People around the world are dying of bacterial infections that were once entirely treatable with conventional antibiotics and as modern medicine advances, the situation stands to get worse, not better.

Dr. Mark Plotkin, an ethnobotanist and the president of the Amazon Conservation Team will speak today at 7:30 p.m. at the Santa Barbara Museum of Natural History on drug-resistant bacteria and his conservation work. Plotkin’s organization aids in the development of cures in western medicine using knowledge gleaned from tribal shamans and their traditional medicine. His appearance is part of a speaking tour plugging his new book, “The Killers Within,” on antibiotic-resistant pathogens.

The first antibiotics were derived from natural chemicals that actually came from bacteria themselves. They were chemical defense mechanisms that the organisms used to kill one another off. The chemicals, when taken alone, were still capable of killing off pathogens in the human body.

The problem with this system of disease control is that bacteria had already been getting around it for years. As one type of bacteria developed killer chemicals, other bacteria would develop defenses against it. So, when drug companies began to manufacture massive amounts of antibiotic chemicals, it was only a matter of time before human pathogens found a way to cope with them.

Tuberculosis, S. aureus, S. pneumo, and Salmonella are just a few diseases that have become resistant to multiple antibiotics. Other bacterial infections are close behind.

“I think that if you look at it evolutionarily, all of them will,” Plotkin said. “If we don’t start using antibiotics more carefully, the ones that I’m really worried about personally are Staph aureus, which is the deadliest of all and Strep pneumo, because I have kids. I mean, there’s seven million cases of earache in this country a year [mostly due to S. pneumo]. Most of those are pediatric and the resistance has gone from nothing to 45 percent in ten years – do the arithmetic.”

Your body is probably covered in one or more of these types of bacteria already. They live in your nose, mouth, gut, and on your skin. This is called being “colonized” with bacteria. For an infection to begin, the bacteria must gain access to the tissues or the bloodstream via a wound. Many of them require a weakened or suppressed immune system to gain a foothold, but once they do they can be life threatening. For years, doctors have treated such infections with antibiotics – a luxury that is quickly coming to an end.

When bacteria are exposed to small amounts of antibiotics, but not enough to kill them off, they reproduce under selection pressures that favor resistant strains. Once a resistant strain of bacteria develops, antibiotics will actually help it out, because they will eliminate its competition and give it room to grow.

“The bugs have gotten stronger,” Plotkin said. “It’s like they’ve been at the gym, they’ve worked out, and now they’re ready to rock.”

Bacteria are exposed to these non-lethal quantities of antibiotics in several ways. Doctors may over-prescribe antibiotics, accidentally dispensing them for viral infections where they have no effect, but still make nice with your body’s bacterial colonies. When people take home an antibiotic prescription they may take the drugs until they feel better and throw the rest away, even though there are still pathogens left in their bodies.

The worst source of exposure may be feeding centers for livestock, where the animals’ feed is dosed with small amounts of antibiotic. These small doses are known as growth promoters and are used not to fight specific diseases in the animals, but because they are proven to cause the animals to grow larger. People then eat the animals and are colonized by their pathogens, resistant and nonresistant.

The number and variety of resistant bacteria has increased exponentially in recent years, because bacteria are capable of swapping the genes that make them resistant. If you are colonized with a strain of resistant bacteria and a strain of vulnerable bacteria, chances are they are trading genes like playing cards .

“Antibiotics are not the answer and have never been the answer,” Plotkin said. “They need to have been viewed all along as part of the answer and [not doing] that is the mistake we made.”

Researchers are currently working to produce other cures for bacteria. Scientists at UCSB work on bacterial vaccines, which work in the same way as vaccines for viral infections (but may prove to be more versatile). In addition to this avenue, other researchers work on peptides, which are natural antibiotic chemicals produced by animals and humans. Others inject antibodies directly into the bloodstream in the hopes that they will help the body fight infection.

Plotkin said one of the most promising treatments may be the use of bacteriophages. These are viruses that have evolved to prey on bacteria. They appear to be harmless to humans and they play the same evolutionary game as bacteria, developing new methods of attack as the pathogens create new defenses. Though used in the Soviet Union for generations, there are still difficulties in using bacteriophages in medicine. One difficulty in using them as treatment and in getting them approved is the fact that they generally originate in places with high bacterial counts, like sewers and contaminated bodies of water.

“The problems inherent in phage are quite obvious: they’re viruses, they’re living materials,” Plotkin said. “But I went over to Georgia and I reported on this and the stuff that they are able to do is really quite phenomenal. Once again, Americans look down their nose at Soviet science and no one’s anxious to shoot sewage extract into their bloodstream, but if you’re dying of a drug-resistant infection, I think you’ll reconsider right quick.”