What Is Aseptic Technique and Why Is It Important?

"Using aseptic technique consistently helps ensure the safety of your lab personnel and protect your laboratory environment from pathogens and other foreign interferences," said Shawn Dubois, Senior Scientist at IDEXX. "It's essential to achieve reliable, repeatable, and accurate results."

That starts with five crucial steps:

1. Preparing and wearing personal protective equipment (PPE)
2. Cleaning surfaces
3. Sterilizing water, vessels, and equipment
4. Using an autoclave properly, when needed
5. Taking precautions at every step while testing your sample

Here's how you can employ best practices for aseptic technique in your water test lab.

Prepare and Wear PPE

"First, we're going to get the lab prepped," said Dubois. "That will keep lab personnel safe and the area we're working in clean for our test, so we don't contaminate samples."

Imagine your skin as a sponge when it comes into contact with chemicals. To protect this delicate organ, you need to wear PPE, including gloves, safety goggles, and lab coats, before beginning any testing.

Gloves should be disposable nitrile or chemical-resistant coverings that don't let any substance come into contact with your skin. Safety goggles guard against splash hazards and eye damage. Lab coats and long pants (or an equivalent leg covering) shield exposed skin from hazardous substances.

Clean Surfaces

"The next step is to prepare the lab environment where we're testing," Dubois said. "We need to use a cleaning agent on laptops, benchtops, and any other equipment that's potentially going to come in contact with our samples."

Most lab technicians use a disinfectant like isopropyl alcohol (70%) to sterilize surfaces. Spray all surfaces with the cleaning agent, wipe with a clean, sterile rag, and make sure all surfaces are dry before you continue.

"It's always important to check recommendations for dwell time and how to use the cleaning agent to make sure it will be effective," Dubois noted.

In addition, the entire lab work environment should be uncluttered and well-maintained, with no dust on incubators, equipment, or surfaces around benches.

Sterilize Water, Vessels, and Instruments

You must sterilize anything that will come into contact with a sample. This includes water, vessels, pipette tips, and instruments. "You don't want anything left over from a previous test that would either inhibit detection of target bacteria or give higher results than expected," Dubois said.

According to the Standard Methods for the Examination of Water and Wastewater: "Properly cleaned labware, whether made of glass, plastic, or metal and sterilized when appropriate, is essential for microbiological testing. Proper washing ensures that all traces of compounds from previous analyses are removed. Failure to properly wash labware could introduce toxic or nutritive compounds into the analytical testing, which could skew laboratory results."

Using pure laboratory water is a best practice that reduces the introduction of contaminants that can interfere with water testing and produce inaccurate results. Sterile deionized (DI) water, distilled water, reverse osmosis (RO) water, and buffer water are commonly used. You can either purchase sterilized water or sterilize it in the lab using an autoclave or processes such as filtration or distillation.

You can also purchase vessels and other materials pre-sterilized. For example, all IDEXX products are sterilized and shipped ready for use. These convenient and affordable vessels meet U.S. Environmental Protection Agency accuracy guidelines and help eliminate false-positive results due to contamination.

Use sterilized items only once, unless they come into contact with sterile water only. Otherwise, they must be sterilized again, for example, by using an autoclave.

Autoclave Properly

Autoclaves sterilize items using a combination of steam, pressure, and heat (121°C) over a designated period. Special autoclave tape with color-changing stripes helps indicate that items have been properly sterilized.

Autoclaves come in different sizes and types, including the following:

• Benchtop size to large jacketed chamber units
• Units that use direct or indirect contact with steam
• Units that have liquid and/or dry cycles

Limit autoclave use to items rated for use in these tools. Glass and certain plastics may shatter or melt if not rated for autoclave use.

Take Precautions at Every Step

It's vital to proceed with care at every point in the water testing process. Always be vigilant about test surfaces, equipment, and anything coming into contact with them.

"When opening a sample, put the cap on the benchtop with the opening facing up," Dubois emphasized. "Do not touch the inside at any time. When adding reagent to the sample, open it toward the vessel to make sure it goes inside. Also, don't touch the opening of the blister pack to avoid introducing anything into the sample that could interfere with the test."

If you suspect contamination, re-sterilize and restart. This is the only way you can be confident in your water lab test results and ensure you make decisions based on liable, repeatable, and accurate findings.