Liofilchem® Colistin sulfate CS, Antimicrobial Susceptibility Discs, 10 µg

Liofilchem® Colistin sulfate CS discs are antimicrobial susceptibility testing (AST) discs specifically designed to evaluate the susceptibility of Gram-negative bacterial pathogens to Colistin sulfate. These discs provide accurate and reliable results in disc diffusion tests for Pseudomonas aeruginosa, Acinetobacter baumannii, and other Enterobacteriaceae, which are often associated with multidrug-resistant (MDR) infections. Colistin is considered a last-resort antibiotic, making its susceptibility testing essential in clinical and diagnostic microbiology.

Key Features

• Concentrations: Available in 10 µg, 25 µg, and 30 IU.
• Application: For the Kirby-Bauer disc diffusion method.
• Activity: Targets Gram-negative bacteria, including:
  • Pseudomonas aeruginosa
  • Acinetobacter baumannii
  • Klebsiella pneumoniae
  • Escherichia coli
• Compatibility: Compliant with EUCAST and CLSI guidelines for Colistin AST.
• Target Pathogens: Effective against multidrug-resistant Gram-negative bacterial infections.

Test Procedure

1. Preparation of Inoculum:
   • Prepare a 0.5 McFarland standard bacterial suspension in sterile saline.
   • Use a sterile swab to inoculate the suspension evenly onto the surface of a Mueller-Hinton agar plate.
2. Application of the Discs:
   • Place the Liofilchem® Colistin sulfate discs (10 µg, 25 µg, or 30 IU) on the agar surface.
   • Ensure discs are spaced at least 15 mm apart.
3. Incubation:
   • Incubate the plate at 37°C for 16–20 hours under aerobic conditions.
4. Measurement:
   • Measure the diameter of the zone of inhibition (in mm) around each disc.
   • Compare the measured zone with CLSI or EUCAST breakpoint tables.

Quality Control (QC)

Each batch of Liofilchem® Colistin sulfate CS discs is subjected to rigorous quality control testing using reference strains to ensure consistent and reproducible results.

• Note: The absence of inhibition for E. coli ensures the specificity of Colistin against resistant strains.

Interpretation of Results

The zone of inhibition is measured in millimeters (mm) and compared with the appropriate breakpoints provided by EUCAST and CLSI.

EUCAST Breakpoints for Colistin:

• Susceptible (S): Zone ≥ 11 mm
• Resistant (R): Zone < 11 mm

CLSI Breakpoints for Colistin:

• Susceptible (S): Zone ≥ 12 mm
• Intermediate (I): 10–11 mm
• Resistant (R): Zone < 10 mm

Storage Requirements

• Long-term Storage: Store at -20°C for maximum stability.
• Short-term Storage: Store at 2–8°C for up to 30 days.
• Avoid exposure to moisture and heat to maintain disc potency.

Comparison with Other Brands

Advantages of Liofilchem® Colistin Sulfate Discs

1. Versatility: Available in three concentrations for flexible testing.
2. High Sensitivity: Reliable performance for detecting resistance mechanisms.
3. Compliance: Fully compliant with international guidelines (EUCAST and CLSI).
4. Cost-effective: Offers competitive pricing compared to other leading brands.

Conclusion

Liofilchem® Colistin sulfate CS Antimicrobial Susceptibility Discs are robust tools for detecting Colistin susceptibility in Gram-negative bacteria, particularly multidrug-resistant strains. With multiple concentrations available (10 µg, 25 µg, and 30 IU) and strict adherence to international standards, these discs are a preferred choice for clinical and research laboratories worldwide. Liofilchem® discs outperform several competitors in flexibility, reliability, and cost-effectiveness, making them a valuable resource in combating antimicrobial resistance.