lab practical

Base

Bottom part of microscope with light source

Iris diaphragm

Regulates amount of light that reaches specimens

Condenser

Lens below stage that widens or shortens beam of light

Objective lens

Lense with differential magnification, they rotate

Parfocal

Describes multiple structures that lie on the same focal plane

Refraction

Bending of light as it passes through window

Scanning lens

Red

Smallest

x4

Total mag x40

Low power

Yellow

x10

Total mag x100

High power

Blue

x40

Total mag x400

Oil immersion

White

x100

Total mag x1000

Culture

Method of letting microbes reproduce in culture medium

Medium is a mixture of nutrients that support organism growth

Agar

Solidifying agent in solid media

Colony

Group of cells derived from one parent

Subculture

Made from removing a microbe from one medium to a new medium

Colonial morphology

Shape of bacteria in a colony

Turbidity in broth indicates

Bacterial growth

Aseptic

Without contamination

Cell wall

Gives bacteria its shape

3 basic shapes of bacteria

Coccus

Bacillus

Spirillium

Rod arrangements

Single

Pairs(diplo)

Chain(strepto)

Spherical arrangements

Pairs(diplo)

Groups of 4(tetrad)

Cluster(staphylo)

Chain(strepto)

Spiral arrangement

Single

Make a smear from a liquid media

Aseptically transfer loop of broth onto slide

Spread it

Dry

Heat fix

Make a smear from sold media

Aseptically transfer bacteria to a drop of water on a slide

Spread it

Dry

Heat fix

What is a simple stain

Staining procedure consisting of one stain

What is a differential stain

Staining procedures that use 2 or more dyes

Christian gram

Developed gram stain which allows classification for 2 groups

Gram + and gram -

Gram staining

Primary stain- crystal violet

Mordant- iodine

Decolorizer- acetone alcohol

Counterstain- safranin

Gram +

Stain purple

Cell walls are rich in peptidoglycan which decreases cell wall permeability

Gram -

Stain pinkish red

High in lipids, allows for increased permeability

Are clinical specimens mixed or pure

Mixed

Properties used to identify bacteria

Biochemical properties and colonial morphology

A pure cultures must be used for identification

Why is the streak plate technique done

To isolate individual species of bacteria

Why is the spread plate procedure done?

Isolate individual species of bacteria and to determine number of CFU in original culture

Also allows for viable count of cells

What is a colony forming unit(CFU)?

Colony formed from one single parental cell

Mycobacterium

Genus of bacteria that have cell walls that are high in fatty wax content

Their waxy outer layer is mycolic acid which is hard to stain

The dye carbolfuchsin can penetrate the waxy layer if heat and phenol is applied

Once this group is stained they can resist decolorization even if acid alcohol is used

Leprosy and TB are caused by this group

Bacterial cell that is acid fast and stains red and has a cell wall made of mycolic acid belongs to….

Mycobacterium

Kinyoun acid fast staining procedure

Primary stain- carbolfuchsin with 5% phenol

Decolorizer- acid alcohol

Counterstain- methylene blue

Color of acid fast cells

Red

Color of non acid fast cells

Blue

What is a catalyst?

Substance that speeds up chem reaction without permanently changing it

What is an enzyme?

Organic catalyst

No chemical reactions would occur inside a cell without enzymes

Have the ending -ase

Fluid thioglycollate medium indicates

Presence of absence of O2

Resazurin is the indicator in this medium

Hydrogen generator pack

Makes a jar anaerobic

Obligate anaerobe

Can’t grow in O2

Obligate aerobe

Needs O2 to grow

Facultative anaerobe

Grows bets with O2 but can grow without it

Aerotolerant anaerobe

Grows equally well without or without O2

Microaerophile

Grows in small O2 amounts

What does an oxidase test tell us?

Tells us if bacteria produces oxidase

What does a color change in phenol red broth mean?

Tells us if bacterium can ferment sugar in media

This broth consists of a pH indicator called phenol red which indicates a pH change when it changes color

Neutral= red

Acidic= yellow

Alkaline= pink

What is a Durham tube?

Glass tube that sits upside down in phenol red broth and collects gas

What products are formed during fermentation of simple carbohydrates?

Acid and gas, acid turns yellow and gas will collect in the Durham tube

3 simple carbohydrates that can be added to media for biochemical testing

Glucose, sucrose and lactose

Antiseptic

Chemicals used in living tissue to kill microbes

Anti microbial agent

Drugs or chemicals that kill or inhibit growth of microbes

-cidal

Kill

-static

Inhibit

Can a disinfectant be static

No

Two types of bacterial cells that are more resistant to disinfectants

Endospore formers and acid fast

Why is anti microbial susceptibility testing done?

To determine which antibiotic is most effective on infection

AKA Kirby-Bauer test

Kirby-Bauer test

There are filter paper disks with antibiotics in them

Mueller-Hinton Agar is used

Bacterial lawn is streaked into the plate and a disk is placed on top

The disk diffuses into the media

The zone of inhibition(ZOI) is looked for after incubation

What does R and S mean in the Kirby-Bauer test?

Resistant

Susceptible

Antibiotic

Drugs used to treat bacterial infections

Narrow spectrum antibiotic

Antibiotics that are affected by a number of bacteria like penicillin

Broad spectrum antibiotic

Antibiotic infected by a wide range of bacteria like tetracycline

What is enriched media?

Media that allows for many types of bacteria to grow like blood agar

What is differential media

Allows for you to distinguish between 1 group of bacteria from another

Like blood agar and mannitol salt agar

What is selective media?

Allows for some types of bacteria to grow like mannitol salt agar

Fastidious

Only grow in blood agar

They require enriched media to grow

Staphylococci

Gram +, spheres, grow in clusters, catalase+, salt tolerant

They are found in our mucous membranes and skin

S.epidermis

Found in skin and mucous membranes and doesn’t cause disease

S. Saprophyticus

Can be found in body like a UTI in women

S.aureus

Found on skin, internal nares, vagina

Can cause toxic shock syndrome(TSS), food poisoning, meningitis, and pneumonia

Hemolysins

Destroy red blood cells

Coagulase

Coagulates plasma

Gelatinase

Dissolves gelatin

Leucocidin destroys white blood cells

Hyaluronidase

Destroys connective tissues

Staphylokinase

Dissolves fibrin clots

Enterotoxin

Digestive system

What does mannitol salt agar select for?

Salt tolerant bacteria

It has 7.5% NaCl

How is mannitol salt agar differential?

Distinguishes between fermenters and non fermenters

Contains mannitol which causes it to be differential

Why are “hospital” strains of staph a problem?

Have a better chance of being resistant to antibiotics

S. Aureus on blood agar

Yellow

Beta

Coagulase +

Mannitol fermentation

Novobiocin S

S. Epidermidis

White

Gamma

Coagulase #

No mannitol fermentation

Novobiocin S

S. Saprophyticus

Yellow or white

Gamma or alpha

Coagulase -

Possible mannitol fermentation

Novobiocin R

Parts of respiratory tract with microbes present

Upper respiratory, nasal membranes, throat

What defenses help protect respiratory system from microbial invasion?

Mucous, ciliated epithelium

Streptococcus

Gram +, spheres, chains, catalase-

Strep needs to grow in blood agar

Alpha hemolytic strep

BAP turns from red to green, indicates breakdown if hemoglobin

Beta hemolytic strep

Turns from red to colorless

Gamma hemolytic strep

No change in color

What groups do normal flora belong to?

Gamma and alpha

The opportunistic of normal flora cause disease

What groups of streptococcus causes disease?

Strep pyogenese, TSS, strep throat, scarlet fever

What is an antigen?

Antigen is a substance that causes antibodies to be produced

How is strep named?

Lancefield classification system

Groups A-H and K-U

Humans belong to group A

Which part of the digestive system are inhabited by microorganisms?

Small and large intestine

Enterobacteriaceae

Gram -, non-sporing rods, facultative anaerobe

3 species of them

Klebsiella pneumoneae- pneumonia

Shigella dysenteriae- dysentery

Salmonella typhi- typhoid fever

Coliforms

Non pathogens ferment lactose and they are called these