Antibiotic resistance has become a major concern of this world due to misuse and rapid use of antibiotics. This problem causes scientist to find new strategies to combat bacterial pathogens. As many studies have been done for this purpose, phage therapy is mostly discussed topic at present days.
Frederick Twort in 1915 and Fe’lix d’He’relle in 1917 first observed that viruses have antibacterial activities. Since then, phages had been being used against dome bacteria. But due to discovery of antibiotics in 1929 and its rapid emergence in 1940, the concept of phage application died out in west. But in 1980s, bacteriophages attracted new attention due to rapid emergence of multidrug resistant bacteria. Scientist focused on searching new alternatives to these antibibiotics and considered phages to be more potential`for the treatment of bacterial infection, as it has some effective advantages.
In this context, ten foodborne bacterial pathogen have been discussed, that are prevented by several lytic bacteriophages.
10 phage used in the food industry:
BCP-1 phage is used against Bacillus cereus a food poisoning agent causing diarrhea and vomiting. This bacteria is found on various foods such as milk, cheese, cereal, rice, red pepper and fermented food. More than 104 cfu/g of B. cereus can causes contamination in these foods. As BCP-1 is only specific to B. cereus, it can’t inhibit other gram positive or negative strains of bacteria. Therefore, it can’t eradicate other beneficial microorganisms.
2. Esp1-3 and ESP 732-2:
Enterobacter sakazakii is an opportunistic pathogen, causes life-threatening infection in intestine and nervous system with 40-80% mortality rate in infant. This bacterium is mainly found in milk powder and other infant formula. Other food sources for this bacterium are cereal fruits vegetables milk meat and fish. Two phages – ESP 1–3 and ESP 732–1 – cause eradication of E. sakazakii at phage level of 109cfu/ml. As inhibition by phage ESP 1–3 and ESP 732–1 occurs at 24°C and at any temperature respectively, phage ESP 732–1 has greater effectiveness than phage ESP 1–3.
3. Cocktail BEC8:
Escherichia coli O157:H7 is one of the major foodborne bacterial pathogen, causing contamination of green leafy vegetables and fruits. It causes human gastrointestinal disease by consuming these vegetables and foods. The phage cocktails BEC8 – consist of eight phages – has a great effect on E. coli O157:H7. But on the combination of trans-cinnamaldehyde with BEC8, it gives much more impact to eradicate E. coli. The mixture of BEC8 and trans-cinnamaldehyde, applied on lettuce and spinach surface, causes inhibition of pathogens by 5cfu/leaf within 10 min to 1 hours. But on individual treatment, BEC8 and TC can causes reduction by 1cfu and 3cfu per leaf after one day at below 8°C temperature.
Listeria monocytogenes, a major food borne pathogen causes meningitis and septicemia, and it often causes fatal death. Cheese is one of the major foods contaminated by this bacterium. Chesee specially soft cheese are good media for listeria growth. A lytic bacteriophage A511 can inhibit the growth of L. monocytogenes on cheese during its production and ripening phase. The host range of this phage is limited to listeria genus. That is; they are specific to Listeria monocytogenes along with other species of listeria genus. The potentiality of the phage is highest when microbial load is at 100cfu/cm2 or below. The phage can reduce the microbes level on the surface of the cheese from 100cfu/cm2 to 1cfu/cm2.
Salmonellosis, a common intestinal infection is caused by Salmonella spp. This disease includes diarrhea, vomiting, abdominal pain, chills, fever and headache etc. Salmonella is mainly found on raw milk, cheese, raw meat, raw eggs, fruits and vegetables. Phage SJ2 is used on cheese to control S. enteritidis. This treatment causes the reduction of Salmonella by 1 to 2 log in raw and pasteurized milk cheeses within 24h after addition of phages.
6. SD-11, SF-A2,SS-92:
The genus Shigella, a food borne bacterial pathogen comprises four type of species: S. flexneri, S. dysenteriae, S. sonnei, and S. boydii. This genera causes severe intestinal infection called shigellosis. The symptoms of this disease includes diarrhea (sometimes bloody diarrhea), fever and abdominal pain. Shigella phages (SD-11, SF-A2,SS-92) are applied to control these pathogens. Although single phages or a phage cocktail may be applied, more phages (3 × 108 pfu/g) have a greater efficacy. Phage cocktail can decrease the pathogen level by upto 2 log cycle within 48 hours, while all pathogens are eradicated at 72hrs with phage cocktail treatment.
7. Phi 88, Phi 35:
S. aureus is one of the major cause of outbreaks occurred by consuming milk cheese, and other dairy product. A little concentration of 103 cfu/ml of S. aureus in cheese can produce enterotoxin A, which causes vomiting and diarrhea. A cocktail phage – combination of phi88 and phi35 – can eradicate 3 ×106 cfu/ml of S. aureus from cheese in ultra-high-temperature (UHT).
8. Phage fHe-Yen3-01, fHe-Yen9-01, fHe-Yen9-02, and fHe-Yen9-03:
Yersinia enterocolitica, a common food borne bacterial pathogen causes Yersiniosis, a zoonotic infection, symptoms of which includes septicemia, enterocolitis, fever, bloody diarrhea, abdominal pain and mesenteric lymphadenitis. Four phages (fHe-Yen3-01, and fHe-Yen9-01, fHe-Yen9-02, and fHe-Yen9-03) have been studied to reduce this pathogen from contaminated raw pork, ready to eat pork and milk. This treatment causes the reduction of Y. enterocolitica by 1 to 3 log from contaminated raw pork and 1-2 logs from contaminated kitchen utensils, such as wooden and plastic cutting boards and knives, and artificial hands.
9. Phages phiCP39O and phiCP26F:
C. perfringes is also a causative agent of foodborne disease. It produces enterotoxins during spore formulation causing diarrhea and abdominal cramp. It also produces alpha toxins when poultry is infected with it. Other symptoms occurred by this bacteria includes gas gangrene (clostridial myonecrosis), necrotic enteritis, and gastrointestinal infections in humans. A study showed that two phages -phiCP39O and phiCP26F- cause the reduction of C. perfringes by 3 log cfu/ml, cultured on brain heart infusion agar plates.
Campylobacter jejuni causes human campylobacteriosis symptoms of which include fever, bloody diarrhea, abdominal pain, and malaise. These diseases are occurred by consuming undercooked poultry meat, unpasteurized milk, and contaminated water. A phage phi2 is used to control this pathogen. The phage can eradicate C. jejuni level by ~ 1 log from the surface of poultry skin after the addition of phage phi2.