MicroLab Final Exam (Updated)

What is the first test before EnteroTube or IMViC?

Oxidase test.

Why is oxidase run before EnteroTube?

To determine if organism is an enteric (oxidase-) or non-enteric (oxidase+).

What does the EnteroTube test identify?

Gram-negative, oxidase-negative enterics.

What is the EnteroTube test based on?

Multiple biochemical reactions converted into a numeric code.

What is a facultative anaerobe?

Can grow with or without oxygen.

What is a fecal coliform?

Bacteria indicating fecal contamination (e.g., E. coli).

What are enterics?

Gram-negative rods living in the gut.

What does IMViC stand for?

Indole, Methyl Red, Voges-Proskauer, Citrate.

What is the IMViC pattern for E. coli?

++--

What is the IMViC pattern for Enterobacter?

--++

What does Indole detect?

Tryptophan breakdown.

What does a positive MR indicate?

Mixed-acid fermentation.

What does VP detect?

Acetoin production.

What indicates a positive result for Citrate?

Blue.

What is Kirby-Bauer?

Antibiotic susceptibility test using zones of inhibition.

What media is used in the Kirby-Bauer test?

Mueller-Hinton agar.

What is the agar depth for the Kirby-Bauer test?

4 mm.

What are the incubation conditions for the Kirby-Bauer test?

24h at 37°C.

What is the standard bacterial density for the Kirby-Bauer test?

McFarland 0.5 (~1.5 × 10⁸ cells/mL).

What does a large zone indicate?

Susceptible.

What does no zone indicate?

Resistant.

How is sensitive defined?

Growth inhibited at standard antibiotic dose.

What does intermediate mean in antibiotic sensitivity?

Variable effectiveness.

How is resistant defined?

Growth not inhibited.

What is MIC?

Lowest antibiotic concentration that prevents growth.

Is MIC measured using disks?

No, it is measured using broth dilution.

Why don't antibiotics lyse human cells?

They target bacterial-specific structures (cell wall, ribosomes, DNA gyrase).

What are the two primary cavity-causing organisms?

Strep mutans, Lactobacillus acidophilus.

What do cavity-causing organisms produce?

Lactic acid.

What are dental caries?

Infectious tooth decay caused by acid erosion.

What is Snyder used for?

Detect acid-producing oral bacteria.

What makes Snyder selective?

Low pH inhibits non-acid tolerant bacteria.

What makes Snyder differential?

Color change via pH indicator.

What is the indicator used in Snyder?

Bromocresol green.

What does yellow indicate in Snyder test?

Positive (high cavity risk).

What is alpha hemolysis?

Green, partial lysis.

What is beta hemolysis?

Clear zone.

What is gamma hemolysis?

None.

What is Group A Strep?

Strep pyogenes

What diseases are caused by Group A Strep?

Strep throat, rheumatic fever.

What is the CAMP test result for Group A Strep?

Negative.

What is the bacitracin sensitivity for Group A Strep?

Sensitive.

Group B Streptococcus

A type of bacteria known as Streptococcus agalactiae, commonly found in the intestines and genital tract.

CAMP test

A laboratory test used to identify Group B Streptococcus by observing its synergistic hemolysis with Staphylococcus aureus.

Neonatal sepsis

A serious infection in newborns that can be caused by Group B Streptococcus during delivery.

Intrapartum antibiotic prophylaxis

Administration of antibiotics during labor to prevent transmission of Group B Streptococcus to the newborn.

Risk factors for GBS infection

Factors such as premature birth, prolonged rupture of membranes, and maternal fever during labor that increase the likelihood of GBS transmission.

Colonization

The presence of bacteria in the body without causing disease; many women can be carriers of Group B Streptococcus.

Screening for GBS

Testing pregnant women for the presence of Group B Streptococcus, typically done between 35-37 weeks of gestation.

GBS vaccine

A potential vaccine currently under research aimed at preventing Group B Streptococcus infections in newborns.

Symptoms of GBS infection in adults

Can include fever, chills, and signs of infection, particularly in pregnant women.

Vertical transmission

The transfer of bacteria from mother to baby during childbirth, a common route for Group B Streptococcus.

CAMP test

A laboratory test used to identify Group B Streptococcus (GBS) by observing its synergistic hemolytic effect with Staphylococcus aureus.

Group B Streptococcus

A type of bacteria that can cause infections in newborns and pregnant women, often identified using the CAMP test.

Arrowhead hemolysis

A specific pattern of hemolysis observed in the CAMP test, indicating a positive result for Group B Streptococcus.

Synergistic hemolysis

The enhanced breakdown of red blood cells that occurs when two different bacteria are present, as seen in the CAMP test.

Staphylococcus aureus

A common bacterium that, when combined with Group B Streptococcus in the CAMP test, produces a characteristic hemolytic pattern.

What tests does bile esculin detect?

Bile tolerance and esculin hydrolysis.

What is the positive appearance of the bile esculin test?

Black medium.

Which organisms are positive for the bile esculin test?

Enterococcus and Strep bovis.

What grows in 6.5% NaCl?

Enterococcus faecalis.

What does 6.5% NaCl differentiate?

Enterococcus vs Group D Strep.

What are the steps of PCR in order?

Swab → RNA → RT → PCR → Gel

What is reverse transcriptase?

RNA → cDNA

What is Taq polymerase?

DNA copying enzyme.

What is denaturation in thermocycling?

Strand separation.

What happens during annealing?

Primers bind.

What occurs during extension?

DNA synthesized.

What direction does DNA move in gel electrophoresis?

Toward the positive electrode.

What does smaller size mean in gel electrophoresis?

Faster movement.

What dye is commonly used in gel electrophoresis?

Ethidium bromide.

What does the CAMP test identify?

Group B Strep.

What is a positive sign of the CAMP test?

Arrowhead hemolysis.

What is Group B Strep?

Strep agalactiae.

What is the claim to fame of Group B Strep?

CAMP positive.

What tests does bile esculin detect?

Bile tolerance and esculin hydrolysis.

What is the positive appearance of the bile esculin test?

Black medium.

Which organisms are positive for the bile esculin test?

Enterococcus and Strep bovis.

What does PCR detect?

RNA

What does ELISA detect?

Antibodies

What does an antigen test detect?

Viral protein

IgM

A type of antibody that is produced first in response to an infection, indicating recent exposure.

IgG

The most abundant antibody in the blood, providing long-term immunity and indicating past exposure to an antigen.

Primary immune response

The initial immune response to a new antigen, characterized by the production of IgM antibodies.

Secondary immune response

The immune response upon re-exposure to an antigen, primarily involving IgG antibodies.

Affinity maturation

The process by which B cells produce antibodies with increased binding strength during an immune response.

Half-life of IgM

Approximately 5 days, reflecting its transient nature in the immune response.

Half-life of IgG

Approximately 21 days, allowing for prolonged immunity.

Isotype switching

The process by which B cells change the class of antibody they produce, often from IgM to IgG.

Neutralization

The mechanism by which antibodies block the ability of pathogens to infect cells.

Opsonization

The process by which antibodies mark pathogens for destruction by phagocytes.

What does Sabouraud agar detect?

Fungi.

What does Chocolate agar grow?

Neisseria and Haemophilus.

What does catalase distinguish?

Staph (+) vs Strep (-).

What does oxidase distinguish?

Enterics (-) from Pseudomonas (+).

IgM = ?

Recent

IgG = ?

Past

what reaction is happening during the indole test

Tryptophan hydrolysis (tryptophanase)