A Comprehensive Guide to Detecting and Handling Laboratory Contamination

Laboratory contamination is a critical issue in cell culture that should never be overlooked. It can arise from various sources, including the environment, handling techniques, and reagents, and can significantly affect the growth, function, and reliability of experimental results. When contamination is detected, it is essential to immediately isolate and treat the contaminated cultures, determine the type of contamination, and trace the source to prevent further spread.

In this article, we will provide a detailed guide to detecting and handling contamination in cell culture, enabling you to quickly troubleshoot and eliminate contamination to ensure smooth experimental progress.

Common Types of Contamination

01 Bacterial Contamination
Under the microscope, bacteria appear as small, spherical, or rod-shaped particles much smaller than cells. They often fill the spaces between cells or within the culture medium. Bacteria proliferate rapidly, consume nutrients quickly, and can cause the medium to turn yellow or cloudy. Severe contamination may also result in a foul odor.

02 Fungal Contamination
Under the microscope, fungal contamination is often characterized by filamentous hyphae or intertwined fungal clumps. In the early stages, the medium may not appear cloudy, and its color may remain unchanged, making early detection difficult. Initially, fungal contamination affects only localized cell growth, but prolonged contamination can cause a noticeable decline in overall cell health or even cell death.

03 Mycoplasma Contamination
Mycoplasma contamination cannot be detected using a standard light microscope. Cells infected with mycoplasma often exhibit increased debris, poor viability, and slowed growth.

04 Nanobacteria Contamination
Nanobacteria contamination is visible under the microscope as numerous black dots and fragments around the cells and in the culture medium. The medium remains clear, but over time, the black dots and debris increase. Nanobacteria compete with cells for nutrients, resulting in declining cell health and, ultimately, cell death.

Steps for Detecting Contamination
Specialized cell culture media are synthetic media and typically need to be supplemented with serum or serum substitutes to be prepared as complete media for use.

Inspect the Laboratory Environment

• Cleaning and Disinfection: Ensure daily cleaning and disinfection of incubators, biosafety cabinets, microscopes, and other equipment using appropriate cleaning agents and disinfectants before and after each use.
• Air Filtration Systems: Check that the laboratory's air filtration system (e.g., HEPA filters) is functioning properly. Replace filters regularly to maintain clean and well-circulated air.
• Environmental Conditions: Maintain optimal laboratory conditions, including proper temperature, humidity, and ventilation. Poor ventilation or high humidity can promote microbial growth.

Evaluate Personal Handling Practices

• Protective Equipment: Always wear appropriate personal protective equipment, such as lab coats, gloves, masks, and goggles, during cell culture handling.
• Aseptic Techniques: Follow strict aseptic techniques, such as disinfecting hands, avoiding direct contact with sterile items, and minimizing exposure of cultures to open air.
• Handling Tools: Avoid using contaminated tools or consumables, such as pipettes or flasks, that have been used previously without sterilization.

Examine Reagents and Consumables

• Source of Reagents: Ensure that all reagents and consumables are sourced from reputable suppliers. Inspect them for abnormalities before use.
• Sterilization: Thoroughly sterilize self-prepared reagents or non-sterile consumables using sterile filtration or autoclaving.
• Packaging and Storage: Verify the integrity of packaging before use and store reagents under appropriate conditions to avoid degradation (e.g., avoid high temperatures, humidity, or direct light).

Check the Cells

• Self-Cultured Cells: If contamination is detected in self-cultured and frozen cells, thaw other vials from the same batch. If contamination is consistently observed, discard the entire batch.
• Purchased Cells: If contamination is found in purchased cell lines, verify whether the contamination originated from the supplier. Always choose reliable cell suppliers to minimize contamination risks.

Post-contamination Handling

01 Environmental Decontamination
Wipe down all work surfaces and equipment (inside and outside) with 75% ethanol to disinfect. Use formaldehyde or ozone fumigation to decontaminate the cell culture lab. Alternatively, use specialized products, such as Pricella® Room SafeGuard, for thorough sterilization.

02 Treating Contaminated Cells
• Bacterial Contamination: If contamination is minor and the cell line is valuable, attempt treatment with antibiotics. Ensure that contaminated cultures are isolated from uncontaminated cells to prevent cross-contamination.
• Mycoplasma or Nanobacteria Contamination: If the contamination is not severe, try using specialized elimination reagents, such as Pricella® Anti-Mycoplasma Treatment Reagent or Anti-Nanobacteria Treatment Reagent, and monitor for improvements in cell condition. If cell viability remains poor after treatment, discard the contaminated cells after disinfection to prevent further complications.