Announcements:
 
 
Today’s Plan:
 
Start Epidemiology
and Disease Transmission
 
 
Unit 5. Survey - Role of Microbes in Health and Disease
 
A. Environmental Microbiology – applications of microbial interactions
B. Medical Microbiology
1.Epidemiology
a. Terminology
b. Reservoirs - where pathogens persist
c. Transmission
i. contact
ii. food and water
iii. air via droplets, dust, soil
iv. vectors
a) mechanical
b) biological
 

Epidemiology

Study of disease transmission

 
Indigenous Microbes

Live naturally on the organism

“used-to” the environment/conditions
Help to thwart competitors/pathogens

 

How do we get disease?
 
  • Direct Contact
 
  • Fomites

                Telephones, toilets, coins etc.

                Transfer from inanimate objects
                Anywhere there is a toilet, there
                    is a need for Sani-Touch.TM”
  • Poor water quality and poor hygiene practices
            Used to water crops

            Used to wash foods

 
            Lack of immune response for tourists
  • Droplets

        Breath, sneezing, coughing, spitting

  • Particles like dust and soil
 
        Black Mold

 

  • Vectors –where were these flies last?
        Plate incubated after cockroach walked on it
        Do want this walking on your dinner plate?

 

Mosquito- malaria, west nile virus, yellow fever
Dust mites- allergies skin infections asthma
Bubonic Plague
 

Center for Disease Control (CDC)

Atlanta, GA

SARS

 
Epidemiology

Unit 4. Survey - Role of Microbes in Health and Disease

 
A. Environmental Microbiology
B. Medical Microbiology
1. Epidemiology
2. Significant/Interesting Human Diseases
a. Skin
 Staph and Strep
Streptococcus pyogenes
Group A Strep
Invasive - flesh-eating strep
Staphylococcus aureus
Toxic Shock Syndrome
MRSA
b. Nervous system
 Meningitis
c. Cardiovascular and lymphatic system
 Hemorrhagic fevers
 Lyme disease
 The plague
 

Skin cross section

Figure 21.1
Hair follicles provide
a pathway for organisms
to invade deeper layers
 

Staphylococcus aureus  Streptococcus pyogenes

S. Aureus is a key nosocomial pathogen
 
Nosocomial means contracted in the hospital
S. Aureus is a key nosocomial pathogen.
Transmitted on skin
Pathogenic
Exposed to antibiotics (resistant
 

Biochemical Tests

•

Coagulase Test

–Tests for clotting of blood fibrin
–S. aureus pathogens are coagulase +
–S. epidermidis non-pathogenic coagulase –
–Clots keep away phagocytes

 

•
•Catalase Test- H2O2ΰH2O and O2
–Cat + is Staphylococcus
–Cat – is Streptococcus
 

Beta Hemolysis

Toxins destroy red blood cells

in blood agar.
 
If toxin lyses RBC is can
usually lyse other cells
 

Jim Henson

Died from bacterial pneumonia  from group A strep
 

Strep throat-non-invasive GAS

Streptococcus pyogenes = GAS = Group A Streptococcus
 

Impetigo = non-invasive GAS

Also Staphylococcus aureus
 

Erysipelas = non-invasive GAS

Bacteria causes lifting of the skin
Often a progression from Strep throat
 
Flesh eating strep infection
 
Progression
Day 1 - trivial wound or bruise (scratch, bug bite)
Day 2 - redness, heat, swelling, pain
Day 3 - color changes from red to purple, blisters
Day 4-5 - purple areas become gangrenous

Day 7-10 - Dead skin separates, patient is dull and unresponsive, shock.

 
Treatment
Debridement, amputation,
antibiotics
 
Prevention
Clean wounds and watch them
WASH YOUR HANDS
 

Toxic Shock Syndrome

Toxins produced from S. aureus in the blood stream
 
From surgery, packings, tampons, etc.
 
Scalded skin syndrome is late stages
 

Methicillin Resistant Staphylococcus aureus (MRSA)

Best prevention, Wash your hands!
 

Meningitis-Caused by bacteria, viruses fungi and protozoans

Bacterial meningitis is serious, viral is usually not severe
Tough to enter

 

•Encephalitis -Brain inflammation

 

•
•Meningitis- inflammation of area surrounding brain and spinal cord
•
•Inflammation increases the permeability of the blood/brain barrier
Capsules

protect bacterial pathogens

Neisseria meningitidis
Streptococcus pneumoniae
Haemophilus influenzae
These 3 account for 70% of the cases and 70% of deaths
 
Toxins and cell waste cause shock and death