Microbiology 2

Question 1

How do you classify microorganisms?

Answer 1

Appearance/Structural features
Growth Requirements
Enzyme/metabolic tests
Molecular tests

Question 2

Wha are the different shapes of bacteria?

Answer 2

Cocci
Bacilli
Spiral shaped

Question 3

Describe Streptococcus and Staphylococcus?

Answer 3

Strep = strips 
Staph = clusters

Question 4

What colour stain do you get with gram negative and gram positive?

Answer 4

Negative = pink - single layer of peptidoglycan
Positive = purple - huge layer of peptidoglycan

Question 5

What organisms dont stain well with gram stain?

Answer 5

Mycobacterium TB - due to waxy cell wall that doesn’t take up cell wall
Treponema pallidum - causes syphilis (spirochaete organism)

Question 6

What are the differences between aerobic and obligate aerobes?

Answer 6

Aerobic - grow in air/O2

Obligate = NEED O2

Question 7

What is the difference between obligate anaerobes and facultative anaerobes?

Answer 7

Obligate = Killed by O2
Facultative = tollerate O2

Question 8

What is a selective media?

Answer 8

A substance in which in the presence of it it permits growth of one organisms over another one.

Question 9

What is a differential media?

Answer 9

The incorporation of chemicals produces visible changes in colonies that facilitate identification (differentiation)

Question 10

Describe haemolysis?

Answer 10

Important in classification of streptococcus. Shows haemolysis of blood on blood agar plates.

Question 11

Describe the different types of haemolysis?

Answer 11

Alpha = partial haemolysis - causes a greenish discolouration
Beta = completely haemolysis - most aggressive organisms as they produce toxins that lyse the red blood cells on the plate
Gamma = no haemolysis

Question 12

What organisms are, alpha, beta and non-haemolytic?

Answer 12

Alpha = viridian's, pneumoniae
Beta = Group strep A (strep. pyrogens) and B 
Non = enterococcus

Question 13

Describe in more detail step. pneumonia?

Answer 13

Gram positive cocci in chans or pairs
Commonest cause of pneumonia, can also cause meningitis
Part of normal URT flora in many people

Question 14

Describe strep Viridian’s in more detail?

Answer 14

Gram positive cocci in chains
Common commensals of URT, bowel and vagina, but can cause infection in a normally sterile site
Endocarditis can be caused by this

Question 15

Describe strep (group A) aka strep pyogenes?

Answer 15

most pathogenic of all strep
causes tonsillitis, soft tissue and skin infections, sepsis (puerperal) (throat and skin infections)
Strains still sensitive to penicillin

Question 16

Describe enterococcus?

Answer 16

non haemolytic strep
part of the normal bowel flora
Common cause of UTI

Question 17

Describe staphylococcus?

Answer 17

Grows best in O2
Clusters positive cocci
Use the coagulase test to distngust between staph. aureus etc

Question 18

Describe the coagulase test?

Answer 18

A test to distinguish staph aureus (common pathogen) from the other coagulase negative staph (common skin commensals)

Question 19

What happens in the coagulase test?

Answer 19

Golden colour = staph aureus

White colour = coagulase negative staph

Question 20

Describe the coagulase negative staph group?

Answer 20

Contains - staph epidermis, staph hominis etc
Common skin commensals that usually dont cause harm
Common cause of joint and prosthetic heart valve infection and IV injections

Question 21

What can staph aureus cause?

Answer 21

Skin and wound infections

Question 22

What is one of ht most commonest causes of bacteraemia?

Answer 22

Staph aureus
Bacteria in the blood spread
infection at any site may result in bacteria getting into the bloodstream - patient maybe become septic.
Infection may spread to other parts of the body (heart valves)

Question 23

What do you treat MRSA resistant aureus with?

Answer 23

Flucloxacillin

Question 24

What is fever?

Answer 24

Temperature higher than 38 degrees

Question 25

How does fever fight infection?

Answer 25

When an infection is sensed ion the body, the prostaglandin E increased the body’s thermal set point, which causes the body to shiver, causing fever, which gives you an increased survival from infection

Question 26

Describe sepsis

Answer 26

Small blood vessels become leaky and loose fluid in the tissues
Lower blood volume require the heart to work harder (increases HR)
Poor tissue oxygen perfusion means blood supply to organs decreases to keep blood flowing to the brain
the blood clotting system is activated causing blood clotting in tiny vessels - which uses up the clotting factors - increasing the risk of haemorrhage