In a finding that may pave the way for the development of drugs to fight bacteria that are resistant to antibiotics, researchers in Missouri have discovered how one class of bacteria infects cells.

Bacteria known as gram-positive bacteria, which include the organisms that cause strep throat and rheumatic fever, infect cells by drilling holes in the cells' outer membranes, according to a report in the January 12th issue of the journal Cell.

According to Dr. Michael Caparon, of Washington University in St. Louis, who led the research, gram-positive bacteria introduce poisonous toxins into cells in a two-step process. A bacterium uses one protein to puncture a cell's membrane, and then another protein enters the cell, he explained in an interview with Reuters Health. In this way the bacterium is able to interfere with the cell's normal activities, without having to enter the cell itself, Caparon said.

Developing new drugs against gram-positive bacteria is important because the organisms ``are responsible for five of the top six bacterial infections that are now resistant to multiple antibiotics available today,'' Caparon said in a statement.

The researchers based the findings on experiments with a gram-positive bacterium called Streptococcus pyogenes. Staphylococcus, or staph, is another disease-causing gram-positive bacterium. Like several other strains of gram-positive bacteria, staph is becoming increasingly resistant to antibiotics.

While a similar system of injecting proteins occurs in gram-negative bacteria like E. coli and Salmonella, until now, it had not been identified in gram-positive bacteria, the researchers report.

In the interview, Caparon explained that the next step in the research is to figure out how proteins navigate their way into the holes in cell membranes.

There probably is some ``active mechanism'' that guides the proteins into the cells, according to the Missouri researcher. Otherwise, many of the proteins would not be able to find the openings. If that mechanism could be identified, drugs that block the proteins' action might protect cells from harmful bacteria, Caparon said.

``New classes of current antibiotics simply buy us a little time. We have to come up with new ways of thinking about the problem,'' Caparon said in a statement.

(From ChinaDaily)