No abstract

BackgroundCrohn's disease (CD) is a high morbidity chronic inflammatory disorder of unknown aetiology. Adherent-invasive Escherichia coli (AIEC) has been recently implicated in the origin and perpetuation of CD. Because bacterial biofilms in the gut mucosa are suspected to play a role in CD and biofilm formation is a feature of certain pathogenic E. coli strains, we compared the biofilm formation capacity of 27 AIEC and 38 non-AIEC strains isolated from the intestinal mucosa. Biofilm formation capacity was then contrasted with the AIEC phenotype, the serotype, the phylotype, and the presence of virulence genes.ResultsSpecific biofilm formation (SBF) indices were higher amongst AIEC than non-AIEC strains (P = 0.012). In addition, 65.4% of moderate to strong biofilms producers were AIEC, whereas 74.4% of weak biofilm producers were non-AIEC (P = 0.002). These data indicate that AIEC strains were more efficient biofilm producers than non-AIEC strains. Moreover, adhesion (P = 0.009) and invasion (P = 0.003) indices correlated positively with higher SBF indices. Additionally, motility (100%, P < 0.001), H1 type flagellin (53.8%, P < 0.001), serogroups O83 (19.2%, P = 0.008) and O22 (26.9%, P = 0.001), the presence of virulence genes such as sfa/focDE (38.5%, P = 0.003) and ibeA (26.9%, P = 0.017), and B2 phylotype (80.8%, P < 0.001) were frequent characteristics amongst biofilm producers.ConclusionThe principal contribution of the present work is the finding that biofilm formation capacity is a novel, complementary pathogenic feature of the recently described AIEC pathovar. Characterization of AIEC specific genetic determinants, and the regulatory pathways, involved in biofilm formation will likely bring new insights into AIEC pathogenesis.

In four patients with alkaline-encrusted cystitis, Corynebacterium group D2 was isolated from consecutive urine cultures and stones. Encrusted cystitis occurred in bladders harboring inflammatory or tumorous lesions in patients with chronic or recurrent urinary tract infections appearing after surgery or instrumentation. The urease activity of Corynebacterium group D2 and the neutralization of this enzyme by acetohydroxamic acid are shown. Clinical improvement, disappearance of struvite crystals, and decrease of the urine pH were obtained when these bacteria were eliminated from urine samples. Corynebacterium group D2 strains were highly resistant to many antimicrobial agents but were highly susceptible to norfloxacin and vancomycin when tested at two pHs (7.4 and 8.5).

No abstract

The minimum dosage of antibiotics that reduced mortality in bacteraemic rats inoculated with two different Escherichia coli isolates was determined in an attempt to study the therapeutic importance of the inoculum effect. Low mortality rates (0-5%) at 48 h were obtained when antibiotics with minimal or no inoculum effect (ampicillin, cefuroxime, cefoxitin and gentamicin) were administered to yield serum levels 5 to 14 times the MIC, while antibiotics with a pronounced inoculum effect (piperacillin, cefotaxime and aztreonam) had to be administered to yield serum levels 57 to more than 1000 times the MIC determined with a standard (low) inoculum. All of the antibiotics with inoculum effect studied here are administered empirically in clinical practice at a higher dose than the microbiological and pharmacokinetic data would indicate (in order to reach peak serum concentrations exceeding the MICs of the pathogens by 4-10 times). Our experiment suggests that such high and empirical doses of antibiotics with inoculum effect may be justified.