A comparison of monomicrobial versus polymicrobial Enterococcus faecalis bacteriuria in a French University Hospital

Canine uropathogenic and avian pathogenic Escherichia coli harboring conjugative plasmids exhibit augmented growth and exopolysaccharide production in response to Enterococcus faecalis

Uropathogenic Escherichia coli (UPEC) and avian pathogenic Escherichia coli (APEC) are extraintestinal pathogenic Escherichia coli (ExPEC) that infect dogs and poultry. These agents occur both as single-species infections and, commonly, in co-infection with Enterococcus faecalis (EF); however, it is unclear how EF co-infections modulate ExPEC virulence. Genetic drivers of interspecies interactions affecting virulence were identified using macrocolony co-culture, chicken embryo co-infection experiments, and whole-genome sequence analysis of ExPEC and EF clinical isolates. Ten of 11 UPEC strains originally co-isolated with EF exhibited a growth advantage when co-cultured with EF on iron-limited, semi-solid media in contrast to growing alone (P < 0.01). Phylogenetic analyses of these UPEC and 18 previously screened APEC indicated the growth-response phenotype was conserved in ExPEC despite strain diversity. When genomes of EF-responsive ExPEC were compared to non-responsive ExPEC genomes, EF-induced growth was associated with siderophore, exopolysaccharide (EPS), and plasmid conjugative transfer genes. Two matched pairs of EF-responsive and non-responsive ExPEC were selected for further characterization by macrocolony proximity and chicken embryo lethality assays. EF-responsive ExPEC produced 5 to 16 times more EPS in proximity to EF and were more lethal to embryos alone and during co-infection with EF compared to non-responsive ExPEC (P < 0.05). A responsive APEC strain cured of its conjugative plasmid lost the enhanced growth and EPS production response to EF. These data demonstrate that ExPEC growth augmentation by EF occurs in UPEC and APEC strains and is linked to conjugative virulence plasmids and EPS production, which are widely conserved ExPEC virulence determinants.

Linezolid in enterococcal urinary tract infection: a multicentre study

PURPOSE

Few data have been published on the efficacy of linezolid in enterococcal urinary tract infection (e-UTI). The aims of this study were to describe the characteristics of patients with enterococci UTI treated with linezolid, and to evaluate the efficacy and the tolerance of linezolid treatment.

METHODS

An observational multicentre retrospective study was conducted in 5 hospitals in France. Patients were included if they met the following criteria: ≥18 years, clinical and microbiological criteria for enterococcal UTI and linezolid treatment > 48 h. Primary outcome was clinical failure.

RESULTS

Eighty-one patients were included between January 2015 and December 2021. The median age was 73.0 [64; 83] years and 47 (58%) were men. The median Charlson comorbidity index was 3.00 [2; 6]. E. faecium was reported in 65 (80%) cases and E. faecalis in 26 cases (32%). Polymicrobial infections occurred in 41 (51%) cases. No enterococci was resistant to vancomycin. Before linezolid prescription an empiric antimicrobial treatment was started in 48 (59%) cases and was effective against enterococci in 19/48 (39.5%) patients for a median of 3.5 days [2.0; 4.0]. The median duration of linezolid antibiotic treatment was 13 days [10; 14]. Three adverse events were reported, none were serious but one led to discontinuation of treatment. Treatment failure was reported in 2 cases (2.5%).

CONCLUSION

This study provides evidence for efficacy and safety of linezolid in enterococcal UTI.

Multispecies bacterial invasion of human host cells

Urinary tract infection (UTI), one of the most common bacterial infections worldwide, is a typical example of an infection that is often polymicrobial in nature. While the overall infection course is known on a macroscale, bacterial behavior is not fully understood at the cellular level and bacterial pathophysiology during multispecies infection is not well characterized. Here, using clinically relevant bacteria, human epithelial bladder cells and human urine, we establish co-infection models combined with high resolution imaging to compare single- and multi-species bladder cell invasion events in three common uropathogens: uropathogenic Escherichia coli (UPEC), Klebsiella pneumoniae and Enterococcus faecalis. While all three species invaded the bladder cells, under flow conditions the Gram-positive E. faecalis was significantly less invasive compared to the Gram-negative UPEC and K. pneumoniae. When introduced simultaneously during an infection experiment, all three bacterial species sometimes invaded the same bladder cell, at differing frequencies suggesting complex interactions between bacterial species and bladder cells. Inside host cells, we observed encasement of E. faecalis colonies specifically by UPEC. During subsequent dispersal from the host cells, only the Gram-negative bacteria underwent infection-related filamentation (IRF). Taken together, our data suggest that bacterial multispecies invasions of single bladder cells are frequent and support earlier studies showing intraspecies cooperation on a biochemical level during UTI.

A Bird's-Eye View of the Pathophysiologic Role of the Human Urobiota in Health and Disease: Can We Modulate It?

For a long time, urine has been considered sterile in physiological conditions, thanks to the particular structure of the urinary tract and the production of uromodulin or Tamm-Horsfall protein (THP) by it. More recently, thanks to the development and use of new technologies, i.e., next-generation sequencing and expanded urine culture, the identification of a microbial community in the urine, the so-called urobiota, became possible. Major phyla detected in the urine are represented by Firmicutes, Bacteroidetes, Proteobacteria, and Actinobacteria. Particularly, the female urobiota is largely represented by Lactobacillus spp., which are very active against urinary pathogenic Escherichia (E.) coli (UPEC) strains via the generation of lactic acid and hydrogen peroxide. Gut dysbiosis accounts for recurrent urinary tract infections (UTIs), so-called gut-bladder axis syndrome with the formation of intracellular bacterial communities in the course of acute cystitis. However, other chronic urinary tract infections are caused by bacterial strains of intestinal derivation. Monomicrobial and polymicrobial infections account for the outcome of acute and chronic UTIs, even including prostatitis and chronic pelvic pain. E. coli isolates have been shown to be more invasive and resistant to antibiotics. Probiotics, fecal microbial transplantation, phage therapy, antimicrobial peptides, and immune-mediated therapies, even including vaccines for the treatment of UTIs, will be described.

Genetic and functional enrichments associated with Enterococcus faecalis isolated from the urinary tract

IMPORTANCE

Urinary tract infection (UTI) is a global health issue that imposes a substantial burden on healthcare systems. Women are disproportionately affected by UTI, with >60% of women experiencing at least one UTI in their lifetime. UTIs can recur, particularly in postmenopausal women, leading to diminished quality of life and potentially life-threatening complications. Understanding how pathogens colonize and survive in the urinary tract is necessary to identify new therapeutic targets that are urgently needed due to rising rates of antimicrobial resistance. How Enterococcus faecalis, a bacterium commonly associated with UTI, adapts to the urinary tract remains understudied. Here, we generated a collection of high-quality closed genome assemblies of clinical urinary E. faecalis isolated from the urine of postmenopausal women that we used alongside detailed clinical metadata to perform a robust comparative genomic investigation of genetic factors that may be involved in E. faecalis survival in the urinary tract.

Functional and genetic adaptations contributing to Enterococcus faecalis persistence in the female urinary tract

Enterococcus faecalis is the leading Gram-positive bacterial species implicated in urinary tract infection (UTI). An opportunistic pathogen, E. faecalis is a commensal of the human gastrointestinal tract (GIT) and its presence in the GIT is a predisposing factor for UTI. The mechanisms by which E. faecalis colonizes and survives in the urinary tract (UT) are poorly understood, especially in uncomplicated or recurrent UTI. The UT is distinct from the GIT and is characterized by a sparse nutrient landscape and unique environmental stressors. In this study, we isolated and sequenced a collection of 37 clinical E. faecalis strains from the urine of primarily postmenopausal women. We generated 33 closed genome assemblies and four highly contiguous draft assemblies and conducted a comparative genomics to identify genetic features enriched in urinary E. faecalis with respect to E. faecalis isolated from the human GIT and blood. Phylogenetic analysis revealed high diversity among urinary strains and a closer relatedness between urine and gut isolates than blood isolates. Plasmid replicon (rep) typing further underscored possible UT-GIT interconnection identifying nine shared rep types between urine and gut E. faecalis . Both genotypic and phenotypic analysis of antimicrobial resistance among urinary E. faecalis revealed infrequent resistance to front-line UTI antibiotics nitrofurantoin and fluoroquinolones and no vancomycin resistance. Finally, we identified 19 candidate genes enriched among urinary strains that may play a role in adaptation to the UT. These genes are involved in the core processes of sugar transport, cobalamin import, glucose metabolism, and post-transcriptional regulation of gene expression.

IMPORTANCE

Urinary tract infection (UTI) is a global health issue that imposes substantial burden on healthcare systems. Women are disproportionately affected by UTI with >60% of women experiencing at least one UTI in their lifetime. UTIs can recur, particularly in postmenopausal women, leading to diminished quality of life and potentially life-threatening complications. Understanding how pathogens colonize and survive in the urinary tract is necessary to identify new therapeutic targets that are urgently needed due to rising rates of antimicrobial resistance. How Enterococcus faecalis , a bacterium commonly associated with UTI, adapts to the urinary tract remains understudied. Here, we generated a collection of high-quality closed genome assemblies of clinical urinary E. faecalis isolated from the urine of postmenopausal women that we used alongside detailed clinical metadata to perform a robust comparative genomic investigation of genetic factors that may mediate urinary E. faecalis adaptation to the female urinary tract.

The Coexistence of Bacterial Species Restructures Biofilm Architecture and Increases Tolerance to Antimicrobial Agents

Chronic infections caused by polymicrobial biofilms are often difficult to treat effectively, partially due to the elevated tolerance of polymicrobial biofilms to antimicrobial treatments. It is known that interspecific interactions influence polymicrobial biofilm formation. However, the underlying role of the coexistence of bacterial species in polymicrobial biofilm formation is not fully understood. Here, we investigated the effect of the coexistence of Enterococcus faecalis, Escherichia coli O157:H7, and Salmonella enteritidis on triple-species biofilm formation. Our results demonstrated that the coexistence of these three species enhanced the biofilm biomass and led to restructuring of the biofilm into a tower-like architecture. Furthermore, the proportions of polysaccharides, proteins, and eDNAs in the extracellular matrix (ECM) composition of the triple-species biofilm were significantly changed compared to those in the E. faecalis mono-species biofilm. Finally, we analyzed the transcriptomic profile of E. faecalis in response to coexistence with E. coli and S. enteritidis in the triple-species biofilm. The results suggested that E. faecalis established dominance and restructured the triple-species biofilm by enhancing nutrient transport and biosynthesis of amino acids, upregulating central carbon metabolism, manipulating the microenvironment through "biological weapons," and activating versatile stress response regulators. Together, the results of this pilot study reveal the nature of E. faecalis-harboring triple-species biofilms with a static biofilm model and provide novel insights for further understanding interspecies interactions and the clinical treatment of polymicrobial biofilms. IMPORTANCE Bacterial biofilms possess distinct community properties that affect various aspects of our daily lives. In particular, biofilms exhibit increased tolerance to chemical disinfectants, antimicrobial agents, and host immune responses. Multispecies biofilms are undoubtedly the dominant form of biofilms in nature. Thus, there is a pressing need for more research directed at delineating the nature of multispecies biofilms and the effects of the properties on the development and survival of the biofilm community. Here, we address the effects of the coexistence of Enterococcus faecalis, Escherichia coli, and Salmonella enteritidis on triple-species biofilm formation with a static model. In combination with transcriptomic analyses, this pilot study explores the potential underlying mechanisms that lead to the dominance of E. faecalis in triple-species biofilms. Our findings provide novel insights into the nature of triple-species biofilms and indicate that the composition of multispecies biofilms should be a key consideration when determining antimicrobial treatments.

Intracellular bacterial communities in patient with recurrent urinary tract infection caused by Staphylococcus spp and Streptococcus agalactiae: a case report and literature review

Background

 Urinary tract infections (UTI) are among the most frequent pathologies worldwide. Uropathogenic Escherichia coli (UPEC) is the leading etiological agent; however, depending on the patient's characteristics, the etiology may include some atypical pathogens. Some pathogenic bacteria can internalize in the urothelial and phagocytic cells complicating treatment and timely diagnosis.

Case presentation

We present a clinical case of a married female patient with urological alteration, constant catheterization, and urethral dilation with recurrent UTI for ten years, with five episodes per year and reports of negative urine culture. The microscopic analysis revealed intracellular bacterial communities (IBC) and pyocytes with active bacteria. A protocol was designed for the release of intracellular bacteria in urine samples; without the proposed treatment, the urine culture was negative. However, upon releasing the internalized bacteria, we obtained a polymicrobial urine culture. We isolated and identified Staphylococcus aureus, Staphylococcus epidermidis, Staphylococcus simulans, and Streptococcus agalactiae. All microorganisms were sensitive to nitrofurans and sulfas. The patient is under treatment with nitrofurantoin and continuous follow-up by our workgroup.

Conclusions

 It is essential to look for IBC and pyocytes with active bacteria in patients with recurrent UTIs to avoid false-negative urine culture results and provide timely treatment. Polymicrobial culture must be considered depending on the patient and clinical history.

Systematic Review of Literature Examining Bacterial Urinary Tract Infections in Diabetes

This systematic review addresses the central research question, "what is known from the published, peer-reviewed literature about the impact of diabetes on the risk of bacterial urinary tract infections (UTI)?" We examine the results from laboratory studies where researchers have successfully adapted mouse models of diabetes to study the pathophysiology of ascending UTI. These studies have identified molecular and cellular effectors shaping immune defenses against infection of the diabetic urinary tract. In addition, we present evidence from clinical studies that in addition to diabetes, female gender, increased age, and diabetes-associated hyperglycemia, glycosuria, and immune impairment are important risk factors which further increase the risk of UTI in diabetic individuals. Clinical studies also show that the uropathogenic genera causing UTI are largely similar between diabetic and nondiabetic individuals, although diabetes significantly increases risk of UTI by drug-resistant uropathogenic bacteria.

Prospective assessment of catheter-associated bacteriuria clinical presentation, epidemiology, and colonization dynamics in nursing home residents

BACKGROUND

Catheterization facilitates continuous bacteriuria, for which the clinical significance remains unclear. This study aimed to determine the clinical presentation, epidemiology, and dynamics of bacteriuria in a cohort of long-term catheterized nursing home residents.

METHODS

Prospective urine culture, urinalysis, chart review, and assessment of signs and symptoms of infection were performed weekly for 19 study participants over 7 months. All bacteria ≥ 1 × 10³ cfu/mL were cultured, isolated, identified, and tested for susceptibility to select antimicrobials.

RESULTS

In total, 226 of the 234 urine samples were polymicrobial (97%), with an average of 4.7 isolates per weekly specimen. A total of 228 urine samples (97%) exhibited ≥ 1 × 10⁶ CFU/mL, 220 (94%) exhibited abnormal urinalysis, 126 (54%) were associated with at least 1 possible sign or symptom of infection, and 82 (35%) would potentially meet a standardized definition of catheter-associated urinary tract infection (CAUTI), but only 3 had a caregiver diagnosis of CAUTI. Bacterial isolates (286; 30%) were resistant to a tested antimicrobial agent, and bacteriuria composition was remarkably stable despite a combined total of 54 catheter changes and 23 weeks of antimicrobial use.

CONCLUSION

Bacteriuria composition was largely polymicrobial, including persistent colonization by organisms previously considered to be urine culture contaminants. Neither antimicrobial use nor catheter changes sterilized the urine, at most resulting in transient reductions in bacterial burden followed by new acquisition of resistant isolates. Thus, this patient population exhibits a high prevalence of bacteriuria coupled with potential indicators of infection, necessitating further exploration to identify sensitive markers of true infection.

FUNDING

This work was supported by the NIH (R00 DK105205, R01 DK123158, UL1 TR001412).

Polymicrobial interactions in the urinary tract: is the enemy of my enemy my friend?

The vast majority of research pertaining to urinary tract infection has focused on a single pathogen in isolation, and predominantly Escherichia coli. However, polymicrobial urine colonization and infection are prevalent in several patient populations, including individuals with urinary catheters. The progression from asymptomatic colonization to symptomatic infection and severe disease is likely shaped by interactions between traditional pathogens as well as constituents of the normal urinary microbiota. Recent studies have begun to experimentally dissect the contribution of polymicrobial interactions to disease outcomes in the urinary tract, including their role in development of antimicrobial-resistant biofilm communities, modulating the innate immune response, tissue damage, and sepsis. This review aims to summarize the epidemiology of polymicrobial urine colonization, provide an overview of common urinary tract pathogens, and present key microbe-microbe and host-microbe interactions that influence infection progression, persistence, and severity.

A Rare Opportunist, Morganella morganii, Decreases Severity of Polymicrobial Catheter-Associated Urinary Tract Infection

Catheter-associated urinary tract infections (CAUTIs) are common hospital-acquired infections and frequently polymicrobial, which complicates effective treatment. However, few studies experimentally address the consequences of polymicrobial interactions within the urinary tract, and the clinical significance of polymicrobial bacteriuria is not fully understood. Proteus mirabilis is one of the most common causes of monomicrobial and polymicrobial CAUTI and frequently cocolonizes with Enterococcus faecalis, Escherichia coli, Providencia stuartii, and Morganella morganiiP. mirabilis infections are particularly challenging due to its potent urease enzyme, which facilitates formation of struvite crystals, catheter encrustation, blockage, and formation of urinary stones. We previously determined that interactions between P. mirabilis and other uropathogens can enhance P. mirabilis urease activity, resulting in greater disease severity during experimental polymicrobial infection. Our present work reveals that M. morganii acts on P. mirabilis in a contact-independent manner to decrease urease activity. Furthermore, M. morganii actively prevents urease enhancement by E. faecalis, P. stuartii, and E. coli Importantly, these interactions translate to modulation of disease severity during experimental CAUTI, predominantly through a urease-dependent mechanism. Thus, products secreted by multiple bacterial species in the milieu of the catheterized urinary tract can directly impact prognosis.

[CORRESPONDENCE OF POLYMICROBIAL BACTERIURIA IN THE UNCOMPLICATED URINARY TRACT INFECTION OF THE PREMENOPAUSAL WOMAN]

(Objectives) We report the clinical features about polymicrobial bacteria detection cases in the uncomplicated urinary tract infection of the premenopausal woman from the voided midstream urine culture. (Methods) We retrospectively reviewed the premenopausal woman from 18-49 years patients visited Sendai City Hospital from April, 2006 to December, 2014, diagnosed uncomplicated cystitis or uncomplicated pyelonephritis. We analyzed for 375 specimens from the voided midstream urine culture. (Results) Among 375 specimens, the urine culture-positive for uropathogens were 211 specimens. The monomicrobial bacterial were detected in 184 specimens (87.2%) and polymicrobial bacterial specimens were 27 specimens (12.8%). The most combination group was the caused bacteria and periurethral microorganisms in 20 specimens (74.1%). Then 6 periurethral microorganisms specimens (22.2%), the caused bacteria were only 1 specimen was overlapped (3.7%). The case of urinary tract infections recurrence or revealed voiding dysfunction that need periodic treatment were more prevalent in the polymicrobial than the monomicrobial group (22.2% vs 9.8%, p=0.043). (Conclusions) When polymicrobial bacteria were detected in uncomplicated urinary tract infection in premenopausal woman, it was confirmed that there were the most combinations of caused bacteria and periurethral microorganisms. In these cases, treatment intended for only the caused bacteria. A risk of the infection recurrence and voiding dysfunction were statistically significant higher rate in the polymicrobial bacteria detection cases, and it might be necessary to consider that search to complicated urinary tract infection.

Association of Enterococcus spp. with Severe Combat Extremity Injury, Intensive Care, and Polymicrobial Wound Infection

BACKGROUND

Combat-related extremity wound infections can complicate the recovery of injured military personnel. The Enterococcus genus contains both commensal and pathogenic bacteria found in many combat wounds. We describe the patient population susceptible to Enterococcus infection, the characteristics of Enterococcus spp. isolated from combat-related wounds, and the microbiological profile of Enterococcus-positive wounds.

METHODS

Patient and culture data were obtained from the Trauma Infectious Disease Outcomes Study. Subjects were divided into a case group with enterococcal extremity wound infections and a comparator group with wound infections caused by other micro-organisms.

RESULTS

Case and comparator subjects had similar patterns of injury and infection. Case subjects had higher Injury Severity Scores (33 vs. 30; p < 0.001), longer hospitalization at U.S. facilities (55 vs. 40 days; p = 0.004), and required more large-volume blood transfusions (>20 units) within 24 h post-injury (53% vs. 30%; p < 0.001). Approximately 60% of case subjects had three or more infections, and 91% had one or more polymicrobial infections, compared with 43% and 50%, respectively, in the comparator group. The thigh was the most common site of Enterococcus spp. isolation, contributing 50% of isolates. Enterococcus faecium was the predominant species isolated from case-group infections overall (66%), as well as in polymicrobial infections (74%). Frequent co-colonizing microbes in polymicrobial wound infections with Enterococcus were other ESKAPE pathogens (64%) (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae [and Escherichia coli], Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp.) and fungi (35%).

CONCLUSIONS

The specific pathogenicity of Enterococcus relative to other pathogens in polymicrobial wounds is unknown. Identifying strain-specific outcomes and investigating the interactions of Enterococcus strains with other wound pathogens could provide additional tools and strategies for infection mitigation in combat-related wounds.

Model systems for the study of Enterococcal colonization and infection

Enterococcus faecalis and Enterococcus faecium are common inhabitants of the human gastrointestinal tract, as well as frequent opportunistic pathogens. Enterococci cause a range of infections including, most frequently, infections of the urinary tract, catheterized urinary tract, bloodstream, wounds and surgical sites, and heart valves in endocarditis. Enterococcal infections are often biofilm-associated, polymicrobial in nature, and resistant to antibiotics of last resort. Understanding Enterococcal mechanisms of colonization and pathogenesis are important for identifying new ways to manage and intervene with these infections. We review vertebrate and invertebrate model systems applied to study the most common E. faecalis and E. faecium infections, with emphasis on recent findings examining Enterococcal-host interactions using these models. We discuss strengths and shortcomings of each model, propose future animal models not yet applied to study mono- and polymicrobial infections involving E. faecalis and E. faecium, and comment on the significance of anti-virulence strategies derived from a fundamental understanding of host-pathogen interactions in model systems.

Interaction networks, ecological stability, and collective antibiotic tolerance in polymicrobial infections

Polymicrobial infections constitute small ecosystems that accommodate several bacterial species. Commonly, these bacteria are investigated in isolation. However, it is unknown to what extent the isolates interact and whether their interactions alter bacterial growth and ecosystem resilience in the presence and absence of antibiotics. We quantified the complete ecological interaction network for 72 bacterial isolates collected from 23 individuals diagnosed with polymicrobial urinary tract infections and found that most interactions cluster based on evolutionary relatedness. Statistical network analysis revealed that competitive and cooperative reciprocal interactions are enriched in the global network, while cooperative interactions are depleted in the individual host community networks. A population dynamics model parameterized by our measurements suggests that interactions restrict community stability, explaining the observed species diversity of these communities. We further show that the clinical isolates frequently protect each other from clinically relevant antibiotics. Together, these results highlight that ecological interactions are crucial for the growth and survival of bacteria in polymicrobial infection communities and affect their assembly and resilience.