Breakthrough could help prevent spread of ‘superbugs’ in medical centers

Dangerous microbes in hospitals can be detected in numbers as low as just one cell, according to a study led by scientists at the J. Craig Venter Institute in La Jolla. The study could lead to more effective identification of deadly “superbugs” before they gain a firm foothold.

Hospitals have been frustrated in stopping superbug invasions because most of the bacteria that hospitals are concerned with don’t grow well in cell cultures, said Dr. David Brenner, UC San Diego’s vice chancellor for health sciences and dean of the school of medicine. So such pathogens can stick around undetected until they land in a vulnerable patient.

The researchers examined bacteria in a “biofilm” taken from a hospital bathroom sink. Biofilms are sticky masses of bacteria especially resistant to eradication. Researchers found a single cell of a bacterium that causes periodontal disease, Porphyromonas gingivalis, along with 24 other species of bacteria, some dangerous and some harmless.

Moreover, the researchers produced a nearly complete genome sequence of the P. gingivalis bacterium. They identified potentially dangerous differences between it and three other strains that already have been sequenced. These changes may make it easier for the strain to survive outside its human host, the researchers said.

The study was published Friday in the journal Genome Research. Its first author was Jeffrey McLean, a staff scientist at the Venter Institute. Roger Lasken, director of single-cell genomics at the Venter Institute, was the senior author. Other authors included UC San Diego’s Mike Ziegler, Glenn Tesler and Pavel A. Pevzner.

Lasken invented the study’s single-cell genome sequencing technology more than a decade ago. The method amplifies the minute quantities of DNA present in one cell so it can be detected. Pevzner and other researchers have helped improve it.

Biofilms shelter bacteria from the environment, creating a troublesome reservoir of infection, Lasken said.

“It’s well understood now that they’re critical to the way that patients get infected,” Lasken said. “The bacteria create the biofilms, and they coat medical instruments, water supplies, catheters, needles, and they are transmitted from hand to patients.”

Because many of these bacteria are slow-growing in cell cultures, detecting them directly in biofilms may provide a significant advance in preventing infection, Lasken said.

The new study is significant because the technology was applied to bacteria in an actual hospital setting, Brenner said. The next step is to do a larger study and identify bacteria throughout the hospital, he said.

“So what the hope is, if we can understand the flow of bacteria in a hospital, and particularly the flow of drug-resistant bacteria, we can develop novel ways to intervene,” Brenner said, listing the questions this research could answer.

“How do bacteria get into the hospital? How do they get transported from one place to another? One patient has drug-resistant bacteria, how does it spread to other patients in the hospital? Is it on the gurneys, is it on the sinks, or the doors?”

Answering these questions hasn’t been possible for lack of a way to find bacteria before an outbreak, Brenner said.

“Right now, we’re at the mercy of cultures,” Brenner said. “If it’s culture-negative, we assume it’s OK. And this is the breakthrough. It will no longer depend on cultures.”


