ID part 2 Resistant enzymes and treatments

Question 1

ESBLs

Answer 1

identified with CTX-M present
Most common in E. Coli, Klebsiella, Proteus mirabilis

Treatment of choice is carbapenems
Meropenem, Impenem, Doripenem, Ertapenem

Question 2

Carbapenemase

Answer 2

Identified with KPC present
Most common in K. Pneumonia, K. Oxytoca, E.Coli, E. Cloacae, E. Aerogenes, P. Mirabills

Causes resistance to whole B- lactam class (Penecillins, Cephalosporins, carbapenems, Monobactams)

Treatment of choice is usually a b-lactam with a b-lactamase inhibitor
Avycaz - ceftazidime/avibactam
Vabomere - meropenem/vaborbactam

Question 3

Metallo-B-Lactamases

Answer 3

Identified with NDM
present in P. aeruginosa, Acinetobacter spp., and enterobacterales
Resistance to all B-lactams except monobactams (aztreonam)

Treatment Cefiderocol

Question 4

OXA-Type

Answer 4

Identified with OXA-48
Common in Acinetobacter baumannii and Pseudomonas aeruginosa

Treatment: Cefiderocol or Sulbactam/durlobactam

Question 5

AmpC inducible mechanism

Answer 5

AmpC helps recycle cell wall degredation products but can be a b-Lactamase at low levels
AmpG brings in degredation products to the iner membrane and AmpD generates UDP-N- acetyl which will bind to AmpR and turn off AmpC which is desired

Presence of B-Lactam is AmpG is bringing in degredation products faster and AmpD cannot make UDP fast enought and these degredation products then compete to bind to AmpR which turns on the AmpC gene and cause hyperexpresion of AmpC b-lactamases to inactivate our B-Lactam drugs (if we remove inducer we can go back to normal state)

Problem arises when there are Mutations specifically in AmpD so the degradation products continuously stimulate AmpC b-lactamase production without b-lactam present

Question 6

AmpC inducers

Answer 6

Found in Hafnia alvei, Enterobacter cloacae, Citrobacter freudii, Klebsiella aerogenes, Yersinia enterocolitica (HECK YES) - EXAM Q

Most commonly seen in Enterobacter cloacae, Citrobacter freudii, Klebsiella aerogenes,

Question 7

Strong inducers of AmpC

Answer 7

Penicillin G, ampicillin

Question 8

Weak Inducers of AmpC

Answer 8

Ceftriaxone is known to induce AmpC the most out of other 3rd generation Cephalosporins and patient will become resistant if AmpC is activated

Question 9

AmpC treatment

Answer 9

Cefepime - still a weak inducer of AmpC but it is still able to work even with AmpC induced

Second line treatment is carbapenems (meropenem, Imipenem)

Question 10

Resistance to vancomycin

Answer 10

Target site (D-Ala-D-Ala) alteration that leads to resistance
Rapid diagnostic test will show VanA or VanB

Treatment: Daptomycin or linezolid

Question 11

Penicillin binding proteins (PBPs) resistance

Answer 11

Leads to beta lactam resistance
ususally seen as Methicillin resistant staphylococcus aureus

Epressed by mecA gene

Treatment: Ceftaroline, Ceftobiprole, vancomycin, daptomycin, linezolid

Question 12

Efflux pumps resistance

Answer 12

Important resistance mechanism for P aeruginosa