Environmental Health Microbiology ENVR 421

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Environmental Health MicrobiologyENVR 421

• Lecture 1
• Mark D. Sobsey

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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 almost 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 (e.g., into deep tissues via wounds)
• Microbes are almost everywhere on the planet and
  the more we look the more places we find them

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Routes or Pathways of Exposure for
Environmentally Transmitted Infectious Diseases

• Water
• Wastes
• Food
• Fomites
• Vectors
• many human pathogens have animal reservoirs
  zoonoses
• Air
• Soil
• Sediment

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Pathogen-Human/Animal-Environmental Relationships

• Many human pathogens are potentially transmitted
  by multiple environmental routes
• Some pathogens exist in the environment
  independent from human hosts
• their existence and perpetuation is not dependent
  on human or (for some) even animal hosts
• Other pathogens depend exclusively on human for
  their existence and perpetuation
• Viruses smallpox (Variola) virus (eradicated)
  poliovirus
• Bacteria Shigella spp. Salmonella typhi
• Parasites Ascaris lumbricoides (round worm)

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History of Microbiology and Infectious Diseases
Role of Water in Cholera Transmission - London

• Water, wastes and microbes are traditional/histori
  cal 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.

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Sir John Snow and his Maps of the Water Plants
of London
http//www.ph.ucla.edu/epi/snow.htmlBROAD
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Sir John Snows 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

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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 lt5 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

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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

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Classes or Categories of Pathogenic
MicroorganismsThe Microbial World
Viruses smallest (0.02-0.3 µm diameter)
simplest nucleic acid protein coat (
lipoprotein envelope) Bacteria 0.5-2.0 µm
diameter prokaryotes cellular simple internal
organization binary fission. Protozoa most gt2
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 (25-150 µm) to pose health risks from
human and animal wastes in water.
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THE MICROBIAL WORLD SIZES OF MICROBES
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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).

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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

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Enteroviruses 27-30 nm diameter
single-stranded RNA icosahedral protein coat
(capsid)
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Human Rotavirus 75 nm diameter
double-layered capsid double-stranded,
segmented RNA
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ADENOVIRUSES 80 nm diameter double-stranded
DNA protein coat with attachment fibers
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Procaryotes Bacteria and Others

• Cellular organisms
• Simple internal organization
• Multiply by binary fission
• Diameter 0.5-1.0 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

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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

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Escherichia coli cells 0.5 x 1.0
micrometers Typical rod-shaped bacteria fecal
indicator and pathogenic strains
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Procaryotic Cell (left) and Eucaryotic Cell
(right)
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Unicellular Eucaryotes The Protists

• Complex internal organization
• organelles nucleus, mitochondria, etc.
• Wide range of sizes 2 micrometers and larger

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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

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Cryptosporidium parvum oocysts 5 ?m
diameterAcid fast stain of fecal preparation
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Giardia lamblia flagellate protozoan
parasite Giardia lamblia cyst 10 x 8 micrometers
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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
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More Protists Algae

• Photosynthetic
• Rigid cell wall
• Wide range of sizes and shapes
• 2 micrometers and larger

Nostoc
Anabaena and Aphanocapsa
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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.

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Roundworm Ascaris lumbricoides
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Roundworms Hookworms
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Recommended Readings

• Relevant material in any microbiology text
• Indicators for Waterborne Pathogens, National
  Research Council, National Academy of Sciences,
  National Academy Press, Washington, DC, 2004.
• Chapters 1, 3 and 4
• Water Quality Guidelines, Standards and Health.
  2001. L. Fewtrell and J. Bartram, eds., IWA
  Publishing, London, for WHO, Geneva.
• Chapter 4, 5 and 13
• Assessing microbial safety of drinking water
  Improving approaches and methods, 2003. A.
  Dufour, M. Snozzi, W. Koster, J. Bartram, E.
  Ronchi and L. Fewtrell, eds., IWA Publishing,
  London for WHO, Geneva.
• Chapters 1, 2 and 8