This post is part of a series. For Part 2, The Dirty Secret Lurking in Your Kitchen: The Kitchen Sponge, click here.

By: Pooja Sharma

The heart of your home, your kitchen, might not be as germ-free as you think. Dirt and grime often gather around in the areas where we least suspect them to be. You are doing your dishes, scrubbing the stove, cleaning the countertops, yet you are missing out on some pretty germy places in your kitchen. Read on to learn about the 5 of the dirtiest places in your kitchen where bacteria are lurking.


A new study by German researchers proved that your outwardly innocuous kitchen sponge is home to a whopping 362 different kinds of bacteria. The number is quite high to what was estimated earlier by the scientists. This also means that kitchen sponges hold more germs than your toilet.

The sponge attracts bacteria because they are warm, wet, and frequently come into contact with skin, food residue, and other surfaces – giving it a perfect condition for the microbes to thrive. It was also found that 5 out of the 10 most common bacteria present in the sponge has ‘pathogenic potential’, which means they can cause diseases in humans. And among them is also a microbe called Moraxella osloensis, a bacteria that can easily sicken those with weakened immune system. Although, the risk that bacteria in sponges pose is not yet assessed.

We discuss more about this fascinating study in Part 2 of this series.


The researchers found that boiling, cleaning, microwaving the sponges does not get rid of these bacteria. It might reduce the bacteria by 60%, but not significantly eliminate it. The only way to protect yourself from the sponge bacteria is to change the kitchen sponge every week. This is the only solution that the researchers have come up with that is the best for of prevention.


Refrigerator drawers can harbor an average of 7850 bacteria colony forming units per square centimeter. This number is 750 times the level that is considered safe for storage of foods. The common microbes that were found included Salmonella, E. coli, Listeria, yeast, and mold.

Top 2 reasons so as to why refrigerator drawers are full of bacteria are:

  1. Some fruits/vegetables don’t get washed before entering the refrigerator. They are washed before using them. These unwashed fruits/vegetables can contaminate other foods and drawers with the bacteria lurking around on them.
  2. The same thing can happen with raw meat when its juices gather around other foods and corners of shelves. Other packaged products, like milk, sauces, butter etc., can also cause bacteria to grow.


To make sure that your drawers are protected from bacterial colonies, it’s important to clean all the shelves/drawers of your refrigerator at least twice monthly. Use warm water or warm wash cloth to clean the interiors.


Various studies have suggested that bacteria loves coffee as much as we do. It turns out that coffee machine’s water reservoir, the cup containing coffee grounds and drip trays all contain millions of harmful bacteria and mold. The type of bacteria includes Listeria monocytogenes, Staphylococcus, Streptococcus, E. coli, and Pseudomonas. All of them are pathogenic bacteria, which means that they can easily sicken coffee drinkers.


  1. Wipe your machine with a slightly warm wash cloth after almost every use.
  2. Change the water you use every day to reduce the number of thriving bacteria significantly. Never forget to close the lid of the water tank.
  3. Wash your hands before using the machine.
  4. Flush the entire coffee machine with vinegar once a week. Fill your water reservoir with 50% white vinegar and 50% water. Run the mixture through the brewer. Stop the brew when half of the mixture remains inside the machine. Let it sit for around 30-60 minutes. Empty the machine and run the brewer with water for a few times.


Cutting boards can hold 200 times more coliform bacteria than your toilet. Yikes! The amount and kind of germs that grow depends on the material of the board, how many times you wash it, cracks in the surface and direction of wood fibers. Cracks and grooves on the surface of the cutting board significantly increases the number and growth of bacteria on the cutting board. It was very difficult to manually clean or stop the microbes from multiplying.


  1. Using wooden board is a safer choice than plastic cutting boards. This is because wooden boards are less porous and don’t absorb moisture. They are also able to resist scarring from knives. Bacteria can easily grow through these small cracks.
  2. All cutting boards should be washed after each use. Sanitizing them once or twice in a month, with 1 tbsp of liquid chlorine bleach per gallon water, can help too. Just rinse them with this solution. Wash with plain water and let it dry.
  3. Keep separate cutting boards for raw meat and fresh fruits/vegetables. Juices and bacteria from raw meat, seafood, or poultry can easily contaminate your other foods that require no cooking.


In a 2013 study by NSF international, 14 of the most common kitchen items were tested for the presence of 4 microbes that include: Salmonella, E.Coli, yeast and mold and Listeria. It was found that the can opener tested positive for 3 of them: Salmonella, E.Coli and yeast and mold. Wiping the can opener with a dishcloth or running it under water doesn’t seem to help much. Instead, the moist environment just increased the thriving bacteria that landed there by any can of food or drinks you opened with it. Both E.Coli and Salmonella are linked to most common food poisoning cases in US and any infection can cause severe vomiting, diarrhea and abdominal pain.


Clean your can opener in a dishwasher each time you do your dishes. Wash it in hot water with soap and let it air dry.

Cleaning it with vinegar and a toothbrush can also help. Soak the can opener in diluted vinegar solution for a few hours or overnight. After the soaking is done, clean it with a toothbrush to make sure that all the gunk and lingering particles are removed properly. Rinse it under water and let it dry.