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ABSTRACT: To investigate the relative role of the red dry and rough (rdar) and brown dry and rough (bdar) morphotypes on hydrophobicity and ability to attach to abiotic surfaces of poultry-associated Salmonella strains with a focus on S. Sofia.
Cellulose synthase gene null mutants were constructed in five Salmonella strains converting them from rdar to bdar morphotypes. One S. Sofia null mutant displayed reduced hydrophobicity and attachment to Teflon® relative to its parent strain. The S. Virchow and S. Infantis null mutants attached less well to glass relative to their parent strains.
The rdar or bdar morphotype may influence S. Sofia persistence but did not explain why bdar strains predominate in this serotype.
This work provides some insight into why some Salmonella strains survive in poultry environments and may ultimately contribute to their control.
Letters in Applied Microbiology 09/2011; 53(5):581-4. · 1.62 Impact Factor
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ABSTRACT: Salmonella can adhere to poultry and food contact surfaces and persist to cause diseases. Adhesion of Salmonella Sofia (n = 14), S. Typhimurium (n = 6), S. Infantis (n = 3) and S. Virchow (n = 2) to Teflon, stainless steel, glass, rubber and polyurethane were assayed using epifluorescence microscopy. Surface free energies of bacteria and materials were calculated using contact angle values and interfacial free energy between isolates and materials determined. Surface roughness of the materials was analysed using atomic force microscopy. S. Sofia isolates adhered in higher numbers (P < 0.05) to all materials compared to other serovars. The mean number of cells of S. Sofia isolates attaching to Teflon were significantly higher (P < 0.05) compared to all materials except stainless steel (P > 0.05). Mean roughness values ranged from 82.26 nm (Teflon) to 1.34 nm (glass). Correlations between the apolar component of the surface free energy of materials (gamma(S)(LW)) and bacterial adhesion (R(2) = 0.80), and between gamma(S)(LW) and the surface roughness of the materials (R(2) = 0.71) were found. Materials more positive in interfacial free energies had the highest number of adhering bacteria. Generalised surface property measurements were found to be useful in characterising Salmonella attachment but the degree of variability in results suggests that other factors, such as flagella or membrane proteins, could also contribute.
Food Microbiology 12/2009; 26(8):853-9. · 3.28 Impact Factor
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ABSTRACT: Salmonella enterica is one of the most important foodborne pathogens. Salmonella enterica subsp. II 4,12:b:- (Salmonella Sofia) is commonly found in Australian poultry. It has been suggested that physicochemical properties such as surface charge and hydrophobicity may affect bacterial attachment to surfaces and their ability to persist in food systems. A possible link between hydrophobicity cell surface charge and persistence of Salmonella from the poultry system was examined. Hydrophobicity of Salmonella Sofia (n = 14), Salmonella Typhimurium (n = 6), Salmonella Infantis (n = 3), and Salmonella Virchow (n = 2) was assayed using hydrophobic interaction chromatography, bacterial adherence to hydrocarbons (BATH), using xylene or hexadecane, and the contact angle method (CAM). Cellular surface charge (CSC) of the isolates was determined using zeta potential measurements. The majority (12 of 14) of Salmonella Sofia isolates were found to be hydrophobic when assayed using BATH with xylene, except isolates S1635 and S1636, and the other serovars were found to be hydrophilic. Salmonella Sofia isolates were not significantly different (P > 0.05) from isolates of other serovars as measured by hydrophobic interaction, BATH with hexadecane, or the CAM. No significant differences (P > 0.05) in zeta potential measurements were observed between isolates. Principal component analysis using results from all four measures of hydrophobicity allowed clear differentiation between isolates of the serovar Salmonella Sofia (except S1635 and S1636) and those of other Salmonella serovars. Differences in physicochemical properties may be a contributing factor to the Salmonella Sofia serovar's ability to attach to surfaces and persist in a food system.
Journal of food protection 12/2008; 71(12):2421-8. · 1.94 Impact Factor
