Outbreak of salmonella in mangoes highlights need for food safety advances

By Deborah Kotz, Globe Staff

As if worrying about mosquito-borne diseases and hanta virus weren’t enough, we now need to take precautions about getting infected with listeria from ricotta cheese or salmonella from mangoes after two illness outbreaks were announced this week by government officials.

An outbreak of listeria from ricotta cheese sold in Massachusetts and 17 other states has caused three deaths so far and 14 hospitalizations, according to the federal Centers for Disease Control and Prevention; so far, the state hasn’t counted any reported cases, but we’ve been told to avoid the Frescolina brand of ricotta salata cheese.

We also need to take precautions when purchasing mangoes, since 105 Americans over the summer contracted salmonella from eating Daniella brand mangoes imported from Mexico, the US Food and Drug Administration said on Friday. No deaths have been reported.

Food safety is supposed to be improving with the passage last year of the Food Safety and Modernization Act, but implementation of what FDA deputy commissioner Mike Taylor called the “most sweeping overhaul ever,” at a press briefing this week, has been slow and plodding.

New regulations establishing more frequent and systematic inspections of farms and manufacturing plants are still under review, Taylor admitted, and Congress hasn’t yet come up with enough funding to allow the FDA to hire more inspectors.

The agency also hasn’t resolved how to ensure that imported produce, fish, and other foods from foreign countries meet the new safety standards that the U.S. plans to impose.

Salmonella is a number one priority since it’s now the leading cause of food-borne illness in this country sickening thousands every year with vomiting, cramps, and severe diarrhea and leading to hundreds of deaths. “It’s responsible for more cases of food poisoning than all the other pathogens combined,” said Eric Brown who heads the FDA’s microbiology unit at the Center for Food Safety and Applied Nutrition in College Park, Md.

During a media tour of the center earlier this week, Brown provided a glimpse of the future, showing off a new array of $150,000 machines that can map the complete genome of bacteria in food samples to see whether they’re associated with the same outbreak and -- eventually -- to pinpoint their geographic origin since different strains of salmonella, for example, live in different parts of the world.

Such an advance might have helped federal investigators locate the source of the spring outbreak of salmonella in sushi -- that sickened 425 people nationwide including 36 in Massachusetts -- within a day or two. It took more than six weeks to pinpoint the chopped raw tuna that was contaminated to a fishery in India and to stop shipments of the product into the U.S.

So far, FDA scientists have mapped about 200 salmonella strains and where they’re located in the world, but there are thousands of different strains that could cause outbreaks so getting a full working system could take a few more years.

Perhaps more important, though, is to prevent these outbreaks from occurring in the first place. Some of the FDA microbiologists think they may have stumbled onto a solution, at least to keep salmonella off of fresh produce like tomatoes. In trying to determine why so many of the recent salmonella outbreaks associated with tomatoes have been linked back to farms along the East coast and not in California crops, the scientists discovered a strain of good bacteria that live in the California soil and prevent salmonella from gaining a foothold.

The bacteria -- similar to strains found in probiotic supplements -- can be sprayed on tomato plants and, in theory, prevent those plants from harboring bad bacteria like salmonella. “It’s a completely novel approach,” said Brown, but it could be a game changer if the field experiments currently underway prove that it actually works.

For now, we have to cross our fingers and hope that the tomatoes, lettuce, and cantaloupe we buy in the supermarket aren’t contaminated with bacteria. Safe food handling tips recommended by public health officials -- like frequent hand washing after touching raw meat and thorough cooking -- won’t help against bacteria that’s on our fruits and vegetables or in our ricotta cheese.