Salmonella enterica is one of the most ubiquitous enteropathogenic bacterial species on earth, and comprises more than 2500 serovars. Widely known for causing non-typhoidal foodborne infections (95%), and enteric (typhoid) fever in humans, Salmonella colonizes almost all warm- and cold-blooded animals, in addition to its extra-animal environmental strongholds. The last few decades have witnessed the emergence of highly virulent and antibiotic-resistant Salmonella, causing greater morbidity and mortality in humans. The emergence of several Salmonella serotypes resistant to multiple antibiotics in food animals underscores a significant food safety hazard. In this review, we discuss the various antibiotic-resistant Salmonella serotypes in food animals and the food supply, factors that contributed to their emergence, their antibiotic resistance mechanisms, the public health implications of their spread through the food supply, and the potential antibiotic alternatives for controlling them.

The emergence of antibiotic resistance in pathogenic bacteria has led to renewed interest in exploring the potential of plant-derived antimicrobials (PDAs) as an alternative therapeutic strategy to combat microbial infections. Historically, plant extracts have been used as a safe, effective, and natural remedy for ailments and diseases in traditional medicine. Extensive research in the last two decades has identified a plethora of PDAs with a wide spectrum of activity against a variety of fungal and bacterial pathogens causing infections in humans and animals. Active components of many plant extracts have been characterized and are commercially available; however, research delineating the mechanistic basis of their antimicrobial action is scanty. This review highlights the potential of various plant-derived compounds to control pathogenic bacteria, especially the diverse effects exerted by plant compounds on various virulence factors that are critical for pathogenicity inside the host. In addition, the potential effect of PDAs on gut microbiota is discussed.

SUMMARY. Salmonellaenterica serovar Enteritidis and Campylobacter jejuni are 2 major foodborne pathogens transmitted through poultry products. These pathogens

The efficacies of trans -cinnamaldehyde (TC) and eugenol (EG) for reducing Salmonella enterica serovar Enteritidis colonization in broiler chickens were investigated. In three experiments for each compound, 1-day-old chicks ( n = 75/experiment) were randomly assigned to five treatment groups ( n = 15/treatment group): negative control (-ve S . Enteritidis, -ve TC, or EG), compound control (-ve S . Enteritidis, +ve 0.75% [vol/wt] TC or 1% [vol/wt] EG), positive control (+ve S . Enteritidis, -ve TC, or EG), low-dose treatment (+ve S . Enteritidis, +ve 0.5% TC, or 0.75% EG), and high-dose treatment (+ve S . Enteritidis, +ve 0.75% TC, or 1% EG). On day 0, birds were tested for the presence of any inherent Salmonella ( n = 5/experiment). On day 8, birds were inoculated with ∼8.0 log ₁₀ CFU S . Enteritidis, and cecal colonization by S . Enteritidis was ascertained ( n = 10 chicks/experiment) after 24 h (day 9). Six birds from each treatment group were euthanized on days 7 and 10 after inoculation, and cecal S . Enteritidis numbers were determined. TC at 0.5 or 0.75% and EG at 0.75 or 1% consistently reduced ( P < 0.05) S . Enteritidis in the cecum (≥3 log ₁₀ CFU/g) after 10 days of infection in all experiments. Feed intake and body weight were not different for TC treatments ( P > 0.05); however, EG supplementation led to significantly lower ( P < 0.05) body weights. Follow-up in vitro experiments revealed that the subinhibitory concentrations (SICs, the concentrations that did not inhibit Salmonella growth) of TC and EG reduced the motility and invasive abilities of S . Enteritidis and downregulated expression of the motility genes flhC and motA and invasion genes hilA , hilD , and invF . The results suggest that supplementation with TC and EG through feed can reduce S . Enteritidis colonization in chickens.