A microbiological and morphological study of blocked biliary stents

Biliary stent blockage represents the main limitation of the use of such devices in relieving obstructive jaundice due to a variety of malignant and benign conditions. Microbiological and morphological analysis of the occluding sludge present on the inner surface of 30 biliary stents was performed to evaluate the different components of such material and the effect of the antibiotic treatment on the biofilm formation. A highly organized biofilm, constituted by microbial cells embedded in an amorphous matrix together with crystallized bile salts, was observed Enterococcus spp . represented the most common isolate from both occluded and non-occluded stents. The antibiotic therapy, while selecting for multi-resistant bacteria and fungi, might possibly delay the biofilm formation. Key words: biliary stents, microbial colonization, biofilm

In vitro activity of fosfomycin in combination with vancomycin or teicoplanin against Staphylococcus aureus isolated from device-associated infections unresponsive to glycopeptide therapy

Fosfomycin is a molecule that inhibits the early stage of peptidoglycan synthesis and shows a broad-spectrum bactericidal activity against Gram-positive and Gram-negative bacteria. Using the Killing-curve method, we tested the in vitro bactericidal activity of fosfomycin alone or in combination with vancomycin or teicoplanin at a concentration of 8 microg/mL, that is easily achievable in serum at standard dosing regimens, against seven methicillin-resistant Staphylococcus aureus strains, isolated from patients with well documented device-associated infections unresponsive to or relapsing after glycopeptide therapy. MICs of vancomycin ranged from 1 to 4 microg/mL, MICs of teicoplanin from 2 to 8 microg/mL; MICs of fosfomycin were 8 microg/mL for two strains and >128 microg/mL for the remaining strains. The seven strains proved tolerant when tested for vancomycin and teicoplanin used alone at 2x MIC concentration. Fosfomycin was bactericidal (reduction of 2 log of the inoculum) only against the two susceptible strains. In all cases both vancomycin and teicoplanin in combination with fosfomycin developed bactericidal synergism already at a concentration of 1x MIC. If these results are confirmed by in vivo experiments, the combination of fosfomycin with glycopeptides might be useful for treating device-associated infections, and in preventing the phenomenon of increasing MICs for glycopeptides

In vitro activity of fosfomycin in combination with vancomycin or teicoplanin against Staphylococcus aureus isolated from device-associated infections unresponsive to glycopeptide therapy

Fosfomycin is a molecule that inhibits the early stage of peptidoglycan synthesis and shows a broad-spectrum bactericidal activity against Gram-positive and Gram-negative bacteria. Using the Killing-curve method, we tested the in vitro bactericidal activity of fosfomycin alone or in combination with vancomycin or teicoplanin at a concentration of 8 microg/mL, that is easily achievable in serum at standard dosing regimens, against seven methicillin-resistant Staphylococcus aureus strains, isolated from patients with well documented device-associated infections unresponsive to or relapsing after glycopeptide therapy. MICs of vancomycin ranged from 1 to 4 microg/mL, MICs of teicoplanin from 2 to 8 microg/mL; MICs of fosfomycin were 8 microg/mL for two strains and >128 microg/mL for the remaining strains. The seven strains proved tolerant when tested for vancomycin and teicoplanin used alone at 2x MIC concentration. Fosfomycin was bactericidal (reduction of 2 log of the inoculum) only against the two susceptible strains. In all cases both vancomycin and teicoplanin in combination with fosfomycin developed bactericidal synergism already at a concentration of 1x MIC. If these results are confirmed by in vivo experiments, the combination of fosfomycin with glycopeptides might be useful for treating device-associated infections, and in preventing the phenomenon of increasing MICs for glycopeptides

Valuation of a new Cromogenic Agar Medium for the detection of ESBL producing Enterobacteriaceae

Escherichia coli producing ESBL are a major problem in the many different hospitals worldwide causing outbreaks as well as sporadic infections. A novel chromogenic agar medium (ChromID ESBL bioMèrieux, Marcy L’Etoile, France) was tested directly on a total of 162 clinical samples and plated in parallel on to common media including Mac Conkey agar (bioMèrieux, Marcy L’Etoile, France). Colonies presenting a different morphologic aspect and growing on media were identified and tested for susceptibility by VITEK 2 using GN-cards and AST-N013 cards (bioMérieux, Marcy L’Etoile, France) Confirmation of ESBL-producing isolates was performed by combinated double disk. We are not find errors.The chromID ESBL appears as an excellent medium for the screening and presumptive identification of ESBLproducing Enterobacteriaceae directly from clinical samples. Further studies with a wider range of clinical specimens are required to confirm this utility

Role of multispecies microbial biofilms in the occlusion of biliary Stents

Endoscopic stenting is a standard palliative approach for the treatment of a variety of diseases involving biliary obstruction. However, the major limitation of this approach is represented by stent occlusion followed by life-threatening cholangitis, often requiring stent removal and replacement with a new one. Although it is generally believed that microbial colonization of the inner surface of the stent plays an important role in initiating the clogging process, so far available data are not enough for a full understanding of this phenomenon. In fact, it is known that when a biliary stent is inserted across the sphincter of Oddi, the loss of the antimicrobial barrier represented by the sphincter itself and the low pressure in the common bile duct allow reflux of duodenal content, thus promoting an ascending microbial colonization. The sessile mode of growth and the exopolysaccharide production, which leads to the subsequent establishment of a thick biofilm, provides microorganisms with an efficient protection from both antibacterial agents and phagocytic cells. The aim of this study was to analyze the tridimensional structure of the microbial biofilm grown in the lumen of 15 clogged biliary stents and to identify the microbial species involved in the clogging process. Scanning electron microscopy investigations revealed that sludge present in the stent lumen consist of a rich and assorted microbial flora, including aerobic and anaerobic species, mixed with a large amount of amorphous material containing dietary fibres, crystals of cholesterol and other precipitates of bacteria-driven bile salts