CSN BIOL 251 Lab 10 Quiz Study Material (John Carvalho)

Gram-positive cocci can be?

opportunistic pathogens & true pathogens

Name the two types of gram-positive cocci that we will be discussing in class...

staphylococcus aureus (S. aureus) & enterococcus faecalis (E. faecalis)

What is S. aureus?

pyogenic (pus forming), catalase positive, clusters of bacteria that are found in the normal flora of the nares & skin

What is E. faecalis?

chains of bacteria that are found in the gastrointestinal tract

What is one thing that both S. aureus & E. faecalis have in common?

they can cause nosocomial infections (hospital-acquired)

When found in hospitals, what are two things that can be gained by both S. aureus & E. faecalis?

antibiotic resistance genes & virulence factors

When does an epidemic occur?

when the number of new cases of a disease are higher than expected

What types of microorganisms can cause epidemics?

bacteria, virus, etc.

What is the common method used to identify the microbe causing an outbreak?

fingerprint analysis: identification of the microbes nucleic acid using DNA (or RNA)

Give an example of something that can manifest as a result of S. aureus & things it causes.

it can manifest as an abscess & has the ability to invade & cause systemic diseases such as:

- acute endocarditis

- necrolytic pneumonia

- toxic shock syndrome

Enterococcus is a common cause of what type of infections?

blood stream infections

Out of the two previously mentioned bacteria, which one is resistant to Vancomycin?

E. faecalis; vancomycin resistant Enterococcus (VRE)

What is catalase?

an enzyme that breaks down hydrogen peroxide into water & oxygen

What two types of bacteria do not have the catalase enzyme?

anaerobic & microaerophilic bacteria—they are destroyed by the build up of toxic peroxides

Name two types of oxygen metabolites produced by microbes that live in oxygen.

peroxides & superoxide radicals

Describe Staphylococcus saprophyticus

normal flora in the vaginal tract & is associated with urinary tract infections (UTIs); NOT hemolytic on blood agar, is halotolerant, ferments mannitol, & is coagulase-NEGATIVE

Describe Stapylococcus epidermidis

common flora of the skin & is associated with nosocomial infections of the blood; NON-hemolytic on blood, is halotolerant, does not ferment mannitol, is coagulase-NEGATIVE

True or False: Enterococcus produces catalase

False—Staphylococcus produces catalase

When placed on hemolytic blood agar, what does S. aureus tend to produce?

hemolysins

True or False: S. aureus is halotolerant

True—this allows it to grow on salt plates & ferments mannitol

What is coagulase?

an enzyme that causes blood plasma to clot by converting fibrin to fibrinogen, increasing pathogenicity.

Mannitol Salt agar contains...

the mannitol sugar & 7.5% salt (selective)

What color is produced by S. aureus & S. saprophyticus when they ferments mannitol (sugar)?

yellow

True or False: S. epidermidis ferments mannitol

False—S. epidermidis does NOT ferment mannitol & remains red

When living in oxygen rich environments, Staphylococcus must be able to break down what?

reactive oxygen species (ROS) & superoxide radicals—toxic metabolic products of cellular respiration

Hydrogen Peroxide is an example of....

reactive oxygen species (ROS)

Epidemiology

the study of diseases in a population

Outbreak

the occurrence of a disease in a population

(point source or propagated)

What is a point source outbreak?

a common source; all persons exposed become ill at the same time (food poisoning from a restaurant)

Describe a propagated outbreak

disease spread between people (or animals) & the cases increase over time (influenza, common cold)

In a propagated outbreak, the individual that originally had the disease & spreaded it, is referred to as...

index case or patient 0

Pandemic

an epidemic that occurs on a global scale (more than 1 continent)

Communicable

a disease spread between people

A communicable disease can cause...

a propagated outbreak

Non-communicable

a disease spread by a vector (Lyme disease); not spread from person to person, not contagious

Zoonosis

a disease spread from an animal to a human (rabies)

Innate Immunity

non-specific, naturally present at birth

Acquired Immunity

developed as a result of exposure (humoral, cellular immunity)

Herd

the resistance of a group to the invasion or spread of an infectious organism (obtained by vaccination)

When & why do restriction enzymes occur?

naturally in some bacteria to protect them from viral infections (phages)

What is agarose gel?

a porous material that provides a semi-solid medium for DNA to move through

What is the chemical compound found in agarose gel that binds DNA & how does it work?

gel green—it will fluoresce under UV radiation

What is the result of the lack of hemolysin in S. epidermidis & S. saprophyticus?

gamma hemolysis

Epidemiologists

determine how, when, where, who, what are involved in the source/spread of a disease, as well as determining a way to stop the epidemic

Which of the bacteria is the only one that contains Coagulase?

S. aureus

What is the meaning of Runs to Red as it relates to running an agarose gel?

The negatively-charged DNA fragments move from the negative (black) pole towards the positive (red) pole of the apparatus

In electrophoresis, to determine the number & size of DNA fragments, what must they be?

separated

How is this separation accomplished?

using agarose gel electrophoresis

What does this separation allow you to obtain?

a DNA fingerprint

How is DNA distinguished in bacteria?

in a circular, double-stranded form in the cytoplasm (nucleoid)

How is DNA distinguished in protozoa & fungi?

contained within a nucleus and is usually linear, double-stranded (organized within chromosomes) like our DNA

How is DNA distinguished in viruses?

it can be either DNA or RNA, single or double-stranded, circular or linear

How is the catalase test performed?

by placing a loopful of bacteria into a drop of hydrogen peroxide and watching for the formation of oxygen bubbles.

If we see oxygen bubbles form after mixing bacteria with the hydrogen peroxide, we can presume that the unknown bacterium is a species of...

Staphylococcus