Microbio Lab Quiz 2 (2.1 and 2.2)

Epidemiology

the study of how microbes spread within a group or population

• how many are affected

• symtoms

• how the disease is spread

portal of entry

the way a microbe enters and infects a new host (entrance way)

Examples

• Skin (Staphylococcus aureus)

• Gastrointestinal tract (salmonella)

• Respiratory tract (streptococcus pneumoniae)

• Urogenital tract (STDs)

opportunistic pathogen

cause disease when the host’s defenses are compromised

Factors that weaken host defenses

• old age

• surgery

• disease (HIV, cancer, etc.)

• Chemotherapy and immunosuppressive drugs

• Physical and Mental stress

Normal biota (flora)

normal population of microbes present in an organism (outnumber human cells 10 to 1)

Transient organisms

organism found on the skin for a short period of time but do not grow there

Example: mass transit

• contact with contaminated surface but easily removed

• some can cause disease

• do not stay in the body long because of competition between resident microbes

• elimination by the body’s immune system

Vectors

living organisms that transmit disease

Biological vector

an organism in which the parasite undergoes part of its lifecycle (sexual or asexual reproduction) and then transmits the parasite to another organism

• Example: female anopheles mosquito (directly biting)

Mechanical Vector

an organism that transmits a parasite but its not part of its life cycle

• Example: fleas, ticks (indirectly- carrying disease organisms)

Reservoir of infection

an object that allows a microbes to grow, reproduce, and maintain the ability to infect a new host

nutrient substrate

• Examples: burger, soil, and makeup

Fomite

an object that allows a microbe to survive and pass to a new host

any inanimate object

• Examples: phone, pen, bathmat —> athletes foot

Hand washing

soap breaks down the oils on your skin allowing trapped bacteria to be washed away

• break down the cell membranes of the bacteria

Micelles - Hand washing

spheres of lipids that form in aqueous solutions

Example: a corral

Friction

physically remove emulsified skin oil

Aseptic

chemical that kills microbes (used in hospitals)

• Examples: Hydrogen Peroxide and Triclosan

Why do we isolate bacteria?

to isolate a pure bacteria culture

Pure culture

a sample containing a single species of organism

Why do you need a pure bacteria culture?

• Carry out biomedical testing

• determine antibiotic sensitivity

• develop vaccines

• determining nutritional requirements

• study organism that cause disease

Aspectic technique

Handling microbes and material in such a away that minimizes contamination

• Examples: wearing lab coats, hand washing, ulitzing incinerators and cleaning work surfaces before and after transfers

prevents the microbes you re transferring from contaminating the work area or yourself

prevents the microbes on the work area or yourself from being transferred into the samples and then contaminating them

Contamination

presence or possible presence of microbes where they do not belong

Culturing bacteria

agar plates (made from seaweed)

• melts at 100 C

• solidifies 32-46 C

• remains liquid above 46 C

• agar is an addictive not media (does not provide food/nutrients for the bacteria)

agar is a solid surface where bacteria can grow —> isolated colonies

Robert Koch

the father of microbiology

invented agar: derived from seaweed

Is bacteria homotrophic or heterotrophic?

heterotrophic

the organisms cannot synthesize their own organic molecules

Growth media

substrate for bacteria to grow in or upon

Complex Media

had a composition that is not definable by an exact chemcial formula

• uses extracts from other organism (animals, plants, fungi)

• rich in nutrients and support a wide range of bacterial growth

Examples: Tryptic Soy Media

• contains enzymatic digests of casein and soybean in an undefined amount that varies batch to batch

Chemically Defined Media

Pure organic and inorganic compounds are added in exact amounts

narrow range of bacteria growth

Enriched Media

contains a complex of organic substances to grow fastidious organiusms

• Media which specific nutrients are added: blood, serum, hemoglobin, or special growth factors

• blood agar and brain-heart infusion (BHI) agar

Making Media

powdered media dissolved in distilled water

media is dispensed into tubes or bottles according to instructions

autoclave

Autoclave

Instrument used to sterilize (Steam B)

• Temperature: 121 C

• 15 lbs of pressure/ square inch (lbs/ in²)

• 20 minutes: kills all bacteria, fungal spores and viruses

Incubator

holds a constant temperature, used to grow bacterial cultures

Incinerator

device used to sterilize inoculating tools

tools used to transfer bacteria form a culture to sterile media

• inoculating loop

• inoculating needle

Media forms

agar plate

agar deep tube

broth

agar slant

Streak Plate Isolation

method used to separate a mixed culture and develop isolated colonies

isolated colonies form from a single bacterium

• genetically identical

by isolating colonies, further testing can then be carried out

Streak Plate Isolation