24/11/2025
Today, we continue our journey to unravel the mysteries of the endless war between antibiotics and bacteria.
In previous posts, we've explored ✅Extended-Spectrum β-Lactamase-Producing Enterobacterales (ESBLs)
✅AmpC β-Lactamase-Producing Enterobacterales.
Now, we delve deeper into the realm of severe antibacterial resistance with ✅Carbapenem-Resistant Enterobacterales (CRE).
We'll examine the tips and tricks for managing each class.
First, let's categorize CRE infections outside the urinary tract into two main groups:
☑️Infections that are Not Carbapenemase-Producing
☑️Infections that are Carbapenemase-Producing
This article will focus on the second, more complex group. "Carbapenemase-producing CRE"
and it can be further divided into three critical classes based on the enzyme they produce.
🔴1. CRE with KPC Production
Management:
The preferred first-line treatment options for KPC-producing Enterobacterales infections are:
✔️Meropenem-vaborbactam
✔️Ceftazidime-avibactam
I✔️mipenem-cilastatin-relebactam
Cefiderocol serves as an excellent alternative option
🔴2. CRE with OXA-48-Like Production
Management:
For OXA-48-like-producing Enterobacterales,
✔️ ceftazidime-avibactam is the sole preferred treatment from the novel Beta-Lactam/Beta-Lactamase Inhibitor (BL/BLI) class.
But why only Ceftazidime-Avibactam?⁉️
The other novel BL/BLIs are not reliable against OXA-48 due to the specific inhibitor profiles:
✅Meropenem-Vaborbactam (M/V):
Vaborbactam is an excellent inhibitor of KPC but has poor activity against OXA-48-like enzymes.
✅Imipenem-Cilastatin-Relebactam (I/R):
Similarly, Relebactam powerfully inhibits KPC but has weak activity against OXA-48-like enzymes.
Therefore, only avibactam in the ceftazidime-avibactam combination effectively neutralizes the OXA-48 threat. Cefiderocol remains a valuable alternative treatment option.
🔴3. CRE with NDM or Other MBL Production
Management:
The preferred strategies for these formidable infections are:
✔️Ceftazidime-avibactam in combination with aztreonam
✔️Cefiderocol as monotherapy
Why is the "Triple Combination" of Ceftazidime-Avibactam + Aztreonam used? ⁉️
Why not as KPC and OXA 48 only Ceftazidime-avibactam without Aztreonam ⁉️
This is a brilliant pharmacological strategy:
✅Aztreonam's Role: Aztreonam is a unique monobactam beta-lactam that is stable against MBLs and is not hydrolyzed by them.
✅Avibactam's Role: MBL-producing bacteria almost always carry other beta-lactamases (like ESBLs, AmpCs). Avibactam in the ceftazidime-avibactam formulation protects aztreonam from these other enzymes.
☑️☑️In essence, this combination uses aztreonam to target the bacterium while using avibactam as a protector to shield it from all non-MBL enzymes.
This creates a powerful, synergistic effect against an otherwise pan-resistant pathogen.