deposition and electrostatic deposition Lecture 5: Aeromicrobiology Aeromicrobiological Pathway: ▪ The aeromicrobiological pathway describes: 1- The launching of bioaerosols into the air 2- The subsequent transport via diffusion and dispersion of these particles 3- Their deposition Lecture 5: Aeromicrobiology Aeromicrobiological Pathway: Launching: ▪ The process whereby particles become suspended within Earth’s atmosphere is termed launching ▪ Bioaerosols must be launched into the atmosphere to be transported ▪ The launching of bioaerosols is mainly from terrestrial and aquatic sources, with greater airborne concentrations or atmospheric loading being associated with terrestrial sources than with aquatic sources ▪ This phenomenon is related to the limited potential for microorganisms to reproduce while airborne ▪ Launching into the surface boundary layers can include, but is certainly not limited to, diverse mechanisms such as the following: ▪ air turbulence created by the movement of humans, animals, and machines; the generation, storage, treatment, and disposal of waste material; natural mechanical processes such as the action of water and wind on contaminated solid or liquid surfaces; and the release of fungal spores as a result of natural fungal life cycles Lecture 5: Aeromicrobiology Aeromicrobiological Pathway: Transport: ▪ Transport or dispersion is the process by which kinetic energy provided by the movement of air is transferred to airborne particles, with resultant movement from one point to another ▪ This “ energy of motion ” gained by airborne particles is considerable and can result in the dissemination of airborne microorganisms over long distances ▪ Transport of bioaerosols can be defined in terms of time and distance ▪ Some viruses, spores, and spore-forming bacteria have been shown to enter into mesoscale and even macroscale transport ▪ Pandemics are epidemics that occur over a wide geographic area, and influenza has been shown to spread from east to west around the world (e.g., Avian bird flu) Lecture 5: Aeromicrobiology Aeromicrobiological Pathway: Deposition: ▪ An airborne bioaerosol will eventually leave the turbulence of the suspending gas and will ultimately be deposited on a surface by one or a combination of interrelated mechanisms ▪ These mechanisms include: 1- Gravitational settling: The force of gravity acts on all particles heavier than air, pulling them down and essentially providing spatial and temporal limitations to the spread of airborne particles Lecture 5: Aeromicrobiology Aeromicrobiological Pathway: Deposition: 2- Downward molecular diffusion: This can be described as a randomly occurring process caused by natural air currents and eddies that promote and enhance the downward movement of airborne particulates Lecture 5: Aeromicrobiology Aeromicrobiological Pathway: Deposition: 3- Surface impaction: The process by which particles make contact with surfaces, such as leaves, trees, walls, and computers, with impaction there is an associated loss of kinetic energy ▪ In nature, it is rare to find flat, smooth surfaces on which wind currents are unobstructed 4- Rain deposition and electrostatic deposition: Rainfall deposition occurs as a condensation reaction between two particles (raindrop and bioaerosol), which combine and create a bioaerosol with a greater mass, which settles faster Electrostatic deposition also condenses bioaerosols but is based on electrovalent particle attraction ▪ All particles tend to have some type of associated charge ▪ Microorganisms typically have an overall negative charge associated with their surfaces at neutral Ph ▪ These negatively charged particles can associate with other positively charged airborne particles, resulting in electrostatic condensation Lecture 5: Aeromicrobiology Microbial Survival in the Air: ▪ Many microorganisms have specific mechanisms that allow them to be somewhat resistant to the various environmental factors that promote loss of biological activity ▪ Spore-forming bacteria, molds, fungi, and cyst-forming protozoa all have specific mechanisms that protect them from harsh gaseous environments, increasing their ability to survive aerosolization ▪ For organisms that have no such specific mechanisms, survival in aerosols can often be measured in seconds ▪ In contrast, organisms with these mechanisms can survive indefinitely ▪ # Viability is highly dependent on the environment, the amount of time the organism spends in the environment, and the type of microorganism Lecture 5: Aeromicrobiology Microbial Survival in the Air: 1- Relative Humidity: ▪ The relative humidity or the relative water content of the air has been shown to be of major importance in the survival of airborne microorganisms ▪ One mechanism that explains loss of viability in association with very low relative humidity is a structural change in the lipid bilayers of the cell membrane ▪ As water is lost from the cell, the cell membrane bilayer changes from the typical crystalline structure to a gel phase ▪ This structural phase transition affects cell surface protein configurations and ultimately results in inactivation of the cell ▪ Gram-negative bacteria react unfavorably to desiccation, whereas gram-positive cells are more tolerant of desiccation stress Lecture 5: Aeromicrobiology Microbial Survival in the Air: 2- Temperature: ▪ Temperature is a major factor in the inactivation of microorganisms ▪ In general, high temperatures promote inactivation, mainly associated with desiccation and protein denaturation, and lower temperatures promote longer survival times ▪ When temperatures approach freezing, however, some organisms lose viability because of the formation of ice crystals on their surfaces Lecture 5: Aeromicrobiology Microbial Survival in the Air: 3- Radiation: ▪ The main sources of radiation damage to microorganisms including bacteria, viruses, fungi, and protozoa are: Nonionizing radiation (UV) Ionizing radiation (X-rays) causes damage mainly in the form cause several types of DNA of intrastrand dimerization, with the damage, including single- DNA helix becoming distorted as strand breaks, double-strand thymidines are pulled toward one breaks another (Thymine dimers) Lecture 5: Aeromicrobiology Microbial Survival in the Air: 3- Radiation: ▪ Several mechanisms have been shown to protect organisms from radiation damage, these include an association of microbes with larger airborne particles, possession of pigments or carotenoids, high relative humidity, and cloud cover, all of which tend to absorb or shield bioaerosols from radiation ▪ # Many types of organisms also have mechanisms for repair of the DNA damage caused by UV radiation Lecture 5: Aeromicrobiology Microbial Survival in the Air: 4- Oxygen, OAFs, and Ions: ▪ It has been shown that these three factors combine to inactivate many species of airborne microbes ▪ Oxygen toxicity, is not related to the dimolecular form of oxygen (O2), but is instead important in the inactivation of microorganisms when O2 is converted to more reactive forms, these include superoxide radicals (O), hydrogen peroxide (H2O2), and hydroxyl radicals (HO) Lecture 5: Aeromicrobiology Microbial Survival in the Air: 4- Oxygen, OAFs, and Ions: ▪ Open air factor (OAF), it is closely linked to oxygen toxicity and has come to be defined as a mixture of factors produced when ozone and hydrocarbons (generally related to ethylene) ▪ The formation of other ions, such as those containing chlorine, nitrogen, or sulfur, occurs naturally as the result of many processes (including the action of lightning, shearing of water, and the action of various forms of radiation) that displace electrons from gas molecules, Positive ions cause only physical decay of microorganisms (e.g., inactivation of cell surface proteins), whereas negative ions exhibit both physical and biological effects such as internal damage to DNA Lecture 5: Aeromicrobiology Extramural aeromicrobiology: ▪ Extramural aeromicrobiology is the study of microorganisms associated with outdoor environments ▪ In the extramural environment, the expanse of space and the presence of air turbulence are two controlling factors in the movement of bioaerosols ▪ Extramural aeromicrobiology includes the spread of agricultural pathogens and the spread of airborne pathogens associated with waste environments Lecture 5: Aeromicrobiology Extramural aeromicrobiology: Agriculture: ▪ Rice and wheat are two of the major staple crops that are paramount to world food security ▪ Contamination of crops and animals via bioaerosols has a large worldwide economic impact ▪ Major pathogens of such crops are the wheat rust fungi ▪ These spore-forming fungi cause some of the most devastating of all diseases of wheat and other grains Waste Disposal: ▪ There are many hazards inherent in the treatment and disposal of wastewater and biosolid material ▪ Major hazards associated with waste effluents are pathogenic microorganisms including bacteria, viruses, protozoa, and helminths. Wastewater treatment plants utilize activated ▪ sludge and trickling filter systems, and all of these treatment processes potentially create relatively large amounts of aerosols, which have been shown to include pathogenic microorganisms ▪ Other aspects of the treatment process such as composting and land disposal are also associated with the generation of aerosols containing pathogenic microorganisms Lecture 5: Aeromicrobiology Intramural aeromicrobiology: ▪ Intramural environments have limited circulation of external air and much less UV radiation exposure ▪ Indoor environments also have controlled temperature and relative humidity, which are generally in the ranges that allow extended microbial survival ▪ Thus, these conditions are suitable for the accumulation and survival of microorganisms within many enclosed environments, including office buildings, hospitals, laboratories Lecture 5: Aeromicrobiology Intramural aeromicrobiology: Buildings: ▪ Many factors can influence bioaerosols and therefore how “ healthy” or how “ sick” a building is ▪ These include the presence and/or efficiency of air filtering devices, the design and operation of the air circulation systems, the health and hygiene of the occupants, the amount of clean outdoor air circulated through the building, the type of lighting used, the ambient temperature in the building, and the relative humidity Public Health: ▪ Pathogens in the AMB pathway can be a potential source of deadly diseases, but AMB pathway also has potential for use in immunization against disease Hospitals and Laboratories: ▪ Hospitals and microbiology laboratories are the two indoor environments with perhaps the greatest potential for the aerosolization of pathogenic microorganisms ▪ Hospitals, because they are centers for the treatment of patients with diseases ▪ The microbiological laboratory is also a breeding ground for pathogenic agents, because of this, handling procedures have been developed and refined to protect laboratory workers The End