Henry L. Schreiber

Selective depletion of uropathogenic E. coli from the gut by a FimH antagonist

Urinary tract infections (UTIs) caused by uropathogenic Escherichia coli (UPEC) affect 150 million people annually. Despite effective antibiotic therapy, 30–50% of patients experience recurrent UTIs. In addition, the growing prevalence of UPEC that are resistant to last-line antibiotic treatments, and more recently to carbapenems and colistin, make UTI a prime example of the antibiotic-resistance crisis and emphasize the need for new approaches to treat and prevent bacterial infections. UPEC strains establish reservoirs in the gut from which they are shed in the faeces, and can colonize the periurethral area or vagina and subsequently ascend through the urethra to the urinary tract, where they cause UTIs. UPEC isolates encode up to 16 distinct chaperone-usher pathway pili, and each pilus type may enable colonization of a habitat in the host or environment. For example, the type 1 pilus adhesin FimH binds mannose on the bladder surface, and mediates colonization of the bladder. However, little is known about the mechanisms underlying UPEC persistence in the gut. Here, using a mouse model, we show that F17-like and type 1 pili promote intestinal colonization and show distinct binding to epithelial cells distributed along colonic crypts. Phylogenomic and structural analyses reveal that F17-like pili are closely related to pilus types carried by intestinal pathogens, but are restricted to extra-intestinal pathogenic E. coli. Moreover, we show that targeting FimH with M4284, a high-affinity inhibitory mannoside, reduces intestinal colonization of genetically diverse UPEC isolates, while simultaneously treating UTI, without notably disrupting the structural configuration of the gut microbiota. By selectively depleting intestinal UPEC reservoirs, mannosides could markedly reduce the rate of UTIs and recurrent UTIs.

From Physiology to Pharmacy: Developments in the Pathogenesis and Treatment of Recurrent Urinary Tract Infections

Urinary tract infections (UTIs) are common, and over half of women report having had at least one in their lifetime. Nearly a third of these women experience recurrent UTI episodes, but the mechanisms of these recurrences are not fully elucidated. Frequent use of antimicrobials for treatment and prevention of UTIs and other infections has contributed to the evolution of multidrug-resistant microorganisms globally. This is a looming worldwide crisis that has created an urgent need for novel strategies for the treatment and prevention of UTIs. Furthering our understanding of the mechanisms of recurrent UTIs, from both host and bacterial perspectives, will be paramount in developing targeted management strategies. In this review, we discuss recent findings regarding recurrent UTIs in women, including progress in our understanding of the mechanisms of recurrence as well as emerging treatments.

Bacterial virulence phenotypes of Escherichia coli and host susceptibility determine risk for urinary tract infections

Risk for urinary tract infections is determined by a combination of host susceptibility determinants and diverse Escherichia coli phenotypes. Examining the many facets of Escherichia coli Urinary tract infections (UTIs) are most commonly caused by uropathogenic Escherichia coli (UPEC). In a new study, Schreiber et al. undertook an interdisciplinary analysis of an extensive panel of UTI-associated E. coli strains. They discovered strain-dependent variation in the colonization of two mouse models of UTI. The expression of conserved bacterial behaviors, such as metabolism and motility, diverged markedly among these strains and was a better predictor of bladder colonization than carriage of any set of genes, including previously identified putative urovirulence factors. These findings suggest that UTI risk is determined by the pairing of variable host susceptibilities with bacterial virulence phenotypes governed by both gene content and expression. Urinary tract infections (UTIs) are caused by uropathogenic Escherichia coli (UPEC) strains. In contrast to many enteric E. coli pathogroups, no genetic signature has been identified for UPEC strains. We conducted a high-resolution comparative genomic study using E. coli isolates collected from the urine of women suffering from frequent recurrent UTIs. These isolates were genetically diverse and varied in their urovirulence, that is, their ability to infect the bladder in a mouse model of cystitis. We found no set of genes, including previously defined putative urovirulence factors (PUFs), that were predictive of urovirulence. In addition, in some patients, the E. coli strain causing a recurrent UTI had fewer PUFs than the supplanted strain. In competitive experimental infections in mice, the supplanting strain was more efficient at colonizing the mouse bladder than the supplanted strain. Despite the lack of a clear genomic signature for urovirulence, comparative transcriptomic and phenotypic analyses revealed that the expression of key conserved functions during culture, such as motility and metabolism, could be used to predict subsequent colonization of the mouse bladder. Together, our findings suggest that UTI risk and outcome may be determined by complex interactions between host susceptibility and the urovirulence potential of diverse bacterial strains.

Antibody-Based Therapy for Enterococcal Catheter-Associated Urinary Tract Infections

ABSTRACT Gram-positive bacteria in the genus Enterococcus are a frequent cause of catheter-associated urinary tract infection (CAUTI), a disease whose treatment is increasingly challenged by multiantibiotic-resistant strains. We have recently shown that E. faecalis uses the Ebp pilus, a heteropolymeric surface fiber, to bind the host protein fibrinogen as a critical step in CAUTI pathogenesis. Fibrinogen is deposited on catheters due to catheter-induced inflammation and is recognized by the N-terminal domain of EbpA (EbpANTD), the Ebp pilus’s adhesin. In a murine model, vaccination with EbpANTD confers significant protection against CAUTI. Here, we explored the mechanism of protection using passive transfer of immune sera to show that antisera blocking EbpANTD-fibrinogen interactions not only is prophylactic but also can act therapeutically to reduce bacterial titers of an existing infection. Analysis of 55 clinical CAUTI, bloodstream, and gastrointestinal isolates, including E. faecalis, E. faecium, and vancomycin-resistant enterococci (VRE), revealed a diversity of levels of EbpA expression and fibrinogen-binding efficiency in vitro. Strikingly, analysis of 10 strains representative of fibrinogen-binding diversity demonstrated that, irrespective of EbpA levels, EbpANTD antibodies were universally protective. The results indicate that, despite diversity in levels of fibrinogen binding, strategies that target the disruption of EbpANTD-fibrinogen interactions have considerable promise for treatment of CAUTI. IMPORTANCE Urinary catheterization is a routine medical procedure, and it has been estimated that 30 million Foley catheters are used annually in the United States. Importantly, placement of a urinary catheter renders the patient susceptible to developing a catheter-associated urinary tract infection, accounting for 1 million cases per year. Additionally, these infections can lead to serious complications, including bloodstream infection and death. Enterococcus strains are a common cause of these infections, and management of enterococcal infections has been more difficult in recent years due to the development of antibiotic resistance and the ability of strains to disseminate, resulting in a major threat in hospital settings. In this study, we developed an antibiotic-sparing treatment that is effective against diverse enterococcal isolates, including vancomycin-resistant enterococci, during catheter-associated urinary tract infections. Urinary catheterization is a routine medical procedure, and it has been estimated that 30 million Foley catheters are used annually in the United States. Importantly, placement of a urinary catheter renders the patient susceptible to developing a catheter-associated urinary tract infection, accounting for 1 million cases per year. Additionally, these infections can lead to serious complications, including bloodstream infection and death. Enterococcus strains are a common cause of these infections, and management of enterococcal infections has been more difficult in recent years due to the development of antibiotic resistance and the ability of strains to disseminate, resulting in a major threat in hospital settings. In this study, we developed an antibiotic-sparing treatment that is effective against diverse enterococcal isolates, including vancomycin-resistant enterococci, during catheter-associated urinary tract infections.

Precision antimicrobial therapeutics: the path of least resistance?

The emergence of drug-resistant pathogens has led to a decline in the efficacy of traditional antimicrobial therapy. The rise in resistance has been driven by widespread use, and in some cases misuse, of antibacterial agents in treating a variety of infections. A growing body of research has begun to elucidate the harmful effects of broad-spectrum antibiotic therapy on the beneficial host microbiota. To combat these threats, increasing effort is being directed toward the development of precision antimicrobial therapeutics that target key virulence determinants of specific pathogens while leaving the remainder of the host microbiota undisturbed. This includes the recent development of small molecules termed “mannosides” that specifically target uropathogenic E. coli (UPEC). Mannosides are glycomimetics of the natural mannosylated host receptor for type 1 pili, extracellular appendages that promotes UPEC colonization in the intestine. Type 1 pili are also critical for colonization and infection in the bladder. In both cases, mannosides act as molecular decoys which potently prevent bacteria from binding to host tissues. In mice, oral treatment with mannosides simultaneously clears active bladder infection and removes intestinal UPEC while leaving the gut microbiota structure relatively unchanged. Similar treatment strategies successfully target other pathogens, like adherent-invasive E. coli (AIEC), an organism associated with Crohn’s disease (CD), in mouse models. While not without its challenges, antibiotic-sparing therapeutic approaches hold great promise in a variety of disease systems, including UTI, CD, otitis media (OM), and others. In this perspective we highlight the benefits, progress, and roadblocks to the development of precision antimicrobial therapeutics.

Catheterization alters bladder ecology to potentiate Staphylococcus aureus infection of the urinary tract

Significance Staphylococcus aureus is a cause of catheter-associated urinary tract infections (CAUTIs). S. aureus CAUTIs are problematic because they are usually caused by antibiotic-resistant strains, and patients who develop these infections have a high risk of developing serious complications. Catheterization in humans and mice causes damage in the bladder that results in the release of host protein fibrinogen (Fg). This study suggests that S. aureus exploits the presence of Fg via interactions mediated by the Fg-binding protein ClfB to facilitate colonization of the bladder and the catheter to cause a persistent infection in both mice and humans. Insights into S. aureus CAUTI pathogenesis is facilitating the development of more-targeted therapies to better treat these infections. Methicillin-resistant Staphylococcus aureus (MRSA) is an emerging cause of catheter-associated urinary tract infection (CAUTI), which frequently progresses to more serious invasive infections. We adapted a mouse model of CAUTI to investigate how catheterization increases an individual’s susceptibility to MRSA UTI. This analysis revealed that catheterization was required for MRSA to achieve high-level, persistent infection in the bladder. As shown previously, catheter placement induced an inflammatory response resulting in the release of the host protein fibrinogen (Fg), which coated the bladder and implant. Following infection, we showed that MRSA attached to the urothelium and implant in patterns that colocalized with deposited Fg. Furthermore, MRSA exacerbated the host inflammatory response to stimulate the additional release and accumulation of Fg in the urinary tract, which facilitated MRSA colonization. Consistent with this model, analysis of catheters from patients with S. aureus-positive cultures revealed colocalization of Fg, which was deposited on the catheter, with S. aureus. Clumping Factors A and B (ClfA and ClfB) have been shown to contribute to MRSA–Fg interactions in other models of disease. We found that mutants in clfA had significantly greater Fg-binding defects than mutants in clfB in several in vitro assays. Paradoxically, only the ClfB− strain was significantly attenuated in the CAUTI model. Together, these data suggest that catheterization alters the urinary tract environment to promote MRSA CAUTI pathogenesis by inducing the release of Fg, which the pathogen enhances to persist in the urinary tract despite the host’s robust immune response.

Narrowing the spectrum: the new frontier of precision antimicrobials.

Editorial summaryAntibiotics have become the standard of care for bacterial infections. However, rising rates of antibiotic-resistant infections are outpacing the development of new antimicrobials. Broad-spectrum antibiotics also harm beneficial microbial communities inhabiting humans. To combat antibiotic resistance and protect these communities, new precision antimicrobials must be engineered to target specific pathogens.

Cryo-Em Structure of Type 1 Pilus

Urinary tract infections (UTIs) are caused by a wide range of pathogens, but the most common causative agent of UTIs is uropathogenic Escherichia coli (UPEC). Virtually all uropathogenic strains of ...

MP23-19 FIBRINOGEN DEPOSITS ON URINARY CATHETERS IN A TIME-DEPENDENT MATTER AND CO-LOCALIZES WITH E. FAECALIS IN PATIENTS WITH POSITIVE E. FAECALIS URINE CULTURES

INTRODUCTION AND OBJECTIVES: There is mounting evidence that fibrinogen deposition on urinary catheters is a key step in the pathogenesis of catheter-associated urinary tract infection (CAUTI). The aim of this study was to investigate whether fibrinogen and Enterococcus faecalis co-localize on catheters acquired from patients with post-operative urine cultures positive for E. faecalis. METHODS: Urinary catheters from a series of 50 patients undergoing elective urologic procedures were collected post-operatively and analyzed via immunofluorescence to detect deposited fibrinogen. Pearson correlation was performed to measure the correlation between fibrinogen deposition and dwell time. Additional catheters and urine cultures were collected at time of catheter removal. Catheters from patients with positive Enterococcus cultures were probed for fibrinogen and Enterococcus via immunofluorescence. RESULTS: A total of 50 adult patients undergoing urinary catheterization as standard of care were prospectively identified at our institution. Fibrinogen concentration quantified as mg/catheter using a standard curve was highly correlated with catheter dwell time (r1⁄40.63; p<0.0001) (Figure 1). E. faecalis was capable of binding to fibrinogen on these catheters ex vivo.Five additional catheters were obtained from patients with E. faecalis-positive post-operative urine cultures. Fibrinogen was present at all time points (18 hours, 1 day, 1 day, 8 days, 9 days) and co-localized with E. faecalis (Figure 2) in vivo. CONCLUSIONS: We have previously shown that fibrinogen deposits on urinary catheters, and that E. faecalis is capable of binding to these catheters ex vivo. In this study, we demonstrate that E. faecalis co-localizes with fibrinogen in catheterized patients with urine cultures positive for E. faecalis. This data strengthens the clinical association of fibrinogen deposition with CAUTI and suggests that targeting the binding of E. faecalis with fibrinogen may help reduce the rate of Enterococcus CAUTI. Source of Funding: 1F32DK104516-01 (ALF-M), and National Institute of Allergy and Infectious Diseases and National Institute of Diabetes and Digestive and Kidney Diseases Grants R01-DK051406, R01-AI108749-01 and P50DK0645400 (ALF-M, JNW, HLS, JSP, MGC, SJH).