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Outbreak of infections linked to raw oysters appears to be over

Outbreak of infections linked to raw oysters appears to be over

The CDC has declared a U.S. outbreak of foodborne illnesses is over. A week before the declaration the implicated harvest area in Mexico was reopened.

Public health officials continue to urge consumers to avoid raw seafood, especially in warmer months because warmer water makes it easier for pathogens to reproduce.

Sixteen people from five states were confirmed infected with gastrointestinal illnesses from Dec. 16, 2018, through April 17 this year. Two people had to be admitted to hospitals. Epidemiological and traceback evidence indicated raw oysters from Estero El Cardon in Baja California Sur, Mexico, were the likely source of this outbreak, according to the outbreak update from the U.S. Centers for Disease Control and Prevention.

Consulting with officials from the U.S. Food and Drug Administration, public health officials in Mexico closed the implicated harvest area on May 7. The area reopened for business as of June 13, according to an update from the FDA. 

Several pathogens were detected in sick people who reported eating oysters from the Estreo El Cardon area. Some people were infected with more than one pathogen. Laboratory-confirmed pathogens included: 

  • Four cases of Shigella flexneri infection
  • Two cases of Vibrio parahaemolyticus infection
  • One case of Vibrio parahaemolyticus and Shiga toxin-producing Escherichia coli (STEC) non-O157 coinfection
  • One case of Vibrio parahaemolyticus and Shigella flexneri coinfection
  • One case of Shigella flexneri and Campylobacter lari coinfection
  • One case of Vibrio albensis infection
  • One case of norovirus genogroup 1 infection
  • One case of infection with Vibrio of unknown species
  • Four cases of illness without a pathogen identified
  • The FDA reported the oysters were distributed primarily to California, Nevada, New York, and Arizona. The implicated shellfish was sold to wholesale distributors with direct sales to restaurants and not to grocery retail outlets. The CDC reported results of interviews conducted with 15 of the 16 infected people.

“All 15 people who were interviewed reported eating raw oysters from different restaurants in California and Nevada. State health officials collected traceback information for 15 cases and found that oysters were shipped by Sol Azul, S.A. de C.V. (MX 01 SS) and harvested from Estero El Cardon, and were distributed to California, Nevada, New York, and Arizona,” according to the CDC. 

“It is possible that additional states received these oysters either directly from Mexico or through further distribution within the United States.”

Antibiotic resistance
Whole genome sequencing analysis of one Campylobacter lari isolate and five Vibrio parahaemolyticus isolates from ill people predicted resistance to ampicillin, according to the CDC. Ampicillin is not a recommended antibiotic for Campylobacter lari or Vibrio parahaemolyticus infections. 

Analysis of five Shigella flexneri isolates from ill people predicted resistance to ampicillin, chloramphenicol, streptomycin, and tetracycline. These findings are unlikely to affect treatment because other antibiotics are more commonly used until resistance results are available. No resistance was predicted for one STEC isolate from an ill person.

Source: Food Safety News

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