Abstract
BackgroundMotility is an important component of Salmonella enterica serovar Typhimurium (ST) pathogenesis allowing the bacteria to move into appropriate niches, across the mucus layer and invade the intestinal epithelium. In vitro, flagellum-associated motility is closely related to the invasive properties of ST. The probiotic yeast Saccharomyces boulardii BIOCODEX (S.b-B) is widely prescribed for the prophylaxis and treatment of diarrheal diseases caused by bacteria or antibiotics. In case of Salmonella infection, S.b-B has been shown to decrease ST invasion of T84 colon cell line. The present study was designed to investigate the impact of S.b-B on ST motility.Methodology/Principal FindingsExperiments were performed on human colonic T84 cells infected by the Salmonella strain 1344 alone or in the presence of S.b-B. The motility of Salmonella was recorded by time-lapse video microscopy. Next, a manual tracking was performed to analyze bacteria dynamics (MTrackJ plugin, NIH image J software). This revealed that the speed of bacterial movement was modified in the presence of S.b-B. The median curvilinear velocity (CLV) of Salmonella incubated alone with T84 decreased from 43.3 µm/sec to 31.2 µm/sec in the presence of S.b-B. Measurement of track linearity (TL) showed similar trends: S.b-B decreased by 15% the number of bacteria with linear tract (LT) and increased by 22% the number of bacteria with rotator tract (RT). Correlation between ST motility and invasion was further established by studying a non-motile flagella-deficient ST strain. Indeed this strain that moved with a CLV of 0.5 µm/sec, presented a majority of RT and a significant decrease in invasion properties. Importantly, we show that S.b-B modified the motility of the pathogenic strain SL1344 and significantly decreased invasion of T84 cells by this strain.ConclusionsThis study reveals that S.b-B modifies Salmonella's motility and trajectory which may account for the modification of Salmonella's invasion.
Highlights
A wide range of antibiotics are used to treat human salmonellosis
Real time computer tracking has been already used to assess the motility of Rhodobacter sphaeroides, Rhodospirullum rubrum and Salmonella Typhimurium [24]
In the present study we used a 2D-time-lapse video microscopy to record bacterial movements in cultures of human colonic T84 cells infected by Salmonella Typhimurium alone or in the presence of the probiotic yeast strain S.b-B
Summary
A wide range of antibiotics are used to treat human salmonellosis. Development of new strategies to prevent or treat infectious diseases has become crucial and targeting of the physical properties of bacteria can constitute such a new strategy. In case of intestinal pathogenic bacteria, the combination of motility and chemotaxis enables bacteria to detect and pursue nutrients, and to reach their preferred niches for colonization. For instance the intestinal epithelium is covered with mucus glycocalyx, motility likely enables bacteria to pass through and reach enterocytes. In case of enteropathogenic bacteria, motility and chemotaxis have been studied primarily using Escherichia coli and Salmonella enterica serovar Typhimurim [5,6]. Motility is an important component of Salmonella enterica serovar Typhimurium (ST) pathogenesis allowing the bacteria to move into appropriate niches, across the mucus layer and invade the intestinal epithelium. The present study was designed to investigate the impact of S.b-B on ST motility
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