Aztreonam Avibactam for NDM-Producing Bacteria: Mechanism, Clinical Evidence and Treatment Considerations
NDM-producing Gram-negative bacteria are an important cause of antimicrobial resistance because New Delhi metallo-beta-lactamase (NDM) can inactivate many beta-lactam antibiotics, including carbapenems. Treating infections caused by these organisms can therefore be challenging, particularly when additional resistance mechanisms are present.
The combination of aztreonam and avibactam has attracted clinical interest because it combines a beta-lactam antibiotic that is stable to metallo-beta-lactamases with a beta-lactamase inhibitor that can inhibit several serine beta-lactamases.
This complementary activity provides an important scientific basis for studying aztreonam-avibactam against NDM-producing Gram-negative bacteria.
This article explains the relationship between NDM resistance and aztreonam-avibactam, including the mechanism, clinical evidence, susceptibility testing and important treatment considerations.
What Is NDM?
NDM stands for New Delhi metallo-beta-lactamase.
It is a type of metallo-beta-lactamase (MBL) produced by certain Gram-negative bacteria. NDM enzymes belong to the broader group of beta-lactamases that can hydrolyze many beta-lactam antibiotics.
NDM-producing organisms are particularly concerning because NDM can hydrolyze carbapenems, which are often used for treating serious infections caused by multidrug-resistant Gram-negative bacteria.
NDM genes are commonly associated with mobile genetic elements, allowing resistance determinants to spread between bacterial populations.
NDM-producing organisms can include:
- Escherichia coli
- Klebsiella pneumoniae
- other Enterobacterales
- selected non-fermenting Gram-negative organisms
The clinical significance depends on the organism, infection site, susceptibility profile and presence of additional resistance mechanisms.
Why Is NDM Resistance Difficult to Treat?
NDM is different from many commonly discussed serine beta-lactamases.
Metallo-beta-lactamases use zinc ions at their active site and can hydrolyze a broad range of beta-lactam antibiotics.
A major limitation is that commonly used beta-lactamase inhibitors such as some traditional serine-beta-lactamase inhibitors do not directly inhibit NDM.
This means that simply adding a conventional beta-lactamase inhibitor to a beta-lactam does not necessarily restore activity against an NDM-producing organism.
NDM-producing bacteria can also carry other resistance mechanisms at the same time.
For example, an organism may produce:
- NDM;
- ESBLs;
- AmpC enzymes;
- porin alterations;
- efflux mechanisms; or
- other resistance determinants.
This combination can make antimicrobial susceptibility and treatment selection more complicated.
How Does Aztreonam Help Against NDM?
Aztreonam is a monobactam beta-lactam antibiotic.
One important characteristic of aztreonam in the context of MBL-producing organisms is its relative stability to hydrolysis by metallo-beta-lactamases such as NDM.
However, this does not mean that aztreonam alone is universally effective against NDM-producing bacteria.
Why?
Because NDM-producing organisms may simultaneously produce other beta-lactamases that can hydrolyze aztreonam.
For example, an NDM-producing organism may also produce an ESBL or AmpC enzyme.
Therefore, even though NDM itself does not efficiently destroy aztreonam, other beta-lactamases can compromise aztreonam activity.
This creates the scientific rationale for combining aztreonam with an appropriate beta-lactamase inhibitor.
What Role Does Avibactam Play?
Avibactam is a non-beta-lactam beta-lactamase inhibitor with activity against several clinically important serine beta-lactamases.
These include certain:
- class A beta-lactamases;
- extended-spectrum beta-lactamases;
- KPC enzymes; and
- class C AmpC enzymes.
Avibactam does not directly inhibit metallo-beta-lactamases such as NDM.
This distinction is extremely important.
The role of avibactam in the combination is not to inhibit NDM itself. Instead, avibactam can inhibit relevant serine beta-lactamases that may coexist with NDM, thereby helping protect aztreonam from hydrolysis.
How Does Aztreonam + Avibactam Work Against NDM-Producing Bacteria?
The combination can be understood through a complementary mechanism.
Step 1: NDM Is Present
The bacterial organism produces NDM, a metallo-beta-lactamase capable of hydrolyzing many beta-lactam antibiotics.
Step 2: Aztreonam Provides the Beta-Lactam Activity
Aztreonam acts on bacterial cell-wall synthesis by binding to susceptible penicillin-binding proteins.
Its relative stability to metallo-beta-lactamases provides the foundation for its use in this combination.
Step 3: Other Beta-Lactamases May Threaten Aztreonam
The same bacterial organism may also produce enzymes such as ESBLs or AmpC that can hydrolyze aztreonam.
Step 4: Avibactam Inhibits Relevant Serine Beta-Lactamases
Avibactam inhibits susceptible serine beta-lactamases, helping protect aztreonam from enzymatic hydrolysis.
Step 5: The Combination Restores Antibacterial Activity in Appropriate Isolates
By combining these complementary activities, aztreonam-avibactam can provide antibacterial activity against selected organisms producing NDM and other beta-lactamases.
This is the central scientific rationale behind the combination.
Aztreonam Alone vs Aztreonam + Avibactam
Understanding the difference between aztreonam alone and the combination is important.
| Feature | Aztreonam | Aztreonam + Avibactam |
|---|---|---|
| Beta-lactam antibiotic | Yes | Yes |
| Monobactam | Yes | Yes |
| Activity affected by NDM | Relatively stable to NDM | Retains the aztreonam component’s MBL stability |
| Serine beta-lactamase protection | Limited | Avibactam provides inhibition of susceptible serine beta-lactamases |
| Rationale for NDM-producing organisms | Limited by co-produced enzymes | Designed to address combined beta-lactamase mechanisms |
| Clinical use | Depends on susceptibility and indication | Depends on susceptibility, indication and applicable guidance |
The key point is that avibactam does not neutralize NDM itself.
Instead, it helps address the additional serine beta-lactamase activity that can otherwise compromise aztreonam.
What Does Clinical Evidence Show?
Clinical research has evaluated aztreonam-avibactam in serious infections involving resistant Gram-negative bacteria.
Two important clinical programs include REVISIT and ASSEMBLE.
REVISIT
The REVISIT clinical program evaluated aztreonam-avibactam in patients with serious infections caused by resistant Gram-negative bacteria.
The study contributed clinical evidence concerning the efficacy and safety of the combination in complicated infections.
However, clinical trial findings should be interpreted according to the specific study population, comparator, infection type and microbiological characteristics.
ASSEMBLE
The ASSEMBLE program specifically contributed evidence concerning infections involving metallo-beta-lactamase-producing Gram-negative bacteria.
This is particularly relevant to NDM because NDM is one of the most clinically important MBLs.
The study population was relatively limited, so results should not be interpreted as evidence that every NDM-producing isolate will respond to aztreonam-avibactam.
Clinical treatment still requires susceptibility information and consideration of the individual infection.
Does Aztreonam Avibactam Work Against All NDM-Producing Bacteria?
No.
The presence of NDM alone should not be interpreted as an automatic guarantee of susceptibility.
Several factors can influence the activity of aztreonam-avibactam, including:
- additional beta-lactamases;
- changes in bacterial permeability;
- porin alterations;
- efflux mechanisms;
- alterations affecting antibiotic targets;
- organism species;
- infection site; and
- the isolate’s measured susceptibility.
Therefore, microbiological testing remains important.
A laboratory result should be interpreted using the applicable susceptibility-testing method and current breakpoint criteria.
Why Is Susceptibility Testing Important?
Susceptibility testing helps determine whether a bacterial isolate is likely to be inhibited by the antimicrobial combination.
For NDM-producing organisms, this is especially important because resistance mechanisms can occur together.
An isolate may contain NDM plus additional mechanisms that alter the activity of aztreonam-avibactam.
Depending on the organism and laboratory setting, susceptibility testing may involve methods such as:
- broth microdilution;
- minimum inhibitory concentration (MIC) determination; and
- other validated susceptibility methods.
Laboratories should use appropriate standards and current breakpoint information when interpreting results.
For more detail, see the dedicated resource on Aztreonam Avibactam Susceptibility Testing.
NDM Does Not Mean the Same Resistance Profile in Every Isolate
Two bacterial isolates may both be described as NDM-producing but have different overall resistance profiles.
For example:
Isolate A
NDM + limited additional resistance mechanisms
Isolate B
NDM + ESBL + porin changes + additional resistance determinants
Both organisms may produce NDM, but their susceptibility profiles may differ.
This is why antimicrobial selection should be based on the complete microbiological and clinical picture rather than the NDM label alone.
What Are the Clinical Treatment Considerations?
When aztreonam-avibactam is considered for an NDM-producing infection, healthcare professionals should evaluate several factors.
Confirm the Organism
Identification of the causative organism is important.
The clinical significance of an NDM-producing Klebsiella pneumoniae isolate, for example, may differ from that of another Gram-negative organism.
Review Susceptibility Results
Susceptibility testing should be reviewed before treatment decisions are finalized whenever appropriate.
Consider the Infection Site
The site and severity of infection influence antimicrobial selection.
Factors such as:
- bloodstream infection;
- intra-abdominal infection;
- urinary infection;
- hospital-acquired infection; and
- other complicated infections
may require different clinical considerations.
Evaluate Patient-Specific Factors
Healthcare professionals should consider:
- renal function;
- hepatic status;
- allergy history;
- concomitant medications;
- previous antimicrobial exposure; and
- severity of illness.
Follow Current Clinical Guidance
Treatment decisions should be based on current local and international antimicrobial guidance, susceptibility results and applicable prescribing information.
Can Resistance Develop During Aztreonam Avibactam Treatment?
As with antimicrobial therapy generally, resistance can emerge under selective pressure.
Potential mechanisms may include changes involving:
- beta-lactamase expression;
- additional beta-lactamases;
- bacterial permeability;
- porins;
- efflux;
- target alterations; and
- combinations of multiple mechanisms.
The emergence of resistance is therefore an important consideration in antimicrobial stewardship.
Appropriate antimicrobial selection, microbiological testing and clinical monitoring remain important components of responsible use.
Aztreonam Avibactam and NDM: Why the Combination Matters
The scientific importance of aztreonam-avibactam in NDM-producing infections comes from its complementary mechanism.
NDM is a metallo-beta-lactamase.
Avibactam does not inhibit NDM.
Instead:
Aztreonam → provides antibacterial beta-lactam activity and is relatively stable to NDM
Avibactam → inhibits susceptible serine beta-lactamases that may otherwise hydrolyze aztreonam
Together, these activities can help overcome a combination of resistance mechanisms in appropriate bacterial isolates.
This mechanism is fundamentally different from simply using a conventional beta-lactamase inhibitor against an MBL.
Meblanios and Aztreonam + Avibactam Injection
Meblanios is an AIONIOS Pharma product associated with the aztreonam + avibactam injectable combination.
The broader scientific principles discussed in this article describe the aztreonam-avibactam combination and should not automatically be interpreted as product-specific clinical or microbiological claims.
For product-specific information, healthcare professionals should refer to the applicable product documentation.
Meblanios Aztreonam + Avibactam Injection
Frequently Asked Questions
What is NDM?
NDM, or New Delhi metallo-beta-lactamase, is a metallo-beta-lactamase that can hydrolyze many beta-lactam antibiotics, including carbapenems.
Does avibactam inhibit NDM?
No. Avibactam does not directly inhibit metallo-beta-lactamases such as NDM. Its role is to inhibit susceptible serine beta-lactamases that may coexist with NDM.
Why combine aztreonam with avibactam?
Aztreonam is relatively stable against metallo-beta-lactamases, while avibactam can inhibit certain serine beta-lactamases. The combination therefore addresses complementary resistance mechanisms.
Is aztreonam-avibactam effective against every NDM-producing organism?
No. Susceptibility depends on the organism’s complete resistance profile, including additional beta-lactamases and other mechanisms. Susceptibility testing remains important.
Is NDM the same as ESBL?
No. NDM is a metallo-beta-lactamase, whereas ESBLs are generally serine beta-lactamases. They have different biochemical characteristics and inhibitor susceptibility.
Why is susceptibility testing important for NDM-producing bacteria?
Because NDM-producing organisms can carry additional resistance mechanisms. The presence of NDM alone does not establish the complete susceptibility profile of an isolate.
What clinical studies have evaluated aztreonam-avibactam?
Clinical development has included studies such as REVISIT and ASSEMBLE, with ASSEMBLE providing particularly relevant evidence in infections involving metallo-beta-lactamase-producing Gram-negative bacteria.
Conclusion
Aztreonam Avibactam for NDM-producing bacteria represents an important antimicrobial strategy based on complementary mechanisms of action.
NDM itself is not inhibited by avibactam. Instead, aztreonam provides a beta-lactam component with relative stability to metallo-beta-lactamases, while avibactam inhibits susceptible serine beta-lactamases that may otherwise compromise aztreonam activity.
This mechanism provides a scientific rationale for using the combination against selected NDM-producing Gram-negative bacteria.
However, NDM production does not automatically establish susceptibility. Microbiological testing, the complete resistance profile, infection site, patient-specific factors and current clinical guidance should all be considered when evaluating treatment options.
For healthcare professionals managing difficult-to-treat Gram-negative infections, understanding the distinction between NDM activity and serine beta-lactamase inhibition is central to understanding why aztreonam-avibactam has attracted clinical interest.