Micro-patterned surfaces that exploit stigmergy to inhibit biofilm expansion

Twitching motility is a mode of surface translocation that is mediated by the extension and retraction of type IV pili and which, depending on the conditions, enables migration of individual cells or can manifest as a complex multicellular collective behavior that leads to biofilm expansion. When twitching motility occurs at the interface of an abiotic surface and solidified nutrient media, it can lead to the emergence of extensive self-organized patterns of interconnected trails that form as a consequence of the actively migrating bacteria forging a furrow network in the substratum beneath the expanding biofilm. These furrows appear to direct bacterial movements much in the same way that roads and footpaths coordinate motor vehicle and human pedestrian traffic. Self-organizing systems such as these can be accounted for by the concept of stigmergy which describes self-organization that emerges through indirect communication via persistent signals within the environment. Many bacterial communities are able to actively migrate across solid and semi-solid surfaces through complex multicellular collective behaviors such as twitching motility and flagella-mediated swarming motility. Here, we have examined the potential of exploiting the stigmergic behavior of furrow-mediated trail following as a means of controlling bacterial biofilm expansion along abiotic surfaces. We found that incorporation of a series of parallel micro-fabricated furrows significantly impeded active biofilm expansion by Pseudomonas aeruginosa and Proteus vulgaris. We observed that in both cases bacterial movements tended to be directed along the furrows. We also observed that narrow furrows were most effective at disrupting biofilm expansion as they impeded the ability of cells to self-organize into multicellular assemblies required for escape from the furrows and migration into new territory. Our results suggest that the implementation of micro-fabricated furrows that exploit stigmergy may be a novel approach to impeding active biofilm expansion across abiotic surfaces such as those used in medical and industrial settings

Clonal relatedness of Proteus mirabilis strains causing urinary tract infections in companion animals and humans

Research Areas: Microbiology. Veterinary SciencesABSTRACT - Proteus mirabilis is a major cause of urinary tract infection (UTI) in humans and companion animals. This study aimed to evaluate the antimicrobial resistance, virulence and clonal relatedness of P. mirabilis isolated from dogs, cats and humans with UTI. P. mirabilis isolated from companion animals (N = 107) and humans (N = 76) with UTI were compared by PFGE analysis after overnight Nod macro-restriction using Dice/UPGMA with a 1.5% tolerance. Strains were characterized for antimicrobial resistance by disk diffusion. Twenty-four resistance genes and four virulence genes were screened by PCR. Thirty-nine clusters (similarity > 80%) and 73 single pulse-types were detected. Nine clusters included P. mirabilis isolated from community and hospital patients, including strains with 100% similarity. A high number of clusters (43.6%, n = 17/39) included strains from companion animals and humans. Similarity between some companion animal and human strains varied between 80-100%. One strain from a dog was 100% similar to one human community-acquired P. mirabilis. One P. mirabilis from a cat was found to be 94.7% and 92.4% similar to community and hospital patient strains, respectively. P. mirabilis CMY-2-producers did not cluster all together. Nevertheless, cluster C36 included five P. mirabilis from companion animals (similarity 85.8%-95.7%), of which, four (80%) were multidrug-resistant CMY-2-producers. This study shows that companion animals and humans become infected with closely related P. mirabilis strains. The high number of clusters containing companion animals and human strains points to the zoonotic nature of P. mirabilis. These results underline the potential role of companion animals as reservoirs and in the dissemination of uropathogenic P. mirabilis to humans and vice versa.info:eu-repo/semantics/publishedVersio

Biocide Activity against Urinary Catheter Pathogens

Antimicrobial effects of essential oils against bacteria associated with urinary catheter infection was assessed. Tests were performed on 14 different bacterial species cultured either planktonically or as biofilms. Biofilms were found to be up to 8-fold more tolerant of the test agents. Higher antimicrobial tolerance was also evident in tests conducted in artificial urine. Eugenol exhibited higher antimicrobial effects against both planktonic cells and biofilms than did terpinen, tea tree oil, and cineole

Role of swarming in the formation of crystalline Proteus mirabilis biofilms on urinary catheters

The care of many patients undergoing long-term bladder catheterization is frequently complicated by infection with Proteus mirabilis. These organisms colonize the catheter, forming surface biofilm communities, and their urease activity generates alkaline conditions under which crystals of magnesium ammonium phosphate and calcium phosphate are formed and become trapped in the biofilm. As the biofilm develops it obstructs the flow of urine through the catheter, causing either incontinence due to leakage of urine around the catheter or retention of urine in the bladder. The aim of this study was to investigate the role of the surface-associated swarming motility of P. mirabilis in the initiation and development of these crystalline catheter biofilms. A set of stable transposon mutants with a range of swimming and swarming abilities were tested for their ability to colonize silicone surfaces in a parallel-plate flow cell. A laboratory model of the catheterized bladder was then used to examine their ability to form crystalline, catheter-blocking biofilms. The results showed that neither swarming nor swimming motility was required for the attachment of P. mirabilis to silicone. Mutants deficient in swarming and swimming were also capable of forming crystalline biofilms and blocking catheters more rapidly than the wild-type strain

Molecular Epidemiology of Proteus mirabilis Infections of the Catheterized Urinary Tract

Proteus mirabilis compromises the care of many patients undergoing long-term indwelling bladder catheterization. It forms crystalline bacterial biofilms in catheters which block the flow of urine, causing either incontinence due to leakage or painful distention of the bladder due to urinary retention. If it is not dealt with, catheter blockage can lead to pyelonephritis and septicemia. We have examined the epidemiology of catheter-associated P. mirabilis infections by use of pulsed-field gel electrophoresis (PFGE) of NotI restriction enzyme digests of bacterial DNA. This technique was shown to be more discriminatory than the classical phenotypic Dienes typing technique. We demonstrated that each of 42 isolates from diverse environmental sources and 10 of 12 isolates from blood, wound swabs, and mid-stream urine samples of hospitalized patients had distinct genotypes. Examination of a set of 55 isolates of P. mirabilis, each from a different clinical or environmental source, identified 49 distinct genotypes and 43 Dienes types. The index of discrimination was 0.993 for the PFGE method and 0.988 for the Dienes method. Applying the PFGE method to isolates from catheter-associated urinary tract infections confirmed that the strains present in the crystalline catheter biofilms were identical to those isolated from the same patient's urine. An analysis of samples taken during a prospective study of infections in catheterized nursing home patients revealed that a single genotype of P. mirabilis can persist in the urinary tract despite many changes of catheter, periods of noncatheterization, and antibiotic therapy

Does the valve-regulated release of urine from the bladder decrease encrustation and blockage of indwelling catheters by crystalline Proteus mirabilis biofilms?

We tested whether valve regulated, intermittent flow of urine from catheterized bladders decreases catheter encrustation. Materials and Methods Laboratory models of the catheterized bladder were infected with Proteus mirabilis. Urine was allowed to drain continuously through the catheters or regulated by valves to drain intermittently at predetermined intervals. The time that catheters required to become blocked was recorded and encrustation was visualized by scanning electron microscopy. Results When a manual valve was used to drain urine from the bladder at 2-hour intervals 4 times during the day, catheters required significantly longer to become blocked than those on continuous drainage (mean 62.6 vs 35.9 hours, p = 0.039). A similar 1.7-fold increase occurred when urine was drained at 4-hour intervals 3 times daily. Experiments with an automatic valve in which urine was released at 2 or 4-hour intervals through the day and night also showed a significant increase in mean time to blockage compared with continuous drainage (p = 0.001). Scanning electron microscopy confirmed that crystalline biofilm was less extensive on valve regulated catheters. Conclusions Valve regulated, intermittent flow of urine through catheters increases the time that catheters require to become blocked with crystalline biofilm. The most beneficial effect was recorded when urine was released from the bladder at 4-hour intervals throughout the day and night by an automatic valve