Biofilm formation may be an independent virulence factor in wild-type Staphylococcus saprophyticus strain 7108 in contrast to wild-type strain CCM 883

Abstract number: 1732_111

Szabados F., Strate K., Kaase M., Sakinc T., Anders A., Gatermann S.

S. saprophyticus is second only to E. coli the most important causative organism of uncomplicated urinary tract infection in young female outpatients. Compared to S. aureus and S. epidermidis only very few virulence factors in S. saprophyticus have been described, for example Ssp, a surface-associated lipase, Aas, an autolysin adhesin, SdrI, a collagen binding protein, and urease activity. Purportedly, the uropathogenicity of S. saprophyticus can be attributed to its ability to cope with the high range of variation in salt- and urea-concentration in human urine.

The aim of this study was to elucidate virulence factors of uropathogenicity.

Methods: Bacterial growth was examined under different conditions using a modified model of artificial urine as previously described. Bacterial aggregation was observed in bright light and electron micrographs. Biofilm formation was tested using native polystyrene and crystalline pre-coated microtiter plates.

Results: In S. saprophyticus strain CCM 883, in contrast to wild-type strain 7108, generation-time was increased. In S. saprophyticus wild-type strains 7108 and 9325, bacterial aggregation appeared near large crystal structures in contrast to its urease negative derivative strain GJ1187 and the wild type strain CCM 883. In native polystyrene and crystalline pre-coated microtiter plates, biofilm formation was observed in strain 7108 in contrast to strain CCM 883. The biofilm formation in S. saprophyticus seems independent of agr-, Ssp-, SdrI, since no difference between knockout mutants to wild type strain was observed.

Conclusion: Bacterial aggregation could be due to increased adhesion. The lipase activity may modulate hydrophobicity and Ca2+ binding. Higher local Ca2+ concentration, as well as strengthened bacterial aggregation, may lead to increased crystal formation. Bacteria may adhere to crystals, additionally to the later mechanism due to biofilm formation. In crystallisation process, bacteria were embedded into the crystal structure. This may be a new model of infectious stone genesis. This study strongly suggest that S. saprophyticus wild-type strain CCM 883 lacks important virulence factors in contrast to wild-type strain 7108 and biofilm formation may play an important role in S. saprophyticus urinary tract infection.

Session Details

Date: 31/03/2007
Time: 00:00-00:00
Session name: European Society of Clinical Microbiology and Infectious Diseases
Location: ICC, Munich, Germany
Presentation type:
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