Microbiology

Question 1

Who is at risk of hep b, c and HIV?

Answer 1

Injecting drug users

Question 2

What should you test as markers of ongoing or previous hep B infection?

Answer 2

hep B surface antigen (HBsAg) and core antibody (anti-HBc IgG)

Question 3

What will provide evidence of previous hep B immunization?

Answer 3

Hepatitis B surface antibody (anti-HBs)

Question 4

Marker of previous natural infection with hep B?

Answer 4

Anti-HBc

Question 5

Groups who should be offered hep B vaccination?

Answer 5

Likely contact with infected individuals, likely contact with high-prevalence populations, likely contact with infected blood or blood products, people for whom HBV would be a severe health problem, individuals at occupational risk.

Question 6

Basic first aid for needlestick injury?

Answer 6

 Wash off splashes with soap and running water.
 Encourage bleeding if skin broken
 Wash out splashes from the eye using an eye-wash bottle or copious amounts of tap water.

Question 7

Admin actions after needlestick injury?

Answer 7

 Make a careful record of the source and nature of the contamination.
 Report the accident to a superior.
 Immediately contact occupational health.

Question 8

Preventative measures to minimise risk of needle stick injuries?

Answer 8

 Immunisation against hep B.
 Needlesafe devices used as extensively as possible.
 Training in appropriate methods of taking blood and disposing of sharps
 Sharps bins should be widely available and used appropriately (not overfilled)

Question 9

In hep B what does core IgM positivity indicate?

Answer 9

Recent infection

Question 10

In hep B what does HBeAg positivity indicate?

Answer 10

Blood is highly infectious

Question 11

Definition of SIRS?

Answer 11

SIRS = RR >20, HR >90, temp >38, WCC 12.

Question 12

Definition of sepsis?

Answer 12

Sepsis = SIRS + evidence of infection

Question 13

Severe sepsis definition?

Answer 13

Severe sepsis = organ dysfunction

Question 14

Definition of septic shock?

Answer 14

Septic shock = persistent hypotension despite adequate fluid resuscitation.

Question 15

Commonest causes of surgical site infections following a ‘clean procedure’?

Answer 15

Staph aureus and Strep pyogenes

Question 16

What is strep pyogenes?

Answer 16

Group A B-haemolytic streptococcus

Question 17

Rarer causes of wound infection?

Answer 17

Anaerobic organisms (e.g. Bacteriodes spp, clostridium spp) and group B B-haemolytic streptococci

Question 18

Appropriate first line abx for surgical site infection?

Answer 18

IV flucloxacillin - covers both streptococci and methicillin sensitive s.aureus

Question 19

Appropriate abx regimen for Meticillin-sensitive Staph. Aureus?

Answer 19

Flucloxacillin. If penicillin allergic, clindamycin, clarithromycin or vancomycin (glycopeptide). Clindamycin avoided in >65 because of CDI risk.

Question 20

Appropriate abx regimen for streptococcus pyogenes?

Answer 20

Benzylpenicillin, with oral switch to phenoxymethylpenicillin or amoxicillin. If penicllin allergic, options include clarithromycin, clindamycin and vancomycin.

Question 21

Appropriate abx regimen for MRSA?

Answer 21

Vancomycin, with oral switch to e.g. clarithromycin, tetracycline or linezolid

Question 22

Most likely organism for PVE?

Answer 22

Coagulase negative Staphlycoccus (CNS) = predominant cause of early onset PVE. Viridans streptococci (usual cause of native valve infective endocarditis) = main cause of late onset PVE.

Question 23

Usual treatment of CNS PVE?

Answer 23

Usual treatment of CNS PVE would be comination of vancomycin and rifampicin for 6-8 weeks, with gentamicin for first two weeks.

Question 24

Why do coagulase negative staphylococci infect prosthetic valves?

Answer 24

• Coagulase-negative staphylococci produce an exopolysaccharide (slime) which mediates adhesion, both to other organisms and to inanimate (plastic) surfaces).

Question 25

Measures to prevent infection spread on ward?

Answer 25

• Communication, hand hygiene, protective clothing, environmental decontamination, ensuite room if possible (if not, own commode), reducing to a safe minimum the number of staff entering isolation rooms, close door to isolation rooms, correct disposal of waste and bodily fluids.

Question 26

Empirical abx treatment for CAP?

Answer 26

• CAP  IV co-amoxiclav and clarithromycin (empirical). Co-amoxiclav will treat step pneumoniae/H.influenzae, clarithromycin added for atypicals. However, broad spectrum, so risk of C.diff.

Question 27

what is step pneumoniae?

Answer 27

gram positive coccus

Question 28

Appropriate abx for soft tissue infections?

Answer 28

fluxcloxacillin (staph and strep), vancomycin (if allergic to penicillin or got history of MRSA).

Question 29

Most likely organism for soft tissue infections?

Answer 29

B-haemolytic streptococci and staph aureus.

Question 30

Abx most associated with C diff?

Answer 30

• Fluoroquinolones, clindamycin, cephalosporins, penicillins