coli O157:H7, Gemella sanguinis, Granulicatella spp., Morganella morganii ssp. morganii, Pantoea ananatis, Pantoea eucalypti, Raoultella terrigena, Shigella dysenteriae, Shigella flexneri and Shigella sonnei were also identified. Among fungi, Candida carpophila, Candida humilis, Candida milleri, Kazachstania barnettii and Pichia guilliermondii were additionally identified. At macroscopical observation (Fig. 3), both the outer (Fig. 3a) and the inner surfaces, obtained by bisecting stents’ segments along their longitudinal

axis (Fig. 3b), were found to be more or less covered or filled by a yellow brownish, soft and heterogeneous material, respectively. In Fig. 4, common nonmicrobial sludge components have been observed VX-809 mouse by SEM including dietary fibers (Fig. 4a), as a result of duodenal reflux, and crystals that were tentatively identified as calcium selleck products bilirubinate and calcium palmitate, respectively (Fig. 4b and c). SEM observation of longitudinal sections of partially occluded stents (Fig. 5) revealed the early phase of sludge formation (Fig. 5a). At a higher magnification,

it was possible to recognize coccoid bacterial cells (Fig. 5b), rod-shaped bacteria (Fig. 5c) and fungal cells (Fig. 5d). Fig. 5c clearly shows the typical appearance of sludge in direct contact with the bile flow as indicated by the mucous material in which bacteria are immersed and grow as a biofilm. As observed by SEM (Fig. 6), in the cross-section of a stent segment, the dehydration procedures for sample observation frequently caused a cleavage (Fig. 6a) at the interface between the biliary sludge content and the stent lumen. In Fig. 6b, the ‘sludge Morin Hydrate side’ of this cleavage is shown in which both coccoid cells and their imprints are observed, while in Fig. 6c, a portion of sludge matrix, devoid of bacteria, but still attached to the lumen surface, can be observed. The sludge detachment from the inner stents’ lumen caused by the dehydration procedure evidenced,

in almost all samples, clusters of microbial cells closely bound to the polymeric stent surface (Fig. 6d, e and f). All the 19 isolated anaerobic strains were investigated for their ability to produce slime in vitro. Among the 12 Gram-negative anaerobic isolated strains tested for slime production, those belonging to the species Bacteroides fragilis, Fusobacterium necrophorum, Prevotella intermedia and Veillonella spp. were strong slime producers, while the strain of Prevotella bivia was a weak producer and the three Bacteroides strains of B. capillosus, Bacteroides distasonis and Bacteroides oralis were nonproducers (Table 3). With respect to the six Gram-positive anaerobic strains isolated, five were strong producers (Clostridium baratii, Clostridium perfringens, Peptostreptococcus magnus, Veillonella spp. and F.