Bacteria revealed: Sponges harbour most germs in kitchens

Several areas of the kitchens were tested for particularly harmful pathogens including Salmonella, Escherichia coli (E. coli), Faecal streptococci (FS), Pseudomonas aeruginosa (P. aeruginosa), Bacillus cereus (B. cereus), Clostridium perfringens (C. perfringens) and Staphylococcus aureus (S. aureus).

According to the study, some of the items that are most vital to the cleaning process harbour the most germs. 100% of sinks tested positive for P. aeruginosa and 25% for FS, whereas 88% of sponges had P. aeruginosa, 25% had FS and 12% had E. coli. Bacteria can thrive on damp surfaces, and due to the nature and purpose of your kitchen sink and sponge, bacteria transferred from hands, plates and other objects can linger in the moisture. Properly drying cloths and surfaces can reduce bacterial populations.

• 100% of floors tested had traces of aeruginosa and 12% of FS
• Sinks had a total concentration of 24,000 f aeruginosa and 3,280 of FS
• The average tea towel is only cleaned every two-and-a-half weeks, the sink every 25 days and the sponge every 15 days
• The average floor is only cleaned every five weeks
• 37% of Brits do not clean their oven handle.

Kitchens are cleaner than expected. In fact, there were no traces of Salmonella found in any of the kitchens tested. Lab technician at the University of Lincoln, Dr Jonathan Hughes, said: “As damp environments provide excellent conditions for bacterial growth, you should ring out and dry cloths, towels and sponges between uses. You should also ensure that you regularly disinfect and wash reusable cloths or towels, or switch to new ones if using disposable cloths or sponges.”

The study revealed that the pathogen P. aeruginosa is definitely the head of the household, as traces of it were found on 100% of sinks and floors, and 88% of sponges, countertops and fridge shelves. This pathogen is found in soil and vegetation, and enters your kitchen on unwashed vegetables. It is known to cause symptoms such as skin irritation, abbesses and wounds.

The second most prevalent germ in the kitchen is Faecal streptococci (FS). This pathogen was found on 62% of the items swabbed, including the sponge, sink, floor, countertop and the oven handle. It is found in the intestines of humans and animals and detecting it in tests means there is a strong indication of faecal matter contamination. Such contamination can lead to symptoms of food poisoning such as, vomiting, diarrhoea and nausea.

Dr Hughes advised: “The surface levels of bacteria in a normal kitchen are usually well below the levels required for infection of healthy individuals and so are unlikely to lead to illness - unless coupled with a pre-existing health complaint or if the person infected is immunocompromised.”

• There was no detection of Salmonella, cereus or Staphylococcus aureus in any of the kitchens tested
• Your oven handle is the cleanest area in the kitchen, with 50% returning negative results of all pathogens tested. Among the remaining 50%, all tested positive for traces of aeruginosa and 12% tested positive for FS
• Professional cleaners can help to banish the bacteria in your kitchen.

If you want to get rid of the bacteria in your house, the easiest way to keep you and your family safe is to have a thorough cleaning routine. For example, the average fridge is only cleaned every four-months-and-two-weeks, which could be why 88% of fridges had detections of P. aeruginosa. Similarly, the average sink is cleaned every 25 days, which may be why it ranked second germiest place in the kitchen.

Dr Hughes concluded: “Following basic kitchen hygiene rules coupled with correct food preparation methods will reduce the risk of food poisoning. These rules can be grouped into four Cs: cleaning, cooking, chilling and cross-contamination.”

• Cleaners are key: the kitchen that had the least amount of bacterial detections (five detections across eight areas, out of a maximum of 48) employed a cleaner to work regularly
• Retired couples that cleaned daily also had five detections of bacteria across eight areas
• You can see the full research as well as Dr. Hughes advises here.