Sex Pheromone Response, Clumping, and Slime Production in Enterococcal Strains Isolated from Occluded Biliary Stents

Abstract

Bile-resistant bacteria, particularly gram-positive Enterococcus faecalis and Enterococcus faecium, play an important role in biliary stent occlusion, because their sessile mode of growth protects them against host defenses and antimicrobial agents. Twelve E. faecalis and seven E. faecium strains isolated from occluded biliary stents have been investigated for slime production, presence of aggregation substance genes, and ability to adhere to Caco-2 cells. Ten isolates were strong producers of slime, and seven isolates produced clumps when exposed to pheromones of E. faecalis JH2-2 and/or OG1RF. The small E. faecium clumps differed from the large clumps of E. faecalis and were similar to those of E. faecium LS10(pBRG1) carrying a pheromone response plasmid. After induction with pheromones, the adhesion to Caco-2 cells of clumping-positive strains was found to increase from two-to fourfold. Amplicons of the expected size were detected in three clumpingpositive and three clumping-negative E. faecalis isolates by using primers (agg) internal to a highly conserved region of the E. faecalis pheromone response plasmids pAD1, pPD1, and pCF10 and primers internal to prgB of the E. faecalis plasmid pCF10. The agg/prgB-positive E. faecalis strains were also positive in Southern hybridization experiments with a prgB-specific probe. No PCR products were obtained with the same primers from four clumping-positive isolates (one E. faecalis and three E. faecium strains), which were also Southern hybridization negative. Our results demonstrate that slime production and pheromone response are both present in isolated enterococci, suggesting that clinical strains with these features might have a selective advantage in colonizing biliary stents.

Occurrence of the Transferable Copper Resistance Gene tcrB among Fecal Enterococci of U.S. Feedlot Cattle Fed Copper-Supplemented Diets

“…The intra-and interspecies transferability of tcrB gene in our study is in agreement with our earlier studies with pig isolates (10,11). Interestingly, the conjugation frequency was higher in the interspecies assay, possibly because of the production of pheromones (peptide signal) by the recipient E. faecalis isolate strains, which are specific for a particular plasmid or a group of related plasmids (37,38). In this pheromone-inducible plasmid transfer, the recipient bacterium excretes the peptide pheromone molecule into the medium, where it can diffuse to a donor cell, thus facilitating transfer of antibiotic resistance determinants.…”

VanA-Type Enterococci from Humans, Animals, and Food: Species Distribution, Population Structure, Tn 1546 Typing and Location, and Virulence Determinants

“…For ␤-hemolysis detection, strains were grown on horse blood agar plates for 1 to 2 days at 37°C. Biofilm formation was tested using the slime production assay described previously (17).…”

“…Esp is a surface protein involved in the ability to colonize and in immune evasion in E. faecalis and E. faecium (21,24). Enterococci are also known to produce slime (17,18) and to form biofilms, which have been regarded as virulence features of clinical isolates (16,18). North 1997 VI1, VI46 2002 MI24, MI25, MI26, MI28, MI29, MI30, MI31, MI32, MI33, MI34, MI54, MI55, MI56, MI57, MI58, MI59, MI60 Center 1997 AN8 2002 AN7, AN9, AN12, AN13, AN14, AN15, AN16, AN17, AN19, AN20, AN23, AN47, AN48, AN49, AN50, AN51, Several reviews have addressed the genetic basis, reservoirs, and spread of glycopeptide resistance in enterococci (7,9,51) and enterococcal virulence (24,27,47).…”

Plastic Biliary Stent Occlusion: Factors Involved and Possible Preventive Approaches

“…This study indicates that the production of slime exhibited by most enterococcal isolates plays an important role in the colonization and subsequent occlusion of biliary stents, suggesting that aggregation substance is implicated in the occlusion process and that enterococci carrying aggregation substance genes have a selective advantage in endoprosthesis colonization. [54][55][56] The accumulation of biliary sludge is thought to be a multifactorial process in which, other than microbial growth, slime production and biofilm formation, a significant role is played by some bacterial enzymes (table 2). Chemical analyses have shown that, in addition to the nonbacterial constituents listed in table 2, calcium bilirubinate and calcium palmitate are commonly present in biliary sludge.…”