Micro lab Quiz 7

Epidemiology

Science that deals with when and where diseases occur and how they are transmitted in the human population

Endemic diseases

A disease always present in a population; a constant presence and/or usual prevalence of a disease or infectious agent in a population within a geographic area

Example of an endemic disease

Common cold

Epidemic disease

Many people in a given area acquire a disease in a short period of time

Example of an epidemic disease

Influenza

Pandemic disease

The disease is spread over the population of many continents

Example of pandemic

COVID-19

Index case

first case of a disease

Vectors

Mechanical or biological transmission

• Mosquitos are big offenders

Direct transmission

Spread between hosts via direct contact or droplet spread

Mechanism transmission

indirect transmission on the surface of a

mechanical vector such as an insect

• Think of an insect carrying bacteria on its feet and then landing on your food

• The vector itself is not infected

Biological transmission

indirect transmission via the saliva of a

biological vector

• Think of a mosquito carrying Zika or Malaria

• The vector itself is infected and will spread it from person to person

Host

an organism that harbors the pathogen

Pathogen

a disease-causing microorganism which needs to come in contact with the host to cause disease

Reservoir

continual source of infection or disease; can be a human, an animal, or a non-living thing such as soil

Example of reservoir

Rodents such as rats and squirrels serve as reservoirs for the bacteria Yersinia pestis, the causative agent of plague

Carrier

a person that harbors a disease but is not displaying any signs of disease

Typhoid Mary

was a cook who unknowingly infected 51-122 people with typhoid fever. Three people were confirmed to have died, but some estimates think 50 may have perished. First asymptomatic case in U.S.

Calculate infection rate

# of infected persons/ population at risk

Physical methods of control

Heat, dry heat, moist heat, UV light,

Heat

Different bacteria exhibit different tolerances to heat (also pH, media,

etc.)

Psychrophilic

15⁰C or below

Psychrotrophic

20-30⁰C

Mesophilic

25-40⁰C

Thermophilic

45-65⁰C

Hyperthermophilic

80⁰C or above

Dry heat

Not as effective at transferring heat to cells

• Examples: hot oven, Bunsen burner flame

• At 170⁰C it would take two hours for sterilization

Moist heat

Very effective at transferring heat to cells

• Examples: boiling, pasteurization, autoclaving

• Pasteurization: 63⁰C for 30 min or 72⁰C for 15 sec

• Boiling: 100⁰C for 10 min

UV light

Come mostly from space but some is produced on earth

• Ionizing vs nonionizing

• UVA, UVB, UVC

• We need UVB rays to synthesize Vitamin D

• Tanning should be limited to 13 minutes 3 times a week

• Mutagens

UV Damage Mechanism and Repair

UV light induces thymine dimers

• Photolyases can fix thymine dimers

• Light repair or photoreactivation

• Dark Repair

Disinfectant

are chemicals that lower the levels of microbes on the

surfaces of inanimate objects

Antiseptics

decrease the number of microbes on living tissue

Anti microbial agents

No single chemical is the best!

• Decide effectiveness based on concentration, length of contact, and

whether it is lethal or inhibiting

Genus Pseudomonas

Gram negative bacillus with one or more flagella to provide motility

• Very diverse genus, especially in regards to metabolic activities

• Non-spore forming

• Non-coliform

• Catalase positive

• Oxidase variable (will change from species to species

Pseudomonas aeruginosa

Oxidase positive species of Pseudomonas with a single flagella

• Commonly found in the environment and on human skin

• Typically created green colonies due to secondary metabolites

• Species name aeruginosa is a Latin word meaning verdigris

• Considered the greatest threat to humans due to its increasing

antibiotic resistance and is an opportunistic pathogen

Antibiosis

Process where an organism produces a substance that is harmful to another organism

Example: snake venom

Antibiotics

Are medicines derived from antibodies that’s used to kill or inhibit that substance

80% of antibiotics produced in the US are utilized

by livestock

How Antibiotics Work

Different methods

• Inhibition of cell wall formation (peptidoglycan)

• Inhibition of DNA synthesis, which prevents propagation so your

immune system has more of a fighting chance

Not a One Size Fits All Situation

Physicians must match the correct antibiotic to the correct organism

at the correct strength

• Antibiotic resistance

• MRSA, VRE, MDR-TB, and CRE

Disk-Diffusion Method

Tests the effectiveness of antibiotics again specific bacteria

• The antimicrobial agent diffuses from the disk from an area of high concentration to low concentration. If the

agent is effective it will inhibit bacterial growth

• Will create Zone of Inhibition, which is a circle around the antibiotic where bacterial colonies do not grow

Antibiotic discoveries

Louis Pasteur learned that infecting animals with Pseudomonas aeruginosa protected them from Bacillus anthracis

• Alexander Fleming found that Penicillium mold could inhibit the growth of many gram-positive cocci and Neisseria. This discovery led to the

creation of penicillin, the world’s first broadly effective antibiotic substance