Microbiology

Question 0

What are the three gram positive cocci?

Answer 0

The three gram positive cocci all have occurs in their name:
Staphlococcus forms clusters of cocci

Streptococcus and enterococcus form strips of cocci

Question 1

What does a red gram stain mean? What does a blue gram stain mean?

Answer 1

A gram stain stains for a peptidoglycan layer. A red gram stain is gram negative. The bacteria do not have a peptidoglycan layer. Positive stains blue. Gram positive cells are resistant to penicillin and lysosomes attack

Question 2

What are the two gram positive rods that form spores?

Answer 2

Bacillus and clostridium

Question 3

What are the two gram positive rods that do not form spores?

Answer 3

Corynebacterium and lysteria

Question 4

What is a gram negative diploccus?

Answer 4

Neisseria

Question 5

What is a gram negative spiral shaped organism?

Answer 5

The spirochete a. This group includes treponema pallidum

Question 6

How do you visualise mycobacterium?

Answer 6

You visualise mycobacterium using an acid fast stain.

Question 7

How do you visualise spirochetes?

Answer 7

Visualise spirochetes using darkfeild microscope.

Question 8

What are the gram negative rods?

Answer 8

Gram negative rods include the enteris; E. coli, shigella, salmonella, yersinia, klebsiella, proteus, enterobacter, serratia, vibrio, campylobacter, Helicobacter, pseudomonas, bacteroides.
They also include haemophilis, bordetella, legionella, yersinia, francisella, brucella, pasteurella, gardnerella.

Question 9

What is gram negative pleomorphic?

Answer 9

Chlamydia and rickettsia

Question 10

What has no cell wall and therefore cannot be stained?

Answer 10

Mycoplasma

Question 11

What are the three enzymes that bacteria may possess to break down oxygen free radical?

Answer 11

Catalase, peroxidase, supraoxiddismutase.

Question 12

What is an obligate aerobe?

Answer 12

An obligate aerobe need oxygen and use glycolysis and the krebs cycle. They need enzymes to break down oxidative free radicals. Obligate aerobes include:
Gram positive: bacillus cereus, nocardia
Gram negative: neisseria, pseudomonas, bordetella, legionella, brucella
Acid fast: mycobacterium, nocardia

Question 13

What are facultative anaerobes?

Answer 13

Facultative anaerobes are aerobic, but can survive without it if they need to. Facultative anaerobes include:
Gram positive: staphlococcus, bacillus anthracis, corynebacterium, listeria, actinomyces
Gram negative: most other gram negative rods
No cell wall: mycoplasma

Question 14

What are microaerophilic anaerobes?

Answer 14

Microaerophilic anaerobes use fermentation and have no electron transport chain,mount can tolerate low amounts of oxygen.
Gram positive: enterococcus, streptococcus,
Gram negative: spirochetes (treponema, borrelia, leptospira), campylobacter

Question 15

What are the obligate anaerobes?

Answer 15

Obligate anaerobes die in the presence of oxygen.
Gram positive: clostridium
Gram negative: bacteroides

Question 16

What is an endospore?

Answer 16

Endospore are metabolically dormant forms of bacteria that are resistant to heat (boiling), cold, drying, and chemical agents.they have a multi layered coat that has lots of protective stuff. They form when there is a shortage of needed nutrients and can lie dormant for years. They are killed by autoclaving. There are a only 2 bacteria that form spores. They are both gram positive rods. The aerobic bacillus, and the anaerobic clostridium.

Question 17

What is a beta lactate antibiotic?

Answer 17

A beta lactate antibiotic is a broad class consisting of anything that contains a beta lactate ring. This includes penicillin derivatives (penams), cephalosporins (cephams), monobactams, and carbopenams. Most beta lactate work by inhibiting cell wall synthesis.

Question 18

What is group a beta heamolytic streptococcus? What illnesses does it cause?

Answer 18

Group A beta heamolytic streptococcus is also known as strep pyogenes (which means pus producing). It causes ‘strep throat’, rheumatic fever, and post streptococcal glomerulonephritis.

Question 19

What are ASO titre?

Answer 19

ASO titres are titres of anti streptolysin O (ASO) antibodies. Streptolysin O is an antibody that destroys red and white blood cells. It is found in beta heamolytic streptococcus group A ( strep pyogenes). The enzyme is antigenic, and antibodies develop against it. Following pharyngeal or systemic infection ASO antibodies develop. You can order an ASO antibody titre on patients blood to confirm recent infection.

Question 20

What is streptococcal pharyngitis? How should it be managed?

Answer 20

Streptococcal pharyngitis is the classic strep throat with red swollen tonsils, high temp, and swollen lymph nodes. It usually lasts 5 days (penicillin helps speed recovery). Exudate be pharyngitis can also be caused by viruses, a throat swab should be sent for a Rapid Antigen Detection Test (RADT). These tests can be completed in minutes and are highly specific to strep pyogenes. A throat culture should also be sent because the antigen test is not as sensitive.

Question 21

What skin infections are caused by strep pyogenes and by staph aureus?

Answer 21

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