quiz 2-microbio lab

Complex media

Support growth of a wide range of organisms

Selective

Select growth of a specific type of bacteria

Differential Media

Differentiate between bacteria based on different physiological characteristics

What is Mannitol Salt Agar (MSA) selective for?

salt-tolerant microorganism 

What color is MSA if it can ferment  

yellow- mannitol

What color if MSA is negative 

red/pink

What is MSA differential for and why?

Mannitol fermentation and because it contains the carbohydrate mannitol and the pH indicator phenol red 

What is Phenol red added to

pH indicator

What is mannitol added as

carbon source

What is Eosin Methylene Blue(EMB) Agar selective for

gram-neg microorganisms

What do eosin and methylene blue dyes inhibit?

gram-pos 

What does purple indict for EMB

pos for lactose fermentation

What does colorless indict for EMB

neg for lactose fermentation

What does metallic indict for EMB

ferments lactose and strong acid production

What is EMB differential for

lactose fermentation

Phenol Red carbohydrate Broth

Test for the fermentation of carbohydrates and gas production

What does it mean if phenol Red is yellow with a positive Durham tube.

pos for fermentation of carbohydrate and gas production

What does it mean if phenol Red is red

neg for fermentation of carbohydrates and gas production

What does the VP(a precursor of 2,3-butanediol) test for

production of acetion

What color is VP if it is pos

Red, after adding Barritt’s reagents

What color is VP if it is neg

No color change/copper color

what does Kligler’s slant test for 

Ferment glucose and lactose, and the production of hydrogen sulfide (H₂S)

Fully red kligler’s slant

does not ferment lactose and glucose or H2S

Fully yellow 

Ferments glucose and lactose and gas but neg for h2s

Yellow slant/black butt

pos for lactose, gas production and H2S

Red slant/black butt

Positive for cysteine desulfurase activity

How do you detect Indole production?

Kovac’s reagent

What does the broth in indole contain?

tryptophan

What does it mean if indole is red

pos for enzyme indole

What does it mean if indole is yellowish/clear top

neg for enzyme indole

What does phenylalanine deaminase detect?

presence of enzyme phenylalanine deaminase

what is phenylalanine deaminase detected by 

ferric chloride 

what does it mean if phenylalanine is neg 

yellow/clear 

what does it mean if phenylalanine is pos and color

produced the enzyme phenylalanine deaminase and green

Motility test

if motile: move from center

if not motile: stay in center

Antiseptic

Product which destroys or inhibits growth of microorganism in or on living tissue 

Ex of antiseptic

Iodine

silver nitrate

triclosan

ethanol 

Disinfectant

product which destroys or inhibits growth of microorganisms on inanimate objects 

Ex of disinfectant 

Cresols(lysol)

bleach 

alpha hemolysis

Involves partial hemolysis of blood cells due to damage caused by hydrogen peroxide produced by organism 

Beta hemolysis

Involves complete hemolysis of blood cells due to the action of cytokines such as streptolysin enzyme

 Catalase test

breaks down hydrogen peroxide to water and oxygen gas

What does it mean if catalase test is pos

Positive of oxygen production (bubbling)

What does it mean if catalase test is neg

it will have no change

Oxidase test

If enzyme cytochrome oxidase is produced

What does it mean if the oxidase test is positive

pink

What does it mean if the oxidase test is negative

no color

Minimum bactericidal concentration

Minimum concentration of agent at which the target bacterium is killed rather than inhibited

Simmon’s citrate 

test for utilization of citrate as sole carbon source for growth

What is the carbon source for Simmon’s citrate

citrate 

pH indicator for Simmon’s citrate

bromothymol blue

What color does Simmon’s citrate turn into if it is pos

blue

What color does Simmon’s citrate turn into if it is neg

green

What does Urease test for

production of enzyme urease

What color does Urease turn into if it is neg

yellow

what color does Urease turn into if it is pos 

pink

What can UV light do

Used to control microbial growth

Factors that limit usefulness of UV light for decobtamination 

cannot penetrate surface 

more effective at killing some organisms than other 

Strict Aerobe

Needs O2 for cellular respiration

will die without

Facultative Anaerobe

Can use O2 for cellular respiration

If O2 is not present will use alternate electron acceptors 

Aerotolerant Anaerobe

does not use O2 for cellular respiration use alternate electron acceptors

O2 is not toxic for them

Strict Anaerobe

Does not use O2 for cellular respiration. Uses alternate electron acceptors

O2 is toxic to them

Oxygen indicator of FTG tubes

Resazurin, red when O2 is present

Reducing agent for FTG

Thioglycolate

Brewer agar plates O2 indicator

Resazurin

Brewer agar plates reducing agent

Thioglycolate

Palladium Catalyst

Making water get released from gasPak

What is the Initial dilution formula? 

Initial Dilution =Volume transferred/ total volume 

Next dilution formula

Next dilution= Volume transferred/total volume)x previous dilution

What is the stock formula

[stock]= (CFU/Vol.plated)x Dilution factor

Normal flora

Found in specific area of the body due to environmental conditions like pH, O₂ availability, moisture,etc.

Blood agar

Enrichment media that is generally used for the cultivation of throat microorganisms 

Common throat colonizers releases hemolysins 

What is an example of beta hemolysis? 

Streptococcus pyogenes, which causes strep throat 

What is an example of alpha hemolysis?

Streptococcus pneumoniae is the cause of pneumonia. Usually Caused by the Viridans group of streptococcus, which are a normal part of the mouth flora

Non-hemolytic

Sometimes called y-hemolysis, no lysis of red blood cells, andnon-clearing of blood cells around the colony

Examples of non-hemolytic

Enterococcus faecalis is a common inhabitant of the GI tract

Resident flora

Permanently live on and in the human body, forming a symbiotic relationship with the host 

Transient flora

Microorganisms that do not permanently colonize the skin because they are found on the surface and can be more easily removed by good hygiene practices. 

Kirby-Bauer Antimicrobial Sensitivity Testing

Standardized diffusion procedure that uses Mueller-Hinton agar, a standard mixed medium

Mueller-Hinton Medium 

Growth medium to culture bacterial isolates and test their susceptibility to antibiotics.

Chemotherapeutic agents

chemicals that can treat infectious diseases caused by microorganisms 

what does Chemotherapeutic interfere with

Microbial metabolism, halting the growth of (bacteriostatic) or killing (bactericidal) the targeted microorganisms 

What are the two groups of chemotherapeutic agents

Antibiotics and synthetic drugs

Antibiotics

Made and secreted by other microorganisms, which may be synthesized and modified in a lab 

Synthetic drugs

Man-made and synthesized in lab

Minimum Inhibitory Concentration (MIC)

The lowest concentration at which bacterial growth will be inhibited 

How is the MIC determined by?

Doing a dilution series of the antibiotics and adding the microorganisms to various drug concentrations 

Minimum Bactericidal Concentration (MBC)

• Minimum concentration of the agent at which the target bacterium is killed (rather than just inhibited) 

How is the MBC determined?

• Must perform a minimum inhibitory concentration (MIC) test.

• Take samples from the wells where no growth was observed in the MIC test, and then plate them on an antibiotic-free agar plate.

Enterobacteriaceae

are a group of bacteria that are endogenous to the internal tracts of mammals

What genre does Enterobacteriaceae use?

Salmonella, shigella,enterobacter, Escherichia, Klebsiella and Proteus 

UV light

An effective method to kill microorganisms through the production of pyrimidine dimers in DNA that impair DNA replication and gene expression 

Are endospores resistant to UV light and other forms of radiation? 

yes 

What are factors that limit the usefulness of UV light for contamination? 

• Cannot penetrate surfaces 

• More effective at killing some organisms than others (ex.Bacterial spores can be resistant) 

What do UV light form?

Pyrimidine dimers in the DNA of vegetative cells much faster than it does in endospores, which are resistant structures that offer protections against radiation.

Microaerophilic 

• Require a limited amount of oxygen 

• Excess oxygen inhibits oxidative enzymes and results in death 

• Only grow in environments with limited amounts of oxygen 

Fluid Thioglycollate (FTG) tubes

Differentiate organisms based on their oxygen requirements

What is the reducing agent of FTG

Contains sodium thioglycolate, which reduces free oxygen in the medium to water

What is the oxygen indicator of FTG

Resazurin

What color does FTG turn when oxygen is present

pink/red