Infectious diseases

Question 1

Carbapenemase producing bacteria

Answer 1

Class A: KPC
Class B: metallo-betalactamases (MBLs) - zinc dependent: i.e. NDM
Class D:OXA type enzyme - preferentially hydrolyse oxacillin rather than penicillin

Question 2

Bacteriocidal

Answer 2

penicillins
cephalosporins
aminoglycosides
nitrofurantoin
metronidazole
quinolones
rifampicin
isoniazid

Question 3

bacteriostatic

Answer 3

chloramphenicol
macrolides
tetracyclines
sulphonamides
trimethoprim

Question 4

When to add vancomycin in neutropenic sepsis?

Answer 4

• suspected catheter related infection
• resistant organism identified
• hypotensive/haemodynamic instability
• recetly taken co-trim or cipro

Question 5

Which organism has inducible resistance to cephalosporins?

Answer 5

Enterobacter
Serratia marcescens
Citrobacter freundii
Hafnia spp.
Aeromonas or Acinetobacter
Proteus vulgaris
Providencia
Pseudomonas
Morganella morganii

produces a** chromosomally encoded beta-lactamase,** referred to as the cefuroxime-hydrolyzing beta-lactamase (cefuroximase or CumA), which hydrolyzes **cephalosporins. **

Treating these organisms with cephalosporins induces the production of a beta-lactamase via the AmpC gene.

Question 6

pneumococcal vaccines

Answer 6

There are 2 types of pneumococcal vaccine:

• A pneumococcal protein-conjugate vaccine (PCV13; Prevnar 13) that includes capsular polysaccharide antigens covalently linked to a nontoxic protein that is nearly identical to diphtheria toxin.
• A pneumococcal polysaccharide vaccine (**PPSV23; **Pneumovax 23, Pnu-Immune) that includes 23 purified capsular polysaccharide antigens
• For patients undergoing emergency/urgent splenectomy it is recommended to give the vaccine series 14 days after splenectomy.
• The recommendation is to give the PCV13 first followed by the PPSV23 8 weeks later. If this is for an elective/planned splenectomy this can be completed 10-12 weeks prior to surgery so that the last vaccination is given at least 14 days prior to the operation.

Question 7

HIV transmission in pregnancy and breastfeeding

Answer 7

• without antiretroviral therapy:
  > risk of Mother-to-child transmission between 15-45% with 90% of this risk being in the perinatal period.
  > risk of transmission through breastfeeding was estimated to be 14%

The risk of transmission is linked to the mother’s viral load

In women who have viral suppression on antiretroviral treatment (ART) at the time of conception and who maintain adherence to ART and viral suppression throughout pregnancy, delivery, and breastfeeding, perinatal HIV transmission is reduced to <1 percent.