A spring foodborne illness outbreak linked to a previously obscure strain of E. coli bacteria highlights an era of heightened public scrutiny and safety regulation for produce growers, industry observers say.

The nation’s produce industry is in the crosshairs of the public health surveillance system following recent E. coli outbreaks, said Michael Doyle, director of the University of Georgia’s Center for Food Safety, which has published more than 50 E. coli reports over the past seven years.

As testing technology becomes more sophisticated, “the system is picking up outbreaks that would not have been detected three or four years ago,” Doyle said. “If the produce industry is going to stay ahead of the curve — and there are kinks in the armor — it’s going to have to fill these gaps quickly.”

E. coli can be found in the intestines of cattle, and outbreaks have historically involved ground beef tainted with the most commonly-found strain, known as O157:H7. But over the past few years, produce industry concerns have grown following outbreaks stemming from contaminated lettuce and spinach.

In 2006, E. coli O157:H7-tainted spinach from California was blamed for the deaths of three people and illnesses in 200 others. Earlier this year, shredded romaine lettuce contaminated with E. coli O145, a lesser-known strain, sickened at least 26 people in five states. Three of those people suffered kidney failure, though no deaths were reported.

But the romaine lettuce case brought a unique twist: It was the country’s first reported E. coli outbreak linked to O145, according to the U.S. Centers for Disease Control and Prevention.

In a May statement on the romaine lettuce outbreak, the CDC described O145 as an “emerging bacterial pathogen” that can produce the same illnesses as the O157 strains responsible for nearly all reported E. coli illnesses from the past dozen years.

An Ohio company, Freshway Foods, recalled romaine products after the Food and Drug Administration determined the tainted lettuce likely came from one of the firm’s processing plants.

Of the more than 333 U.S. E. coli outbreaks since 1998 involving the eight most dangerous strains of the bacteria, more than 95% were linked to O157, according to CDC data.

It’s not clear whether contamination from O145 and other less-common strains is on the rise, or if recent cases reflect improved or more-frequent testing.

There is limited data on the occurrence of non-O157 strains, according to the CDC, meaning O145 illnesses may go unreported. Many laboratories do not test for non-O157 strains because they’re more difficult to identify, the CDC said.

Whatever the case, U.S. fruit and vegetable growers already face a changing regulatory landscape as the Obama administration steps up efforts to tighten food standards, and produce industry officials see expanded E. coli testing and other safety measures on the way.

Earthbound Farm’s science advisors “strongly recommended” screening for six non-O157 E. coli strains, knowing that such strains may be included in new U.S. food regulations, said Samantha Cabaluna, communications director for the San Juan Batista, Calif., company.

The less-common E. coli strains are “not a fully recognized issue in foodborne pathogens,” Cabaluna said.

Among U.S. growers, testing raw products for E. coli is “fairly limited” to lettuce, spinach and other leafy greens that have had a recent history of outbreaks, said Bob Whitaker, chief science officer with the Produce Marketing Association.

While the “overwhelming majority” of U.S. leafy greens growers are doing some kind of E. coli testing, little screening is done for the less-common strains, he said.

Over the past year, “many companies are looking at a more general screening for all types of E. coli, not just O157,” Whitaker said. “Testing and other safety practices are improving and will continue to improve among growers. I don’t see pressure for testing to go away.”

Tests conducted by Earthbound Farm, a San Juan Bautista, Cal.-based organic salad greens grower, suggest non-O157 strains are becoming more of a problem.

Of 120,000 microbial tests last year, about one in 1,000 showed presence of pathogens, and the “vast majority” were non-O157 E. coli strains, according to Earthbound Farm spokeswoman Samantha Cabaluna.

Pinning down E. coli sources is tricky for vegetable growers, observers say. E. coli may be spread through tainted irrigation water, runoff from nearby cattle ranches or by wild animals.

Additionally, the industry has many “risky” practices, said Boyle, of the Center for Food Safety, particularly in harvesting and processing. For example, head lettuce can be contaminated by E. coli from harvesting blades that come in contact with soil then cut and core the plant, he said, citing a 2008 study he helped conduct.

In coming years, pressure will probably only increase on the produce industry to strengthen pathogen testing and other safety practices, Boyle said.

Whitaker said there is a huge focus by the industry on E. coli, but cautions that testing has limitations and must be part of a broader safety program that keeps pathogens away from food in the first place.

“When these things happen, we’ve got to learn so this doesn’t happen again,” he said, referring to recent E. coli outbreaks. “Today, we know more than we knew in the past. This is a tremendous opportunity to improve our performance.”