Interaction of Salmonella typhimurium and Salmonella enteritidis with polystyrene does not correlate with virulence in young chickens

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 tounderstanding 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 ofeither 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 (

Microbial Fuel Cells and Microbial Ecology: Applications in Ruminant Health and Production Research

Microbial fuel cell (MFC) systems employ the catalytic activity of microbes to produce electricity from the oxidation of organic, and in some cases inorganic, substrates. MFC systems have been primarily explored for their use in bioremediation and bioenergy applications; however, these systems also offer a unique strategy for the cultivation of synergistic microbial communities. It has been hypothesized that the mechanism(s) of microbial electron transfer that enable electricity production in MFCs may be a cooperative strategy within mixed microbial consortia that is associated with, or is an alternative to, interspecies hydrogen (H2) transfer. Microbial fermentation processes and methanogenesis in ruminant animals are highly dependent on the consumption and production of H2in the rumen. Given the crucial role that H2 plays in ruminant digestion, it is desirable to understand the microbial relationships that control H2 partial pressures within the rumen; MFCs may serve as unique tools for studying this complex ecological system. Further, MFC systems offer a novel approach to studying biofilms that form under different redox conditions and may be applied to achieve a greater understanding of how microbial biofilms impact animal health. Here, we present a brief summary of the efforts made towards understanding rumen microbial ecology, microbial biofilms related to animal health, and how MFCs may be further applied in ruminant research

Cultivation in different growth media affects the expression of the cell surface hydrophobicity of bacteria

Environmental factors may greatly influence the expression of cell surface components of bacterial pathogens. Few studies have described the effect of growth conditions on the cell surface hydrophobicity of bacterial isolates of certain Gramnegative and Gram-positive bacteria. The present study describes the effects of CUltivation in four common liquid growth media on the cell surface hydrophobicity of non-clinical Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus using the microbial adhesion to hydrocarbon (MATH) test which assesses the partition of bacterial cells into a hydrocarbon phase. It was observed that growth in all the test media yielded cells with varying surface hydrophobicity increasing in the order: nutrient broth&lt;tryptic soy broth&lt;brain heart infusion broth&lt;MacConkey broth, irrespective of the test strain. The changes were however, more pronounced in the Gram-positive strain. It was also observed that the surface of Staphylococcus aureus was more hydrophobic than that of Escherichia coli, irrespective of the cultivation media. The outcome of this work further point to the fact that environmental changes can influence cell surface hydrophobicity of bacteria which in turn can affect their adhesion to certain kinds of host targets through hydrophobic interactions.Key words: Hydrophobicity; Escherichia coli; Staphylococcus aureus; Growth medi

Survivability of Salmonella typhimurium L1388 and Salmonella enteritidis L1225 under stressful growth conditions

In an earlier study with Salmonella typhimurium L1388 (ST) and Salmonella enteritidis L1225 (SE) isolated from diseased chickens, we found that SE formed more biofilm than ST on abiotic surfaces in a time-dependent manner. Since the ability of salmonellae to survive extreme environment is related to their virulence, the present study examined the survival of Salmonella typhimurium L1388 and Salmonella nteritidis L1225 under the usual stresses that salmonellae encounter during their life cycle. This is with a view to understanding the strains’ stress tolerance that could be used to explain their virulence. Incubation at 37oC for various time periods was done for: i) stationary phase (SP) cells at pH 2.6; ii) log-phase (LP) cells at pH 4.0; log-phase or stationary phase cells in broth containing iii) hydrogen peroxide, iv) sodium chloride and v) ethanol; vi) stationary phase cells in Hank’s balanced salt solution (single strength) containing 10% human serum; and vii) prolong stationary phase cells. Stationary phase cells were also incubated at 52oC for 15 min. Surviving cells at the various incubation times were counted on trypticase soy agar (TSA) after appropriate dilution in saline and overnight incubation at 37oC. Growth iron-poor medium was determined by growing a single bacterial colony in Medium A with shaking at 37oC or 40oC for 24 h. Statistics was done by one-way analysis-of-variance (ANOVA) at P = 0.05. Differences in the survival of ST and SE were insignificant (p>0.05) in acid pH at both pH 4.0 (p = 0.3783) and pH 2.6 (p = 0.4711); at high salinity for log-phase (p = 0.1416) and stationary phase (p = 0.1816) cells; in ethanol (p = 0.5984), human serum (p = 0.8139), prolonged stationary phase (p = 0.3506); and under heat (p = 0.5766). SE was significantly (p<0.05; p = 0.0031) more tolerant to oxidative-killing by hydrogen peroxide. Culturable growth of the ST and SE in an iron-poor medium A revealed insignificant differences at 37oC (p = 0.8381) but marginally significant at 40oC (p = 0.0508). Thus, with the exception of survival in hydrogen peroxide, SE had similar response pattern with ST to the usual stresses that salmonellae encounter during their life cycle, despite the former’s preferential ability to form biofilm on abiotic surfaces. The relationship between the observed enhanced ability of SE to survive in hydrogen peroxide and virulence need to be investigated in subsequent study