Thanks to all that participated on last week polls.
Answers (% right):
1 AmpC (75)
2 ESBL (80)
3 KPC (80)
4 NDM (84)
5 OprD-mediated (80)
Let’s talk about commonly encountered resistance phenotypes.
#IDMedEd #IDTwitter #IDFellows
Answers (% right):
1 AmpC (75)
2 ESBL (80)
3 KPC (80)
4 NDM (84)
5 OprD-mediated (80)
Let’s talk about commonly encountered resistance phenotypes.
#IDMedEd #IDTwitter #IDFellows
There are a four major types of gram-negative resistance mechanisms:
1.Enzymatic degradation
2.Change in binding site (e.g. MecA)
3.Loss of porin channels
4.Efflux pumps.
We will review here 1 and 3.
1.Enzymatic degradation
2.Change in binding site (e.g. MecA)
3.Loss of porin channels
4.Efflux pumps.
We will review here 1 and 3.
The most widely used classification of β-lactamases is the Ambler classification.
- Serine β-L vs. Metallo β-L
- A, B, C, D
See this brief commentary on the classification academic.oup.com/jac/article/55…
- Serine β-L vs. Metallo β-L
- A, B, C, D
See this brief commentary on the classification academic.oup.com/jac/article/55…
However, to help identify phenotypes in clinical practice, maybe this table can be more helpful. Hope it helps #IDfellows learn and recognize them.
Please provide feedback and suggestions for future versions.
Shoutout to @sukritibanthiya for creating this amazing infographic.
Please provide feedback and suggestions for future versions.
Shoutout to @sukritibanthiya for creating this amazing infographic.
AmpC β-lactamases (Class C); Case 1
- “SPACE organisms”: Serratia, Pseudomonas, Acinetobacter, Citrobacter, and Enterobacter
Or
- Recently found AMPCHES (Credit to Dr. Arias @SuperBugDoc). May be easier to remember to some
Add A: Aeromonas/Acinetobacter
- “SPACE organisms”: Serratia, Pseudomonas, Acinetobacter, Citrobacter, and Enterobacter
Or
- Recently found AMPCHES (Credit to Dr. Arias @SuperBugDoc). May be easier to remember to some
Add A: Aeromonas/Acinetobacter
AmpC β-lactamases (Class C)
Key identifiers:
•Reliably R to Cephamycins (cefoxitin).
•Cefepime can overcome inactivation and activity is retained.
•Phenotype: Derepressed (low vs. high level production) vs. inducible production (repressed)
Continues...
Key identifiers:
•Reliably R to Cephamycins (cefoxitin).
•Cefepime can overcome inactivation and activity is retained.
•Phenotype: Derepressed (low vs. high level production) vs. inducible production (repressed)
Continues...
...
•Basal–minimal production irrespective of βL presence (<3%🦠)
•Inducible–production at baseline, transiently & reversibly⬆️in presence of βL, reversible, most 🦠
•Constitutive–mutant🦠that always produce ⬆️quantities irrespective of presence of βL;AKA “stably derepressed”
•Basal–minimal production irrespective of βL presence (<3%🦠)
•Inducible–production at baseline, transiently & reversibly⬆️in presence of βL, reversible, most 🦠
•Constitutive–mutant🦠that always produce ⬆️quantities irrespective of presence of βL;AKA “stably derepressed”
ESBL-producing; Case 2
Key identifiers:
•Ceftriaxone/PCN resistant.
•Cephamycins (cefoxitin) susceptible.
•Cefepime often tests susceptible. Some institutions won’t report Cefepime because of possible worsening outcomes
Molecular dx: CTX-M (most frequent US), TEM, SHV
Key identifiers:
•Ceftriaxone/PCN resistant.
•Cephamycins (cefoxitin) susceptible.
•Cefepime often tests susceptible. Some institutions won’t report Cefepime because of possible worsening outcomes
Molecular dx: CTX-M (most frequent US), TEM, SHV
Serine carbapenemases: KPC (class-A), OXA-48 (class-D); Case 3
Key identifiers:
•Resistant to all traditional β-lactams, including carbapenems.
•Inhibited by avibactam (Avycaz), vaborbactam (Vabomere), relebactam (Recabrio).
Molecular diagnosis: KPC, OXA-48
Key identifiers:
•Resistant to all traditional β-lactams, including carbapenems.
•Inhibited by avibactam (Avycaz), vaborbactam (Vabomere), relebactam (Recabrio).
Molecular diagnosis: KPC, OXA-48
Metallo-β-lactamases: (NDM, VIM, IMP); Case 4
Key identifiers:
•Resistant to all β-lactams.
•MBL dont hydrolyze Aztreonam, but organisms usually co-carry other β -lactamases (i.e. AmpC). Thus, combination Aztreonam–Avibactam can have activity.
Molecular dx: NDM, VIM, IMP
Key identifiers:
•Resistant to all β-lactams.
•MBL dont hydrolyze Aztreonam, but organisms usually co-carry other β -lactamases (i.e. AmpC). Thus, combination Aztreonam–Avibactam can have activity.
Molecular dx: NDM, VIM, IMP
OprD-mediated; Case 5
Organisms: Pseudomonas aeruginosa
OprD is porin that facilitates diffusion of carbapenems into the cell. Decreased expression results in resistance.
Key identifiers:
• Resistant to carbapenems, especially imipenem
Organisms: Pseudomonas aeruginosa
OprD is porin that facilitates diffusion of carbapenems into the cell. Decreased expression results in resistance.
Key identifiers:
• Resistant to carbapenems, especially imipenem
That is it! Hope you enjoy it. Thanks for the feedback and for sharing!
We will post new polls on resistant gram-negative treatment followed by tweetorials on the management very soon. Stay tuned!
Authors: @LeMiguelChavez @InfectiousDan
Infographic: @sukritibanthiya
We will post new polls on resistant gram-negative treatment followed by tweetorials on the management very soon. Stay tuned!
Authors: @LeMiguelChavez @InfectiousDan
Infographic: @sukritibanthiya
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