Microbiology – Chapter 13
Pathology: Science of study of disease
Etiology: Cause of disease; often microbial
Flu – etiological agent, Influenza virus
Tb – M. tuberculosis
Pathogenesis: development of disease in the host Norwalk virus; Fecal – oral, diarrhea
Disease: altered state of health, host body is
changed, upset of homeostasis
Microbiology – Chapter 13
Epidemiology: Science of the study of how
diseases are acquired and spread in a
population
Outside assignment 3: Note that the last
question has been changed to focus on MDR
bacterial infections. Be sure to get a copy of
the last page from instructor
** You may have to do some research ato
answer all of the questions. Use other Micro.
Books or other research tools. ***
Microbiology – Chapter 13
Relationship between organisms:
Normal flora: normal inhabitants of the host
ex. S.epidermidis on skin, E.coli in
intestine
Commensalism – One organism benefits; the
other unaffected; can be opportunistic
infector
Mutualism: both benefit; E. coli makes us
Vit. K; We provide nice environment and food
Microbiology – Chapter 13
Parasitism: One benefits at the other’s
expense; tapeworm or leach
Virulence: potency; how quickly they infect,
spread, cause tissue damage or disease
symptoms Influenza A H5N1, very virulent
form of flu, or encapsulated pneumococci
Virulence factors: factors that cause disease
or aid in spread of disease quickly in host or
to other hosts (more later)
Microbiology – Chapter 13
Pathogen: actual agent of disease, MRSA –
S. aureus
BACTERIAL, VIRAL, FUNGAL, HELMINTH
Carrier: Infected healthy individual, no
symptoms (asymptomatic), or very mild form
of disease, yet they both can spread disease
to others – many bacterial and viral
pathogens
Classic case was typhoid Mary (look it up)
Microbiology – Chapter 13
Reservoir: Where pathogen is maintained ,
can be in an organism (animal), in the
environment (stagnant water - Legionella), or
even in soil (Clostridia)
Vector: Agent that spreads pathogens from
host to host
1. Arthropod: flea; mosquito, tick
2. Inanimate: things, toys, dirty hands,
needles, (sometimes called
“fomites”)
Microbiology – Chapter 13
Nosocomial infections: hospital acquired
infections – see table in text and know it
Next slide******
MRSA both HA and CA
Pseudomonas - respiratory impaired, burn
patients
E. coli and Proteus – UTI; long term catheter
patients
Fig. 13.13
Review Koch’s postulates
Microbiology – Chapter 13
Nine routes of infection
**** Know this; be able to list and give an
example of each****
1. Respiratory droplets: cough sneeze, air
born droplets
Flu, colds, Strep throat even Staph
infections of wounds
Fig. 13.12
Microbiology – Chapter 13
2. Fomites
Inanimate objects that spread disease agents
Shared drinking cups, baby toys in a nursery,
contaminated sharps
** add pictures**
Microbiology – Chapter 13
3. Direct body contact- Oh what fun!!
Person to person:
STD,
Impetigo
Microbiology – Chapter 13
4. Fecal – Oral
Feces contamination of food water, even dirty hands (hands are a vector,
or even a house fly or roach)
Enteric diarrheal disease;Helminth
Protozoans: Giardia, Balntidium
Microbiology – Chapter 13
5. Arthropod Vectors
Flies, fleas, mosquito, tick
Fig. 13.11
Microbiology – Chapter 13
6. Airborne
Particles suspended in air (dry; dust), travel long distances;
tb, anthrax spores (potential for WMD), Respiratory fungal
infections (Histoplasma)
Microbiology – Chapter 13
7. Parenteral
Direct transmission via blood: universal precautions
HIV, HVB, HVC
Microbiology – Chapter 13
8. Deep Wound trauma
Gas gangrene and tetanus, even wound botulism
Beaman’s world
infant tetanus
Microbiology – Chapter 13
9. Horizontal: Mother to infant
Prenatal: across the placenta; HIV
Perinatal: at birth, STD like gonorrhea and
syphilis, even Chlamydia blindness
Microbiology – Chapter 13
• 9. Horizontal: Mother to infant
• Perinatal: at birth, STD like gonorrhea and
syphilis, even Chlamydia blindness
Microbiology – Chapter 13
Virulence factors
Virulence factors – factors that aid or enhances the microbes ability to
invade and spread within the host (know for test) Ex. List the
categories of “virulence” factors in microbes; explain each category,
and give an example of a disease causing agent for each category.
Adherence: In order for a microbe to cause disease it first must adhere
to a host surface. Some microbes produce materials or structures
that allow them to adhere (stick) to membranes or surfaces, and
thus escape defenses
Pili (fimbriae) – Neisseria gonorrhea, if a strain has no pili it is not
pathogenic. The chemicals that allow such attachment are called
“adhesins” – They are often glycoproteins or protein that bind to
receptors on host cell surfaces.
Glycocalyx – The capsule again is a tightly bound polyscaccharide
material on the outside of certain bacterial cells (part of a bacterial
envelope). Streptococcus pneumoniae is good example. Virulent
strains are encapsulated; non-virulent strains are not. Recall the
classic “Griffith experiment” from chapter 9? Transformation?
Spikes – Viral envelopes of some viruses, Influenza a, H5N1
Fig. 13.4
Microbiology – Chapter 13
Other adhesions
N. menigitidis (bacterial meningitis agent)
produces protein a, a surface
adhesion on the pili
Mycoplasma pneumonia (atypical
bacterial pneumonia) has a surface
adhesion that binds to receptor on
mucus membrane lining of the
respiratory tract
Other Adhesions
SEM of Pseudomonas, Gram (-)
Microbiology – Chapter 13
Toxins – Poisonous microbial bypoducts that are produced
by the microbe and diffuse into tissues causing
damage/ enhance invasion/ avoid defenses
Exotoxins – excreted outside of cell, both Gram+ and Gram –
bacteria produce some of these highly destructive proteins.
Staphylococcus aureus - Staph exotoxin that causes FBI
Another causes “SSSS” Staph Scalded Skin
Syndrome (exfoliate)
C. botulinum – most powerful neurotoxin, - a taste can kill you
Streptococcus pyogenes - has several tissue destroying toxins;
Necrotoxin of flesh eating Strep would be a good example.
Endotoxin – Released by many Gram (-) bacteria when cells lyse,
Examples:
Lipid A, lps in many pathogenic enteric bacteria like
Shigella, can
cause high fevers and
even shock.
•Endotoxin - Lipid A – raises fever, and shock in
Gram (-) pathogens
Endotoxin - Lipid A – raises fever, and shock in
Gram (-) pathogens
Fig. 13.6
Microbiology – Chapter 13
Enzymes that help invasion
Collagenase – breaks down collagen, the protein holding cells
together, thus allows spreading. Clostridia that invade tissue
can produce these proteases to digest connective tissue
elements (C. perfringens)
Hyaluronidase – breaks down hyaluronic acid, the polysachharide
that may hold some cells together, S. pyogenes produces such
an enzyme
Causes necrosis and blackening of tissue (inches of
progression in hours)
Coagulase – Affects the fibrin in blood causing it to clot, Staph
aureus produces one and maybe prevents phagocytosis.
Hemolysin – This exotoxin is an enzyme and lyses RBC. S.
pyogenes
Alpha and Beta Hemolysis of the Strep.
Virulence Factors
• Enzymes: Collagenase, Hyaluronidase
Virulence Factors
• Enzymes: Hemolysin – lyse RBC
Microbiology – Chapter 13
Evading defenses – Once in tissue some
organisms can “evade” the natural defense of a
host.
Capsule – Phagocytes can’t engulf the pathogen – S.
pneumoniae
Surface proteins – Proteins prevent phagocytosis
(leukostatin, leukocydins of Staph and Strep)
Survive inside phagocyte – Get a free ride and spread
(Tubercle bacillus, Listeria bacillus, and others)
Evade immune response - Genetic variability occurs
and the result is that antibodies lose effectiveness
quickly – genetic shift/drift of the antigenic nature of
the Influenza A virus, (FDA today is meeting to
SWAG for next years vaccine)
Virulence Factors
• Evade defenses: Capsule – resisting
phagocytosis, Strep.
Virulence Factors
• Adherence: Glycocalyx (capsule)
Virulence Factors
• Surface proteins : Leukocydin, S. aureus
• (MRSA) – Attacks WBC’S
M. tuberculosis inside lung
macrophage
Virulence Factors
• Survive inside phagocyte, tubercle
bacillus
•
Evading immune response
• Influenza
Virulence Factors
• Evade immune response : Influenza A
• H5N1 – “Bird Flu”
•
Microbiology – Chapter 13
Iron binding – Iron is tightly bound in our bodies and microbes need it to
grow,
Those organisms that can acquire it have and advantage and can
spread faster;
more virulent – Cholera is an example, HIB (H. influenza B)