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Antibiotics reduce effectiveness of pathogen-killing lactic acid bacteria - study

By Mark Astley , 31-Aug-2012

Antibiotic residues in uncured pepperoni, salami and chorizo sausages are potent enough to reduce the effectiveness of lactic-acid producing bacteria designed to make the products safe for consumption, researchers have discovered.

According to research conducted by researchers at the University of Copenhagen and University College Cork in Ireland, antibiotic residues in fermented sausages could be high enough to slow the fermentation process.

The fermentation process helps to solidify and acidify the sausages. Manufacturers inoculate sausage meat with lactic acid-producing bacteria, which should destroy foodborne pathogens such as Salmonella and E.coli O157:H7.

Antibiotics are used to treat disease and promote growth in livestock, residues of which can eventually end up in meat

The University of Copenhagen’s Professor Hanne Ingmer, who supervised the research, told FoodProductionDaily.com that fermented sausages are occasionally the cause of serious bacterial infections, but that until now it has never been understood why.

Sausage-linked outbreaks

During the course of the study, antibiotics were added to meat that had been inoculated with lactic acid-producing bacteria and common foodborne pathogens E.coli O157:H7 and Salmonella enterica.

Ingmer and her team discovered that several of the different starter cultures of lactic acid-producing bacteria were sensitive to the added antibiotics and as a result did not acidify the sausage meat effectively.

They also discovered that while effectiveness of the lactic acid-producing bacteria was reduced, the antibiotic residues had no effect on the foodborne pathogens present.

“We discovered that antibiotic residues are able to inhibit the growth of lactic acid bacteria,” said Ingmer. “That bacterium is necessary to help solidify the sausages and boost their acid levels to kill dangerous pathogens.”

“If that is the case, it could allow those dangerous pathogens to survive the production process.”

“This could be one of the reasons for the outbreaks that are often linked to salami and pepperoni sausages. That is what we are speculating,” said Ingmer.

Manufacturers “concerned”

Ingmer added that those manufacturers who had been involved in the study had been “surprised and concerned” by the findings.

But, Ingmer added, the study could lead to the development of new processes or additives to combat the risk of foodborne illness.

According to Ingmer, it should be possible to use lactic acid-producing bacteria that are less susceptible to antibiotics. She added, however, that efforts should start with livestock farmers and limiting the use of antibiotics in farm animal.

“That is a good strategy to prevent this problem,” she said.

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