Mass Spectrometry Identifies Bacteria Resistant to Colistin

A method using mass spectrometry has been successfully developed to quickly and accurately diagnose drug-resistant bacterial infections, as well as to distinguish between the two main mechanisms of resistance.

The research was a collaboration led by Dr. Laurent Dortet, from South Paris University (Paris, France), and Dr. Gerald Larrouy-Maumus and Prof. Alain Filloux from Imperial College London (London, UK). The team tested Escherichia coli and Klebsiella pneumoniae, both members of Enterobacteriacae. Some strains have become resistant to nearly all available antibiotics. Colistin often remains the only treatment option for these multidrug resistant bacteria, but some strains have now also developed colistin resistance.

Previous research has shown that chromosome-encoded and plasmid-encoded colistin resistance has arisen. Plasmid-encoded resistance is considered more dangerous because it can be passed on from one type of bacteria to other types.

“This plasmid-encoded resistance is particularly worrying because it has the potential to spread quickly and easily and, if that happens, last resort drugs like colistin could also become obsolete,” said Dr. Dortet, "If, on the other hand, we are able to rapidly identify bacteria that have this type of resistance, we can take measures to stop its spread. This might include isolating the patient in a separate room where they are treated by dedicated medical staff.”

The researchers tested 134 different colonies of bacteria using a mass spectrometer. They found that it was possible to distinguish not only between colistin resistant and nonresistant bacteria, but also which bacteria have plasmid-encoded resistance. Also, the test can be carried out in around 15 minutes and would cost less than 1 USD per sample.

“The exciting thing about this technique is that it relies on technology that is already available in most hospitals. This means that it could be rolled out quickly and cheaply, and potentially have a rapid impact on tackling drug resistance,” said Dr. Larrouy-Maumus.

The researchers are now working with Imperial Innovations, Imperial College London’s technology transfer office, to patent the technique and develop it for clinical use in hospital laboratories.

The test could also be useful for screening veterinary samples, where levels of colistin-resistance are known to be high. It might also be used for testing whether new drugs are able restore bacteria’s vulnerability to colistin.

“The rapid detection of colistin resistance will be of enormous value in healthcare. It will enable early interventions to control transmission, protect patients, and improve individual patient management,” said Prof. Alison Holmes, of Imperial, “Outside healthcare, it will also have enormous potential in farming and meat production. The ability to discriminate the different mechanisms of colistin resistance will also generate a greater understanding.”

The study was presented at the 27th European Congress of Clinical Microbiology and Infectious Diseases (April 22-25, 2017, Vienna, Austria).