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Infrared light used to outwit sneaky, deadly bacteria

September 1, 2013 2:02pm
Researchers have devised a way to turn the tables on a sneaky strain of bacteria that can cause life-threatening diseases, based on a technique using infrared light.
Scientists at the University of Veterinary Medicine, Vienna said the technique lets them differentiate strains that can cause chronic infections and those that cannot.
"In principle, germs have two choices when they infect a host: attack or hide – in technical terms virulence or persistence. If they attack, they risk destroying the host and consequently themselves, whereas if they hide, they may be outcompeted by others. A detailed knowledge of the mechanisms of virulence and persistence and the way bacteria switch between them will help us to develop novel and more effective therapies," said Monika Ehling-Schulz, head of Grunert’s institute.
Results of the study have been published in the “Journal of Clinical Microbiology.”
The researchers cited the case of the Staphylococcus aureus (S. aureus) bacterium, which frequently colonizes the skin and the upper respiratory tract of humans.
While a healthy immune system can fight the microorganism, the pathogen can spread and lead to life-threatening diseases of the lungs, the heart and other organs once the immune system is weakened.
Evading the immune system
S. aureus also produces toxins in foods and can cause serious food poisoning, the university noted.
"Its effects are not confined to humans: in cattle, S. aureus frequently causes inflammation of the udders, so the bacterium is also of great interest in veterinary medicine," it added.
S. aureus may be aggressive or evasive – but the aggressive type, which can form capsules and multiply rapidly, is quickly recognized by the immune system.
On the other hand, the capsule-free forms can survive within cells and are less likely to be recognized by the immune system – they can play “hide and seek” before they attack and are may cause chronic infections that are harder to treat.
"Recent studies suggest that in the course of adapting to its host (human or animal) S. aureus undergoes a form of microevolution, during which it loses its capsule. The capsule-free form evades the host immune system and can even survive antibiotic treatment," it added.
Infrared light
But Tom Grunert and colleagues developed a way to distinguish the capsules without the use of antibodies, using a physical procedure known as FTIR or Fourier Transform Infrared Spectroscopy.
"Infrared light is shone on the microorganisms to be tested and the resulting spectral data are input into a supervised self-learning system, a so called artificial neuronal network, which uses the data to work out the type of capsule," the university said.
"With the new method we can routinely test patient samples with a success rate of up to 99 percent," Grunert said. – KDM, GMA News 
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