Effect of daptomycin and vancomycin on Staphylococcus epidermidis biofilms: An in vitro assessment using fluorescence in situ hybridization

Colonization of in-dwelling catheters by microbial biofilms is a major concern in patient health eventually leading to catheter-related blood stream infections. Biofilms are less susceptible to standard antibiotic therapies that are effective against planktonic bacteria. Standard procedure for the detection of microorganisms on the catheter tip is culture. However, viable but non-culturable cells (VBNCs) may be missed. The aim of this study was to evaluate the use of fluorescence in situ hybridization (FISH) as an indicator to visualize and quantify the effect of the antibiotics daptomycin and vancomycin on biofilms in situ. We established an in vitro catheter biofilm model of Staphylococcus epidermidis biofilms on polyurethane catheters. Biofilm activity was measured by FISH and correlated to colony forming units (CFU) data. Digital image analysis was used for quantification of total biofilm mass and the area of the FISH positive biofilm cells. FISH showed a pronounced effect of both antibiotics on the biofilms, with daptomycin having a significantly stronger effect in terms of both reduction of biofilm mass and number of FISH-positive cells. This supports the anti-biofilm capacity of daptomycin. Interestingly, neither antibiotic was able to eradicate all of the FISH-positive cells. In summary, FISH succeeded in visualization, quantification, and localization of antibiotic activity on biofilms. This technique adds a new tool to the arsenal of test systems for anti-biofilm compounds. FISH is a valuable complementary technique to CFU since it can be highly standardized and provides information on biofilm architecture and quantity and localization of survivor cells

Whipple's Disease: Diagnostic Value of rpoB Gene PCR from Peripheral Blood Mononuclear Cells.

International audienceIntroductionChronic infection with Tropheryma whipplei, known as Whipple’s disease (WD), classically affects the gastrointestinal tract, but any organ system may be affected, and isolated manifestations occur. Reliable diagnosis based on a combination of periodic acid–Schiff (PAS) staining, T. whipplei-specific immunohistochemistry (IHC), and polymerase chain reaction (PCR) from duodenal biopsies may be challenging in cases without classical gastrointestinal infection, so the need for additional diagnostic materials is urgent.ObjectiveOur objective was to evaluate additional diagnostic possibilities for WD.MethodsWe analyzed samples from 20 patients with WD and 18 control subjects in a prospective observational pilot study. In addition to WD diagnosis by PAS staining, T. whipplei-specific IHC and PCR of duodenal or extra intestinal tissues, whole EDTA blood, peripheral blood mononuclear cells (PBMCs) and PBMC fractions enriched with or depleted of cluster of differentiation (CD)-14+ cells were examined using T. whipplei rpoB gene PCR.ResultsTropheryma whipplei DNA was detected in 35 of 60 (58.3%) preparations from 16 of 20 patients with WD, most of whom lacked gastrointestinal signs and characteristic PAS-positive duodenal macrophages.ConclusionThis study provides evidence for the potential suitability of blood, particularly PBMCs, as material to assist in the diagnosis of WD via rpoB gene real-time PCR. Thus, PCR from blood preparations can be helpful for diagnostic decision making in atypical cases of WD