Abstract

Salmonella typhimurium and Salmonella enteritidis are the most frequently isolated serotypes in human and animal Salmonella infections. The in vitro surface colonization characteristics of S. typhimurium L1388 and S. enteritidis L1225 on hydrophobic surfaces were assessed with a view to understanding their surface preference in relation to in vivo virulence. Although both S. typhimurium and S. enteritidis preferentially colonized polystyrene under normal nutrient-rich growth medium, S. typhimurium formed significantly (P < 0.05: P = 0.000008) smaller amounts of biofilm than S. enteritidis. The biofilm formed on polystyrene was optimum at different times, 200 min and 400 min for S. enteritidis and S. typhimurium, respectively. S. typhimurium also formed significantly (P < 0.05) less biofilm than S. enteritidis when the growth medium was supplemented with 100 mM each of either D-(+)-mannose (P = 0.0001), D-(+)-glucose (P = 0.0005), D-(-)-mannitol (P = 0.00002) or xylose (P = 00009). Biofilms formed by S. enteritidis following growth in sugar-supplemented medium were not significantly different from that following growth in non-supplemented medium; but significant (P < 0.05) reduction in amounts of biofilm formed by S. typhimuriumwere produced by only mannitol (P = 0.0008) and xylose (P = 0.00004). Growth in sodium chloride-supplemented medium resulted in significantly (P < 0.05) less biofilm formed by both S. typhimurium (P = 0.0084) and S. enteritidis (P = 0.0002); even though the quantity formed by S. typhimuriumwas significantly (P < 0.05: P = 0.0098) more than that by S. enteritidis. Both strains formed significantly less biofilm on polystyrene when cultured in a starvation medium for 24 h. They also do not differ significantly from each other in their extent of adherence to polystyrene and 14-day chick mortality. Overall, the interaction of S. typhimurium and S. enteritidis with polystyrene does not correlate with virulence in young chickens.

Key words: Biofilm, Salmonella typhimurium, Salmonella enteritidis, chickens, surface.