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Medycyna Doświadczalna i Mikrobiologia 2013, 65(3): 149-159

Fenotypowa ocena hydrofobowości powierzchni oraz zdolności do tworzenia biofilmu przez gronkowce koagulazo-ujemne izolowane z zakażeń od noworodków z bardzo małą masą urodzeniową
[Phenotypic evaluation of hydrophobicity and the ability to produce biofilm in coagulase-negative staphylococci isolated from infected very-low-birth-weight newborns]

M. Grzebyk, M. Brzychczy-Włoch, A. Piotrowska, P. Krzyściak, P.B. Heczko, M. Bulanda

Streszczenie

Ocenie poddano powierzchniowe właściwości oraz zdolność do produkcji śluzu i tworzenia biofilmu przez kliniczne izolaty z gatunku Staphylococcus epidermidis oraz Staphylococcus hemolyticus, pochodzące z zakażeń od noworodków z bardzo małą masą urodzeniową. Na podstawie wyników uzyskanych kilkoma metodami fenotypowymi, stwierdzono, że izolaty S. haemolyticus wykazywały statystycznie istotnie silniejszą zdolność do produkcji śluzu oraz tworzenia biofilmu, niż izolaty S. epidermidis.

Abstract

Introduction: Coagulase-negative staphylococci (CNS), particularly Staphylococcus epidermidis and Staphylococcus haemolyticus, are the leading cause of infection among infants with very low birth weight (<1500 g). The most important virulence factor of these pathogens is their ability to form biofilm. The aim of this study was to evaluate the surface properties, the ability to produce slime and biofilm formation of S. epidermidis and S. haemolyticus strains isolated from infections in very low birth weight neonates. Methods: Isolates of S. epidermidis (n=60) and S. haemolyticus (n=38) were obtained from neonates, hospitalized in two neonatal intensive care units in Poland. Cell surface hydrophobicity was determined by autoagglutination test (AA) in 0.9% NaCl and salt aggregation test (SAT) in ammonium sulphate solution. In order to determine the ability to produce slime, Christiensen’s tube test with safranin staining and Congo Red Agar (CRA) test were carried out. The quantitative assessment of biofilm production was determined by crystal violet (CV) assay.Results: Based on the AA test, it was demonstrated that almost all S. epidermidis and S. haemolyticus isolates showed no agglutination in sodium chloride saline. The SAT test indicated that the greatest number of S. epidermidis isolates aggregated in concentration of 2 M, whereas, for S. haemolyticus, it was 0.5 M. In the Christiensen’s method, the largest amount of the S. epidermidis isolates produced a small amount of slime (40%), whereas 68% of the S. haemolyticus isolates produced a large amount of slime. In CRA test, in both species, the most common result was the bacterial culture colour being almost black, which corresponds to low production of biofilm. Quantitative assessment of biofilm production in CV assay revealed that while 97% of the S. heamolyticus isolates produced high levels of biofilm, similar results were observed in only 43% of the S. epidermidis isolates.Conclusions: Based on the results obtained by phenotypic methods, it was demonstrated that the S. haemolyticus isolates showed a statistically significant stronger ability to produce mucus and form biofilm than the isolates of S. epidermidis.

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