Microbiology Lab Practical II

All questions from the study guide are in now! :)

Anaerobic

Without oxygen

Presence or absence of oxygen

What does fluid thioglycolate medium indicte?

Place a hydrogen packet and a catalyst in the jar (the hydrogen reacts with oxygen in the air).

How do we make a jar anaerobic?

Obligate anaerobe

Cannot grow when O₂ is present

Obligate aerobe

Grows only when O₂ is available

Facultative anaerobe

Grows best when O₂ is available, but also grows without it

Aerotolerant Anaerobe

Grows equally well with or without O₂

Microaerophile

Grows only if small amounts of O₂ are available

In the bottom half of the tube

Where does most growth of obligate anaerobes occur in thioglycolate medium?

Within the red zone at the top of the tube

Where does most growth of obligate aerobes occur in thioglycolate medium?

All the way through the tube (most within the red zone at the top of the tube)

Where does most growth of facultative anaerobes occur in thioglycolate medium?

Even growth all the way through the tube

Where does most growth of aerotolerant anaerobes occur in thioglycolate medium?

Just below the red zone near the top of the tube

Where does most growth of microaerophiles occur in thioglycolate medium?

Whether or not the bacteria make oxidase (enzyme essential for aerobic respiration)

What does the oxidase test reveal?

Hydrogen peroxide

What does catalase break down?

oxygen and water

When catalase breaks down hydrogen peroxide, what are the results?

Whether or not the bacterium has the enzymes necessary to ferment the sugar in the tube

What does a color change in phenol red broth indicate?

Red

What color is phenol red broth when the pH changes to neutral?

Yellow

What color is phenol red broth when the pH changes to acidic?

Pink

What color is phenol red broth when the pH changes to alkaline?

Durham tube

A tiny tube that sits upside down in the phenol broth tubes and collects gas.

Acid and gas

What two products may be produced during fermentation of simple carbohydrates?

Acid turns phenol red to yellow

How is acid identified in the fermentation test?

Gas collects in the Durham tube

How is gas identified in the fermentation test?

Yes

Can you have acid without gas or gas without acid in a fermentation test?

Glucose, sucrose, and lactose

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

Chemical used on objects/surfaces to decrease the amount of microbes

Disinfectant

Chemicals used on living tissues to decrease the amount of microbes

Antiseptic

Antimicrobial agent

A general term for drugs or chemicals that either kell or slow the growth of microbes

Antibiotic

A drug used to treat bacterial infections

Narrow spectrum antibiotic

An antibiotic that is effective against a restricted number of bacteria

penicillin and amoxicillin

Name two narrow spectrum antibiotics

Broad spectrum antibiotic

An antibiotic that is effective against a wide range of both gram-positive and gram-negative bacteria

ampicillin, chloramphenicol, and tetracycline

Name 3 broad spectrum antibiotics

-cidal

Suffix for “to kill”

Static

Suffix for “to inhibit”

Kill

A disinfectant must ____ the pathogen while in contact with them

Acid fast (mycobacterium) and endospore forming

What are two types of bacteria that are more resistant to disinfectants

To determine which antibiotic is most effective against a particular infection

Why is antimicrobial susceptibility testing done?

The Kirby-Bauer Test

What is the name of the antimicrobial susceptibility test also known as the filter paper disk agar diffusion method?

An antibiotic or antimicrobial agent

In the Kirby-Bauer test, what is in the filter paper disks?

Mueller-Hinton Agar

In the Kirby-Bauer test, what kind of agar is used?

A bacterial lawn

In the Kirby-Bauer test, what is streaked onto the plate?

On top of the bacteria directly on the plate

In the Kirby-Bauer test, where are the filter paper disks placed?

It diffuses into the agar

In the Kirby-Bauer test, what happens to the antimicrobial agent in the disk after it contacts the agar?

The zone of inhibition

In the Kirby-Bauer test, after incubation, what does one look for on the plates?

Resistant

What does “R” mean in interpretation?

Comparing the width of the zone of inhibition with a standard table

How is resistance determined?

Susceptible

What does “S” mean in interpretation

Comparing the width of the zone of inhibition with a standard table

How is susceptibility determined?

Enriched media

Media that enables many types of bacteria to grow

Blood agar and chocolate agar

What are some examples of enriched media?

Differential media

Media that allows you to distinguish one group of bacteria from another

Blood agar and mannitol salt agar

What are examples of differential media?

Gram-positive spheres that grow in irregular clusters. Catalase positive and salt-tolerant.

Describe the characteristics of Staphylococci

It is found on the skin and mucous membranes

Where is S. Epidermidis normally found?

No

Does S. epidermis cause any diseases?

It is found within our bodies.

Where is S. saprophyticus normally found?

Yes, UTI’s in women

Does S. saprophyticus cause any diseases?

On the skin, the internal nares, and the female reproductive system

Where is S. aureus normally found?

Yes- toxic shock syndrome, food poisoning, and pneumonia

Does S. aureus cause any diseases?

Destroy red blood cells

What do hemolysins do?

Coagulates plasma

What does coagulase do?

Destroys WBCs

What does leucocidin do?

Destroys connective tissue

What does hyaluronidase do?

Dissolves fibrin clots

What does staphylokinase do?

Effects the digestive system (produced in food)

What does enterotoxin do?

Staph aureus

What staph species produces all of the following:

Hemolysins

Coagulase

Leucocidin

Hyaluronidase

Staphylokinase

Enterotoxin

Salt tolerant (halophilic) bacteria

What does Mannitol Salt Agar (MSA) select for?

7.5% salt (NaCl)

What ingredient is present in MSA that causes it to be selective?

It distinguishes between mannitol fermenters and non-mannitol fermenters

How is MSA differential?

Mannitol and phenol red

What ingredient(s) are present in MSA that cause it to be differential?

Yellow

What color is S. aureus on blood agar?

White

What color is S. epidermis on blood agar?

Yellow or white

What color is S. saprophyticus on blood agar?

Beta

What type of hemolysis does S. aureus have on blood agar?

Gamma

What type of hemolysis does S. epidermis have on blood agar?

Alpha or gamma

What type of hemolysis does S. saprophyticus have on blood agar?

Positive

Is S. aureus coagulase positive or negative?

negative

Is S. epidermidis coagulase positive or negative?

negative

Is S. saprophyticus coagulase positive or negative?

Yes

Is S. aureus a mannitol fermenter?

No

Is S. epidermidis a mannitol fermenter?

Generally yes

Is S. saprophyticus a mannitol fermenter?

Susceptible

Is S. aureus novobiocin susceptible or resistant?

Susceptible

Is S. epidermidis novobiocin susceptible or resistant?

Resistant

Is S. saprophyticus novobiocin sensitive or resistant?

Gram-positive spheres arranged in chains, generally catalase negative

Describe members of the genus streptococcus

It requires enriched media to grow

What does is mean is a bacteria is fastidious?

Blood agar

What type of media do strep need to grow on?

Turns from red to a greenish color

Describe a blood agar plate with alpha hemolytic strep

Becomes colorless (represents breakdown of hemoglobin)

Describe a blood agar plate with beta hemolytic strep

No change (looks like normal growth)

Describe a blood agar plate with gamma hemolytic strep

Beta hemolytic: Strep pyogenes

Which hemolytic group causes disease?

Toxic shock syndrome, strep throat, scarlet fever

What diseases are caused by a member of the beta hemolytic (strep pyogenes) group?

A substance that causes antibodies to be produced

What is an antigen?

The Lancefield Classification System: A-H and K-U

How are these strep named?

Group A

Human pathogens belong to which group?

Gram negative, non-endospore forming rods. Facultative anaerobes

Describe Enterobacteriaceae

• Klebsiella pnemoninae: pnemonia

• Shigella dysenteriae: Dysentery

• Salmonella typi: typhoid fever

Name three species of pathogenic Enterobacteriaceae and the diseases they cause