Disc Diffusion Method – Rosco Diagnostica Neo-Sensitabs

Overview of the Disc Diffusion Method

The disc diffusion method is a widely used technique for assessing the antimicrobial susceptibility of bacteria. It involves placing antibiotic-impregnated discs on an agar plate inoculated with bacteria. The method is straightforward, cost-effective, and provides clear visual results that help guide appropriate antibiotic therapy.

What are Neo-Sensitabs?

Neo-Sensitabs, produced by Rosco Diagnostica, are a specialized form of antimicrobial susceptibility testing discs. Unlike traditional paper discs, Neo-Sensitabs are tablet-based and designed to provide more consistent and accurate results in susceptibility testing. These tablets contain precise amounts of antibiotics or combinations of antibiotics and are used in the disc diffusion method to determine the susceptibility of bacterial strains to specific antibiotics.

Key Features of Neo-Sensitabs

• Tablet Format: Neo-Sensitabs are tablet-based rather than paper-based, offering greater stability and consistency in the release of antibiotics into the agar.
• High Potency: Each Neo-Sensitab contains a high concentration of the active substance, ensuring reliable and reproducible results.
• Wide Range of Antibiotics: Rosco Diagnostica offers Neo-Sensitabs for a broad spectrum of antibiotics, including those used in combination therapies, which are essential for detecting multidrug-resistant organisms.
• Standardization: Neo-Sensitabs are manufactured under strict quality control conditions, ensuring consistent performance and reliability across different batches.

How Neo-Sensitabs are Used in the Disc Diffusion Method

The procedure for using Neo-Sensitabs in the disc diffusion method is similar to the standard protocol, with some specific considerations:

1. Preparation of the Bacterial Inoculum

A pure bacterial culture is grown and standardized to a specific turbidity, typically using the McFarland standard, to ensure consistent results.

2. Inoculation of the Agar Plate

The standardized bacterial suspension is spread evenly across the surface of a Mueller-Hinton agar plate to create a uniform bacterial lawn.

3. Application of Neo-Sensitabs

Neo-Sensitabs are placed on the surface of the inoculated agar plate using sterile forceps or a dispenser designed for the tablets. The placement of these tablets is critical, as they need to be properly spaced to prevent overlapping zones of inhibition.

4. Incubation

The agar plate is incubated at the appropriate temperature, usually 35-37°C, for 16-18 hours. During this period, the antibiotics in the Neo-Sensitabs diffuse into the agar and inhibit bacterial growth around the tablets.

5. Measurement and Interpretation

After incubation, the zones of inhibition around each Neo-Sensitab are measured in millimeters. These measurements are then compared to standardized interpretive criteria to determine whether the bacteria are susceptible, intermediate, or resistant to the antibiotics tested.

Advantages of Using Neo-Sensitabs

• Enhanced Accuracy: The tablet format of Neo-Sensitabs ensures a more consistent release of antibiotics, leading to more accurate and reproducible results compared to traditional paper discs.
• Stability: Neo-Sensitabs have a longer shelf life and maintain their potency better than conventional paper discs, which can degrade over time.
• Broad Application: Neo-Sensitabs are available for a wide range of antibiotics, including those used in routine clinical practice and those required for testing resistant strains.
• User-Friendly: The tablets are easy to handle, and their clear labeling reduces the risk of errors during testing.

Applications in Clinical Microbiology

Neo-Sensitabs are extensively used in clinical microbiology laboratories to determine the susceptibility of bacterial pathogens to antibiotics. They are particularly valuable in environments where precise and reliable results are crucial, such as in the detection of multidrug-resistant organisms. Their consistent performance helps clinicians choose the most effective antibiotic therapy, thereby improving patient outcomes and contributing to better antibiotic stewardship.