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Standardization of salt aggregation test for reproducible determination of cell‐surface hydrophobicity with special reference to Staphylococcus species
Author(s) -
Rozoonyi F.,
Szitha Katalin R.,
Hjertén S.,
Wadström T.
Publication year - 1985
Publication title -
journal of applied bacteriology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.889
H-Index - 156
eISSN - 1365-2672
pISSN - 0021-8847
DOI - 10.1111/j.1365-2672.1985.tb03345.x
Subject(s) - staphylococcus aureus , coagulase , bacterial cell structure , chemistry , agglutination (biology) , microbiology and biotechnology , staphylococcus , chromatography , biology , bacteria , antigen , immunology , genetics
The laboratory conditions for reproducible routine determination of staphylococcal cell‐surface hydrophobicity by the salt aggregation test were standardized. Fresh bacterial suspensions standardized to 5 times 10 9 cfu/ml gave the most reproducible results with both Staphylococcus aureus and coagulase‐negative staphylococci. For relatively hydrophobic strains a 5‐min reading time was necessary to detect bacterial aggregation in ammonium sulphate solutions ranging from 0.1 M to 1.5 M, pH 6.8. A × 10 hand lens facilitated reading aggregations. Overnight storage of bacterial suspensions at 20d̀C reduced cell‐surface hydrophobicity of all species, while storage at 4d̀C reduced the hydrophobic nature of Staph. aureus strains. The hydrophobicity of coagulase‐negative staphylococci rarely changed at 4d̀C. A 10‐fold dilution of fresh, standardized bacterial suspensions made it impossible to detect bacterial aggregation in ammonium sulphate solutions even with a hand lens. Under standardized conditions three types of staphylococcal cell aggregations were observed. The first looked like the slide agglutination for O antigens of Enterobacteriaceae, the second resembled H‐agglutination, while the third had a filamentous appearance. These patterns indicated that more than one component might contribute to cell‐surface hydrophobicity of both Staph. aureus and coagulase‐negative staphylococci, or the same component might have different position on the cell surface.