Analysis of different genetic traits and their association with biofilm formation in Staphylococcus epidermidis isolates from central venous catheter infections

Abstract

The aim of the present study was to characterize clinical isolates of Staphylococcus epidermidis, one of the bacterial species most often implicated in foreign-body-associated infections, for their ability to form biofilms and for the presence of mecA and IS256 element. Sixty-seven Staphylococcus epidermidis clinical isolates, obtained from implantable medical devices, were investigated. Overall, 70% of the strains were positive for ica operon genes, 85% possessed atlE, and 46% contained aap. In 89% of the population, the Congo red agar test confirmed the correlation between the presence of ica genes and slime expression. Almost all of the strains could be classified as biofilm producers by both the crystal violet assay and microscopy. The bacterial population studied showed a very high frequency of strains positive for mecA as well as for the IS256 element. Although well-structured biofilms have been previously observed only in those strains possessing genes belonging to the ica operon, this study demonstrates that strains lacking specific biofilm-formation determinants can be isolated from catheters and can form a biofilm in vitro. Hence, different and yet-to-be identified factors may work together in the formation and organization of complex staphylococcal microbial communities and sustain infections associated with implanted medical devices.

Slime layer formation and the prevalence of mecA and aap genes in Staphylococcus epidermidis isolates

“…Comparing different studies, there is a similarity between the CRA results and genotype characterization of the Ica locus detected by PCR [17,20]. Since determining slime layer production can lead to the recognition of the biofilm producing staphylococci [11,23], evaluating slime production was considered a key focus for study [20].…”

“…PCR analysis: The collection of isolates was screened for the presence of mecA and aap genes by PCR, using previously described primers as follows [19,20].…”

“…DNA amplification was performed in a thermocycler (Eppendorf, Hamburg, Germany) in a final volume of 50 µl: containing 10 µl of 10X PCR buffer; 3.5 µl of Mgcl2 (10mM); 0.2mM dNTPmix; 20 ρM of each primer;1U of Taq polymerase (Fermentas, Opelstrasse, Germany); and 4 µl of template DNA. Amplification was performed by denaturation at 97°C for 6 minutes (first denaturation), followed by 35 cycles according to the following program: denaturation at 92°C for 30 seconds, annealing at 55°C for 30 seconds, and an extension at 72°C for 45 seconds plus a final extension at 72°C for 10 minutes [19,20].…”

“…PCR products were resolved by electrophoresis through a 1% agarose gel containing ethidium bromide [20]. DNA molecular weight standard 100 bp (Fermentas, Opelstrasse, Germany) was used as the marker (Figure 1).…”

Baroinactivation of Staphylococcus epidermidis - mathematical model and its verification using human and cow milk

“…According to Petrelli et al (2006), these microorganisms can create a biofilm on the surface of medical implants and contribute to the proliferation of staphylococci colonies on such devices.…”