|[Photo source : Shutterstock]|
Food poisoning is considered a high health concern especially when food handling or preparation is involved. Certain types of bacteria can contaminate food supply and may even cause an outbreak.
In an article published in Nature, it was shown how a bacteriophage expressed in plants succeeded in eliminating various colonies of the bacterium Clostridium perfringens, a microorganism that can cause food poisoning.
Researchers in the study demonstrated six lysins belonging to two different families (N-acetylmuramoyl-L-alanine amidase and glycosyl hydrolase 25) that are active against a panel of enteropathogenic C. perfringens strains under salinity and acidity conditions relevant to food preparation environments. They also used plant-expressed lysins to prevent multiplication of C. perfringens on cooked meat. This exhibited far better elimination of microbes than nisin, the only currently approved bacteriocin food preservative to control the pathogen.
The results of the study can pose a solution to the problem of food-related diarrhea by having bacteriophage lysins used as food additives or food-processing aids. Such antimicrobials can be produced cost-effectively and are in ample supply in green plants. By using edible plant species as production hosts, the need for expensive product purification can be reduced.
Food-borne diseases and antimicrobials
C. perfringens has been implicated in some Clostridium difficile negative cases of antibiotic-associated diarrhea. C. perfringens enterotoxin detection methods are not part of the routine laboratory investigation of such cases. Testing for this toxin in fecal samples from patients with antibiotic-associated diarrhea and sporadic diarrhea on a routine basis will have considerable resource implications. In addition, establishing the true burden of C. perfringens antibiotic-associated diarrhea is important before optimum control and treatment measures can be defined.
Staphylococcus aureus and Clostridium perfringens are the most frequently cited alternative causes of antibiotic-associated diarrhea. Clostridium perfringens type A is an important cause of bacterial food poisoning worldwide. There is mounting evidence to suggest that enterotoxigenic C. perfringens strains can play a role in the etiology of diarrheal disease distinct from food poisoning, including antibiotic-associated diarrhea and sporadic diarrhea in humans. Clostridium perfringens forms part of the normal human gut flora in small numbers—up to 103 colony-forming units (cfu)/g. Ingestion of large numbers of vegetative cells (≥ 108 enterotoxin-producing organisms) of C. perfringens leads to diarrheal illness, as in cases of food-borne disease. The organisms multiply in the small intestine and sporulate, releasing C. perfringens enterotoxin (CPEnt), which is responsible for the classic symptoms of food poisoning. In addition, spores from these bacteria contribute to its pathogenicity.
The antibiotics associated with these cases were penicillin, cephalosporins, augmentin, erythromycin, trimethoprim, and nitrofurantoin.
Bacteriocins are ribosomally synthesized peptides or proteins with antimicrobial activity, produced by different groups of bacteria such as those that produce lactic acid. Several bacteriocins offer potential applications in food preservation, and their use in the food industry can help reduce the addition of chemical preservatives with far richer nutritional content and more organic made.
This can be an alternative to satisfy the increasing consumer’s demands for safe, fresh-tasting, ready-to-eat, minimally processed foods, and also to develop "novel" food products (e.g. less acidic, or with a lower salt content). In addition to the available commercial preparations of nisin and pediocin PA-1/AcH, other bacteriocins (like lacticin 3147, enterocin AS-48, or variacin) also offer promising perspectives.
Broad-spectrum bacteriocins present potential wider uses, while narrow-spectrum bacteriocins can be used more specifically to selectively inhibit certain high-risk bacteria in foods like Listeria monocytogenes without affecting harmless microbiota.
Bacteriocins can be added to foods in the form of concentrated preparations as food preservatives, shelf-life extenders, additives, or ingredients, or they can be produced as bio food packaging. In recent years, application of bacteriocins as part of hurdle technology has gained great attention. Several bacteriocins show additive or synergistic effects when used in combination with other antimicrobial agents, including chemical preservatives, natural phenolic compounds, as well as other antimicrobial proteins. This, as well as the combined use of different bacteriocins may also be an attractive approach to avoid development of resistant strains. The combination of bacteriocins and physical treatments like high-pressure processing or pulsed electric fields also offer good opportunities for more effective preservation of foods, providing an additional barrier to more refractile forms like bacterial endospores as well. The effectiveness of bacteriocins is often dictated by environmental factors like pH, temperature, food composition, and structure, as well as the food microbiota.
Bacteriocins are generally recognized as "natural" compounds able to influence the safety and quality of foods. In past years, a lot of work has been aimed to the detection, purification, and characterization of bacteriocins, as well as to their use in food preservation strategies. These biopreservatives can be used in a number of ways in food systems, and application of bacteriocins from lactic acid bacteria (LAB) promote the microbial stability of both fermented and non-fermented vegetable food products using bacteriocinogenic strains as starter cultures, protective cultures, or co-cultures and the employment of pure bacteriocins as food additives.
Foods are also considered complex ecosystems in which microbial interactions influence the microbial balance and proliferation of beneficial or harmful bacteria. This can include how these microorganisms can potentially lead to diseases or not.
Developments in food processing and the researches in food ecosystems can provide further understanding in acquiring new sources of bacteriocins and the many genomes that are obtained from it.
|[Photo source : Shutterstock]|