Abstract
Escherichia coli and Staphylococcus aureus are two food pathogens that cause severe food poisonings. Another problem found on a global level is the continuous increase of antimicrobial resistance in bacteria isolated from food. This study aimed to evaluate the antibacterial activity of Lactobacillus plantarum against pathogenic bacteria including E. coli and S. aureus and to study if L. plantarum with antibacterial activity contained the most plantaricin genes or not. A total of 50 lactic acid bacteria isolates (LAB) were evaluated for antibacterial activity and identified plantaricin genes by polymerase chain reaction (PCR) methods. Seven LAB isolates with antibacterial activity against S. aureus and E. coli were identified as Lactobacillus based on morphological physiological and biochemical properties. Using species-specific PCR and 16S rRNA gene sequencing, B0039 was identified as Lactobacillus paracasei, other isolates were identified as L. plantarum. 3 strains tested positive for all the genes in the plnABCD operon. The plnEFI operon was detected in four strains. Genes encoding for the two-peptide plnJ/K were detected only in 2 strains. Finally, the plnG/V was also found in 3 strains of L. plantarm. The plantarum gene sequences of B0055 were 97 to 100% similarity with the L. plantarum WCFS1. The findings suggest that LAB with bacteriocin genes can be used as an alternative mechanism to control drug resistant foodborne pathogens. Key worlds: Lactobacillus, antibacterial activity, plantaricin gene, Staphylococcus aureus, Escherichia coli.
Highlights
IntroductionMany food-poisoning outbreaks of E. coli have been associated with contaminated food, such as beef, pork, chicken and water (Wang, 2008)
This study aimed to evaluate the antibacterial activity of Lactobacillus plantarum against pathogenic bacteria including E. coli and S. aureus and to study if L. plantarum with antibacterial activity contained the most plantaricin genes or not
Antimicrobial activity reduced after addition of pepsin on the spent cell-free supernatant (SCS) of lactic acid bacteria isolates (LAB), the reduction of diameters of inhibition zones against E. coli and S. aureus ranged between 2 and 7 mm (Table 3)
Summary
Many food-poisoning outbreaks of E. coli have been associated with contaminated food, such as beef, pork, chicken and water (Wang, 2008). S. aureus may produce a number of toxins, the most important ones with respect to foodborne illness belong to the family of heat-stable staphylococcal enterotoxins (SEs). Another public health concern is associated with the increased incidence of antibiotic-resistant strains isolated from poultry meat (Dan et al, 2015). As more bacteria become resistant to traditional antibiotics, this leads to emergence and re-emergence of multidrugresistant pathogens
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