Bacterial biofilms cause numerous problems in health care and industry; notably, biofilms are associated with a large number of infections. Biofilm-dwelling bacteria are particularly resistant to antibiotics, making it hard to eradicate biofilm-associated infections. Bacteria rely on efflux pumps to get rid of toxic substances. We discovered that efflux pumps are highly active in bacterial biofilms, thus making efflux pumps attractive targets for antibiofilm measures. A number of efflux pump inhibitors (EPIs) are known. EPIs were shown to reduce biofilm formation, and in combination they could abolish biofilm formation completely. Also, EPIs were able to block the antibiotic tolerance of biofilms. The results of this feasibility study might pave the way for new treatments for biofilm-related infections and may be exploited for prevention of biofilms in general.

Many bacterial infections are associated with biofilm formation. Bacterial biofilms can develop on essentially all kinds of surfaces, producing chronic and often intractable infections. Escherichia coli is an important pathogen causing a wide range of gastrointestinal infections. E. coli strain Nissle 1917 has been used for many decades as a probiotic against a variety of intestinal disorders and is probably the best field-tested E. coli strain in the world. Here we have investigated the biofilm-forming capacity of Nissle 1917. We found that the strain was a good biofilm former. Not only was it significantly better at biofilm formation than enteropathogenic, enterotoxigenic and enterohaemorrhagic E. coli strains, it was also able to outcompete such strains during biofilm formation. The results support the notion of bacterial prophylaxis employing Nissle 1917 and may partially explain why the strain has a beneficial effect on many intestinal disorders. INTRODUCTIONMany bacteria live as sessile communities adhered to surfaces, rather than as planktonic isolated cells. These compact microbial consortia, referred to as biofilms, are commonly associated with many economic and health problems (Costerton et al., 1999). In medicine, biofilmassociated infections have a major impact on permanent and temporary artificial implants placed in the human body, often with devastating consequences. Many persistent and chronic bacterial infections are now believed to be linked to the formation of biofilms (Costerton et al., 1995(Costerton et al., , 1999. Bacterial biofilms can develop on many living surfaces and virtually all artificial implants, producing chronic and often intractable infections. Notable biofilm-associated infections include chronic cystitis, endocarditis, otitis media, periodontitis, prostatitis, wound infections and catheter-and stent-associated infections (Warren, 2001;Costerton et al., 2003;Parsek & Singh, 2003;Brady et al., 2008). Bacterial biofilms have been reported to affect 90 % of indwelling stents in patients (Reid et al., 1992). Biofilm-forming Escherichia coli strains are responsible for most infections in patients with indwelling bladder catheters (Warren, 2001). Biofilm-associated bacteria are often hard to eradicate by antibiotics and can tolerate hundred-or thousandfold higher doses than the corresponding planktonic bacteria (Costerton et al., 1999). E. coli has also been reported to be able to form intracellular biofilm-like aggregates inside bladder cells, making them hard to reach by both host defence mechanisms and antibiotics (Anderson et al., 2003).E. coli strain Nissle 1917, of serotype O6 : K5 : H1, is an excellent colonizer of the human gut and has been reported to be able to colonize and establish itself in the human intestine even in the presence of a natural resident bacterial flora (Lodinova-Zadnikova et al., 1992;Schulze & Sonnenborn, 1995;Lodinova-Zadnikova & Sonnenborn, 1997). The strain was originally isolated during World War I from a soldier who escaped a severe outbreak of dia...

Urinary tract infection (UTI) is the most common infection in patients with indwelling urinary catheters, and bacterial biofilm formation is a major problem in this type of infection. Escherichia coli is responsible for the large majority of UTIs. Free iron is strictly limited in the human urinary tract and there is fierce competition between the host and infectious bacteria for this essential metal. Urinary tract infectious E. coli have highly efficient mechanisms of iron acquisition, one of which is the yersiniabactin system. The fyuA gene, encoding the yersiniabactin receptor, is one of the most upregulated genes in biofilm; it was upregulated 63-fold in the E. coli UTI strain VR50. FyuA was found to be highly important for biofilm formation in iron-poor environments such as human urine. Mutants in fyuA show aberrant biofilm formation and the cells become filamentous; a VR50fyuA mutant showed a 92 % reduction in biofilm formation in urine flow-cell chambers compared with the wild-type. The FyuA/yersiniabactin system is known to be important for virulence. Here we demonstrate a direct link between FyuA and biofilm formation in iron-poor environments. We also show that the availability of iron greatly influences UTI strains' ability to form biofilm. INTRODUCTIONIron is essential for bacterial growth. Bacteria face ironlimiting conditions in the mammalian host, where free iron is strictly limited and iron is normally bound to sequestering proteins such as transferrin and lactoferrin. To counter such iron-limiting conditions bacteria use different highly efficient mechanisms of iron acquisition. A typical high-affinity iron-uptake system consists of a lowmolecular-mass Fe 3+ -chelating compound, known as a siderophore, combined with its cognate membrane-located receptor (Martinez et al., 1990). Such iron-acquisition systems are generally regarded as important virulence or fitness factors. A range of enterobacteria contain a gene cluster called the high-pathogenicity island (HPI) encoding proteins for biosynthesis of the yersiniabactin (Ybt) siderophore and its uptake system (Rakin et al., 1999;Schubert et al., 1998Schubert et al., , 2004. The HPI is widespread among members of the Enterobacteriaceae and is essential for virulence in Yersinia and certain pathotypes of Escherichia coli (Schubert et al., 2004). One of the important genes residing on the HPI is fyuA, encoding the 71 kDa outer-membrane protein FyuA (ferric yersiniabactin uptake), which act as a receptor for Fe-Ybt siderophore uptake (Heesemann et al., 1993;Rakin et al., 1994;Schubert et al., 2002). The fyuA gene has been associated with virulence in many members of the Enterobacteriaceae (Schubert et al., , 2002.Urinary tract infection (UTI) is a serious health problem that affects millions of people each year (Stamm & Norrby, 2001). The recurrence rate is high, and often the infections are particularly troublesome and become chronic with multiple episodes. UTI usually starts as a bladder infection but often ascends to affect the kidneys and ultimatel...

Urinary tract infection (UTI) is an important health problem worldwide, with many millions of cases each year, and Escherichia coli is the most common organism causing UTI in humans. Also, E. coli is responsible for most infections in patients with chronic indwelling bladder catheter. The two asymptomatic bacteriuria (ABU) E. coli strains 83972 and VR50 are significantly better biofilm formers in their natural growth medium, human urine, than the two uropathogenic E. coli isolates CFT073 and 536. We used DNA microarrays to monitor the expression profile during biofilm growth in urine of the two ABU strains 83972 and VR50. Significant differences in expression levels were seen between the biofilm expression profiles of the two strains with the corresponding planktonic expression profiles in morpholinepropanesulfonic acid minimal laboratory medium and human urine; 417 and 355 genes were up-and down-regulated, respectively, during biofilm growth in urine of 83972 and VR50. Many genes involved in transcription and stress were up-regulated in biofilm-grown cells. The role in biofilm formation of four of the up-regulated genes, i.e., yceP, yqgA, ygiD, and aaeX, was investigated by creating single-knockout mutant versions of 83972 and VR50; all mutants showed reduced biofilm formation in urine by 18 to 43% compared with the wild type (P < 0.05). Also, the expression profile of strain 83972 in the human urinary tract partially overlaps with the biofilm expression profile.Bacteria generally live attached to surfaces rather than as planktonic isolated cells. Often adhered bacteria form sessile communities, also referred to as biofilms, and these are commonly associated with many health problems (10). Biofilms can form on virtually any type of surface. In the medical field bacterial biofilms have attracted particular attention, because many persistent and chronic bacterial infections, including periodontitis, otitis media, biliary tract infection, and endocarditis, are now believed to be linked to the formation of biofilms. Also, virtually all medical implants are prone to colonization by bacteria, and the resultant biofilms often serve as a source for recurrent infections. Bacterial biofilm infections are particularly problematic, because sessile bacteria can withstand host immune defense mechanisms and are extremely resistant to antibiotics, biocides, and hydrodynamic shear forces that can efficiently clear corresponding planktonic bacteria (9, 10).Urinary tract infection (UTI) is a serious health problem that affects millions of people each year (49). The recurrence rate is high, and often the infections are particularly troublesome and become chronic, with multiple episodes. UTI usually starts as a bladder infection but often ascends to affect the kidneys and ultimately can result in renal failure or dissemination to the blood. UTI is the most common infection in patients with indwelling bladder catheters, and bacteriuria is essentially unavoidable in this patient group, with an infection rate of ϳ100% within 1 month (...

Management of bacterial infections is becoming increasingly difficult due to the emergence and increasing prevalence of bacterial pathogens that are resistant to available antibiotics. Conventional antibiotics generally kill bacteria by interfering with vital cellular functions, an approach that imposes selection pressure for resistant bacteria. New approaches are urgently needed. Targeting bacterial virulence functions directly is an attractive alternative. An obvious target is bacterial adhesion. Bacterial adhesion to surfaces is the first step in colonization, invasion, and biofilm formation. As such, adhesion represents the Achilles heel of crucial pathogenic functions. It follows that interference with adhesion can reduce bacterial virulence. Here, we illustrate this important topic with examples of techniques being developed that can inhibit bacterial adhesion. Some of these will become valuable weapons for preventing pathogen contamination and fighting infectious diseases in the future.