New antibiotics needed: Staphylococcus aureus

Posted on March 17, 2020   by Laura Cox

In 2017, the World Health Organization (WHO) published the ’12 Priority Pathogens’: a list of 12 microbes that are becoming increasingly resistant to current antimicrobials. These 12 pathogens are thought by WHO to pose the greatest threat to human health.

© Dr Mike Cadogan / CC BY-SA

Friedrich Julius Rosenbach

Staphylococcus aureus

Named after the gold-coloured colonies it forms when cultured in the lab, Staphylococcus aureus was discovered by German scientist Freidrich Julius. S. aureus is a common microbe; it usually does not cause disease and is carried by around 25% of adults. When this bacterium does cause infections however, it can be extremely fatal, with one in five invasive S. aureus infections (such as pneumonia or endocarditis) resulting in the death of the patient.

In the early 1940s, doctors discovered that penicillin could be used to treat S. aureus infections, which had previously been fatal in the majority of patients. By the end of the decade, the majority of S. aureus infections were resistant to penicillin, and mortality was on the rise again.

 

The secret stowaway

Although S. aureus is not part of the normal human microbiota, it frequently colonises the skin, upper respiratory tract and gut mucosa without causing disease. The bacterium has evolved alongside humans and can live undetected in the nose without causing symptoms or infection. As a result, S. aureus can spread through populations easily and lay dormant in the body for years. The complications of this arise when bacteria invade and infection occurs.

© iStock/Henrik Dolle

A losing battle

It seems like every time a new antibiotic was used to treat S. aureus infections; the bacteria become resistant within a few years. Meticillin-resistant S. aureus (MRSA) began to emerge in 1961 and have been causing an increasing burden on healthcare systems since. As S. aureus acquires resistance to more antibiotics, treatment options dwindle and finding an effective treatment for staph infections becomes more and more challenging.

In 1997, another worrying development occurred, with reports of higher and higher doses of the last resort antibiotic vancomycin being required to clear MRSA infections. Two recently developed antibiotics brought hope for treating vancomycin resistant MRSA; daptomycin and linezolid, which are used sparingly to treat only the most life-threatening infections. Although rare, strains of S. aureus have already shown resistance to these new drugs.

Genomic insights

In their review ‘Using genomics to understand methicillin- and vancomycin-resistant Staphylococcus aureus’, Stefano Giulieri, Steven Yong and Deborah Williamson discuss identify the molecular mechanisms of S. aureus resistance and use genomics to track the spread of resistance genes through microbial communities. This open-access review, published in the journal Microbial Genomics, is the tenth in the New Antibiotics Needed collection.

More from our New Antibiotics Needed blog series:
Shigella
Salmonella
Enterobacteriaceae
Campylobacter
Haemophilus influenzae
Neisseria gonorrhoeae
Acinetobacter baumannii
Enterococcus faecium
Streptococcus pneumoniae