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Nuclear energy

Bacteria detector

In Rio, within two hours a laboratory identifies pathogenic micro organisms

COPPE / UFRJNeutrongraphic images of baccillus: Staphylococcus epidermidisCOPPE / UFRJ

Surrounded by young scientists in the laboratory where she is researching applied nuclear physics, professor Vergínia Reis Crispim shows a small plastic plate as her trophy: for months this plate impregnated with bacteria circulated in Rio de Janeiro between her laboratory, in the Coordination of Post Graduate Programs (Coppe) of the Federal University (UFRJ), and the reactor of the Institute of Nuclear Energy (IEN), in an area of national security only used by researchers. The researchers had the authorization for the following test: place the plate in the reactor and bombard it with a stream of neutrons so as to obtain images of the bacteria. Objective: to create a rapid method of identifying micro organisms that cause illnesses.

The plate handled by professor Vergínia, who coordinated the research, brings prints or traces of a bacterium. For the researchers, it is the proof that they have achieved their objective. Besides being able to visualize and identify bacteria by an unprecedented method, the team from the Neutrongraphy in Real Time Laboratory of Coppe discovered that they could carry this out in only a few hours – while via the conventional methods it would take on average three days to identify a bacterium.

Immediate treatment
Speed in diagnosis is essential in the treatment of infections caused by bacteria, mainly when attending under emergency conditions to patients with lowered immunology. “Our method allows for the physical mapping of the bacterium. By the shape, we can say to which group it belong and can start treatment almost immediately with the correct type of antibiotic”, explains Vergínia. The use of the correct antibiotic even lowers the danger of the appearance of mutations in the bacterium which strengthen its resistance to medicines, one of the current most serious problems in Public Health.

The method was tested on three classes of bacteria – bacillus, coccus and spirillum. These classes of bacteria cause diarrhea (Escherichia coli), respiratory infections (Staphylococcus and Streptococcus), leptospirosis (Leptospira), syphilis (Treponema) and tuberculosis (Mycobacterium tuberculosis). For this last illness, the conventional diagnosis can take as long as fifteen days. In the technique developed at Coppe, contaminated blood, urine and feces samples are placed in a compound of boron and this chemical element envelopes the bacteria like a type of mantel.

Afterwards, they are placed in the reactor and bombarded with a beam of neutrons which begin to react with the boron atoms, provoking fissures on the CR-39, the plastic detector on which the sample was collected, printing on it marks which reveal the shape of the bacterium – this is the image called a neutrongraph or radiograph with neutrons. After the chemical development of the CR-39 plate, one only needs to observe the image with an optical microscope to identify the type of bacterium present. “The most recent tests indicate that all of the stages can be carried out in less than two hours using a conventional optical microscope.”

Software and an irradiator
Now the researchers are developing a computer program to identify the bacterium through the neutrongraph images. “This software program will need to be capable of recognizing the shape of the bacterium without any human interference”, says the physicist Joana D’arc Ramos Lopes, who is preparing her doctorate thesis on the new identification technique, which is in the process of being patented. The team also intends to develop a compact irradiator for clinical analysis laboratories. In the meantime, the experiments are being carried out in a very large size reactor, proper for research: the Argonaut belonging to the IEN.

“We are estimating a cost of R$ 15,000 for the compact system, a value very competitive with the traditional clinical analysis equipment”, says Vergínia. The methodology has other applications. In tests, bacteria can already be identified in water. In this way, the technique could serve for examinations of potability that identify bacteria in samples taken from wells, water tanks, rivers and lakes. The researchers have already identified spirillum and streptococcus in neutrongraph images of water samples, for example.

Virus and explosives
Capable of causing more than one hundred types of illnesses, viruses are also the target of the Coppe team. Through radiography with neutrons, the engineer Reinaldo Wacha detected the influenza A virus, which causes the common cold. However, viruses are much more difficult to identify. “They are much smaller than bacteria and suffer lots of mutations”, explains the researcher. In another line of research, the fruit of the research by the physicist Ademir Xavier da Silva, the objective is to apply neutrongraphics in drugs and explosives detection.

In tests, he has detected samples of explosives and of cocaine in different forms and degrees of purity, conditioned in aluminum tubes and submitted to hiding by lead, smoke, aluminum, plastics, leather, iron and cloth. “The results obtained in the detection of drugs and explosives hidden using various types of material have been most encouraging”, says Vergínia.