At the beginning of my career I was involved in a study that aimed at the discovery of potential new antibiotics, and since then I have always had an interest in the subject.
Antibiotics are drugs that are commonly prescribed to treat bacterial infections. This class of compounds is naturally produced by microorganisms as a weapon against infection, as first observed by Alexander Fleming in 1929: the discovery and characterization of penicillin revolutionized the treatment of infectious diseases.
Penicillin was used for the first time to counteract pneumococcal infections among the military personnel during World War II. After the war, it became available for general use and so did other antibiotics. However, soon the optimism started to fade due to the appearance of bacterial strains with the acquired ability to grow in the presence of antibiotics to which they used to be susceptible. This phenomenon is known as antibiotic resistance.
Once resistance appears, the antibiotic loses its ability to cure the infection, and a different, more powerful antibiotic is needed.
Unfortunately, I believe that not many people not working in this sector understand the imminent threat that antibiotic resistance is to the entire world. As the World Health Organisation (WHO) states on their web page: antibiotic resistance is one of the biggest threats to global health today. It can affect anyone, of any age, in any country. This is very true.
Even though resistance is a natural phenomenon, the rate at which the current antibiotics available on the market become ineffective is increased by the misuse of these drugs in humans and animals.
It is, therefore, crucial that we continue the quest towards the discovery of new drugs able to treat these resistant pathogens.
A recent paper published in Nature gives us an intriguing hint of where we should be looking to individuate novel effective compounds. The answer is most captivating: apparently, we do not need to look far, because the answer could already be in our body!
Zipperer and co-workers remind us that the majority of systemic bacterial infections by multi-drug resistant bacteria (which means resistant to the majority of antibiotics available on the market) are caused by bacteria that generally colonise human body surfaces. These bacteria are naturally present in a percentage of the population (for nasal Staphylococcus aureus this percentage is, for example, around 30%), and remain quiescent and controlled by our body generally until the human carrier undergoes surgery or suffers from immunosuppression or trauma. In those instances, multi-drug resistant organisms are more likely to take over and give rise to invasive infections.
If this phenomenon is well recognised, it is not yet perfectly understood how our body prevents colonisation of the pathogen in healthy individuals. What scientists know is that factors involved are complex and related both to the genetics of the host and also to his microbiota (commensal microorganisms that share our body space). In their study, Zipperer and colleagues observed that the bacterium Staphylococcus lugdunensis (S. lugdunensis: a friendly bacterium belonging to our nasal microbiota) plays a crucial role in keeping the potentially multi resistant Staphylococcus aureus (S. aureus) from invading our nose. In fact, S. lugdunensis is able to produce a molecule (which was named lugdunin in the study) that acts as an antibiotic against S. aureus.
This discovery is invaluable for many reasons. Not only lugdonin is on the right path to becoming a novel potent antibiotic, but also and foremost this is the first reported case in which a probiotic bacterium not belonging to the gut is found to be fundamental for the prevention of systemic infections.
Indeed, the authors state: Our study suggests that the probiotics concept should be extended to body sites other than the gut, such as the nasal mucous membranes.
A good answer to the discovery of new potential antibiotic could be much closer than we thought: so close to be likely already within us. We just need to start looking.
1. Zipperer, A. et al. Human commensals producing a novel antibiotic impair pathogen colonization. Nat. Rev. Drug Discov. 535, 511-516 (2016).
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