Glenn Werneburg: Thanks so much for having me. It's great to be here, and thanks for UroToday for the invitation as well. So we will first start a little bit in terms of what's the definition of this intracellular bacterial community? So this is the idea that there are intracellular aggregates of bacteria, and typically in the animal models, they've been shown to be uropathogenic E. coli bacteria, within uroepithelial cells. And the idea is that they're believed to arise during acute infection and to reseed the urinary tract for recurrence of urinary tract infection. And we know that about 50% of patients, of female patients, who have a UTI go on to have a recurrence within that same year, and about 50% of those recur again. This is a main issue clinically, and the underlying etiology of this is not yet clear. But we'll describe some of the evidence that these IBC entities do or do not exist in human bladders. They're believed to resist host immune defenses and antibiotics, and thus pose a reservoir to reseed the urinary tract. Now they've been described extensively and reproducibly, but almost all of this is in rodent models. I'll talk a little bit about some of the ancillary evidence for their existence in the human bladders, and some of the strengths and the limitations of the evidence that we have to date. So what is the evidence in the animal models? This is actually pretty strong, and it's been reproduced.
Some of the evidence accumulated over two decades ago now. So here's a number of very beautiful images. They're confocal microscopy images. We can see that we have uroplakin stained in red here. You have nuclei in blue. We can see that we have the most superficial layer of uroepithelial cells identified by having two nuclei, all the way on screen right there, you can see a couple of nuclei in these cells; together with the green indicating E. coli in the cytoplasm of these cells. In the bottom left of the screen is one of these nice merged images showing the uroepithelial cell intact with its two nuclei, indicating the superficial layer, as well as the E. coli present within the cell. In other words, an intracellular bacterial community. And there's a lot of corroborating evidence in terms of electron microscopy as well, such as what is shown at the bottom of the screen there. There's a little outpocketing of the uroepithelium, and this is consistent with what may indeed also be an IBC. Again, all of this is in the mouse models. All of this is in the animal literature. Now to go from there to humans, why is this important? First of all, all of what we know about IBCs or the vast majority of this has been extrapolated from the data and other animal data that I've just shown you. And there's no definitive evidence as of yet for or definitively against the presence of IBCs in the human bladder. But there is some indirect evidence that provides some biologic plausibility for the presence of these IBCs in the human bladder. I'll tell you some of that next.
And here are human specimens, but here is that the human specimens are voided specimens. So these are urine samples that have been collected after a patient with a recurrent UTI diagnosis has voided. And what we can see here is uroplakin in red and E. coli in green, on the screen left there. And you can see that the uroplakin and E. coli are co-localizing. This is consistent with an IBC-like entity. The key though is that this is in the voided urine specimen. This is not in the bladder wall itself. And there are other corroborative reports. Again, scanning electron microscopy and transmission electron microscopy shown in the center of the screen here that also suggest that these appear to be IBC-like entities. And the investigators, and a lot of this comes from Scott Hultgren's group and others, they're even able to isolate bacteria from these IBC-like entities and introduce them into a mouse model and take the bacteria through the IBC life cycle, demonstrating a phenotype in the mouse model. So there is strong evidence in the mouse literature for the existence of the IBCs. There's evidence in the human literature for these IBC-like entities to be present within the urine, but that doesn't necessarily speak to their presence or existence within the bladder wall itself. And why is that important? Well, the idea is that like a biofilm, the IBC may evade immunity and antibiotics, and that if these exist in the human bladder wall, their elimination is necessary to achieve a source control for recurrence of urinary tract infection.
So it's important to understand whether they exist because then we can understand whether or not we need to target them for source control. And if they exist, what are the targeting modalities to eradicate these IBCs? Well, the principle is that denudation of the urothelium would be necessary, and that can be accomplished in a couple of ways. One that's been described is bladder fulguration. A number of studies have now shown that fulguration of the bladder in very select patient populations may be associated with reduced UTI recurrence risk. And most of these studies are single-arm and/or retrospective, but it provides some biologic plausibility that denudation of the uroepithelium may reduce UTI recurrence. So we look forward to future trials wherein there's a randomization and placebo control. But there is some evidence suggestive that in these select patient populations, denudation of the uroepithelium through fulguration or other modalities may perhaps reduce UTI recurrence risk. Another possibility is through chemical denudation of the uroepithelium. This has been less studied in humans. Some opportunities might include protamine sulfate or other cationic compounds, and there is some evidence in the animal models that demonstrate that microbes can perhaps be eradicated through the use of these and other agents as well. So in conclusion, we've identified IBCs over decades in the mouse models. We have developed an understanding that the IBC-like entities exist in human urine specimens, but we haven't yet identified them in the bladder wall. And if they exist in the bladder wall, we haven't yet determined whether or not they contribute to the pathogenicity of recurrence of urinary tract infection. Thanks.
Alan Wein: Yeah, thank you so much. That was a great review. Have you seen any of the material that Philippe Zimmern has produced with those odd-looking lesions in the bladder, and actually biopsying those and seeing what were described as the intracellular bacteria in those?
Glenn Werneburg: Yeah, great question. So a lot of that work in terms of the fulguration has come from that group, and there is some exciting work to be able to further understand what's present within these bladder walls. So what that group and others have described is biopsying the wall, as you've suggested. And they've demonstrated that bacteria appear to exist within the wall in very small communities. So in many cases you can see five to 10 bacteria in some of those studies. These IBCs that have been described in the animal model are orders of magnitude greater number of bacteria. So how it relates between the mouse models, what's been described there and how it may be different in the humans, that's a little bit of a gap in the translational knowledge. I think that's a great first step that they have. They've shown that there are these entities within the bladder wall, whether and how many bacteria are present within a single uroepithelial cell, I think a lot of those questions remain open. And finally, one of the key aspects here is that they have to be a community structure that allows them to protect themselves from immunity and from antibiotics. So the presence of some E. coli within a wall of the bladder may or may not reflect what's been described as the intracellular bacterial community in the murine models.
Alan Wein: Got it. Yeah, I think that they now have or just had approved a grant allowing them to compare cystoscopy with identification of these little red, almost ulcerative lesions in the bladder, and then fulgurating these against conventional therapy, which I believe has been equated to like six months of nitrofurantoin, and then following the patients after that for six more months and seeing what the results are. So tell me, how would you then suggest that, let's say I have someone coming in the office that has recurrent urinary tract infections, pretty much all E. coli. Problem is that they've been septic at least once, maybe twice; they've been on a variety of what I would call advanced antibiotics for each one of these episodes and then stopped. One of the cephalosporins or something like Cipro or something, something that you wouldn't ordinarily recommend, but all the other antibiotics have failed. How would you manage these patients on a chronic basis? What would your advice to them be, or what would you give them, based on current evidence, in an effort to at least decrease the frequency of these?
Glenn Werneburg: Yeah, excellent question. It gets right to the crux of this. So what you've described is one of these patients really in the advanced areas in terms of UTI management. So of course we treat the UTI at hand. And then the next question which you've asked, and is what we're asking, is how do we prevent recurrence in the future? And antibiotic prophylaxis is a historic option. It has its issues, it has collateral damage, it has selection for resistance. Maybe there's no other oral agent that can be used for that. What we try to do is avoid the antibiotic prophylaxis and use some of the other agents that we have available, like a urinary antiseptic, for example, methenamine hippurate, or Hiprex, that combined with things like cranberry, things like, if it's a female patient, vaginal estrogen, all of these can be ancillary modalities that can reduce UTI risk. And these are in the AUA guidelines and others.
There are patients, though, that still have recurrent UTI following all of these. And we talk about instillation therapy at this point. There's some opportunity for antibiotic instillation therapy to reduce UTI recurrence without selecting for antibiotic resistance, at least theoretically to the same extent that you would from an oral antibiotic. But after all of these are exhausted, these patients often are patients that wind up becoming candidates for bladder removal, cystectomy, and a urinary diversion of some sort. So these patients are patients wherein new modalities like fulguration of the bladder may be a fantastic alternative. So I'm really looking forward to the trials that you've just described, to be able to understand whether this is effective. We have some evidence in support of that, as well of safety. But these randomized controlled trials will be very important to understand how that's going to fit into our clinical framework and to select the patients wherein this will be most effective.
Alan Wein: Listen, thank you so much. It's been really informative, and I appreciate your coming on the channel and telling us about this aspect of urinary tract infection.
Glenn Werneburg: Absolutely. It's been great to be here. Thank you.