Researchers at University of Copenhagen and University College Cork found that antibiotic residues in fresh meat interfered with the lactic acid producing bacteria that is added during the curing process to make fermented sausages such as salami, pepperoni and chorizo.
The study revealed that even antibiotic concentrations that fell within US and EU legal limits were high enough to slow the fermentation process, increasing the risk that pathogens such as E.coli and Salmonella would survive.
Lead author professor Hanne Ingmer, of the Faculty of Health and Medical Sciences at the University of Copenhagen, said that the research explained why fermented sausages occasionally cause serious bacterial infections. She added that while the antibiotics seemed to target the beneficial bacteria, they appeared to leave the pathogens alone.
“At low concentrations and at regulatory levels set by authorities, we could see that the lactic acid bacteria are more susceptible to the antibiotics than the pathogens are,” she said.
“So basically, we can have a situation where residual antibiotics in the meat can prevent or reduce fermentation by the lactic acid bacteria but these concentrations do not effect survival or even multiplication of pathogens.”
Small scale experiments
The study, which was published in mBio, the online open-access journal of the American Society for Microbiology, was carried out using small scale laboratory experiments.
Ingmer and her team added antibiotics to meat inoculated with lactic acid producing bacteria and the E.coli and Salmonella pathogens, then observed the fermentation process, noting whether the pathogens survived. They found that several different cultures of lactic-acid-producing bacteria did not acidify the sausage meat sufficiently when antibiotics were present.
Ingmer said that it was now important to conduct similar tests in manufacturing facilities to see “whether this is a problem in a real life facility”.
She added that manufacturers with good quality control systems would be able to catch most problems with fermentation, but that it would be easy to miss a batch of sausages which had not fermented properly. She said that while it may be possible to develop cultures of lactic acid bacteria that tolerate low levels of antibiotics, the best solution would be to reduce antibiotics in meat.
“The obvious solution is to eliminate the use of antibiotics as growth promoters and closely monitor the use of antibiotics in treating farm animal diseases,” she said.