Host species-specific translocation of Escherichia coli

Patterns of Circulating Microbiota during the Acute Phase Following ST-Segment Elevation Myocardial Infarction Predict Long-Term Cardiovascular Events

Limited information exists regarding whether circulating microbiota could predict long-term clinical outcomes following ST-segment elevation myocardial infarction (STEMI). A total of 244 consecutive patients with STEMI were followed for 2.8 years, and 64 first major adverse cardiovascular events (MACEs) were recorded. Both microbiota abundance [Corynebacterium tuberculostearicum (HR, 1.28; 95% CI, 1.03-1.58) and Staphylococcus aureus (S. aureus) (HR, 1.16; 95% CI, 1.02-1.33) ] and microbiota clusters (Cluster 2 versus Cluster 1: HR, 1.84; 95% CI, 1.04-3.27) could independently predict MACE. Furthermore, a model based on established independent predictors alone was significantly improved by the addition of different microbiota patterns. In addition, CD14⁺⁺CD16⁺ monocytes (Mon2) had a significant mediation effect on the microbiota patterns → MACE association. The present study demonstrated that the abundance and clusters of circulating microbiota are associated with future adverse cardiovascular events independent of traditional risk factors, which were partially mediated by an increase in Mon2.

Isolation and Characterization of Nocardiae Associated with Foaming Coastal Marine Waters

Nocardiosis is an infectious disease caused by Nocardia species that occurs worldwide, albeit more prevalently in tropical/subtropical regions. It can appear as either acute, subacute or as a chronic infection mostly with those with a compromised/weakened immune system. Inhalation of spores and or mycelium fragments is the main transmission route for developing pulmonary nocardiosis. In contrast, cutaneous nocardiosis usually occurs via direct contact. In the subtropical region of the Sunshine Coast in Australia foaming events with thick and persistent and orange-brown color foam have been observed during summer seasons in the near shore marine environments. This study reports the existence of nocardiae in these near shore marine environments by the use of a novel isolation method which used the gas requirements of nocardiae as a selective battery. A total of 32 nocardiae were isolated with the use of this novel method and subsequently conducted molecular identification methods confirmed that the isolates belonged to the genus Nocardia. Twenty-one isolates out of the 32 were closely related to N. nova strains MGA115 and one was related to CBU 09/875, in addition when compared with human pathogenic nocardiae twenty of the isolates were found to be related to N. nova strain JCM 6044. Isolates displayed varied resistance against some of the antibiotics tested when interpretation threshold recommended the Comite de L'Antibiogramme de la Societe Francaise de Microbiologie were used. The highest level of resistance against cefotaxime (n = 27) and ceftriaxone (n = 24). Some of the isolates (n = 6) that displayed resistance to selected antibiotics also possessed potential human pathogenic characteristics such as adherence and translocation through human long epithelial cells as well as displaying phage resistance (n = 26). They might thus present a potential public health risk if frequently encountered through exposure to aerosols generated by the foam as well as direct contact through a wound. Preventative measures to control the growth of nocardiae in such environments such as the control of pollutants, might prevent potential infections that might be caused by these bacteria in humans as well as in marine animals.

Assessing Pseudomonas aeruginosa Autoinducer Effects on Mammalian Epithelial Cells

The human mucosal environment in the gut is rich with interactions between microbiota and mammalian epithelia. Microbes such as the Gram-negative bacterium Pseudomonas aeruginosa may use quorum sensing to communicate with other microorganisms and mammalian cells to alter gene expression. Here, we present methodologies to evaluate the effects of P. aeruginosa N-(3-oxo-dodecanoyl)-L-homoserine lactone (3O-C₁₂-HSL) on Caco-2 cell monolayers. First, we describe a method for assessing barrier function and permeability of epithelial cells when exposed to 3O-C₁₂-HSL by measuring transepithelial electrical resistance (TER) and paracellular flow using fluorescently labeled dextran. Secondly, we detail methods to investigate the effect of 3O-C₁₂-HSL on protein-protein interactions of epithelial junction proteins. Lastly, we will detail imaging techniques to visualize Caco-2 barrier disruption following exposure to 3O-C₁₂-HSL through the use of confocal laser scanning microscopy (CLSM) and a super resolution technique, stimulated emission depletion (STED) microscopy, to achieve nanoscale visualization of Caco-2 monolayers.

Genomic Comparison of Translocating and Non-Translocating Escherichia coli

Translocation of E. coli across the gut epithelium can result in fatal sepsis in post-surgical patients. In vitro and in vivo experiments have identified the existence of a novel pathotype of translocating E. coli (TEC) that employs an unknown mechanism for translocating across epithelial cells to the mesenteric lymph nodes and the blood stream in both humans and animal models. In this study the genomes of four TEC strains isolated from the mesenteric lymph nodes of a fatal case of hospitalised patient (HMLN-1), blood of pigs after experimental shock (PC-1) and after non-lethal haemorrhage in rats (KIC-1 and KIC-2) were sequenced in order to identify the genes associated with their adhesion and/or translocation. To facilitate the comparison, the genomes of a non-adhering, non-translocating E. coli (46–4) and adhering but non-translocating E. coli (73–89) were also sequenced and compared. Whole genome comparison revealed that three (HMLN-1, PC-1 and KIC-2) of the four TEC strains carried a genomic island that encodes a Type 6 Secretion System that may contribute to adhesion of the bacteria to gut epithelial cells. The human TEC strain HMLN-1 also carried the invasion ibeA gene, which was absent in the animal TEC strains and is likely to be associated with host-specific translocation. Phylogenetic analysis revealed that the four TEC strains were distributed amongst three distinct E. coli phylogroups, which was supported by the presence of phylogroup specific fimbriae gene clusters. The genomic comparison has identified potential genes that can be targeted with knock-out experiments to further characterise the mechanisms of E. coli translocation.

A combination of PhP typing and β-d-glucuronidase gene sequence variation analysis for differentiation of Escherichia coli from humans and animals

We investigated the usefulness of the β-d-glucuronidase gene variance in Escherichia coli as a microbial source tracking tool using a novel algorithm for comparison of sequences from a prescreened set of host-specific isolates using a high-resolution PhP typing method. A total of 65 common biochemical phenotypes belonging to 318 E. coli strains isolated from humans and domestic and wild animals were analysed for nucleotide variations at 10 loci along a 518 bp fragment of the 1812 bp β-d-glucuronidase gene. Neighbour-joining analysis of loci variations revealed 86 (76.8%) human isolates and 91.2% of animal isolates were correctly identified. Pairwise hierarchical clustering improved assignment; where 92 (82.1%) human and 204 (99%) animal strains were assigned to their respective cluster. Our data show that initial typing of isolates and selection of common types from different hosts prior to analysis of the β-d-glucuronidase gene sequence improves source identification. We also concluded that numerical profiling of the nucleotide variations can be used as a valuable approach to differentiate human from animal E. coli. This study signifies the usefulness of the β-d-glucuronidase gene as a marker for differentiating human faecal pollution from animal sources.

Analysis of the virulence of an atypical enteropathogenic Escherichia coli strain in vitro and in vivo and the influence of type three secretion system

Atypical enteropathogenic Escherichia coli (aEPEC) inject various effectors into intestinal cells through a type three secretion system (T3SS), causing attaching and effacing (A/E) lesions. We investigated the role of T3SS in the ability of the aEPEC 1711-4 strain to interact with enterocytes in vitro (Caco-2 cells) and in vivo (rabbit ileal loops) and to translocate the rat intestinal mucosa in vivo. A T3SS isogenic mutant strain was constructed, which showed marked reduction in the ability to associate and invade but not to persist inside Caco-2 cells. After rabbit infection, only aEPEC 1711-4 was detected inside enterocytes at 8 and 24 hours pointing to a T3SS-dependent invasive potential in vivo. In contrast to aEPEC 1711-4, the T3SS-deficient strain no longer produced A/E lesions or induced macrophage infiltration. We also demonstrated that the ability of aEPEC 1711-4 to translocate through mesenteric lymph nodes to spleen and liver in a rat model depends on a functional T3SS, since a decreased number of T3SS mutant bacteria were recovered from extraintestinal sites. These findings indicate that the full virulence potential of aEPEC 1711-4 depends on a functional T3SS, which contributes to efficient adhesion/invasion in vitro and in vivo and to bacterial translocation to extraintestinal sites.

Prevalence and pathogenesis of extended-spectrum beta-lactamase producing Escherichia coli causing urinary tract infection in hospitalized patients

A total of 296 E. coli strains isolated from hospitalized patients with urinary tract infection were included in this study. These strains were tested for their resistance to 22 antimicrobial drugs and the presence of ESBLs genes coding for TEM, SHV, OXA, and CTX-M. We further characterized them for their interaction with a renal cell line (A-498) and a gastrointestinal cell line (Caco-2). Strains were also typed using a combination of RAPD-PCR, PhP-typing and phylogenetic grouping. Only eight strains (2.7 %) were confirmed as ESBLs producers. The most common clonal type contained 35 isolates and only two of them were ESBLs producers and both showed a high degree of adhesion to both cell lines but only one was able to translocate in Caco-2 cells. These strains belonged to phylogenetic group B2, were resistant to nine antibiotics and carried CTX-M-type of ESBL. The remaining six strains belonged to single clones with different phylogenetic groups and ESBL genotypes and were resistant to between 12 and 15 antibiotics. They also showed a high rate of adhesion to A-498 cells (19 ± 2 to 35 ± 3 CFU/cell) and all translocated in this cell line. The rate of adhesion of ESBL-producing strains to Caco-2 cells (11 ± 3.4 CFU/cell) was significantly lower than A-498 cells (26 ± 8 CFU/cell) (p = 0.0002) and only four of them translocated in Caco-2 cells. Our results suggest that the ESBL-producing clones of E. coli have a potential to translocate and cause septicemia in hospitalized patients with UTI.

Virulence characteristics of translocating Escherichia coli and the interleukin-8 response to infection

Four efficiently translocating Escherichia coli (TEC) strains isolated from the blood of humans (HMLN-1), pigs (PC-1) and rats (KIC-1 and KIC-2) were tested for their ability to adhere and translocate across human gut epithelial Caco-2 and HT-29 cells, to elicit a proinflammatory response and for the presence of 47 pathogenic E. coli virulence genes. HMLN-1 and PC-1 were more efficient in adhesion and translocation than rat strains, had identical biochemical phenotype (BPT) and serotype (O77:H18) and phylogenetic group (D). KIC-2 adhered more than KIC-1, belonged to different BPT and serotype but the same phylogenetic group as KIC-1. TEC strains elicited significantly higher IL-8 response in both cell lines (P < 0.05) and monocytic THP-1 (P < 0.0001) cells than non-TEC strains. KIC-2 induced the highest IL-8 response which may be associated with its immunostimulatory flagellin. Apart from adhesin genes fimH and bmaE that were carried by all strains, HMLN-1 and PC-1 carried capsule synthesis gene kpsMT III and KIC-2 carried the EAST1 toxin gene. The lack of known virulence genes and the ability of TEC to efficiently adhere and translocate whilst causing proinflammatory response suggests that these strains may carry as yet unidentified genes that enable their translocating ability.