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It’s a dilemma lots of doctors often face; their patient has a bacterial infection but which species? Is it bug A which means starting the patient on antibiotic Y? Or is it bug B which means antibiotic Y will be no use and the patient will need antibiotic X instead? Most of the time, its a case of grow the bug and see, which can mean delays in the patient getting the right treatment. This dilemma is what is driving the search for faster diagnostic tests which can be carried out at the patients hospital bed or GP’s surgery.

Researchers at the University of Vermont have reported in the Journal of Breath Research (yes there really is a journal dedicated to breath research…) that they could distinguish between the ‘breathprints’ of uninfected mice and mice with lungs stuffed full of Pseudomonas aeruginosa (a common killer of people suffering from the genetic disease cystic fibrosis) or the hospital superbug Staphylococcus aureus. They collected the animal’s breath* and then analysed them using secondary electrospray ionization mass spectrometry (SESI-MS)**. The technique provided unique spectra that could be used to tell all of the groups of mice apart. Which is pretty cool. The hope is that one day doctors will be able to get a patient with a lung infection to breathe into something like an inhaler or breathalyser to collect the patients breath which could then be analysed to detect the volatile compounds released by the infecting bacteria. In this case they had to use what sounds like quite a fancy pants piece of equipment so not exactly bedside diagnostics. I’m holding out for sniffer bees.

*Doesn’t sound pretty… this from the Materials & Methods section: “The mice were anesthetized with pentobarbital 24 h after infection and their tracheas were cannulated. The mice were placed on the ventilators (Flexivent, SCIREQ, Montreal, QC, Canada) and paralyzed with intraperitoneal pancuronium bromide (0.5 mg kg−1), and an ECG was applied to monitor heart rate to ensure proper anesthesia. Breath coming out of the ventilator was collected in Tedlar bags (SKC, Eighty Four, PA) at 180 breaths min−1 with a positive end-expiratory pressure (PEEP) of 3 cm H2O for 1 h.”

**No idea what that is either and wikipedia isn’t being overly helpful. The Materials & Methods section basically says the breath was put into a reaction chamber and sprayed with formic acid and then spectra collected.

Reference:
Zhu et al (2013). Detecting bacterial lung infections: in vivo evaluation of in vitro volatile fingerprints. J. Breath Res. 7: doi:10.1088/1752-7155/7/1/016003. (Open Access)