Identification of urovirulence traits in Escherichia coli by comparison of urinary and rectal E. coli isolates from dogs with urinary tract infection

Antimicrobial resistance and prevalence of canine uropathogens at the Western College of Veterinary Medicine Veterinary Teaching Hospital, 2002-2007

Between January 2002 and June 2007, uropathogens were isolated from 473 of 1557 canine urine samples submitted to Prairie Diagnostic Services from the Western College of Veterinary Medicine Veterinary Teaching Hospital. Culture and susceptibility results were analyzed, retrospectively, to estimate the prevalence of common bacterial uropathogens in dogs with urinary tract infections and to identify changes in antimicrobial resistance. The most common pathogens identified were Escherichia coli, Staphylococcus intermedius, Enterococcus spp., and Proteus spp. Antimicrobial resistance increased during the study period, particularly among recurrent E. coli isolates. Using the formula to help select rational antimicrobial therapy (FRAT), bacterial isolates were most likely to be susceptible to gentamicin, fluoroquinolones, amoxicillin-clavulanic acid, and groups 4 and 5 (third generation) cephalosporins.

Cranberry juice for prophylaxis of urinary tract infections--conclusions from clinical experience and research

Cranberry juice (Vaccinium macrocarpon) is a widely used and recommended North-American folk remedy for prophylaxis of urinary tract infections (UTI). Clinical trials have documented its efficacy in women with recurrent UTI, but so far not in other groups of patients. The composition of effective cranberry products and its dosage in UTI prophylaxis have not been defined. Intriguing experimental research has identified an anti-adhesive mechanism of cranberry juice that prevents docking of bacteria on host tissues. This efficacy mechanism can be traced in patients' urine following oral intake of cranberry products and appears to be due to proanthocyanidins with an A-type linkage of flavanols. The application of this anti-adhesion mechanism of cranberry-proanthocyandins is currently also investigated in other common diseases of bacterial pathogenesis, for example Helicobacter pylori-associated gastritis and dental caries/periodontal disease. The use of cranberry products appears to be safe and provide additional benefits by anti-oxidant and cholesterol-lowering activity.

Cranberry juice – a well-characterized folk-remedy against bacterial urinary tract infection

Cranberry (Vaccinium macrocarpon) is a North-American folk remedy for treating and preventing infection. Research has identified an anti-adhesive mechanism of cranberry-proanthocyanidins that inhibit docking of bacteria on tissues "in vitro". This efficacy mechanism can be traced in the patient's urine following oral intake of cranberry juice. The efficacy of cranberry juice and extracts as a prophylactic agent against recurrent urinary infections is well documented in women. The anti-adhesion effect of cranberry-proanthocyandins can also be applied for treatment of other common diseases of bacterial pathogenesis, e.g. Helicobacter pylori-associated gastritis and dental caries/periodontal disease.

Weak rolling adhesion enhances bacterial surface colonization

Bacterial adhesion to and subsequent colonization of surfaces are the first steps toward forming biofilms, which are a major concern for implanted medical devices and in many diseases. It has generally been assumed that strong irreversible adhesion is a necessary step for biofilm formation. However, some bacteria, such as Escherichia coli when binding to mannosylated surfaces via the adhesive protein FimH, adhere weakly in a mode that allows them to roll across the surface. Since single-point mutations or even increased shear stress can switch this FimH-mediated adhesion to a strong stationary mode, the FimH system offers a unique opportunity to investigate the role of the strength of adhesion independently from the many other factors that may affect surface colonization. Here we compare levels of surface colonization by E. coli strains that differ in the strength of adhesion as a result of flow conditions or point mutations in FimH. We show that the weak rolling mode of surface adhesion can allow a more rapid spreading during growth on a surface in the presence of fluid flow. Indeed, an attempt to inhibit the adhesion of strongly adherent bacteria by blocking mannose receptors with a soluble inhibitor actually increased the rate of surface colonization by allowing the bacteria to roll. This work suggests that (i) a physiological advantage to the weak adhesion demonstrated by commensal variants of FimH bacteria may be to allow rapid surface colonization and (ii) antiadhesive therapies intended to prevent biofilm formation can have the unintended effect of enhancing the rate of surface colonization.

Relationship between Escherichia coli strains causing urinary tract infection in women and the dominant faecal flora of the same hosts

To clarify whether prevalence or special pathogenicity is more important in determining urinary tract infection (UTI) causation, we compared the biotype, phylogenetic group, and virulence genes of Escherichia coli urine strains from 11 women with acute lower UTI with those of the host's dominant intestinal E. coli strain(s). Twenty-one unique E. coli clones were identified. For three women, the single faecal clone identified was also the host's urine clone, whereas for eight women faecal samples yielded 1 or 2 distinct non-urine clones (total, n = 10), either with (n = 3) or without (n = 5) the concurrent urine clone. The eight urine clones from the latter eight women exhibited significantly greater inferred virulence, according to virulence gene content and phylogenetic background, than did the hosts' 10 corresponding 'faecal only' clones. In contrast, the three urine clones that were detected as the host's sole faecal clone exhibited significantly lower inferred virulence than the other eight urine clones, and were statistically indistinguishable from the 10 'faecal only' clones. In conclusion, special pathogenicity is an important determinant of UTI pathogenesis in women, although prevalence may occasionally allow less virulent strains to cause UTI.

Molecular epidemiology of extraintestinal pathogenic (uropathogenic) Escherichia coli

Molecular epidemiological analyses of extraintestinal pathogenic Escherichia coli (ExPEC), which are also called "uropathogenic E. coli" since they are the principle pathogens in urinary tract infection, involve structured observations of E. coli as they occur in the wild. Careful selection of subjects and use of appropriate methods for genotyping and statistical analysis are required for optimal results. Molecular epidemiological studies have helped to clarify the host-pathogen relationships, phylogenetic background, reservoirs, and transmission pathways of ExPEC, to assess potential vaccine candidates, and to delineate areas for further study. Ongoing discovery of new putative virulence factors (VFs), increasing awareness of the importance of VF expression and molecular variants of VFs, and growing appreciation of transmission as an important contributor to ExPEC infections provide abundant stimulus for future molecular epidemiological studies. Published by Elsevier GmbH.

Phylogenetic and pathotypic comparison of concurrent urine and rectal Escherichia coli isolates from men with febrile urinary tract infection

Among men with febrile urinary tract infection (FUTI), whether the host's fecal flora is the source for the urine strain ("fecal-urethral" hypothesis), and whether pathogenesis is driven by prevalence versus special pathogenicity, are unknown. Accordingly, pretherapy urine isolates from 65 men with FUTI were compared with concurrent rectal isolates from the same hosts according to serotype, genomic profile, phylogenetic group, and virulence genotype. The host's multiple rectal colonies included only the urine clone in 25% of subjects, the urine clone plus additional clones in 22%, and only nonurine clones in 54%. Compared with the 67 unique rectal clones, the 65 urine isolates were significantly enriched for phylogenetic group B2, virulence-associated serotypes, and specific virulence genes and contained more virulence genes (median, 10 versus 6: P < 0.001). In multivariable models, phylogenetic group B2, hlyD (hemolysin), cnf1 (cytotoxic necrotizing factor), iroN (siderophore receptor), ompT (outer membrane protease), and malX (pathogenicity island marker) most strongly predicted urine source. These findings challenge the fecal-urethral and prevalence hypotheses for FUTI pathogenesis and instead strongly support the possibility of alternate infection routes in some men and the special pathogenicity hypothesis. They also identify specific bacterial traits as potential targets for anti-FUTI interventions.

Molecular cloning and characterization of three beta-defensins from canine testes

Mammalian beta-defensins are small cationic peptides possessing broad antimicrobial and physiological activities. Because dogs are particularly resilient to sexually transmitted diseases, it has been proposed that their antimicrobial peptide repertoire might provide insight into novel antimicrobial therapeutics and treatment regimens. To investigate this proposal, we cloned the full-length cDNA of three canine beta-defensin isoforms (cBD-1, -2, and -3) from canine testicular tissues. Their predicted peptides share identical N-terminal 65-amino-acid residues, including the beta-defensin consensus six-cysteine motif. The two longer isoforms, cBD-2 and -3, possess 4 and 34 additional amino acids, respectively, at the C terminus. To evaluate the antimicrobial activity of cBD, a 34-amino-acid peptide derived from the shared mature peptide region was synthesized. Canine beta-defensin displayed broad antimicrobial activity against gram-positive bacteria (Listeria monocytogenes and Staphylococcus aureus; MICs of 6 and 100 mug/ml, respectively), gram-negative bacteria (Escherichia coli, Klebsiella pneumoniae, and Neisseria gonorrhoeae; MICs of 20 to 50, 20, and 50 mug/ml, respectively), and yeast (Candida albicans; MIC of 5 to 50 mug/ml) and lower activity against Ureaplasma urealyticum and U. canigenitalium (MIC of 200 mug/ml). Antimicrobial potency was significantly reduced at salt concentrations higher than 140 mM. All three canine beta-defensins were highly expressed in testis. In situ hybridization indicated that cBD-1 was expressed primarily in Sertoli cells within the seminiferous tubules. In contrast, cBD-2 was located primarily within Leydig cells. The longest isoform, cBD-3, was detected in Sertoli cells and to a lesser extent in the interstitium. The tissue-specific expression and broad antimicrobial activity suggest that canine beta-defensins play an important role in host defense and other physiological functions of the male reproductive system.

Characterization of hemolytic Escherichia coli strains in ferrets: recognition of candidate virulence factor CNF1

Diseases associated with Escherichia coli infection are the subject of renewed interest due to emerging conditions such as hemolytic uremia syndrome. A collection of 15 strains of beta-hemolytic E. coli was isolated from diarrheic feces and diseased tissues of ferrets. All 15 strains were positive in specific PCR assays for the presence of hlyA, pap1, and cnf1. Seven of the cnf1-positive isolates were tested and shown to have a cytopathic effect on HeLa cell monolayers. The pathogenesis of these strains warrants future study.

Antimicrobial resistance of Escherichia coli strains isolated from urine of women with cystitis or pyelonephritis and feces of dogs and healthy humans

OBJECTIVE

To assess the prevalence and patterns of antimicrobial resistance among Escherichia coli strains isolated from the urine of women with cystitis or pyelonephritis and from fecal samples from dogs and healthy humans.

DESIGN

Cross-sectional survey.

SAMPLE POPULATION

Escherichia coli isolates from 82 women with cystitis, 170 women with pyelonephritis, 45 dogs, and 76 healthy human volunteers.

PROCEDURE

Susceptibility to 12 antimicrobial agents was determined by means of disk diffusion testing as specified by the NCCLS.

RESULTS

Overall, the 4 most common antimicrobial resistance patterns were resistance to ampicillin, sulfisoxazole, trimethoprim, and trimethoprim-sulfamethoxazole (n = 45 [12% of all isolates]); ampicillin alone (33 [9%]); ampicillin and sulfisoxazole (29 [8%]); and sulfisoxazole alone (14 [4%]). None of the isolates were resistant to ceftazidime, ciprofloxacin, nitrofurantoin, or piperacillin-tazobactam. Resistance was significantly more common and extensive among isolates from women with cystitis or pyelonephritis than among isolates from healthy humans or dogs. Resistance was least common among isolates from dogs. The only resistance phenotype that was more common among canine isolates than human isolates was resistance to sulfisoxazole alone.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that dogs are unlikely to be an important external reservoir of antimicrobial-resistant E. coli strains causing infections in humans. On the contrary the data suggest that dogs conceivably could acquire resistant E. coli strains from humans.