Salmonella Enteritidis is amongst the most common causes of foodborne salmonellosis. Multi-drug resistant Salmonella strains has been associated with treatment failures. Plant-derived phytochemicals may be an alternative to antibiotics in combating these bacteria. The purpose of this study is to investigate the antibacterial activity of curcumin, carvacrol and styrax liquidus on S. Enteritidis and S. Enteritidis PT4. Minimum inhibitory concentration (MIC) values of these substances were detected at 1.5, 3, 7.5 and 24 h by broth microdilution method to evaluate their time-dependent antibacterial activities. The findings of the present study showed that MIC values of carvacrol, curcumin and styrax liquids for both S. Enteritidis and S. Enteritidis PT4 were 125.0 μg/mL, 132.5 μg/mL, 31.3 mg/mL for 24 h, respectively. Also, a time-dependent change was observed in the MIC values of curcumin. Carvacrol, curcumin and styrax liquidus can be used to provide antimicrobial effect on S. Enteritidis and S. Enteritidis PT4 in food applications, taking into account the MIC values and contact times.

The aim of this study was to investigate the effects of dry extracts of Urtica dioica, Matricaria chamomilla, and Vitex agnus-castus with high phenolic contents on rumen microbial fermentation as compared with those of monensin, a common ionophore antibiotic, using Rumen Simulation Technique (RUSITEC) under normal and acidosis conditions. The treatments were as follows: negative control (no additive), positive control (5 mg/d monensin), and extracts of U. dioica (500 mg/d), M. chamomilla (500 mg/d), and V. agnus-castus (500 mg/d). Neither the plant extracts nor monensin altered the ruminal pH under normal or acidosis conditions. All the treatments affected total volatile fatty acid (VFA) production, propionate production, and dry matter digestibility (DMD), regardless of the fermentation conditions. All three extracts increased (P<0.05) total VFA production similar to that observed with monensin (P<0.05). M. chamomilla and V. agnus-castus increased propionate production and DMD similar to that obtained with monensin (P<0.05). In contrast to the monensin treatment, all three extracts increased acetate production under normal conditions (P<0.05). Under acidosis conditions, acetate production remained unchanged in the U. dioica and V. agnus-castus treatments, as well as in the monensin treatment. Under both conditions, the acetate-to-propionate (A:P) ratio decreased only in the monensin treatment (P<0.05). U. dioica and M. chamomilla had antiprotozoal effects (P<0.05) similar to those of monensin, regardless of the condition. The NH3-N concentration declined only in the V. agnus-castus treatment under acidosis conditions (P<0.05). Similar to the monensin treatment, lactate concentrations remained unchanged in the V. agnus-castus treatment under both conditions. In conclusion, plant extracts stimulated fermentative activity of rumen microorganisms under normal and acidosis conditions. Although they did not improve ruminal pH, U. dioica and V. agnus-castus extracts had more favorable effects on some fermentation parameters under acidosis conditions.

Nisin is a low molecular weight bacteriocin which is produced by Lactococcus lactis. Literature about the effects of nisin on pure cultures of rumen bacteria is scarce. The objective of the present study was to investigate the comparative effects of nisin and monensin on pure cultures of some Gram-positive and Gram-negative rumen bacteria. The antibacterial activity assays of nisin and monensin were carried out using broth microdilution method in anaerobic conditions. Antibacterial effect of monensin on Gram-positive rumen bacteria was higher than nisin. Ruminococcus albus and Eubacterium ruminantium were the most sensitive bacteria to monensin. Growth of these bacteria was inhibited completely by monensin, at 6 and 12 µg/mL concentrations respectively. Nisin exhibited stimulatory effects on R. albus, E. ruminantium and, Streptecoccus bovis (p<0.05), unlike monensin. Both nisin and monensin showed potential antibacterial activity on Ruminococcus flavefaciens and Butyrivibrio fibrisolvens (p<0.05), although they did not inhibit these bacteria completely. Nisin and monensin also did not show inhibitory effect on Methanobacterium formicicum, however the potential antimicrobial activity of monensin on this methanogen was more evident. Gram-negative rumen bacteria, Megasphaera elsdenii and Fibrobacter succinogenes, were resistant to both of nisin and monesin. It was concluded that the different effects of nisin and monensin particularly on some Gram-positive rumen bacteria may be responsible for their inconsistent effects on ruminal fermentation.

The microflora of the intestinal tract is vital to many physiological functions, mainly fermentation and processing of dietary components, control of intestinal epithelial cell proliferation, development of the immune system, and protection against pathogens. Plant extracts have potential for treatment options that protect commensal or beneficial microflora in the intestines while eliminating pathogens. The aim of the present study was to investigate the influence of Pinus brutia (Turkish red pine) bark extract containing phenolic compounds on some commensal and pathogenic bacteria from the intestinal microflora using a microdilution method. P. brutia bark extract did not completely inhibit any intestinal bacteria. However, the extract showed a potential inhibitor activity on Salmonella Typhimurium and Staphylococcus aureus from 75 µg/mL, on Escherichia coli and Fusobacterium nucleatum from 150 µg/mL, and on Clostridium perfringens from 300 µg/mL concentrations (P<0.05). Commensal bacteria were observed to be less sensitive to the extract than those of the pathogenic strains. The extract stimulated moderately the growth of Bifidobacterium bifidum from 75 µg/mL dose (P<0.05). The extract did not show any activity on Lactobacillus acidophilus. A potential inhibitor activity was observed for Bifidobacterium infantis and Lactobacillus casei at 600-2400 µg/mL (P<0.05). As a conclusion, P. brutia bark extract, at 75-300 μg/mL dose range, had a potential to restrict pathogenic bacteria in the intestines while protect commensal or beneficial ones. Specified effects might be mainly attributed to its polyphenolic content.