The human body houses a wide range of bacteria, both inside and out. One is Staphylococcus epidermidis – a happy resident of our skin that does no harm. But if transferred inside the body on an implanted artificial hip, that once friendly skin bacteria can cause a major infection.

Other species in the same family of bacteria can cause mild to life-threatening infections. These are opportunistic pathogens – they can take advantage of a weakened immune system and cause serious harm.

We recovered a total of 600 bacteria from this family around East and West London. They represented 11 different species and were collected from surfaces that people often touch, including ATMs, lift buttons, escalator rails and door handles in the London Underground, shopping centres and general public areas in hospitals.

Out of the 600 bacteria we found, nearly half were multidrug resistant, meaning they were immune to treatment from several types of antibiotics.

Antimicrobial resistance is one of the most important public health threats worldwide. Every year, more than 700,000 people die from infections that can’t be treated with antibiotics, as they’ve been rendered ineffective by multidrug resistant bacteria.

Reservoirs of antibiotic resistance

In our study, all of the bacteria showed at least some resistance to 11 common antibiotics used to treat infections today. More than 80% of the bacteria were immune to treatment with penicillin and fusidic acid – some of the first antibiotics to be discovered and among the oldest still used.

Resistance was less prevalent in newer antibiotics – more than half of the bacteria tested were resistant to erythromycin and just over a quarter were resistant to amoxicillin, tetracycline, oxacillin and cefoxitin.

Although public areas in East and West London harboured high levels of antibiotic resistant bacteria, we found more of them in East London (56.7%) compared to West London (49.6%), probably because more people live closer together in East London than West London.

Read more: Antibiotic resistant 'superbug' genes found in the High Arctic

So why should we be worried if “friendly” bacteria are becoming resistant to the treatments we’ve depended on for decades? Well, we also found lots of different genes which encode resistance to different antibiotics within these bacteria. These were capable of “jumping” from one bacteria to another, meaning multidrug resistance could spread to human pathogens and potentially create “superbugs” that our present arsenal of antibiotics can’t treat.

Bacteria can transfer these genes using plasmids – little DNA loops which bacteria of the same or different species can swap between themselves like bracelets. When bacteria acquire multiple plasmids, they’re effectively loaded with resistance to multiple drugs.

Our research suggests that the places we pass through and the surfaces we touch everyday may be reservoirs for these multidrug resistant bacteria. The fact that there are such high levels of antibiotic resistance within and outside hospitals – where antibiotic use is concentrated – suggests that bacteria may be moving between the two.

This is disturbing. It suggests that infection control in hospitals and public areas may be failing to eradicate the problem. As always, good hand hygiene and better public cleanliness could be the best protection.

We’re undertaking more tests to find out where these bacteria came from and which other species they’re related to. They may have originated with bacteria recovered from hospital patients or from livestock or pets. Antibiotic resistance has been called a global threat as serious as climate change. It will require a concerted global response to tackle it.