Microbiology Lab Techniques Lecture Notes

This set of flashcards includes key terms and definitions based on the lecture notes covering microbiology lab techniques and media differentiation.

Gaspak for anaerobes

Absorbs oxygen.

Gaspak for capnophiles

Generates carbon dioxide.

Appearance difference of Gaspaks

Anaerobe pak is smaller and green; capnophile pak is blue and larger.

H2O2 production

Accidental by-product of the ETC when oxygen is not completely reduced.

Enzyme that breaks down H2O2

Catalase.

Gram reaction and cell morphology for catalase test

Gram positive; Staphylococcus is positive, Streptococcus is negative.

Genus associated with a positive catalase test

Staphylococcus.

Genus associated with a negative catalase test

Streptococcus.

Capnophilic genus discussed

Streptococcus.

Function of the analyte in the oxidase test

Transfers electrons from a donor molecule to oxygen in the ETC.

Gram reaction for organisms tested in oxidase test

Gram-negative cocci or bacilli.

Family testing negative in oxidase test

Enterobacteriaceae.

Growth location of Enterobacteriaceae in the human body

Intestinal tract.

Fermentation capability under anaerobic conditions

Enterobacteriaceae can ferment carbohydrates.

Organisms that can regenerate coenzymes under anaerobic conditions

Facultative anaerobes.

Two genera that are oxidase positive

Pseudomonas and Neisseria.

Diseases caused by oxidase positive organisms

Meningitis (Neisseria) and burns/wounds infections (Pseudomonas).

Selective media

Contains components that prevent the growth of some organisms while allowing others.

Differential media

Contains components to differentiate closely related organisms.

Enriched media

Contains additional or specific nutrients.

Organisms that grow on TBAB

Most organisms without additional nutritional needs.

Organisms that do not grow on TBAB

Organisms with additional nutritional needs.

Organism to identify on TBAB

Pseudomonas aeruginosa identified using a dichotomous key.

Organisms that grow on TSA

Most fastidious and enriched organisms.

What makes TSA differential

Presence of blood agar allows differentiation based on hemolysis.

Exoenzyme

Enzymes secreted into the environment.

Two detected exoenzymes on TSA

Alpha-hemolysins (greenish) and Beta-hemolysins (clear).

What is gamma hemolysis

Organism grows on TSA but does not produce either of the exoenzymes.

Organisms differentiated by exoenzymes on TSA

Streptococcus species.

What makes MSA selective

Contains 7.5% Sodium Chloride.

Differential agent in MSA

Mannitol differentiates species of Staphylococcus.

Characteristic of organisms growing on MSA

Halophiles.

Color of media for S. aureus

Yellow due to fermentation.

Color of media for S. epidermis and S. saprophyticus

Pink due to non-fermentation.

Selective agents in MacConkey agar

Crystal violet and bile salts (inhibit growth of gram-positive organisms).

Differential agent in MacConkey agar

Lactose fermentation.

Organisms that grow on MacConkey

Gram-negative organisms.

Organisms that do not grow on MacConkey

Gram-positive organisms.

Differentiable groups on MacConkey

Escherichia and Salmonella.

Location of organisms showing a positive reaction on MacConkey

Intestines.

Color of colonies showing a positive reaction on MacConkey

Pink.

Color of colonies showing a negative reaction on MacConkey

Colorless.

Main selective agent for Hektoen

Dyes and bile salts (inhibit most gram-positive organisms).

Differential agents for Hektoen

Lactose and thiosulfate.

Groups of organisms differentiated by Hektoen

Normal flora and potential pathogens (Salmonella and Shigella).

Cause of black colonies on Hektoen

Anaerobic conditions and iron from Ferric ammonium citrate.

Genera differentiated on Hektoen and diseases caused

Salmonella and Shigella.

Primary functions of fermentation

Oxidize NADH back to NAD by getting rid of two 3-carbon pyruvates.

Substances in phenol red broths for differentiation

Peptone, phenol red, Durham tube, one carbohydrate.

Glassware detecting gas production in fermentation broths

Durham tube.

Yellow media without gas production in fermentation

Organisms can ferment the carbohydrate, producing acid.

Yellow media with gas production in fermentation

Acid plus gas production.

Color of media exhibiting fuchsia color

Produced when the organism grows but does not ferment carbohydrates, generating ammonia.

Substance used in Simmons Citrate agar as a carbon source

Sodium Citrate.

Color of Simmons Citrate media if the organism grows

Royal blue.

Family differentiated using citrate

Enterobacteriaceae.

Media used along with citrate for differentiation

Brom thymol blue.

Selective agent in Bile Esculin agar

40% bile salts.

Differential agent in Bile Esculin agar

Esculin.

Appearance of positive reaction on Bile Esculin agar

More than half the medium is dark brown or black.

Genera differentiated by Bile Esculin agar

Streptococci and enterococci.

Importance of differentiating genera in Bile Esculin agar

They require different treatments.

Reagent used for detecting coagulase

Rabbit serum.

Substance in reagent interacting with coagulase

Fibrin of blood plasma.

Organisms differentiated by coagulase test

S. aureus (positive) and other Staphylococcus species (negative).

Tests differentiating organisms in coagulase test

Mannitol salt agar and Staphaurex.

Appearance of positive reaction in coagulase test

Coagulated and stuck to the bottom.