Download Microbiology and Pathogens

Microbiology and Pathogens
Teacher - Peter Mitchell
BSc (Anatomy & Histology)
Histology). Dip Health Science (Massage Therapy)
Microbiology
gy is the study
y of organisms
g
not
visible to the naked eye.
Thus requiring the use of a microscope to see
them.
Microscopic organisms are sometimes called
microbes
The biomass of the microbial kingdom
outweighs that of the animal kingdom!
Not all microbes are harmful to humans
“ Despite the fact that the microbial biomass outweighs the total
animal biomass by a factor of 100,
100 most of us sail through life
unbothered by the microbial ocean. They are the host; we the
pampered and tolerated guest. ”
William Boyd (Pathologist)
There are manyy examples
p
of microbes being
g
beneficial to humans
• Some bacteria live in our gut and help digest food
• Some yeasts and bacteria are used in baking, brewing
and cheese making
What are Germs?
Micro organisms are found in abundance throughout
the environment.
Germs are micro organisms that are likely to cause
disease.
Only a very small number of microbes are pathogenic,
i e capable of causing disease
i.e.
Bacteria are just one type of micro-organism,
micro organism,
alongside viruses, fungi and protozoa and parasites
y Direct damage (lysis of cells by intracellular organisms)
y Toxin production (vomiting, diarrhea, paralysis, haemolysis, necrosis)
g
p
y
y
y Damage through inflammation and immune g
g
response
The presence of pathogens does not
automatically
t
ti ll iimply
l di
disease.
Context is important
p
e.g.:
g
E-coli is normally found in the gut and is not
harmful in normal concentrations, however if ecoli numbers increase problems can arise.
OR
If sufficient numbers of e-coli enter the blood via
non-intact skin or mucous membranes, serious
disease can occur.
Smallest
Viruses
Bacteria
Fungi
Protozoa & Parasites
Largest
Wh t is
What
i a virus?
i ?
y It is very small
small, typically 0
0.1um
1um
y It is not a true cell
y It is not an independently living organism. It must be
inside a living cell to replicate
y They have genetic material but lack cell membranes,
cytoplasm and machinery
y The virus uses the host’s cell's machinery and
enzymes to generate virus parts which are later
assembled
bl d iinto
t new virus
i
particles
ti l which
hi h lleave th
the
cell to infect other cells
y It can infect bacteria, fungi, plants, animals and
man
y It may remain viable for long time, even in dry
conditions
y It can survive but does not grow in food
Nearly 1000 different types of viruses are known to infect
humans and it has been estimated that they account for
approx. 60% of human infections. The young, elderly and
immuno-compromised are particularly at risk from virus
infections
Many viral diseases are well known and easily identified:
y from colds and flu to chicken pox and measles
y from mumps and herpes to polio, hepatitis and HIV
From the ‘Clinic Hygiene’ point of view, we are mainly concerned with
virus infections relating to poor personal or surface hygiene
hygiene, and are
thus preventable
y Gastrointestinal infections
Gastroenteritis
Diarrhoea
Infectious intestinal disease
y Respiratory infections
Flu
Fl
Common cold
Bronchitis
y Skin
S
presenting
p ese t g co
conditions
dto s
Papilloma
Herpes – simplex & Zooster
Chicken pox (Poxivirus
(Poxivirus))
Papilloma Virus
Herpes zoster
Herpes simplex
Poxivirus - Chicken pox
Bacteria are p
prokaryotes
y
((membrane and cell wall)) and
have a characteristic cellular organisation.
They are simple,
simple small,
small unicellular organisms
varying in size between 1-20 um long
Damage tissue directly
Also damage tissue by releasing toxins
Bacteria can be classified by shape
Spherical (coccus)
e.g. Staphylococcus
aureus
Spiral/helical
e.g. Treponema
Rod (bacilli)
e.g Escherichia coli
Sphere shaped
Diplococci- bacterial pneumonia
Staphylococcus aureus- wound infections, boils and infected
acne.
Streptococci- common culprits in throat infections
Rod shapedshaped bacilli
tetanus
tuberculosis
Spiral
syphilis
Typical Growth Curve for a Bacteria Population
y Lag Phase
growth is slow whilst they become used to their new environment
and nutrients
y Log Phase
once the metabolic machinery is running, they start multiplying
exponentially, doubling in number every few minutes
y Stationary Phase
as more and more bacteria are competing for nutrients which are
decreasing, growth stops and the number of bacteria stabilises
y Death Phase
toxic waste products build up, nutrients have run out and the
bacteria begin to die
Impetigo
Staphylococcus Aureus “Golden Staph”
Streptococcus Pneumoniae “meningitis”
Acne
Fungi
g are eukaryotic
y
and exist in different g
growth
forms in different environments. They range from small
single cells such as yeasts (~5um) to large complex
structures
such as mushrooms (~5cm)
( 5cm)
The high humidity and temperatures often found in
g
bathrooms and kitchens are conducive to fungal
growth. Mould, or mildew as it is sometimes referred,
likes warmth and moderate
to high humidity
Fungi responsible for human disease can be divided
into two distinct morphological forms
y Yeasts
which grow as oval or spherical single cells like
bacteria and multiply by budding and division
y Filamentous fungi
more commonly known as moulds, consist of long,
branching hyphae forming a mycelium
mycelium. Asexual
reproduction results in formation of spores
The can be responsible for infections
They
They can cause an allergic response
Fungi cause discolouration and deterioration of
household surfaces giving the characteristic
blackening of walls
walls, tile grouting
grouting, plaster and around
window frames
Can cause unpleasant odours which are difficult to
disguise. Fungi such as Aspergillus, Penicillium, and
Alternata have been found to produce volatile organic
compounds
d
Numerous ffungii h
N
have b
been ffound
d tto produce
d
volatile
l til
organic compounds (VOC) and it has been
suggested that these affect the health of persons living
in mouldy houses. Symptoms include headache, eye,
nose and throat irritation and fatigue
VOC’s have been implicated in health issues relating
to sick building syndrome
Spores of toxigenic fungi contain mycotoxins (toxic
secondary metabolites). Many fungal spores are small
enough to reach the alveoli in the lungs. The
mycotoxins may be transported via the blood from the
lung to other body sites,
sites possibly causing other effects
e.g. skin lesions
Fungi cause 2 types of infection:
y Superficial mycoses
y Deep mycoses
Fungus grows on the body surface in skin, hair and nails
Spread by direct contact
Highly contagious and easily spread
E.g.
y Candida albicans ((thrush and nappy
ppy rash))
y Athlete’s foot
y Ring worm
Involve internal organs, usually life-threatening
Rare except in immunocompromised people
Caused by opportunistic fungi (e.g. Aspergillus)
Acquired by inhalation of spores or by entry through
wounds
Some are part of the normal body flora and are harmless
unless the body’s defences are compromised in some way
(e.g. Candida)
Almost all microbial allergens are fungal in origin
Allergic rhinitis (hay fever)
Bronchitis
Asthma
Extrinsic allergic alveolitis
Asthma can be initiated and provoked by allergens
commonly encountered in the general environment,
for example pollens (trees,
(trees grass),
grass) house dust mites
and moulds.
Tinea
Pedis
ed s
Tinea Cruris
Ti
Tinea
C
Corporis
i
Tinea Versicolor
Protozoa are single-celled eukaryotes
Live in water or moist places or other
organisms as parasites
Have a resistant transmissible cyst
stage
Transmission to humans via insect bite
or accidental ingestion of infective
stages
y Cryptosporidium spp.
infects the intestines causing Cryptosporidiosis
Cryptosporidiosis. Large outbreaks
are associated with contaminated water or treatment deficiency of
water supplies
y Gi
Giardia
di lamblia
l bli
causes giardiasis, an infection of the small intestine, spread via
contaminated food and water and by direct person-to-person
contact. Ingestion of one or more cysts may cause disease
y Entamoeba histolytica
an amoeba infecting the large intestine, causes
di h
diarrhoea/dysentery,
/d
t
spread
d via
i contaminated
t i t d water
t or ffood
d
y Toxoplasma gondii
causes toxoplasmosis,
p
, a very
y severe disease that can p
produce
central nervous system disorders
Parasites are larger and more complex than
protozoa.
Common examples of parasites are:
y Tape worms
y Hook worms
y Pin
Pi worms
Worms are very contagious and are transmissible via
the faecal – oral route.
That is; the worm eggs are normally ingested due to
poor hand hygiene and cross contamination of
inanimate objects
Micro-organisms are introduced continually into the clinic via:
people food,
people,
food water,
water insects,
insects air.
air Wet sites such as sinks,
sinks toilets,
toilets
dishcloths and facecloths can also support microbial growth and
themselves become reservoirs of potentially hazardous microorganisms.
T
Towels,
l washing
hi b
basket
k t etc
t
Many organisms occurring in the clinic are of little consequence.
Some organisms have the potential to cause infectious disease
Some people carry highly pathogenic organisms without
themselves being affected - other family members unaware of
hazard
Hands, and a whole range of food and hand contact surfaces,
combine to provide transfer routes that can move pathogens
around the home and ultimately
y into the body
y producing
g infection