Tissue culture is more susceptible to contamination on isolation from tissues, because it no longer has the innate protection offered by the immune system. Fortunately, there are several things you can do to protect your tissue culture against all types of contaminants: 

• Wear a lab coat and gloves to create a barrier protecting the cultured cells from being contaminated by bacteria from your body
• Use your hood correctly and service it regularly so that it works efficiently at all times
• Clean your water bath and incubator regularly 
• Spray a 70% ethanol solution on all lab surfaces and equipment including your personal protective gear to kill any bacteria present on these surfaces
• Sterilize all the lab equipment including beakers, pipette tips, storage vessels, forceps and any other equipment you will be using 
• Minimize the exposure of cells to non-sterile environments
• Make sure to purchase sterile reagents such as PBS, media and others 
• Use filter tips to prevent the solution inside the tip from touching the pipettor
• Inspect your cells regularly under a microscope and check for morphological changes and unusual rate of proliferation
• If you suspect your sample may be contaminated, treat it with 10% bleach
• Use good labeling practice to identify contamination sources more quickly