Thermo Scientific™ Sensititre™ Nephelometer

The Sensititre™ Nephelometer is a specialized turbidity-measuring instrument used in clinical and research microbiology laboratories to standardize bacterial inoculum density for Minimum Inhibitory Concentration (MIC) testing. It ensures that microbial suspensions are prepared at the correct optical density (typically 0.5 McFarland standard) before being used in antimicrobial susceptibility testing (AST).

Key Features & How It Works

1. Turbidity Measurement Principle:
   • Uses nephelometry (light scattering) to measure the cloudiness (turbidity) of a bacterial suspension.
   • Provides consistent and repeatable inoculum density, critical for accurate MIC results.
2. Compact & Portable Design:
   • Small benchtop footprint (19 cm × 9.7 cm × 13.5 cm) and lightweight (0.8 kg).
   • Low power consumption (1W), powered by 8–18V AC/DC.
3. Compatibility:
   • Works with Sensititre™ MIC panels and other broth microdilution systems.
   • Integrates into labs using Thermo Scientific’s antimicrobial susceptibility testing (AST) solutions.

Primary Use Cases

1. Clinical Microbiology Labs – Antimicrobial Susceptibility Testing (AST)

• Application: Preparing standardized bacterial inoculum for MIC testing (e.g., for Sensititre™ MIC panels).
• Workflow Example:
  1. A lab isolates Staphylococcus aureus from a patient’s blood culture.
  2. The nephelometer measures the turbidity of the bacterial suspension to ensure it matches 0.5 McFarland standard.
  3. The standardized suspension is used to inoculate a Sensititre Gram-positive MIC panel.
  4. After incubation, MIC values are read to determine antibiotic resistance/susceptibility.
• Why It’s Important:
  • Inconsistent inoculum density can lead to false resistance or susceptibility results, affecting patient treatment.

2. Research Labs – Studying Bacterial Growth & Antibiotic Resistance

• Application: Standardizing inoculum for time-kill assays, biofilm studies, or resistance mechanism research.
• Workflow Example:
  1. Researchers studying Pseudomonas aeruginosa resistance need to prepare identical bacterial suspensions.
  2. The nephelometer ensures each test starts with the same cell density.
  3. This allows reliable comparison of antibiotic efficacy across experiments.

3. Pharmaceutical & Diagnostic Kit Manufacturing

• Application: Quality control in antibiotic susceptibility test kit production.
• Workflow Example:
  1. A manufacturer produces MIC panels for clinical labs.
  2. The nephelometer verifies that test inoculum meets required turbidity before panel inoculation.
  3. Ensures batch-to-batch consistency in diagnostic test performance.

Advantages Over Manual Turbidity Methods

Maintenance & Best Practices

• Calibration: Regular checks with McFarland standards ensure accuracy.
• Cleaning: Wipe the measurement chamber to avoid biofilm interference.
• Storage: Keep in a dry, dust-free environment when not in use.

Conclusion: Who Should Use This Instrument?

The Sensititre Nephelometer is ideal for:

✔ Clinical labs performing routine AST (e.g., hospitals, reference labs).

✔ Research labs studying bacterial growth & antibiotic resistance.

✔ Diagnostic manufacturers needing QC for MIC panels.

By ensuring consistent inoculum density, it improves reproducibility and accuracy in susceptibility testing—critical for patient care and antibiotic stewardship.