Swab Sampling Technique

Swab sampling is a technique used to collect samples from surfaces or objects for laboratory analysis. It involves using a sterile swab to collect a sample from a specific area or object, which is then sent to a laboratory for testing.

Swab sampling is commonly used in healthcare settings to detect and monitor infectious diseases, such as Methicillin-resistant Staphylococcus aureus (MRSA) and Clostridium difficile (C. diff). It is also used in food safety testing to detect the presence of harmful bacteria, such as Salmonella and E. coli.

To perform a swab sampling, a sterile swab is moistened with a sterile solution and rubbed over the surface or object being tested, applying enough pressure to ensure that the swab collects any microorganisms present. The swab is then placed in a sterile container and sent to the laboratory for analysis.

Swab sampling is a simple and non-invasive technique that can provide valuable information about the presence of microorganisms on surfaces or objects. It is an important tool for infection control and prevention in healthcare settings and for ensuring food safety in the food industry.

Procedure of Swab Sampling:

• Take pre-sterilized readymade cotton swab.
• Add 0 mL sterile normal saline/ 0.1% Peptone water in to swab tube for wetting the cotton bud.
• Bring the swab tubes at the sampling location.
• Aseptically open the swab tube containing with normal saline/ Peptone water solution. Take out the sterile swab partially, press the swab to the internal walls of the tubes gently to remove the excess saline/ peptone water and take it out gently.
• Swab out 5 X 5 cm² area in the direction specified in figure below. Use sterile stainless steel template to measure the area of sampling whenever applicable.

• Place the swab back in the tube.
• After completion of sampling, label each swab with sample name, date of sampling and initial sign of microbiologist and bring the swab to microbiology department.

Procedure of Analysis of Swab Sample:

• Transfer the swab samples to the micro lab-1 through the dynamic pass box between MLT passage to Incubation room and sample shall be transfer as per the respective SOP of Material Flow in the Microbiology Department.
• Sanitize hand with 0.2µ filtered 70% IPA.
• Arrange the sterile manifold unit and pre-incubated SCDA plates in laminar air flow.
• Make the attachments of manifold unit to the suction pump and waste water reservoir.
• Fix the sterilized filtration cup/ funnel on the manifold unit and place the sterilize 0.45 µm membrane filters on the sterile filtration cup and funnel with the help of sterile forceps taking care that the forceps does not damage the filter and touch anywhere.
• Pre-wet the 0.45 μm membrane filter with approx. 100 mL of 0.1 % peptone water. Open the knob of the manifold unit so that the rinsing fluid filters through the membrane.
• Shake the swab sample well and after completion of filtration, transfer the content of swab sample in the filtration cup and open the knob of manifold unit so that the sample filters through the membrane.
• Transfer 3 X 100 mL of rinsing fluid (0.1 % peptone water) in the filtration cup. Filter the rinsing fluid with the help of vacuum pump.
• Remove the filtration cup and transfer the 0.45 µm membrane filter on the surface of pre incubated SCDA media plates with the help of sterile forceps.
• Prepare one negative control plate by filtering 100 mL of sterile 0.1 % peptone water through the 0.45 µm membrane filters and put the 0.45 µm membrane filters on the surface of pre-incubated SCDA plate and incubate along with test samples.
• Incubate the plates with the membrane in inverted position at 22.5 ± 2.5 °C for 72 hours and 32.5 ± 2.5 °C for 48 hours.
• After Completion of incubation period, withdrawn the plate from respective Incubator and observe the plate and record the result .

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