1. Environmental Health Microbiology ENVR 133
Lecture 1
Mark D. Sobsey

2. Microbes and the Environment
Microbes are fundamental and essential to life on earth
Most microbes in the environment are harmless or beneficial
A small proportion of microbes are capable of causing disease in humans and/or other hosts
Some are “frank” pathogens and amost always have the potential to cause illness
Others are “opportunistic” pathogens and only cause illness in compromised hosts or unusual conditions of exposure
Yet others are capable of causing illness when they get into parts of the body by unusual circumstances that are normally unavailable to microbes (deep tissues)
Microbes are almost everywhere on the planet and the more we look the more places we find them

3. Routes or Pathways of Exposure for Environmentally Transmitted Infectious Diseases
Water
Wastes
Food
Fomites
Vectors
many human pathogens have animal reservoirs; zoonoses
Air
Soil
Many pathogens are potentially transmitted by multiple routes

4. History of Microbiology and Infectious Diseases: Role of Water in Cholera Transmission - London
Water, wastes and microbes are traditional/historical concerns
Sir John Snow: cholera in London and the Broad Street pump
A key historical event in environmental health, epidemiology, infectious disease, water hygiene, environmental engineering and GIS: he did it all!
Developed a population-based approach to track the spread of cholera in individual London boroughs; source was unknown
Plotted the distribution of reported cases on a map
In one London borough the source was water polluted by sewage, which entered the Thames above the water intake.
In another it was one water pump.
Snow ordered the handle to be removed from the "Broad Street Pump“; locally the epidemic subsided.
Explained the etiology of cholera and the mechanism of its transmission via contaminated water.

5. Sir John Snow and his Maps of the Water Plants of London

6. Sir John Snow’s 1854 Map of the Broad Street Pump Outbreak
Cholera cases, each marked by a hash, were clustered around the Broad Street Pump and were associated with drinking water from this pump

7. Microbiology and Infectious Diseases
Infectious disease risks from water, poor sanitation and hygiene, food and air are still with us in the developed and developing world
Global Water Supply and Sanitation Assessment 2000
2.4 billion people have inadequate sanitation
1.1 billion people have inadequate/unsafe water
4 billion cases of diarrhea every year
2.2 million deaths from diarrheal disease every year
Most illness and death in children <5 years old
Less services in rural than in urban areas
Urban settlement/slums remain a problem
In the developing world wastewater treatment is rare
Water losses in large urban systems is typically 40%
Millennium Development Goals call for halving by 2015 the number of people lacking sustained access to safe water
a key goal for reducing World poverty

8. Global Burden of Infectious Diarrheal Disease and the Role of Water
Burden of infectious diarrhea is higher in developing than in developed countries
Developed: 1 illness per person per year
Undeveloped: about 5 illnesses per person per year
The attributable fraction of diarrheal illness for different exposure routes or sources may not be very different in developed versus developing countries:
1/4th contact
¼ water
¼ food
1/4 other
Most waterborne disease is caused by microbes – not chemicals

9. Classes or Categories of Pathogenic Microorganisms: The Microbial World
Viruses: smallest ( µm diameter); simplest:
nucleic acid + protein coat (+ lipoprotein envelope)
Bacteria: µm diameter; prokaryotes; cellular; simple internal organization; binary fission.
Protozoa: most >2 µm- 2 mm; eucaryotic; uni-cellular; non-photosynthetic; flexible cell membrane; no cell wall; wide range of sizes and shapes; hardy cysts
Groups: flagellates, amoebae, ciliates, sporozoans (complex life cycle) and microsporidia.
Helminths (Worms): multicellular animals; some are parasites; eggs are small enough ( µm) to pose health risks from human and animal wastes in water.

10. THE MICROBIAL WORLD:
SIZES OF MICROBES

11. Viruses smallest (0.02-0.3 micrometers diameter
simplest (nucleic acid + protein coat (+ lipoprotein envelope)
spherical (icosahedral) or rod-shaped (helical)
no biological activity outside of host cells/or host organisms
obligate intracellular parasites; recruit host cell to make new viruses, often destroying the cell
non-enveloped viruses are most persistent in the environment
protein coat confers stability
enteric viruses are most important for environmental health
transmitted by direct and indirect contact, fecally contaminated water, food, fomites and air.
respiratory viruses also important
transmitted by direct and indirect contact, air and fomites (some by water and food, too).

12. ENTERIC VIRUSES: ~25-100 nm diameter
Nucleic acid + protein coat (+envelope)
Nucleic acid:
DNA or RNA
single or double-stranded
1 or several segments
Capsid (protein coat):
multiple copies of 1 or more proteins in an array
Envelope:
lipid bilayer membrane + glycoproteins)
typically acquired from host cell membranes

13. Enteroviruses: ~27-30 nm diameter; single-stranded RNA; icosahedral protein coat (capsid)

14. Human Rotavirus: ~75 nm diameter; double-layered capsid; double-stranded, segmented RNA

15. ADENOVIRUSES: ~80 nm diameter; double-stranded DNA; protein coat with attachment fibers

16. Procaryotes: Bacteria and Others
Cellular organisms
Simple internal organization
Multiply by binary fission
Diameter ~ micrometer
Envelope: cytoplasmic membrane, cell wall & capsule (polysaccharide)
Some have appendages:
flagella: for locomotion
pili:
attachment to other cells for genetic transfer;
virus receptor site

17. Pathogenic Bacteria
Pathogenic bacteria possess virulence properties in the form of structures or chemical constituents that contribute to pathophysiology
Outer cell membrane of Gram negative bacteria: endotoxin (fever producer)
Exotoxins
Pili: for attachment and effacement to cells and tissues
Invasins: to invade cells
Some bacteria make spores:
highly to physical and chemical agents and
very persistent in the environment
Enteric and respiratory bacteria are important in environmental health

18. Escherichia coli cells: ~0.5 x 1.0 micrometers
Typical rod-shaped bacteria:
fecal indicator and pathogenic strains

19. Procaryotic Cell (left) and Eucaryotic Cell (right)

20. Unicellular Eucaryotes: The Protists
Complex internal organization:
organelles: nucleus, mitochondria, etc.
Wide range of sizes; 2 micrometers and larger

21. Protozoa Important group of protists for environmental health
Uni-cellular; non-photosynthetic; flexible cell membrane; no cell wall
Wide range of sizes and shapes; 2 micrometers to 2 mm
flagellates
amoeba
ciliates
sporozoans (complex life cycle)
microsporidia

22. Cryptosporidium parvum oocysts: ~5 m diameter Acid fast stain of fecal preparation

23. Giardia lamblia: flagellate protozoan parasite
Giardia lamblia cyst: ~10 x 8 micrometers

24. More Protists: Fungi Fungi (yeasts and molds): non-photosynthetic
immotile;
rigid cell wall
Molds:
grow as branched, interlacing chains or filaments (hyphae) called mycelia
Yeasts:
do not form mycelia
grow as single cells that bud
sexual reproduction possible
Mitospores (conidia) of Penicillium, one of the asexual Ascomycota
Yeasts

25. Wide range of sizes and shapes
More Protists: Algae
Photosynthetic
Rigid cell wall
Wide range of sizes and shapes
2 micrometers and larger
Nostoc
Anabaena and Aphanocapsa

26. Helminths (Worms) Multicellular animals
Some are human and/or animal parasites
Eggs are small enough to pose environmental health problems from human and animal excreta in water, food, soil, etc.
Several major groups:
Nematodes (roundworms): ex. Ascaris
Trematodes (flukes; flatworms): ex. Schistosomes
Cestodes (tapeworms): pork and beef tapeworms
Most helminthic disease is not waterborne, but it is associated with water contact, food, and exposure to fecal wastes and fecally contaminated soil.

27. Roundworm: Ascaris lumbricoides

28. Roundworms: Hookworms