A number of these studies used strains of Lactobacillus plantarum. For example, L. plantarum CGMCC 1258 was able to lessen

the negative impact of enteroinvasive Escherichia coli ATCC 43893 serotype O124:NM on TEER (Qin et al., 2009), L. plantarum 299v mitigated the TNF-α-induced decrease in TEER (Ko et al., 2007) and L. plantarum MF1298 attenuated the decrease in TEER induced by Listeria monocytogenes 6896 (Klingberg et al., 2005). The aim of this research was to identify lactobacilli isolates, with an emphasis on L. plantarum, that enhance TEER and therefore have the potential to be used as probiotics targeted at improving PLX-4720 intestinal barrier function. Eight commercially used probiotics were compared to determine which had the greatest positive effect on TEER across intestinal epithelial cell layers, and then the best probiotic was used as a benchmark to evaluate several isolates,

including four L. plantarum strains and 15 human oral isolates. The oral cavity was chosen as a source of potential probiotics because evidence suggests that lactobacilli PLX3397 found in human faeces, and therefore present in the intestines, originate from the oral cavity (Dal Bello & Hertel, 2006; Maukonen et al., 2008). The isolate with the greatest positive effect on TEER was further investigated to evaluate its suitability Masitinib (AB1010) for use as a probiotic, including its ability to tolerate gastrointestinal conditions, to

adhere to intestinal epithelial cells and affect adherence and TEER of enteropathogenic E. coli (EPEC) O127:H6 (E2348/69), a known enteric pathogen (Baldini et al., 1983), during coculture. The source of the bacterial strains used in this study is described in Table 1. Eight commercially used probiotics were chosen on the basis that there were published data showing their efficacy in various in vitro and in vivo models (Table 1). Further strains were either L. plantarum obtained from the Deutsche Sammlung von Mikroorganismen (DSM) or human oral lactobacilli isolates. Human oral isolates were obtained from the mouth lining, tongue and teeth of volunteers using sterile tooth picks, which were incubated individually in 10 mL of Man, Rogosa and Sharpe (MRS) broth overnight at 37 °C (5% CO2) to select for lactic acid bacteria. Cultures were diluted in phosphate-buffered saline (PBS, pH 7.2), plated onto Rogosa agar and incubated in 5% CO2 at 37 °C for 48 h to select for lactobacilli. Putative L. plantarum strains with large white colonies similar to those of known L. plantarum strains were subcultured onto fresh Rogosa agar and incubated at 37 °C (5% CO2) for 48 h. Sample colonies were stored as glycerol stocks at −85 °C. Isolates were identified based on their 16S rRNA gene sequences.