The Liofilchem® Meropenem+Cloxacillin (MR+CL) Antimicrobial Susceptibility Discs are designed for detecting resistance mechanisms, such as AmpC beta-lactamase overproduction, in Gram-negative bacteria, particularly in Enterobacterales. These discs enable the differentiation of resistance mechanisms that render carbapenem antibiotics less effective and assist in guiding treatment options.
Key Features
- Combination Testing:
- Each disc contains Meropenem alone (MR) and Meropenem+Cloxacillin (MR+CL) to identify AmpC beta-lactamase-mediated resistance.
- High Sensitivity:
- Effectively detects AmpC-producing Enterobacterales by comparing zones of inhibition.
- Ease of Use:
- Standardized disc diffusion method compatible with CLSI and EUCAST guidelines.
- Broad Applications:
- Suitable for clinical diagnostics, antimicrobial resistance surveillance, and research studies.
Applications
| Application | Description |
|---|
| Clinical Diagnostics | Identifies AmpC beta-lactamase-mediated resistance in Enterobacterales. |
| Antimicrobial Resistance Studies | Tracks the prevalence of AmpC-producing pathogens in healthcare settings. |
| Pharmaceutical Research | Evaluates the efficacy of carbapenem-based combination therapies. |
Testing Procedure
- Preparation:
- Prepare a bacterial suspension to 0.5 McFarland standard.
- Spread the suspension uniformly on Mueller-Hinton agar plates.
- Application:
- Place the MR and MR+CL discs on the agar surface using sterile forceps.
- Incubation:
- Incubate plates at 35–37°C for 16–20 hours under aerobic conditions.
- Interpretation:
- Measure and compare the zones of inhibition for both discs:
- An increase in the zone diameter by ≥5 mm with MR+CL compared to MR alone indicates AmpC beta-lactamase production.
Storage and Stability
| Condition | Temperature | Duration |
|---|
| Long-Term Storage | -20°C | Until expiration date |
| Short-Term Storage | 2–8°C | Up to 2 weeks |
| During Use | Room Temperature | Immediate use only |
Technical Specifications
| Feature | Details |
|---|
| Active Components | Meropenem (10 µg) and Meropenem+Cloxacillin (10 µg + 200 µg) |
| Test Method | Disc diffusion |
| Compatible Media | Mueller-Hinton agar |
| Incubation Conditions | 35–37°C for 16–20 hours |
| Target Pathogens | Gram-negative bacteria, including AmpC producers |
| Shelf Life | As per expiration date on packaging |
| Pack Sizes | 50 or 100 discs per pack |
Quality Control Data
| Control Organism | Expected Results |
|---|
| Escherichia coli ATCC® 25922 | MR: ≥23 mm; MR+CL: Similar |
| Klebsiella pneumoniae ATCC® 700603 | MR: Reduced zone; MR+CL: Zone diameter increased by ≥5 mm |
| Pseudomonas aeruginosa ATCC® 27853 | MR: ≥18 mm; MR+CL: Similar |
| Staphylococcus aureus ATCC® 29213 | Not applicable (Gram-positive control) |
- Positive Controls: Confirm detection of AmpC-producing strains.
- Negative Controls: Ensure no false-positive results in non-AmpC producers.
Interpretation of Results
| Zone of Inhibition Comparison | Interpretation |
|---|
| MR zone = MR+CL zone | Absence of AmpC production. |
| MR zone ≥5 mm smaller than MR+CL zone | Presence of AmpC-producing bacteria. |
Comparison with Other Disc-Based Tests
| Test Disc | Recommended Use |
|---|
| Meropenem+Cloxacillin (MR+CL) | Specific detection of AmpC beta-lactamase producers. |
| Meropenem+EDTA | Detection of metallo-beta-lactamase producers. |
| Carbapenemase Combination Discs | General detection of carbapenemase-mediated resistance. |
Advantages
| Feature | Benefit |
|---|
| Dual Testing System | Identifies AmpC resistance directly on primary testing. |
| High Sensitivity and Specificity | Reduces false-positive and false-negative results. |
| Ease of Use | Simplified setup minimizes errors and time. |
| Standards Compliance | Adheres to global antimicrobial susceptibility testing guidelines. |
Conclusion
The Liofilchem® Meropenem+Cloxacillin (MR+CL) Antimicrobial Susceptibility Discs provide an efficient and reliable method for detecting AmpC beta-lactamase-mediated resistance in Gram-negative bacteria. Their precision and adherence to international standards make them an invaluable tool for clinical diagnostics and resistance monitoring programs.
https://www.labmartgh.com/shop/product/9175-liofilchem-r-meropenem-cloxacillin-mr-cl-antimicrobial-susceptibility-discs-22007
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