By Kerry Hale

Bathroom Bacteria: Under The Microscope

  • Wednesday 26 September 2018
  • 5 Minute Read

Your bathroom may be a haven of tranquillity and relaxation, but do you know that you could be sharing it with dangerous bacteria such as E. coli and Salmonella? We asked a PhD researcher to find out where these biohazards like to lurk and the best ways to get rid of them.

Is your bathroom clean? It may look spotless, with no water marks in the shower or limescale on the taps, but is it really clean? Bacteria such as Streptococcus, Campylobacter and Escherichia coli (E. coli) lurk in every part of your bathroom and can cause painful symptoms such as stomach cramps, nausea, diarrhoea and vomiting, so it’s vital that you clean all areas of your bathroom at least once a week.

A recent report by Mintel found that multipurpose cleaning fluids are the most commonly used bathroom cleaner by the British public (used by 75% of the population). But are they really the most effective for tackling dirty bathrooms? Do they get rid of all the potentially harmful bacteria and mould?

We wanted to find out, so we asked Marco Mendoza Villa, a PhD researcher from the School of Biological Sciences at Bristol University, to investigate. He chose a typical family bathroom and took swabs from various surfaces, from the floor and basin taps to the shower head and toilet seat. Areas of each surface were then cleaned using two different cleaning solutions from a range of six, before swabs were taken again. Marco then took both sets of swabs back to his lab to find out which bacteria were present, and at what levels, to determine just how effective each cleaning solution was.

The scores on the doors (and the handle and the toilet seat…)

The results of our study are both surprising and, in some cases, horrifying. Before being cleaned, all bathroom surfaces had at least two different types of bacteria present, with one having an alarming eight. In total, there were 11 different types of bacteria detected, from the relatively harmless Micrococcus and Enterobacter aerogenes to the potentially more harmful Salmonella and E. coli.

Of all the surfaces, the door handle was the least infected before cleaning, with just 0.9% of its surface showing bacteria, while the most infected was the shower tray, with a troubling 72% of its surface covered in pathogens. Other areas in dire need of a good scrub were the bathroom basin (71% infected), shower head (32%) and the taps (43%). Perhaps most surprising was the relative cleanliness of the toilet seat, with just 29% of its surface infected with bacteria.

Shower enclosure

Bacteria detected
: Micrococcus, Staphylococcus, E. coli, Streptococcus, Campylobacter.

Cleaning contenders: Multi-surface spray vs Shower cleaner


Given the number of soaps, gels and hair products used in the shower, you’d expect it to be fairly clean before a cleaning product gets anywhere near it – and at just 16% bacteria coverage, you’re not far wrong. The interesting part comes when you compare the cleaning power of a shower cleaner, supposedly formulated for the shower area, and a multi-surface spray. While the multi-surface spray reduced the infected area by an impressive 99.6%, the shower cleaner could only manage 28%.

Winner: Multi-surface spray

Shower Enclosure - before and after cleaning with multi-surface spray

Shower head

Bacteria detected
: E. coli, Staphylococcus, Streptococcus, Enterococcus, Campylobacter, Streptobacillus.

Cleaning contenders: Cream cleaner vs Shower cleaner


The shower head was the fourth dirtiest surface in the bathroom, with 32% covered in bacteria, but cream cleaner managed to reduce the infected area by a satisfying 99%. However, the shower cleaner didn’t do as well, only removing 50% of the bacteria. The shower head is also a notorious haven for limescale, which can be reduced using an array of bathroom cleaners. But the best solution for removing limescale is good old-fashioned vinegar. 

Winner: Cream cleaner

Shower Head - before and after cleaning with cream cleaner

Shower tray

Bacteria detected
: E. coli, Streptococcus, Staphylococcus, Enterobacter aerogenes, Enterococcus, Klebsiella pneumoniae, Streptobacillus, Campylobacter.

Cleaning contenders: Bleach vs Cream cleaner


With an infected area of 72%, made up of eight different types of bacteria, the shower tray was the filthiest surface in the test bathroom and needed some serious cleaning power to get properly clean. That power came in the form of bleach, which removed an impressive 89% of the pathogens. However, cream cleaner only succeeded in making the shower tray more infected, by 2.5%. “This leads me to think that cream cleaner didn’t work on that surface and it just ended up distributing the bacteria more,” says Marco.

Winner: Bleach

Shower Tray - before and after cleaning with bleach

Bathroom floor

Bacteria detected
: E. coli, Enterococcus, Salmonella, Staphylococcus, Streptococcus.

Cleaning contenders: Bleach vs Bathroom wipes


The bathroom floor was relatively clean, with just 23% of its area infected with five different types of bacteria. However, one of those was Salmonella, a dangerous bacteria that can cause diarrhoea, fever, abdominal cramps and vomiting if ingested. Your best bet for getting rid of Salmonella and other bacteria on the bathroom floor is bleach, which in this case reduced the infected area by 99.4%. In contrast, bathroom wipes only reduced the infected area by 7%.

Winner: Bleach

Bathroom Floor - before and after cleaning with wipes

Bathroom door handle

Bacteria detected
: Micrococcus, Staphylococcus, E. coli, Streptococcus.

Cleaning contender: Bathroom wipes


One of the least infected areas in the bathroom, the door handle was tested with wipes, which achieved a 94% reduction in bacteria. As the initial percentage of infected area was so low (0.9%) there was only one cleaning product tested.

Winner: Wipes

Door Handle - before and after cleaning with wipes


Bacteria detected
: E. coli, Streptococcus, Staphylococcus.

Cleaning contenders: Anti-bacterial spray vs Bathroom wipes


The sink was the second most infected area in the entire bathroom. With 71% of its surface covered in bacteria, it was in desperate need of a good clean. Your best bet to get rid of all those unpleasant pathogens is anti-bacterial spray, which reduced the infected area by a whopping 94%. That figure couldn’t be beaten by bathroom wipes, which only managed a paltry 50%.

Winner: Anti-bacterial spray

Basin - before and after cleaning with anti-bacterial spray

Basin taps

Bacteria detected
: E. coli, Streptococcus.

Cleaning contenders: Bathroom wipes vs Multi-surface spray


While bathroom wipes weren’t great on the basin or floor, they were more successful in removing bacteria from the taps, reducing the 43% infected area by half. This was over 30% better than multi-surface spray, which only managed to reduce the infected area by 19%.

Winner: Bathroom wipes

Basin Taps - before and after cleaning with multi-surface spray

Toilet seat

Bacteria detected
: Micrococcus, Staphylococcus, Streptococcus.

Cleaning contenders: Bleach vs Anti-bacterial spray


The humble toilet seat gave us some unexpected results when it came to cleanliness and hygiene. Not only did it have a relatively low area of infection (29%), it was also the only surface in the bathroom that didn’t show the presence of E. coli. Both bleach and anti-bacterial spray performed well on our seat, but, with scores of 99.5% and 93% respectively, it was bleach that came out on top.

Winner: Bleach

Toilet Seat - before and after cleaning with bleach

And the winner is…

Going through the results of all eight surfaces, it’s clear that bleach comes out as the winner in the cleaning stakes. With consistently high reductions in bacteria, it’s the cleaning solution of choice if you really want to get your bathroom free of germs and sparkling clean.

“After analysing all the products, it’s no surprise that bleach revealed the best results as it continuously showed drastic decreases in the infected area by bacteria or fungi,” says Marco. “In some cases neither bacteria nor fungi displayed any growth. A promising substitute for bleach is the anti-bacterial spray since, in some cases, it compares to the effectiveness of bleach.”

Self-cleaning showers

The idea of your shower keeping itself clean may sound like science fiction, but Mira Showers have gone a long way to achieving this. CleanCoat® technology added to their shower enclosures provides an invisible coating that helps to keep the glass sparkling clean, while Mira shower trays with Biocote® technology actually reduce bacteria and mould growth by up to 99.9%. Could no cleaning be the cleaning of the future?

Take a look at Mira’s cleaning hacks to give your bathroom a really deep clean.

How often do you clean your bathroom? Share this story on Facebook or Twitter and ask your friends how clean their bathroom is!

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