Antibiotics part 3, new hopes

Dec ,08 2016

Antibiotic resistance is the new world threat which can be fatal to many people. And it will be even more dangerous if we don’t find alternative treatments or improve our available antibiotics. Specifically, methicillin-resistant S. aureus, or MRSA, is one of the most famous and the most common drug-resistant bacteria. Methicillin is a β-lactam antibiotic, a family that also includes often prescribed penicillins, cephalosporins and carbapenems. MRSA is a significant contributor to infections that are life-threatening and costly to treat as the only remaining antibiotic efficient against MRSA is vancomycin. Worryingly, in 2002, S. aureus strain resistant to vancomycin, or VRSA, was detected in a patient who was co-infected with vancomycin-resistant enterococci.

S. aureus is commonly found on the skin or in the nose and spread easily via skin-to-skin contact. Interestingly, some people can carry S. aureus without any complications while other people don’t carry S. aureus at all. This observation lead scientist to believe that there is a mutual relationship between S. aureus and our immune system. However, the scientist are just beginning to understand this phenomenon which might help to explain why it is so difficult to develop and efficient vaccine against S. aureus infections. S. aureus is often found on many surfaces which comes to the contact with our hands such as keyboards, door handles, pencils etc. In recent years, the number of MRSA is increasing not only in hospitals but also in our environment most likely as a result of antibiotic overuse.

MRSA is spread easily via a handshake, for instance between the doctor and the patient. And as a result, MRSA has been a scourge in the hospitals worldwide for years. However, with the right measures nothing is lost. Data from hospitals in England and Wales showed a promising result since the number of MRSA-associated deaths decreased from 1600 in 2007 to only 364 in 2011. And surprisingly, the main weapon against MRSA was hygiene such as hand washing, which cut down the opportunities for spread of infection. This demonstrates that if the right steps are taken, the threat of antibiotic resistance can be reduced.

Furthermore, scientist are searching for an alternative to antibiotic treatment or new sources of antibiotics. And these sources might often come from unexpected directions. Surprisingly, one of such discoveries came from the research on Antarctic sponges at University of South Florida. Group of Dr. Shaw was studying extracts from species of sponges and corals for over 20 years and they found that many extracts had bioactive and antibiotic properties. In addition, other teams discovered that these extracts had antineoplastic and antiviral activity.

Finally, they identified one extract that efficiently killed up to 98 percent of MRSA in the laboratory. The extract was from a particular sponge Dendrilla membranosa and was named as “darwinolide”. In the nature, this sponge is not heavily preyed by other predators which served to scientist as a hint that the sponge has some form of chemical protection. Hopefully, darwinolide will provide the backbone for a new drug development in the fight against MRSA.

            Dendrilla membranosa.

Very recently, researchers found another unique source of new antibiotics, the human microbiome itself. Normally, the antibiotics are produced only by soil bacteria and fungi and the notion that human microflora can also serve as a source of antimicrobial agents is a promising discovery. The researchers were originally studying why some people carry S. aureus in their nose whereas other people don't. The nose itself is quite inhospitable environment for bacteria to survive with a salty liquid and a tiny amount of nutrients to live on. These conditions might lead to a fierce competition between bacteria for resources, a fight similar to the competition in the soil or other natural environment of bacteria.

The scientists analysed the microbial populations in the noses of hospitalized patients. As they expected, they found that the majority of people carried the well-known Staphylococcus aureus. But surprisingly some people carried another strain of Staphylococci, S. lugdunensis, and these two strains were rarely found together suggesting that S. lugdunensis is a natural rival of S. aureus.

In the laboratory, S. lugdunensis produced an antibiotic compound, which they named as lugdunin, and accordingly lugdunin inhibited the growth of S. aureus in petri dish. In addition, when they applied purified form of lugdunin on the skin of mice infected with S. aureus, it reduced the infection caused by S. aureus as well as by MRSA. Importantly, S. aureus did not evolve resistance even after 30 days of exposure to lugdunin, however, the mechanism of lugdunin action remains unknown.

S. lugdunensis gives us an interesting alternative to the use of antibiotics. Perhaps, we could allow S. lugdunensis to colonize patients at the risk of S. aureus infection, for instance in a form of a probiotics treatment for the nose, and let the bacteria fight against each other. However, S. lugdunensis itself can occasionally cause infections of the heart, joints, skin, and eyes which might be potentially dangerous. Nevertheless, these findings are extremely exciting and suggest that there might be other bacteria producing yet unknown antibiotics within our own body, for example in the gut. After all, the microbial war is an ongoing process.

In the end, our war with microbes is not over yet. With the right measures and global effort the future might be ours again.