Liofilchem™ MTS™ Colistin CS 0.064-1024, MIC Test strips

The Liofilchem™ MTS™ Colistin CS MIC Test Strips are designed for the precise determination of the minimum inhibitory concentration (MIC) of Colistin against bacterial pathogens. Colistin is a last-resort antibiotic used for treating multidrug-resistant Gram-negative bacterial infections caused by organisms such as Pseudomonas aeruginosa, Acinetobacter baumannii, and Klebsiella pneumoniae. This test strip provides a quantitative result for susceptibility testing, offering critical data to guide therapeutic decisions.

Key Features:

• Range: MIC testing from 0.064 µg/mL to 1024 µg/mL.
• Active Drug: Colistin sulfate (Polymyxin E).
• Applications: Used for Gram-negative bacteria, particularly multidrug-resistant pathogens.
• Method: Gradient diffusion method to determine MIC.
• Intended Use: For in vitro diagnostic use in clinical microbiology laboratories.

Test Procedure:

1. Preparation of Inoculum:
   • Prepare a bacterial suspension equivalent to a 0.5 McFarland standard in saline or Mueller-Hinton Broth.
   • Ensure uniform turbidity using a vortex mixer.
2. Preparation of Agar Plate:
   • Use Mueller-Hinton Agar (as per CLSI/EUCAST guidelines) as the medium.
   • Allow the medium to cool and solidify under aseptic conditions before use.
3. Application of Inoculum:
   • Dip a sterile swab into the bacterial suspension.
   • Spread the inoculum evenly across the agar plate surface to achieve a lawn of growth.
4. Placement of MTS™ Colistin Strip:
   • Using sterile forceps or applicator, place the Colistin MTS™ test strip on the surface of the inoculated agar.
   • Ensure the strip adheres fully to the agar without air bubbles.
5. Incubation:
   • Incubate plates at 35 ± 2°C for 16-20 hours in an aerobic atmosphere.
6. Reading Results:
   • After incubation, observe the elliptical zone of inhibition around the strip.
   • Read the MIC value at the point where the ellipse intersects the test strip.

Results Interpretation:

Reference Breakpoints: Interpret MIC values based on standards from EUCAST or CLSI:

Storage and Stability:

• Storage Temperature: Store at -20°C for long-term stability.
• Short-term Storage: Store at 2-8°C for up to 7 days.
• Shelf Life: Ensure strips are used before the expiry date printed on the packaging.
• Precautions: Avoid exposing strips to humidity or light. Handle aseptically.

Quality Control:

Positive Control:

• Pseudomonas aeruginosa ATCC® 27853
  • Expected MIC: 0.5 – 2 µg/mL

Negative Control:

• Escherichia coli ATCC® 25922
  • Expected MIC: Resistant (e.g., >4 µg/mL)

Quality control ensures that each batch of Liofilchem™ MTS™ Colistin test strips performs reliably and provides consistent results.

Comparison with Other Brands:

Advantages of Liofilchem™ MTS™ Colistin MIC Strips:

1. Broad MIC Range: Enables testing of highly resistant strains.
2. EUCAST and CLSI Compatibility: Ensures international standard compliance.
3. Precise Quantification: Offers highly reliable and reproducible results.
4. Cost-effective Alternative: Lower cost compared to bioMérieux Etest®.
5. User-friendly Design: Easy to handle with clear, legible gradients.

The Liofilchem™ MTS™ Colistin CS 0.064-1024, MIC Test Strips provide an accurate, reliable, and efficient solution for susceptibility testing of Gram-negative pathogens. Their compliance with international standards makes them an essential tool for combating multidrug-resistant infections.

Detailed Comparison

1. MTS™ Colistin CS (0.064–1024 µg/mL):

• Key Features:
  • Provides a wide MIC range for routine testing, including isolates with high-level resistance.
  • Enables determination of extremely resistant strains that exceed typical susceptibility thresholds.
• Best Suited For:
  • Routine clinical microbiology labs.
  • Testing highly resistant pathogens such as Klebsiella pneumoniae and Acinetobacter baumannii.
• Limitations:
  • Not ideal for determining MIC values close to clinical breakpoints due to the broader range.

2. MTS™ Colistin CS (0.016–256 µg/mL):

• Key Features:
  • Optimized for isolates near clinical breakpoints, improving accuracy in borderline susceptibility cases.
  • Better resolution for low- to moderate-level resistance compared to the broader range MTS™ (0.064–1024 µg/mL).
• Best Suited For:
  • Scenarios where isolates exhibit MIC values near susceptibility thresholds.
  • Laboratories needing precise differentiation between susceptible and intermediate strains.
• Limitations:
  • Less effective for highly resistant organisms with MIC values exceeding 256 µg/mL.

3. ComASP™ Colistin MIC Panel (0.25–16 µg/mL):

• Key Features:
  • Based on broth microdilution (BMD), the gold-standard for colistin susceptibility testing.
  • Narrow MIC range specifically designed to evaluate clinical breakpoints as per EUCAST.
  • Offers a robust solution for confirmatory testing in cases with ambiguous or conflicting results.
• Best Suited For:
  • Regulatory testing or research to validate resistance mechanisms.
  • Confirmatory testing in laboratories handling critical patient isolates.
• Limitations:
  • Narrow MIC range excludes testing for isolates with high-level resistance (above 16 µg/mL).
  • Requires more technical expertise compared to gradient diffusion methods.

Applications and Purpose of Each Type

Conclusion

• MTS™ Colistin CS (0.064–1024 µg/mL): Ideal for routine susceptibility testing of resistant Gram-negative bacteria, especially those with high MIC values.
• MTS™ Colistin CS (0.016–256 µg/mL): Offers improved resolution for low- and moderate-resistance strains, making it better suited for testing isolates near clinical breakpoints.
• ComASP™ Colistin MIC Panel (0.25–16 µg/mL): Designed for confirmatory resistance testing as per EUCAST gold-standard methods, particularly in cases of ambiguous or conflicting results. This method is essential for regulatory or research purposes.