Professor Battles Bacteria

Wednesday, February 4, 2009

If there were a superhero devoted to fighting infectious disease, Michael Mahan would be the man. As a UCSB professor and researcher, he is fighting a war against opponents with names like salmonella, streptococcus, and pseudomonas, on a daily basis. Could he change the future of the world as we know it? You bet.

“We are limited by our imagination, not by our tools,” he said.

Unlike most comic book superheroes, however, Mahan wages his battles in a lab, researching and developing vaccines in the Molecular, Cellular, and Developmental Biology Department at UCSB. Most recently Mahan, a soft spoken, enthusiastic professor, developed a vaccine against salmonella.

You may be surprised that he chose salmonella, which, while it causes some deaths in the United States, it is most often associated with food poisoning. Worldwide, however, this bacteria is a real killer. About 16 million people worldwide are infected with one salmonella strain or another, Mahan said, and hundreds of thousands die. It is a salmonella strain that causes typhoid fever.

There was another reason as well. “It’s the Cadillac of genetic systems,” said Mahan. It is a model genetic engine, and naturally good for gene swapping, he said. It has a short generation time: 20 to 30 minutes. Other disease-causing bacteria take longer to grow. It takes about four weeks to produce a tuberculosis colony.

Yet another reason for the attention to salmonella is that it is rife throughout the food industry. Mahan found 20 strains of salmonella at a California dairy, and this was not unusual, but the norm. He said that farmers may not even know their animals are infected. While younger cows may die from salmonella, older ones often don’t show any signs of infection. You may feel safe if you’re a vegetarian, but you’re not in the clear. Mahan said salmonella is found all over – in pigs, chickens, cows, and vegetables. “We get salmonella because we are eating contaminated animals and vegetables,” he said.

The vaccine Mahan developed is unique in that it targets a variety of salmonella strains. He said this was important since targeting only one would not stem the tide of infection. The vaccine is being tested in animals, but eventually could be used in humans.

Vaccines are especially important since antibiotic-resistant bacteria are on the rise. “The bacteria are getting smart,” Mahan said. They have an attitude of been there, seen that. With about 2,000 antibiotics on the market, which target bacteria that may have developed a resistance after being exposed to the same drugs for more than 50 years, the battle may not be a fair fight.

Some of these drug-resistant bacteria, such as staphylococcus infections, are most often seen in people in the hospital. “If you’re healthy, the hospital is not a place you want to be,” he said. “If you need to go to the hospital, fine,” he hastened to add. He explained that hospitals have become home to multiple-drug-resistant bacteria, which take the opportunity to set up house when someone has surgery. “Staph is very good at colonizing where sutures are, and in traumatized tissue,” Mahan said. In addition, these bacteria can be easily transported from room to room and person to person.

While you might try to avoid hospitals as a safety measure, this is not the only place you’ll encounter deadly types of bacteria. The pseudomonas bacterium is found in the soil, and can enter our bodies through a cut. It has become antibiotic resistant. “Our bodies are built like castles. They are very good at keeping stuff out,” Mahan said, “but once it gets in . . . .” He trailed off.

A recent high-profile case involving pseudomonas occurred in Brazil. A Brazilian model in her twenties contracted a urinary tract infection that turned into septicemia and eventually killed her. Mahan said her infection was caused by pseudomonas, which is a particularly virulent type of bacteria. Most urinary tract infections are caused by e-coli. The antibiotics she was given didn’t kill the type of bacteria that was attacking her body. Mahan, who is teaching a class on infectious disease at UCSB, said he received many e-mails from his students about this story.

While this case may seem like an unfortunate tragedy, Mahan said these types of infections may become more common. He can foresee a time when they hit the general population with greater frequency. He added, “It’s not like the clock’s ticking. It’s already rung.”

Mahan said drug companies are hesitant to produce new antibiotics for fear of litigation. When new drugs are tested, there may be serious side effects for the users, and the drug companies could get sued, he explained. It was the same with vaccines in the past, he added. Companies were hesitant to produce vaccines, until the government offered them protection from lawsuits.

Mahan’s research is also seen as a form of counter-terrorism. There is a fear that terrorists might use our food, or other means, to transmit deadly diseases. And it has happened. There was the incident with a cult in Oregon in the 1980’s who put salmonella bacteria on food at a fast food restaurant, hoping to infect customers, and alter an election, Mahan said. While this group was unsuccessful, other attacks have been lethal. Anthrax, a type of bacteria commonly found in animals, has been used by domestic terrorists here and elsewhere, killing postal workers and others exposed to it.

One of the challenges in developing live vaccines is to provide optimum protection without adversely affecting those with compromised immune systems, the very young, or the old, he said. Mahan emphasized that the three most important things are “Safety, safety, safety.”