Liofilchem® Isoniazid IZ, Antimicrobial Susceptibility Discs

Liofilchem® Isoniazid IZ Antimicrobial Susceptibility Discs are specialized tools for in vitro susceptibility testing of Mycobacterium tuberculosis and other mycobacterial species. Each disc is impregnated with either 1 µg or 5 µg of Isoniazid, a frontline antimycobacterial antibiotic that inhibits mycolic acid synthesis, a key component of the mycobacterial cell wall. These discs are designed for use with solid media such as Middlebrook 7H10 or Lowenstein-Jensen agar, following standard protocols for mycobacterial drug susceptibility testing (DST). Manufactured under ISO 9001 and ISO 13485 certified processes, these discs deliver consistent and reliable results for tuberculosis control programs, research laboratories, and public health institutions.

Key Features

• Two concentrations available: 1 µg and 5 µg discs for low- and high-level Isoniazid resistance detection.
• First-line TB drug: Essential for DST of Mycobacterium tuberculosis, particularly in multi-drug resistance screening.
• Standardized quality: Produced under ISO-certified quality systems to ensure reproducibility and sterility.
• Solid-media compatible: Ideal for use with Lowenstein-Jensen and Middlebrook 7H10/7H11 media.
• Clear labeling: Color-coded and concentration-printed discs for accurate identification.

Applications and Use Cases

1. Tuberculosis Drug Susceptibility Testing

Used in clinical and public health microbiology labs to:

• Assess susceptibility of Mycobacterium tuberculosis isolates to Isoniazid.
• Detect low-level resistance (mutations in inhA promoter region) with 1 µg discs.
• Detect high-level resistance (mutations in katG gene) with 5 µg discs.
• Guide treatment decisions in:
  • New TB cases
  • Previously treated or relapsed TB patients
  • Suspected multidrug-resistant TB (MDR-TB)

2. National TB Control Programs

• Screen for Isoniazid resistance as part of WHO-recommended first-line drug panels.
• Monitor resistance trends across regional or national populations.
• Support surveillance studies in conjunction with GeneXpert or Line Probe Assays (LPAs).

3. Mycobacteriology Research and Development

• Study resistance mechanisms to Isoniazid and cross-resistance with ethionamide.
• Validate new molecular diagnostics or culture-based DST protocols.
• Use in pharmaceutical QC and drug development workflows for anti-TB compounds.

Use Instructions

1. Prepare Lowenstein-Jensen or Middlebrook 7H10/7H11 agar medium according to TB laboratory standards.
2. Standardize inoculum using a 1 McFarland suspension of M. tuberculosis (per WHO/CLSI guidance).
3. Inoculate the solid media in streak or spot format under aseptic conditions.
4. Apply the Isoniazid disc (1 µg or 5 µg) to the inoculated surface using sterile forceps.
5. Incubate at 35–37 °C in a CO₂-enriched incubator for 10–21 days (depending on the medium and organism).
6. Interpret based on the presence or absence of growth inhibition around the disc, following CLSI M24, WHO, or national TB program guidelines.

Storage and Shelf Life

• Storage Conditions: 2–8 °C (refrigerated), in sealed packaging with desiccant.
• Shelf Life: 24–36 months from the date of manufacture when stored correctly.

Liofilchem® Isoniazid IZ Discs (1 µg, 5 µg) are critical components of tuberculosis drug susceptibility testing, enabling accurate detection of low- and high-level resistance in M. tuberculosis. These discs support early diagnosis, appropriate treatment initiation, and global TB control strategies. Manufactured with precision and compliant with international DST standards, they are an essential resource for TB reference laboratories, public health institutions, and research centers worldwide.