Coagulase Negative Staphylococci

Question 1

What is the main example of Coagulase Negative Staphylococci

Answer 1

Staphylococcus epidermidis

Question 2

What are CNS
(5)

Answer 2

Normal skin commensals which frequently contaminate clinical specimens obtains through the skin

May be implicated in infection

Reservoirs include host colonisation but can also survive on dry surfaces for extended period

Cause generally low grade infections

But opportunistic pathogens that can cause serious infection in debilitated or compromised patients

Question 3

How are CNSs transmissed

Answer 3

Direct contact or indirect contact with contaminated fomites

Question 4

Write about the clinical significance of S. epidermidis
(3)

Answer 4

Important agent of HCAI

Emergence as opportunistic pathogen reflect increased use of invasive procedures and the increasing number of debilitated patients in hospitals

Important source of device-associated infection and HCAI BLIs

Question 5

What kinds of infection can S. epidermidis cause
(5)

Answer 5

Device-associated infection
HCAI BSI
I.V lines (central lines) and feeding lines
Urinary catheters, peritoneal dialysis catheter
Implanted prosthetic devices e.g. heart valves, artificial joints, prosthetic valve endocarditis

Question 6

What are the two methods of pathogenicity for S. epidermidis

Answer 6

1. ability to adhere to biomaterials
2. Production of extracellular slime which results in biofilm production

Question 7

What percentage of strains produce slime

Answer 7

80%

Question 8

Where is S. epidermidis able to produce biofilm

Answer 8

On the surface of prosthetic devices

This is a significant determinant of virulence

Question 9

How does biofilm facilitate virulence?

Answer 9

Through device associated infection

Through increased tolerance to disinfectants, antibiotics and phagocytosis

Question 10

Where can S. saprophyticus be found
(2)

Answer 10

Widely disseminated in the environment

Occurs as part of normal vaginal colonisation

Question 11

In general what infections does S. saprophyticus cause?
(3)

Answer 11

10-20% of primary urinary tract infections in sexually active young women

Opportunistic HCAI

Opportunistic infection in immunocompromised hosts

Question 12

What are micrococcus

Answer 12

Gram-positive cocci, larger than staphylococci and arranged in clusters of 4 to 8

Question 13

Where are micrococcus found?

Answer 13

Found in soil and water

Commensal

May colonise human skin

Question 14

What kinds of infections does micrococcus cause
(2)

Answer 14

Usually non-pathogenic

Occasionally causes opportunistic infection e.f. UTI