2.1

Question 1

coagulase enzyme

Answer 1

converts fibrinogen to fibrin

Question 2

which bacteria produces coagulase enzyme

Answer 2

s aureus

Question 3

coagulase test uses

Answer 3

rabbit plasma

Question 4

coagulase test detects

Answer 4

• Test detects the form of coagulase which is bound to the cell wall of the bacterium

Question 5

coagulase test process

Answer 5

• A few drops of rabbit plasma containing fibrinogen are placed into the glass slide
  
  • A small portion of the bacterial colony is well mixed into the plasma and the fluid is observed for clumping (forms white granules)
  • Clumps indicate fibrin and agglutinated bacteria

Question 6

positive coagulase test

Answer 6

staph aureus
§ A few less commonly encountered staphylococcal species are also coagulase positive but the great majority are S aureus

Question 7

negative coagulase test

Answer 7

coagulase negative staph

Question 8

○ Staph aureus skin and soft tissue disease

Answer 8

folliculitis, furuncles, carbuncles, hidrenitis suppurativa, impetigo, mastitis

Question 9

folliculitis

Answer 9

◊ Small pustules involving hair folliculitis

Question 10

furuncle

Answer 10

® Furuncle (boil)

◊ Abscess originating from folliculitis and extending into subcutaneous tissue

Question 11

carbuncle

Answer 11

® Carbuncle

◊ Coalescence of adjacent furuncles draining to the surface through multiple sinuses

Question 12

hidradenitis suppurative

Answer 12

◊ Chronic abscesses/scarring in areas of skin bearing apocrine sweat glands or sebaceous glands (eg. Axillae

Question 13

impetigo

Answer 13

◊ School sores

◊ Crusting, spreading, inflamed lesions typically around mouth and nose; very contagious

Question 14

mastitis

Answer 14

◊ Infection of the breast sometimes with abscess formation

Question 15

staph bone and joint disease

Answer 15

® Commonest cause of septic arthritis and osteomyelitis

® Infects foreign devices such as pins and plates or prosthetic joints

Question 16

staph bacteraemia

Answer 16

◊ When bacteria are in the bloodstream, normally a sterile site.
◊ May be asymptomatic or associated with muscle aches and pains and fever

Question 17

staph septicaemia

Answer 17

◊ When bacteria in the bloodstream produce a systemic inflammatory response syndrome (SIRS): pyrexia, tachycardia, increased respiratory rate, raised or diminished white cell count.
◊ May progress to hypotension, hypoperfusion, organ dysfunction and death

Question 18

staph endocarditis

Answer 18

® Infection of a heart valve, typically resulting in rapid destruction and loss of function

Question 19

staph diseases

Answer 19

skin and soft tissue 
bone and joint 
endocarditis 
bacteraemia 
septicaemia 
brain, liver, spleen, rebel absecss

Question 20

2 coagulase neg staphs

Answer 20

staph saprophyticus, staph epidermidis

Question 21

○ Staphylococcus saprophyticus

Answer 21

§ Second most common cause of urinary tract infection in sexually active young women (most common cause is Escherichia coli, a gram negative rod)
§ Has particular virulence factors enabling adherance to uroepithelial cells

Question 22

staph saprophyticus virulence factor

Answer 22

enables it to adhere to uroepithelial cells

Question 23

staph saprophyticus causes

Answer 23

UTIs

Question 24

Staphylococcus epidermidis

Answer 24

commensal of the skin

Question 25

staph epidermidis virulence factor

Answer 25

§ Has a particular virulence factor which enables it to establish infection on foreign devices
□ Slime
□ A polysaccharide material secreted by the bacteria and forms the basis of a complex matrix in which the bacteria can multiple on the foreign device
□ Within this matrix the bacteria are protec ted from antibiotics and elements of the hosts immune system
□ Matrix conatning bacteria is known as a biofilm

Question 26

staph epidermidis causes infection when

Answer 26

§ Relatively low in virulence but can cause opportunistic infections, esp when
□ The host epithelial defences are breached
□ A foreign device is present

Question 27

○ Disease caused by other coagulase negative staphylococci

Answer 27

§ Infection of foreign devices 
				□ Orthopaedic screws and plates
				□ Spinal wires 
				□ Intravascular cannulas 
				□ Prosthetic joints 
				□ Intracranial devices 
				□ Prosthetic heart valves 
			§ Infections of foreign devices leads to infection of surrounding tissue 
				□ Osteomyelitis 
				□ Septic arthritis 
				□ Meningitis 
				□ Endocarditis 
				□ Bacteraemia

Question 28

treating foreign device infection with coat negative staphs

Answer 28

§ Foreign devices related infections (regardless of the causative organism) cannot be eradicated with antibiotics alone and the removal of the device is usually necessary for cure

Question 29

○ Coagulase negative staphylococci as contaminants

Answer 29

§ May contaminate specimens which are collected through skin in order to diagnose suspected infection of normally sterile sites
□ Blood collection to diagnose septicaemia
□ Cerebrospinal fluid collection to diagnose meningitis
□ Joint aspirate to diagnose septic arthritis

Question 30

§ Contamination by skin commensal coagulase negative staphylococci, when grown in the laboritory confuse the diagnosis because

Answer 30

□ Cant be differenitated from an S aureus on gram stain

□ Cant tell whether it’s the cause of the infection or a contaminant

Question 31

systemic inflammatory response syndrome (SIRS) is indictaive of

Answer 31

indicative of septicaemia

Question 32

clinical indications of SIRS

Answer 32

pyrexia, tachycardia, increased respiratory rate, raised or diminished white cell count.

Question 33

septicaemia may progress to

Answer 33

hypotension, hypoperfusion, organ dysfunction and death