For a study published in the Journal of Environmental Health in 2007, researchers swabbed lemon slices on drinks at 21 different sites.
They found that almost 70% of the samples produced some sort of bacterial growth, including 25 different microbial species.
The researchers said: “Although lemons have known antibacterial properties, the results of our study indicate that a wide variety of microorganisms may survive on the flesh and the rind of a sliced lemon.
“Operators should be aware that lemon slices added to beverages may include potentially pathogenic microbes (bacteria that can cause infection).
“Further investigations could determine the source of these microorganisms, establish the actual threat (if any) posed by their presence on the rim of a beverage, and develop possible means for preventing the contamination of the lemons."
They added: “It could also be worthwhile to study contamination on other beverage garnishes, such as olives, limes, celery and cherries, and to investigate whether alcoholic beverages have an effect not seen with water and soda.”
Hygiene experts Food Safety Guru said lemons and limes have been on a journey before the fruit reaches the pub.
It has been sprayed with pesticides and transported around the world, stored in warehouses where there is potential pest contamination before being transported to the pub.
The fruit is then handled by staff who may cause cross contamination after handling money, food, and dirty glasses before it gets sliced and popped into a drink.
Prevent cross contamination
It has also issued advice for pubs on how to keep garnishes clean and safe, which includes washing the fruit before slicing it for drinks.
In addition it has advised bar staff to wash their hands frequently with antibacterial soap to help prevent cross contamination when handling different materials.
Ice is another crucial part of a pub’s drinks offer but earlier this year, ice machine suppliers issued advice to help pub operators ensure ice equipment was safe from bacterial contamination.
The advice followed a BBC Watchdog investigation, which found bacteria faeces in ice used in three of the top coffee shop chains – Costa, Starbucks and Caffè Nero.
The tips included keeping the machine clean, using a scoop and ensuring staff wash their hands before and during service.