When you think of bacteria, you probably imagine a fuzzy Petri dish or a well-used toilet seat.
But scientists have revealed that bacteria is probably growing right underneath our noses in an item we carry around and drink from all day long – the reusable water bottle.
A study by US filtration company WaterFilterGuru.com found that an average reusable water bottle has 20.8million colony-forming units (CFUs) of bacteria on it.
The worst offenders were bottles with spout-top and screw-top lids containing 30million CFUs each.
Researchers found two types of bacteria present on the reusable water bottles they tested: gram-negative rods and bacillus.
If swallowed, gram-negative bacteria can cause infections while certain types of bacillus can lead to serious gastrointestinal issues.
In comparison to other germ-filled spots in the home, the average reusable water bottle has five times the bacteria of a computer mouse and 14 times the bacteria of a pet bowl that has been slobbered over by your beloved dog.
Most astonishingly, a reusable water bottle has 40,000 times the bacteria of a toilet seat, according to the study.
The average reusable water bottle has 20.8million colony-forming units (CFUs) of bacteria on it (stock image)
The longer the water bottle is left at room temperature, the more bacteria will grow.
Thankfully, cleaning your water bottle is relatively straightforward and experts recommend washing it once per day.
Dr Primrose Freestone, an associate professor in clinical microbiology at the University of Leicester, suggested in BBC’s Science Focus that you should wash your bottle with hot water over 60°C – as most pathogens are killed at this temperature.
‘Add washing-up liquid, swirl it around and leave for ten minutes,’ she said. ‘Then rinse it with hot water and allow it to dry – overnight is best, as thorough drying will also help to protect against the growth of microbes.’
For bottles that are heavily contaminated with microbes, you should add a half vinegar/half water mixture and allow it to soak for several days before rinsing it with hot water and allowing it to dry.
Dr Freestone added: ‘To avoid getting ill from your water bottle, you should ideally clean it with detergent after each use.
Researchers found gram-negative rods (pictured) on the reusable water bottles they tested. If swallowed, this type of bacteria can cause infections (stock image)
‘It is also important to clean any lids or attachments such as straws as these can also harbour microbes’.
More than 60 per cent of Americans follow Dr Freestone’s advice and clean their water bottles once or more per day, according to the study by WaterFilterGuru.com,
But others were less diligent. One-quarter of respondents only wash their bottles a few times a week, while over 10 per cent clean them a few times a month.
Members of Gen Z cleaned their bottles the least, with 16 per cent washing theirs out only a few times per month.
Once a water bottle is filled, scientists also suggest that you should place it in the refrigerator to limit microbial numbers.
The type of liquid you pour into the bottle also has an effect on what grows inside of it.
Drinks containing sugar may nourish you – but they will also nourish the microbes in your bottle so it is best to avoid protein shakes, fruit juice and energy drinks.
Ideally you should wash your water bottle with detergent every day (stock image)
Interestingly, carbonated drinks such as soda tend to be antimicrobial as the carbon dioxide inhibits the growth of pathogens such as E.coli and Pseudomonas aeruginosa.
But whether your bottle is filled with water, protein shakes or fizzy drinks, it is best to clean it regularly to avoid the build up of bacteria on its inside walls.
If you do not do this, you will likely notice an odd taste or texture the next time you drink from your bottle due to the waste products released by a growing army of microbes.
So the next time you are feeling slightly ill, check in with your water bottle cleaning habits as the bacteria and mould growing right under your nose might be the culprit.