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Salmonella, a bacterial foodborne pathogen, can contaminate meat, milk, and vegetables. While appropriate measures are available to control Salmonella, the inhibitory phytochemicals from plants are gaining increased attention. Punicalagin, a natural antimicrobial, is one of the main active tannins isolated from Punica granatum L. To obtain a broader understanding of the effect of punicalagin on the cell membranes of Salmonella Typhimurium, the growth curves, extracellular potassium concentration, release of cell constituents, intracellular pH, membrane potential, and morphological features were characterized to elucidate the mechanisms of action. Treatment with punicalagin induced an increase in the extracellular concentrations of potassium and a release of cell constituents. A higher pH gradient, an increase in the intracellular pH, and cell membrane depolarization were observed after punicalagin treatment. Electron microscopy observations showed that the cell membrane structures of Salmonella Typhimurium were damaged by punicalagin. It is concluded that punicalagin inhibits the proliferation of Salmonella Typhimurium and destroys the integrity of the cell membrane, leading to a loss of cell homeostasis. These findings indicate that punicalagin has the potential to be developed as a future alternative to control Salmonella Typhimurium contamination in foods and reduce the risk of salmonellosis.

The aim of this study was to determine the prevalence and antimicrobial susceptibility of Escherichia coli in retail whole chicken in the People 9 s Republic of China. Five hundred seventy-six raw whole chicken samples, randomly purchased from 146 farmers' markets or supermarkets in four provinces from March through December 2010, were analyzed for E. coli contamination, and the E. coli isolates were further tested for the presence of virulence genes and antimicrobial susceptibility. The overall positive rate for E. coli in retail chicken was 69.1%. E. coli prevalence was the highest in Beijing (86.8%), followed by Henan province (78.5%), Shaanxi province (65.3%), and the lowest prevalence was found in Sichuan province (45.8%). Among 398 isolates recovered, only the eae gene was detected in one isolate; no other virulence genes were detected. Resistance was most common to tetracycline (84.4%), followed by nalidixic acid (74.1%), ampicillin (71.1%), trimethoprim-sulfamethoxazole (70.1%), amoxicillin-clavulanic acid (68.8%), and streptomycin (58.5%). Lower resistance was detected to chloramphenicol (43.7%), kanamycin (42.7%), ciprofloxacin (30.2%), gentamicin (29.4%), cefoperazone (13.6%), amikacin (12.6%), gatifloxacin (8%), and cefoxitin (7.8%). Only 3.8% of the isolates were susceptible to all tested antimicrobials. Six percent of the isolates displayed resistance to one antimicrobial, 6.3% to two, and 83.9% to three or more of the antimicrobials. Our findings indicate that retail chicken in China was commonly contaminated with E. coli, and many E. coli strains exhibited multiple drug resistance. The implementation of good manufacturing practices throughout the poultry production chain is necessary to reduce E. coli contamination in retail chicken, and the prudent use of antibiotics is imperative in poultry production in China.

Pomegranate rind is rich in tannins that have remarkable antimicrobial activities. This study aimed to evaluate the effects of a tannin-rich fraction from pomegranate rind (TFPR) on Listeria monocytogenes virulence gene expression and on the pathogen's interaction with human epithelial cells. Growth curves were monitored to determine the effect of TFPR on L. monocytogenes growth. The 3-(4,5-dimethylthiazol-2-yl)2,5-diphenyltetrazolium bromide and fluorescence staining assays were used to examine the cytotoxicity of TFPR. The effects of TFPR on L. monocytogenes adhesion to and invasion of epithelial cells were investigated using Caco-2 cells. Real-time quantitative PCR analysis was conducted to quantify mRNA levels of three virulence genes in L. monocytogenes. Results showed that a MIC of TFPR against L. monocytogenes was 5 mg/ml in this study. TFPR exhibited cytotoxicity against Caco-2 cells when the concentration was 2.5 mg/ml. Subinhibitory concentrations of TFPR significantly reduced, in a dose-dependent manner, adhesion to and invasion of Caco-2 cells by L. monocytogenes. When L. monocytogenes was grown in the presence of 2.5 mg/ml TFPR, the transcriptional levels of prfA, inlA, and hly decreased by 17-, 34-, and 28-fold, respectively.