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Bacteria to the future 

By Dawn Wiseman

Last weekend, 20-year old Brazilian model Mariana Bridi died due to rampant infection caused by Pseudomonas aeroginosa. Known to be highly resistant to antibiotics, the bacteria took hold in her system after an initial misdiagnosis delayed appropriate treatment.

If recent developments in bacterial identification by Marcus Lawrence (Chemistry and Biochemistry) and colleagues prove to be as effective as initial tests indicate, the number of tragedies like Bridi’s may significantly decrease.

A few years ago, during a sabbatical at the Université Claude-Bernard in Lyon, France, Lawrence developed a means of producing cheap electric circuits on transparencies for detecting DNA. Soon he was contacted by Biophage Pharma, a Montreal-based biopharmaceutical firm that develops therapeutic and diagnostic products to deal with bacterial contamination.

“Phages are viruses that attack bacteria,” explained Lawrence. “They wanted to know if their phages could be coupled to the circuits to act as sensors for bacterial identification.”

While other types of bacterial sensors exist, they are expensive, not easily portable and require specialized training to use. In addition, these sensors tend towards low specificity, so while they can indicate that bacteria are present, they cannot necessarily identify the exact strain; part of the challenge in tracking down the source of last summer’s listeriosis outbreak was matching the specific bacterial strains found in contaminated meat with a source at the processing plants involved.

Phages are highly specific; each type only infects one kind of bacteria. And phages work relatively quickly, once joined to bacteria they can begin killing the microbes within minutes.

In initial tests, Lawrence and his colleagues managed to couple phages for E. coli to each of the eight working electrodes on the sensor. They then placed a drop of E. coli infected solution on it. In about 10 minutes, they measured a change in the electrical potential of the circuit which indicated the phages had indeed bound to the bacteria and infected them.

The work has caused quite a stir in the chemistry community. Along with a special research profile, it appeared as a feature article in the November 2008 edition of Analytical Chemistry, a journal of the American Chemical Society.

“It does not happen very often that one's work gets singled out like that by a highly regarded international journal,” said Lawrence. “It promotes the fine research being conducted at Concordia in general and particularly in the Department of Chemistry and Biochemistry.”

As he pointed out, the great potential for the sensors is that each electrode can be coupled to a different phage, thereby allowing each sensor to test an infected sample for the presence of a variety of bacteria simultaneously. As 32 sensor arrays are produced per 8.5” x 11” transparency, this approach is very cost effective.

“With this system, we foresee a situation where pretty much anyone with minimal training can go into a site with an unknown source of infection, and by placing samples on our sensors determine the offending microbe in a relatively short time period.”

Not only will this have applications in food production and health care facilities, but it has huge potential for the international security community.

“One of the big security concerns is bioterrorism,” said Lawrence. And his lab is already working in this direction.

“We have now adapted our sensor to the detection of Bacillus Anthracis (anthrax), a potential bioterrorism agent, with positive results that are to be the subject of an upcoming publication.”