Clinical Microbiology

Question 1

What organisms are Prokaryotes and which are Eukaryotes?

Answer 1

Prokaryotes: Bacteria
Eukaryotes: Fungi, Parasites, Animals, Plants

Question 2

What are the key characteristics of Eukaryotes?

Answer 2

True Nucleus
Membrane bound organelles
Mitotic apparatus
linear DNA

Question 3

What is unique to the eukaryotic cell membrane?

Answer 3

Sterols

Question 4

Peptidoglycans

Answer 4

Repeating disaccharides with four amino acid side chains. Unique to Prokaryotic cell wall.

Question 5

What are the various shapes of bacteria?

Answer 5

Cocci- Round
Bacilli- Rod
Spirochetes- Spiralled

Question 6

What are the arrangements of bacteria?

Answer 6

Diplo- in pairs
Strepto- chain like
Staphylo- grapelike clusters

Question 7

What is the smallest bacteria?

Answer 7

Mycoplasma

Question 8

Gram + cell walls contain:

Answer 8

• Thick peptidoglycan layer

- Teichoic acid

Question 9

Gram - cell walls consists of 4 layers:

Answer 9

1. Inner cytoplasmic membrane
2. Periplasmic space
3. thin peptidoglycan layer
4. Lipopolysaccharide

Question 10

What is in the Periplasmic space?

Answer 10

beta-lactamase that degrades beta-lactam drugs (penicillin)

Question 11

What is the structure of LPS?

Answer 11

1. O-antigen (1-50 oligosaccharide different for each bacteria)
2. polysaccharide core
3. Lipid A (endotoxin)

Question 12

Mycobacteria

Answer 12

acid fast bacteria. Resist decolorization from Acid alcohol. Stained with Carbolfuchsin. High concentration of Mycolic acids.

Question 13

Mycolic acid

Answer 13

Resists phagocytosis. Found in TB, MAI, and Leprosy. Acid fast organisms.

Question 14

What are the specialized structures outside the cell wall?

Answer 14

1. Capsule
2. Flagella
3. Pili (Fimbriae)
4. Glycocalyx (slime layer)
5. Endospore

Question 15

How do you stain bacteria capsules?

Answer 15

1. India Ink Stain

2. Quelling reaction: causes swelling of capsule

Question 16

Capsule

Answer 16

Enables bacteria virulence. Prevents phagocytosis. Sugars from capsule are used as antigens in vaccines.

Question 17

Flagella

Answer 17

Whip-like appendages for motility.
Vibrio cholera- 1 flagellum
E. coli- multiple flagella
Shigella- no flagella

Question 18

Most common cause of UTI’s

Answer 18

E.coli and P. mirabilis. Use flagella to propel bacteria up urethra.

Question 19

Pili (fimbriae)

Answer 19

hairlike filaments used for adherence. N. gonorrhea use pili to cause Gonorrhea.

Question 20

Adhesins

Answer 20

adherence factors associated with pili. Bacteria using adhesins include:
E.coli- diarrhea
Bordetella pertussis- Whooping Cough

Question 21

Glycocalyx

Answer 21

Slime layer allows for bacteria adherence.

-Strep mutans

Question 22

Endospore

Answer 22

dormant until proper nutrients. Examples:
Bacillis anthracis
Clostridium botulina

Question 23

Exotoxins

Answer 23

Protein secreted by Gram +.

Neurotoxins and Enterotoxins.

Question 24

Two diseases caused by Enterotoxins

Answer 24

1. Infectious diarrhea: bacteria continuously in GI tract

2. Food poisoning: bacteria grow on food and then ingested.

Question 25

Endotoxins

Answer 25

Lipid A portion of LPS. Released when cell is lysed.

Question 26

considered normal flora on the skin

Answer 26

Staphylococcus epidermidis. Non pathogenic but can cause disease.

Question 27

What are the normal flora of the respiratory tract and their pathogenic counterpart?

Answer 27

Strep Viridans- Strep pyogenes Neisseria- Neisseria menigitidis Staph epidermidis- Staph aureus

Question 28

Eikenella corrodens

Answer 28

Skin and soft tissue infections associated with human bites and clenched-fist injuries

Question 29

B. fragilis

Answer 29

perforation of intestinal wall causing peritonitis

Question 30

lactobacillus

Answer 30

maintains low pH of vagina

Question 31

Group B Streptococci

Answer 31

carried by mother, transferred to child during birth causing sepsis and meningitis.

Question 32

Mycobacterium smegmatis

Answer 32

acid fast organism around female urethras and uncircumcised males