A study conducted at the University of Connecticut in Storrs and recently published in Food Microbiology found that protective bacterial cultures offer a promising mechanism for combating antibiotic-resistant Salmonella in food.
Dennis D’Amico, PhD, associate professor of dairy foods in the University of Connecticut’s College of Agriculture, Health and Natural Resources, led the study as part of his ongoing work involving the use of protective bacterial cultures to prevent illness from foodborne pathogens. He has previously studied the use of bacterial cultures to control the growth of pathogens in food products and to impede their ability to cause sickness.
Dr. D’Amico says that some microbial strains, including many strains of Salmonella, have developed resistance to many of the antibiotics used in human medicine, so the goal of this study was to find an effective way to target those pathogens without using antibiotics. The study authors considered the ability of a protective culture called Hafnia alvei B16 to prevent infection by two Salmonella serovars.
Previously, Dr. D’Amico’s lab had identified Hafnia alvei B16 as effective in inhibiting the growth of both E. coli and Salmonella in milk, and it also successfully stopped the growth of Staphylococcus aureus, preventing it from producing toxin levels sufficient to cause disease in humans.
“Protective cultures like the commercial products we have tested in the lab work against other bacteria in various ways, typically through competitive exclusion and the production of antimicrobial metabolites such as organic acids and bacteriocins,” Dr. D’Amico tells Food Quality & Safety. “They are typically added to products to inactivate or suppress the growth of unwanted microbes. We have shown this [result] with several cultures against several pathogens in food.”
Once ingested, certain pathogens must continue to grow in the gut until the population is large enough to cause disease. Other microbes such as Staph aureus produce a toxin that can cause severe disease if they are allowed to grow unchecked.
The report explains that these cultures can also reduce the virulence of certain pathogens when present together in a food, much like other cultures labeled as probiotics. These cultures can improve food safety by controlling pathogen growth and survival in a food product, thereby attenuating their virulence in food, and/or providing protection against colonization in the host.
“In this case, we see these effects even against antibiotic resistant strains,” Dr. D’Amico says. “The most important takeaway is that these cultures, which are typically used only to control the outgrowth of pathogens in food, have additional functions to provide a multi-pronged approach to improving food safety and public health.”
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