Characterization of unconventional pathogenic Escherichia coli isolated from bloodstream infection: virulence beyond the opportunism.

Extraintestinal pathogenic Escherichia coli (ExPEC) is the leading cause of urinary tract infection worldwide and a critical bloodstream infection agent. There are more than 50 virulence factors (VFs) related to ExPEC pathogenesis; however, many strains isolated from extraintestinal infections are devoid of these factors. Since opportunistic infections may occur in immunocompromised patients, E. coli strains that lack recognized VFs are considered opportunist, and their virulence potential is neglected. We assessed eleven E. coli strains isolated from bloodstream infections and devoid of the most common ExPEC VFs to understand their pathogenic potential. The strains were evaluated according to their capacity to interact in vitro with human eukaryotic cell lineages (Caco-2, T24, HEK293T, and A549 cells), produce type 1 fimbriae and biofilm in diverse media, resist to human sera, and be lethal to Galleria mellonella. One strain displaying all phenotypic traits was sequenced and evaluated. Ten strains adhered to Caco-2 (colon), eight to T24 (bladder), five to HEK-293 T (kidney), and four to A549 (lung) cells. Eight strains produced type 1 fimbriae, ten adhered to abiotic surfaces, nine were serum resistant, and seven were virulent in the G. mellonella model. Six of the eleven E. coli strains displayed traits compatible with pathogens, five of which were isolated from an immune-competent host. The genome of the EC175 strain, isolated from a patient with urosepsis, reveals that the strain belonged to ST504-A, and serotype O11:H11; harbors thirteen VFs genes, including genes encoding UpaG and yersiniabactin as the only ExPEC VFs identified. Together, our results suggest that the ExPEC pathotype includes pathogens from phylogroups A and B1, which harbor VFs that remain to be uncovered.

Virulence Profile, Antibiotic Resistance, and Phylogenetic Relationships among Escherichia coli Strains Isolated from the Feces and Urine of Hospitalized Patients.

Extra-intestinal pathogenic Escherichia coli (ExPEC) may inhabit the human gut microbiota without causing disease. However, if they reach extra-intestinal sites, common cystitis to bloodstream infections may occur, putting patients at risk. To examine the human gut as a source of endogenous infections, we evaluated the E. coli clonal diversity of 18 inpatients' guts and their relationship with strains isolated from urinary tract infection (UTI) in the same hospital. Random amplified polymorphic DNA evaluated the clonal diversity, and the antimicrobial susceptibility was determined by disk diffusion. One isolate of each clone detected was sequenced, and their virulome and resistome were determined. Overall, 177 isolates were screened, among which 32 clones were identified (mean of two clones per patient), with ExPEC strains found in over 75% of the inpatients' guts. Endogenous infection was confirmed in 75% of the cases. ST10, ST59, ST69, ST131, and ST1193 clones and critical mobile drug-resistance encoding genes (blaCTX-M-15, blaOXA-1, blaDHA-1, aac(6')-lb-cr, mcr-1.26, qnrB4, and qnrB19) were identified in the gut of inpatients. The genomic analysis highlighted the diversity of the fecal strains, colonization by lactose-negative E. coli, the high frequency of ExPEC in the gut of inpatients without infections, and the presence of ß-lactamase producing E. coli in the gut of inpatients regardless of the previous antibiotics' usage. Considering that we found more than one ExPEC clone in the gut of several inpatients, surveillance of inpatients' fecal pathogens may prevent UTI caused by E. coli in the hospital and dissemination of risk clones.

Molecular Epidemiology and Presence of Hybrid Pathogenic Escherichia coli among Isolates from Community-Acquired Urinary Tract Infection.

Urinary tract infections (UTI) affect community and healthcare patients worldwide and may have different clinical outcomes. We assessed the phylogenetic origin, the presence of 43 virulence factors (VFs) of diarrheagenic and extraintestinal pathogenic Escherichia coli, and the occurrence of hybrid strains among E. coli isolates from 172 outpatients with different types of UTI. Isolates from phylogroup B2 (46%) prevailed, followed by phylogroups A (15.7%) and B1 (12.2%), with similar phylogenetic distribution in symptomatic and asymptomatic patients. The most frequent VFs according to their functional category were fimA (94.8%), ompA (83.1%), ompT (63.3%), chuA (57.6%), and vat (22%). Using published molecular criteria, 34.3% and 18.0% of the isolates showed intrinsic virulence and uropathogenic potential, respectively. Two strains carried the eae and escV genes and one the aggR gene, which classified them as hybrid strains. These hybrid strains interacted with renal and bladder cells, reinforcing their uropathogenic potential. The frequency of UPEC strains bearing a more pathogenic potential in the outpatients studied was smaller than reported in other regions. Our data contribute to deepening current knowledge about the mechanisms involved in UTI pathogenesis, especially among hybrid UPEC strains, as these could colonize the host's intestine, leading to intestinal infections followed by UTI.

Pic-Producing Escherichia coli Induces High Production of Proinflammatory Mediators by the Host Leading to Death by Sepsis.

Escherichia coli is an important pathogen responsible for a variety of diseases. We have recently shown that Pic, a serine protease secreted by E. coli, mediates immune evasion by the direct cleavage of complement molecules. The aim of this study was to investigate the action of a Pic-producing bacteria in a murine model of sepsis. Mice were infected with Pic-producing E. coli (F5) or F5∆pic mutant. Animal survival was monitored for five days, and a subset of mice was euthanized after 12 h for sample acquisition. The inoculation of Pic-producing bacteria induced 100% death within 24 h. The colony forming units count in the organs was significantly higher in F5. Hematological analysis showed a decrease of total leukocytes. Nitric oxide and cytokines were detected in serum, as well as on peritoneal lavage of the F5 group in higher levels than those detected in the other groups. In addition, immunophenotyping showed a decrease of activated lymphocytes and macrophages in the F5 group. Therefore, Pic represents an important virulence factor, allowing the survival of the bacterium in the bloodstream and several organs, as well as inducing a high production of proinflammatory mediators by the host, and concomitantly a cellular immunosuppression, leading to sepsis and death.

Pic-producing escherichia coli induces high production of proinflammatory mediators by the host leading to death by sepsis

Escherichia coli is an important pathogen responsible for a variety of diseases. We have recently shown that Pic, a serine protease secreted by E. coli, mediates immune evasion by the direct cleavage of complement molecules. The aim of this study was to investigate the action of a Pic-producing bacteria in a murine model of sepsis. Mice were infected with Pic-producing E. coli (F5) or F5?pic mutant. Animal survival was monitored for five days, and a subset of mice was euthanized after 12 h for sample acquisition. The inoculation of Pic-producing bacteria induced 100% death within 24 h. The colony forming units count in the organs was significantly higher in F5. Hematological analysis showed a decrease of total leukocytes. Nitric oxide and cytokines were detected in serum, as well as on peritoneal lavage of the F5 group in higher levels than those detected in the other groups. In addition, immunophenotyping showed a decrease of activated lymphocytes and macrophages in the F5 group. Therefore, Pic represents an important virulence factor, allowing the survival of the bacterium in the bloodstream and several organs, as well as inducing a high production of proinflammatory mediators by the host, and concomitantly a cellular immunosuppression, leading to sepsis and death

Prophylactic Treatment With Simvastatin Modulates the Immune Response and Increases Animal Survival Following Lethal Sepsis Infection.

Chronic use of statins may have anti-inflammatory action, promoting immunomodulation and survival in patients with sepsis. This study aimed to analyze the effects of pretreatment with simvastatin in lethal sepsis induced by cecal ligation and puncture (CLP). Male Swiss mice received prophylactic treatment with simvastatin or pyrogen-free water orally in a single daily dose for 30 days. After this period, the CLP was performed. Naïve and Sham groups were performed as non-infected controls. Animal survival was monitored for 60 h after the CLP. Half of mice were euthanized after 12 h to analyze colony-forming units (CFUs); hematological parameters; production of IL-10, IL-12, IL-6, TNF-α, IFN-γ, and MCP-1; cell counts on peritoneum, bronchoalveolar lavage (BAL), bone marrow, spleen, and mesenteric lymph node; immunephenotyping of T cells and antigen presenting cells and production of hydrogen peroxide (H2O2). Simvastatin induced an increase in survival and a decrease in the CFU count on peritoneum and on BAL cells number, especially lymphocytes. There was an increase in the platelets and lymphocytes number in the Simvastatin group when compared to the CLP group. Simvastatin induced a greater activation and proliferation of CD4+ T cells, as well as an increase in IL-6 and MCP-1 production, in chemotaxis to the peritoneum and in H2O2 secretion at this site. These data suggest that simvastatin has an impact on the survival of animals, as well as immunomodulatory effects in sepsis induced by CLP in mice.