Growth Conditions Influence Expression of Cell Surface Hydrophobicity of Staphylococci and Other Wound Infection Pathogens

Abstract

The initial adhesion of microbes to tissue and solid surfaces can be mediated by hydrophobic interaction. Expression of microbial cell surface hydrophobicity (CSH) is influenced by growth conditions, and often best expressed after growth under nutrient-poor conditions, or "starvation." In the present study, the CSH of 133 strains of Enterobacteriaceae, Staphylococcus aureus, coagulase-negative staphylococci, Enterococcus faecalis, group A streptococcus, Pseudomonas aeruginosa, Clostridium perfringens, Bacteroidesfragilis, Peptococcus magnus, and of 8 Candida albicans strains was measured by the salt aggregation test after growth on hematin agar in a 5% CO2 atmosphere, or under anaerobiosis. Cells of all but 8 strains expressed pronounced or moderate CSH, i.e., they aggregated in 0.01-2 M ammonium sulfate. When the agar surface was covered by human serum (diluted 1:5) to mimic growth conditions in a wound, 94 strains expressed higher CSH, and 44 strains the same CSH as after growth without serum. The CSH of 12 strains of different species was measured after growth on blood, hematin and PDM agar, with or without serum, and in an aerobic or a 5% CO2 atmosphere. The highest CSH was expressed after growth in 5% CO2 with serum, and the lowest growth after on blood agar in aerobic atmosphere. Identical results were obtained with native and heat-inactivated (56 C, 20 min) serum. The reduced surface tension obtained in 5% CO2, as well as yet unidentified serum factors, promotes expression of CSH.

Influence of the growth medium, suspending liquid and measurement temperature on the physico-chemical surface properties of two enterococci strains

“…From the results of hydrophobicity at both temperatures determined by the MATH method (Table 2), it was found that hydrophobicity increased with respect to the control sample when the culture medium was supplemented with serum and decreased if supplemented with urine. This behaviour is similar to that described by water contact angles (Table 4) at 37 ± C but not at 22 ± C. The effect of serum on the hydrophobicity of the cell surface of enterococci is in agreement with the results obtained by Ljungh and Wadstrom [23] when determining the hydrophobicity of different microorganisms (among them E. faecalis) grown with serum. Nevertheless, these authors could not attribute the phenomenon to a speci c serum component.…”

Binding of von Willebrand factor by coagulase-negative staphylococci

“…Generally, bacteria grown on solid media bound rvWF to a greater extent than after growth in liquid media. Nutrient-poor conditions, which promote microbial adhesion to tissue or solid surfaces, did not enhance binding of all species [35]. In the present study 14 Staphylococcus strains, including reference strains, were tested for binding of soluble rvWF, and they all bound rvWF to varying extents.…”

The study of the sterilization effect of gamma ray irradiation of immobilized collagen polypropylene nonwoven fabric surfaces

“…The bacteria concentration in the standard solution was maintained at around 10 8 bacteria/mL. 30 The collagen-bonding samples were incubated with the bacteria solution for 30 min, and then those samples were exposed under varied gamma ray exposure doses. After gamma ray irradiation, the samples were incubated under a controlled atmosphere and observed after 24 h to evaluate their colony formation.…”