The power of LAB
Lactic acid bacteria (LAB) have a significant advantage over other antimicrobials in this age of widespread resistance to antibiotics – but that advantage also requires vigilance.
Targeted administration of some microbes in the form of probiotic products is a well-established approach used in livestock farming for improving animal welfare, boosting performance and preventing or fighting disease. In recent years, these special microbes have rightly received more attention than ever as antibiotic use has been scrutinised and reduced.
Among the pertinent beneficial microbes is a powerful group known as lactic acid bacteria or LAB. They’ve been studied intensively for decades in fact, with several products now on the marketplace and more research and product development to come. “LAB is a diverse category including bacteria belonging to number of genera,” explains Dr Maria Siwek, Professor at University of Technology and Life Sciences in Bydgoszcz, Poland. With colleagues there and at Teagasc Food Research Centre in Ireland, she has recently published analysis on the ability of LAB to control poultry pathogens.
LAB, as the name suggests, produce lactic acid as a by-product of metabolic processes, but they also produce a variety of organic acids such as acetic acid, formic acid, butyric acid and citric acid. “These organic acids create a low pH environment which will adversely affect the regular metabolic functions of most pathogens, such as replication and protein synthesis,” Siwek explains. She adds that “at the same pH level, different antimicrobial activity can be observed as the sensitivity of pathogens to different organic acids may be different.”
Bacteriocins
Apart from organic acids, some LAB also produce four classes of ‘bacteriocins,’ peptides that impede replication or kill pathogenic bacteria through a wide range of mechanisms such as disruption of cell wall synthesis and pore formation in cell walls and membranes. Some LAB strains also produce hydrogen peroxide, diacetyl, ethanol and carbon dioxide which act as broad spectrum anti-microbials. In addition, beyond antimicrobial activity, LAB have health-promoting abilities, such as anti-oxidative activity, improving digestion and other related functions via the gut-brain axis.
When compared to the currently multitude of non-antibiotic antimicrobial control agents that are marketed today (phytobiotics, prebiotics, essential oils, organic acids and synthetic supplements), LAB are powerful because of the simple fact that they are alive. This means they multiply in the body (usually in the small intestine) and keep producing beneficial by-products. “This would be the biggest advantage of the LAB compared to the other alternatives,” Siwek explains. “And although we could expect a resistance of some pathogens (through genetic mutation) to LAB bacteriocins, organic acids produced by LAB can exert a relatively strong and stable antimicrobial activity to a broad-spectrum of species.”
There is a chance that in the future, however, that pathogens could become resistant to the effects of organic acids. Siwek also notes that there is a risk of LAB themselves being exposed to anti-microbial resistance genes from the pathogens and integrating these genes into themselves via the naturally-occurring and common phenomenon of microbial DNA transfer. “This would be the biggest challenge in using LAB in this sector,” she explains. “Continuous research and surveillance is necessary.”
LAB products
A variety of LAB products are available to livestock producers such as FloraZone and Lavipan, some of which also contain yeasts, other types of beneficial bacteria and/or β-Glucan isolated from yeast, which has anti-inflammatory and immune-boosting effects. Other products such as PoultryStar or Probiotics Daily contain multiple LAB strains.
Asked for her thoughts on these live bacteria products, Siwek notes that it’s imperative that manufacturers follow standard protocols and regulations to ensure products cause no harm to livestock. And to ensure efficacy, companies also need to check if the LAB strain they are using will be destroyed by acid and bile in the stomach and take action to protect them as needed (typically through encapsulation) so they arrive alive at their preferred colonisation site, in most cases the small intestine.
Other tests are needed to demonstrate that chosen LABs do not reduce the natural, important diversity of the gut microbiome in the target animal. In addition, in light of LAB potentially integrating genes from pathogens, LABs should also be tested going forward to see if they carry antibiotic resistance genes.
LAB in chicken production
As mentioned, Siwek and her team members have studied LAB in poultry. Specifically, they’ve screened for the LAB strain with the broadest spectrum of activity in inhibiting different strains of two serious bacterial pathogens for broiler chickens, Salmonella and Campylobacter jejuni.
In brand new research conducted with colleagues R.N. Wishna-Kadawarage and R.M. Hickey, Siwek has applied a strain of one of these LAB (Leuconostoc mesenteroides) into broiler chicken eggs. This method of improving gastrointestinal microflora in broiler chickens has been studied extensively, but not against Campylobacter. The team found that L. mesenteroides alone and in combination with a garlic extract were both effective in reducing abundance of C. jejuni in the small intestine when the pathogen was introduced to chicks (that had hatched from treated eggs) at 3 weeks of age, compared to chicks not provided treatment.
Going forward, Siwek and her colleagues note that work must be done to determine whether the studied LAB strains exert different effects in different livestock animals and among their breeds or breeding lines within a given breed.
She adds, “it would be interesting to see how LAB will modify the gut microbiome during normal and pathogen-infected cases. Sometimes certain pathogens may modify the gut microbiome and LAB may act against these modifications (by favouring the bacteria that pathogens are trying to get rid of or vice versa).” Indeed, it’s one of the goals of the EU’s ‘MonoGutHealth’ project to verify the mitigating capacity of selected LAB strains in cases of pathogen infection.
