Host subversion by formation of intracellular bacterial communities in the urinary tract

Phenotypic resistant single-cell characteristics under recurring ampicillin antibiotic exposure in Escherichia coli

Non-heritable, phenotypic drug resistance toward antibiotics challenges antibiotic therapies. Characteristics of such phenotypic resistance have implications for the evolution of heritable resistance. Diverse forms of phenotypic resistance have been described, but phenotypic resistance characteristics remain less explored than genetic resistance. Here, we add novel combinations of single-cell characteristics of phenotypic resistant E. coli cells and compare those to characteristics of susceptible cells of the parental population by exposure to different levels of recurrent ampicillin antibiotic. Contrasting expectations, we did not find commonly described characteristics of phenotypic resistant cells that arrest growth or near growth. We find that under ampicillin exposure, phenotypic resistant cells reduced their growth rate by about 50% compared to growth rates prior to antibiotic exposure. The growth reduction is a delayed alteration to antibiotic exposure, suggesting an induced response and not a stochastic switch or caused by a predetermined state as frequently described. Phenotypic resistant cells exhibiting constant slowed growth survived best under ampicillin exposure and, contrary to expectations, not only fast-growing cells suffered high mortality triggered by ampicillin but also growth-arrested cells. Our findings support diverse modes of phenotypic resistance, and we revealed resistant cell characteristics that have been associated with enhanced genetically fixed resistance evolution, which supports claims of an underappreciated role of phenotypic resistant cells toward genetic resistance evolution. A better understanding of phenotypic resistance will benefit combatting genetic resistance by developing and engulfing effective anti-phenotypic resistance strategies.

IMPORTANCE

Antibiotic resistance is a major challenge for modern medicine. Aside from genetic resistance to antibiotics, phenotypic resistance that is not heritable might play a crucial role for the evolution of antibiotic resistance. Using a highly controlled microfluidic system, we characterize single cells under recurrent exposure to antibiotics. Fluctuating antibiotic exposure is likely experienced under common antibiotic therapies. These phenotypic resistant cell characteristics differ from previously described phenotypic resistance, highlighting the diversity of modes of resistance. The phenotypic characteristics of resistant cells we identify also imply that such cells might provide a stepping stone toward genetic resistance, thereby causing treatment failure.

Modeling airway persistent infection of Moraxella catarrhalis and nontypeable Haemophilus influenzae by using human in vitro models

Non-typeable Haemophilus influenzae (NTHi) and Moraxella catarrhalis (Mcat) are two common respiratory tract pathogens often associated with acute exacerbations in Chronic Obstructive Pulmonary Disease (COPD) as well as with otitis media (OM) in children. Although there is evidence that these pathogens can adopt persistence mechanisms such as biofilm formation, the precise means through which they contribute to disease severity and chronicity remains incompletely understood, posing challenges for their effective eradication. The identification of potential vaccine candidates frequently entails the characterization of the host-pathogen interplay in vitro even though this approach is limited by the fact that conventional models do not permit long term bacterial infections. In the present work, by using air-liquid-interface (ALI) human airway in vitro models, we aimed to recreate COPD-related persistent bacterial infections. In particular, we explored an alternative use of the ALI system consisting in the assembly of an inverted epithelium grown on the basal part of a transwell membrane with the aim to enable the functionality of natural defense mechanisms such as mucociliary clearance and cellular extrusion that are usually hampered during conventional ALI infection experiments. The inversion of the epithelium did not affect tissue differentiation and considerably delayed NTHi or Mcat infection progression, allowing one to monitor host-pathogen interactions for up to three weeks. Notably, the use of these models, coupled with confocal and transmission electron microscopy, revealed unique features associated with NTHi and Mcat infection, highlighting persistence strategies including the formation of intracellular bacterial communities (IBCs) and surface-associated biofilm-like structures. Overall, this study demonstrates the possibility to perform long term host-pathogen investigations in vitro with the aim to define persistence mechanisms adopted by respiratory pathogens and individuate potential new vaccine targets.

Environmental, mechanistic and evolutionary landscape of antibiotic persistence

Recalcitrant infections pose a serious challenge by prolonging antibiotic therapies and contributing to the spread of antibiotic resistance, thereby threatening the successful treatment of bacterial infections. One potential contributing factor in persistent infections is antibiotic persistence, which involves the survival of transiently tolerant subpopulations of bacteria. This review summarizes the current understanding of antibiotic persistence, including its clinical significance and the environmental and evolutionary factors at play. Additionally, we discuss the emerging concept of persister regrowth and potential strategies to combat persister cells. Recent advances highlight the multifaceted nature of persistence, which is controlled by deterministic and stochastic elements and shaped by genetic and environmental factors. To translate in vitro findings to in vivo settings, it is crucial to include the heterogeneity and complexity of bacterial populations in natural environments. As researchers continue to gain a more holistic understanding of this phenomenon and develop effective treatments for persistent bacterial infections, the study of antibiotic persistence is likely to become increasingly complex.

Urinary Tract Infections Caused by Uropathogenic Escherichia coli: Mechanisms of Infection and Treatment Options

Urinary tract infections (UTIs) are common bacterial infections that represent a severe public health problem. They are often caused by Escherichia coli (E. coli), Klebsiella pneumoniae (K. pneumonia), Proteus mirabilis (P. mirabilis), Enterococcus faecalis (E. faecalis), and Staphylococcus saprophyticus (S. saprophyticus). Among these, uropathogenic E. coli (UPEC) are the most common causative agent in both uncomplicated and complicated UTIs. The adaptive evolution of UPEC has been observed in several ways, including changes in colonization, attachment, invasion, and intracellular replication to invade the urothelium and survive intracellularly. While antibiotic therapy has historically been very successful in controlling UTIs, high recurrence rates and increasing antimicrobial resistance among uropathogens threaten to greatly reduce the efficacy of these treatments. Furthermore, the gradual global emergence of multidrug-resistant UPEC has highlighted the need to further explore its pathogenesis and seek alternative therapeutic and preventative strategies. Therefore, a thorough understanding of the clinical status and pathogenesis of UTIs and the advantages and disadvantages of antibiotics as a conventional treatment option could spark a surge in the search for alternative treatment options, especially vaccines and medicinal plants. Such options targeting multiple pathogenic mechanisms of UPEC are expected to be a focus of UTI management in the future to help combat antibiotic resistance.

The clinical implications of bacterial pathogenesis and mucosal immunity in chronic urinary tract infection

Urinary tract infections (UTIs) exert a significant health and economic cost globally. Approximately one in four people with a previous history of UTI continue to develop recurrent or chronic infections. Research on UTI has primarily concentrated on pathogen behavior, with the focus gradually shifting to encompass the host immune response. However, these are centered on mouse models of Escherichia coli infection, which may not fully recapitulate the infective etiology and immune responses seen in humans. The emerging field of the urobiome also inadvertently confounds the discrimination of true UTI-causing pathogens from commensals. This review aims to present a novel perspective on chronic UTI by linking microbiology with immunology, which is commonly divergent in this field of research. It also describes the challenges in understanding chronic UTI pathogenesis and the human bladder immune response, largely conjectured from murine studies. Lastly, it outlines the shortcomings of current diagnostic methods in identifying individuals with chronic UTI and consequently treating them, potentially aggravating their disease due to mismanagement of prior episodes. This discourse highlights the need to consider these knowledge gaps and encourages more relevant studies of UTIs in humans.

Bioinspired drug delivery strategies for repurposing conventional antibiotics against intracellular infections

Bacteria have developed a wealth of strategies to avoid and resist the action of antibiotics, one of which involves pathogens invading and forming reservoirs within host cells. Due to the poor cell membrane permeability, stability and retention of conventional antibiotics, this renders current treatments largely ineffective, since achieving a therapeutically relevant antibiotic concentration at the site of intracellular infection is not possible. To overcome such challenges, current antibiotics are 'repurposed' via reformulation using micro- or nano-carrier systems that effectively encapsulate and deliver therapeutics across cellular membranes of infected cells. Bioinspired materials that imitate the uptake of biological particulates and release antibiotics in response to natural stimuli are recently explored to improve the targeting and specificity of this 'nanoantibiotic' approach. In this review, the mechanisms of internalization and survival of intracellular bacteria are elucidated, effectively accentuating the current treatment challenges for intracellular infections and the implications for repurposing conventional antibiotics. Key case studies of nanoantibiotics that have drawn inspiration from natural biological particles and cellular uptake pathways to effectively eradicate intracellular pathogens are detailed, clearly highlighting the rational for harnessing bioinspired drug delivery strategies.

In Vitro Models for the Study of the Intracellular Activity of Antibiotics

Intracellular bacteria are poorly responsive to antibiotic treatment. Pharmacological studies are thus needed to determine the antibiotics which are the most potent or effective against intracellular bacteria as well as to explore the reasons for poor bacterial responsiveness. An in vitro pharmacodynamic model is described, consisting of (1) phagocytosis of preopsonized bacteria by eukaryotic cells, (2) elimination of noninternalized bacteria with gentamicin, (3) incubation of infected cells with antibiotics, and (4) determination of surviving bacteria by viable cell counting and normalization of the counts based on sample protein content. The use of strains expressing fluorescent proteins under the control of an inducible promoter allows to follow intracellular bacterial division at the individual level and therefore to monitor bacterial persisters that do not multiply anymore.

Understanding the potential of lactobacilli in recurrent UTI prevention

Urinary tract infections (UTIs) are one of the most common infections in women. The only proven preventive strategy for recurrent UTIs is prophylactic antibiotics. Given growing antibiotic resistance, the use of probiotics has been proposed as an alternative to antibiotics. Herein, we discuss the current evidence to support the possibility that exogenous lactobacilli may limit the pathogenicity of uropathogens such as E. coli. Probiotics appear to have a significant potential in prevention of recurrent UTI, however, additional data are needed to understand how they can be effectively used in clinical practice.

The importance of intracellular bacterial biofilm in infectious diseases

Various bacterial species, previously known as extracellular pathogens, can reside inside different host cells by adapting to intracellular modes by forming microbial aggregates with similar characteristics to bacterial biofilms. Additionally, bacterial invasion of human cells leads to failure in antibiotic therapy, as most conventional anti-bacterial agents cannot reach intracellular biofilm in normal concentrations. Various studies have shown that bacteria such as uropathogenic Escherichia coli, Pseudomonas aeruginosa, Borrelia burgdorferi,Moraxella catarrhalis, non-typeable Haemophilus influenzae, Streptococcus pneumonia, and group A Streptococci produce biofilm-like structures within the host cells. For the first time in this review, we will describe and discuss the new information about intracellular bacterial biofilm formation and its importance in bacterial infectious diseases.

Bacterial Biofilm and its Role in the Pathogenesis of Disease

Recognition of the fact that bacterial biofilm may play a role in the pathogenesis of disease has led to an increased focus on identifying diseases that may be biofilm-related. Biofilm infections are typically chronic in nature, as biofilm-residing bacteria can be resilient to both the immune system, antibiotics, and other treatments. This is a comprehensive review describing biofilm diseases in the auditory, the cardiovascular, the digestive, the integumentary, the reproductive, the respiratory, and the urinary system. In most cases reviewed, the biofilms were identified through various imaging technics, in addition to other study approaches. The current knowledge on how biofilm may contribute to the pathogenesis of disease indicates a number of different mechanisms. This spans from biofilm being a mere reservoir of pathogenic bacteria, to playing a more active role, e.g., by contributing to inflammation. Observations also indicate that biofilm does not exclusively occur extracellularly, but may also be formed inside living cells. Furthermore, the presence of biofilm may contribute to development of cancer. In conclusion, this review shows that biofilm is part of many, probably most chronic infections. This is important knowledge for development of effective treatment strategies for such infections.

Bacteria-Responsive Nanoliposomes as Smart Sonotheranostics for Multidrug Resistant Bacterial Infections

Rapid emergence of multidrug resistant (MDR) "superbugs" poses a severe threat to global health. Notably, undeveloped diagnosis and concomitant treatment failure remain highly challenging. Herein, we report a sonotheranostic strategy to achieve bacteria-specific labeling and visualized sonodynamic therapy (SDT). Using maltohexaose-decorated cholesterol and bacteria-responsive lipid compositions, a smart nanoliposomes platform (MLP18) was developed for precise delivery of purpurin 18, a potent sonosensitizer proved in this study. Taking advantage of the bacteria-specific maltodextrin transport pathway, the prepared MLP18 can specifically target the bacterial infection site and accurately distinguish the foci from sterile inflammation or cancer with a highly selective fluorescence/photoacoustic signal on the bacteria-infected site of mice. Moreover, the bacteria-responsive feature of MLP18 activated an efficient release and internalization of high concentration sonosensitizer into bacterial cells, resulting in effective sonodynamic elimination of MDR bacteria. In situ MRI monitoring visualized such potent sonodynamic activity and indicated that MLP18-mediated SDT could successfully eradicate inflammation and abscess from mice with bacterial myositis. In view of the above advantages, the developed nanoliposomes may serve as a promising sonotheranostic platform against MDR bacteria in the areas of healthcare.

Updates on urinary tract infections in kidney transplantation

Urinary tract infection (UTI) represents the most common infection after kidney transplantation; it is associated with an increased risk for acute kidney rejection and impaired graft function in the early post-transplant period. Kidney transplant recipients with UTIs are often clinically asymptomatic due to the immunosuppressive therapy; however, asymptomatic bacteriuria may progress to acute pyelonephritis, bacteremia and urosepsis, particularly in the early post-transplant period, that are independent risk factors for short and long-term graft and patient survival. This article reviews the definitions, incidence, risk factors and the management of UTI in kidney transplant recipients; furthermore, the main controversial and still unanswered questions, regarding the causes of recurrent UTIs, adequate use of antibiotics to avoid antibiotic resistance, dosing and timing for prophylaxis and treatment of symptomatic infections, are also discussed. The emerging definition of urinary microbiota introduces new concepts in understanding the complexity of the disease and might represent the future target for therapeutic interventions.

Clinical, histopathologic, cystoscopic, and fluorescence in situ hybridization analysis of proliferative urethritis in 22 dogs

Background

Proliferative urethritis (PU) is a lower urinary tract disease of dogs characterized by frond‐like lesions in the urethra. The etiology of PU is unknown, although an association with bacterial cystitis is reported.

Objectives

Deep‐seated bacterial cystitis is associated with PU, particularly in dogs with neutrophilic or granulomatous inflammation.

Animals

Twenty‐two client‐owned dogs with PU and 5 control dogs euthanized for non‐urinary disease.

Methods

In retrospective analysis, medical records of dogs with PU from 1986 to 2016 were reviewed. Signalment, clinical signs, cystoscopic findings, antimicrobial use, and results of urine, bladder, or urethral tissue cultures, if available, were recorded. Histopathology was reviewed and classified as lymphocytic‐plasmacytic (LP), neutrophilic, LP‐neutrophilic (LPN), granulomatous, or pleocellular. Eubacterial fluorescence in situ hybridization (FISH) was performed on 18 tissue samples (13 cases, 5 controls), with subsequent evaluation of bacterial species.

Results

Of the 22 dogs, 9 had LP urethritis, 6 had LPN, 4 had pleocellular, and 3 had neutrophilic urethritis. Of note, 7 of 13 PU samples were FISH+ for adherent or invasive bacteria; 1 of 5 controls were FISH+ for adherent bacteria. Five dogs had negative urine and tissue cultures when FISH was positive. There was no association detected between the type of urethral inflammation and the results of urine and tissue culture or FISH.

Conclusions and Clinical Importance

The type of inflammation varied widely in these 22 PU cases. Deep‐seated bacterial urethritis could be contributing to the inflammatory process in some dogs, regardless of the inflammation type. Urine and tissue cultures likely underestimate bacterial colonization of the urethra in dogs.

Local drug delivery in the urinary tract: current challenges and opportunities

Drug delivery is an important consideration in disease treatment. There are many opportunities for novel methods and technologies to hold promising roles in overcoming traditional obstacles. Delivery systems functionalised to boast synergistic antimicrobial effects, specific targeting, and enhanced bioavailability allow for improved therapeutic potential and better patient outcomes. Many of these delivery modalities find clinical practicality in the field of urology, specifically in the treatment of urinary tract infections (UTIs) and offer advantages over conventional methods. The aim of this review article is to discuss the current modalities of treatment for UTIs and the recent technological advancements for optimising drug delivery. We focus on challenges that persist in drug delivery during UTIs including barriers to antimicrobial penetration, drug resistance, biofilm formation and specific targeting limitations. With a discussion on how emerging methods combat these concerns, we present an overview of potential therapies with special emphasis on nanoparticle-based applications.

[Pathogenesis of urinary tract infections : An update]

Urinary tract infections are among the most common bacterial infections worldwide. The management has become a public health concern of socioeconomic importance. Every second woman will experience at least one episode in her lifetime. Due to the emergence of multiresistant pathogens and the developmental void, treatment has become more challenging over the years. Deciphering the complex molecular interaction between host and pathogen is necessary to identify potent treatment targets for future approaches. The objective of this review is to present novel aspects on the pathogenesis of urinary tract infections and its relevance for clinical practice.

Determination of minimum biofilm eradication concentrations of orbifloxacin for canine bacterial uropathogens over different treatment periods

Biofilm formation can cause refractory urinary tract infections (UTIs) in dogs; however, minimum biofilm eradication concentrations (MBECs) of veterinary drugs against canine uropathogens remain to be investigated. In this study, the MBECs of orbifloxacin (OBFX), trimethoprim-sulfamethoxazole (TMS) and amoxicillin/clavulanate (ACV) over different time periods for treatment of canine uropathogenic Escherichia coli (n = 10) were determined. The MBECs of OBFX for other bacterial uropathogens, including Staphylococcus pseudintermedius (n = 5), Pseudomonas aeruginosa (n = 5), Klebsiella pneumoniae (n = 5) and Proteus mirabilis (n = 5) were also determined. Minimum inhibitory concentrations (MICs) were identified for all strains by broth microdilution, and MBECs were determined at 24, 72, and 168 hr using the Calgary biofilm method. The 24 hr MBECs of OBFX, TMS and ACV for the E. coli strains were significantly higher than the MICs (P < 0.05), and the 72 and 168 hr MBECs were significantly lower than those at 24 hr (P < 0.05). In addition, the 24 hr OBFX MBECs for the four other uropathogens were significantly higher than the corresponding MICs (P < 0.05). The 72 and/or 168 hr OBFX MBECs for S. pseudintermedius, K. pneumoniae and P. mirabilis were significantly lower than the 24 hr concentrations (P < 0.05), whereas for P. aeruginosa, no significant difference was found between any of the MBECs (P > 0.05). These data indicate that the administration period and uropathogenic bacterial species are important factors affecting the efficacy of OBFX treatment of biofilm-related UTIs in dogs.

Urosepsis: Overview of the Diagnostic and Treatment Challenges

Urosepsis is defined as sepsis caused by an infection in the urogenital tract. In approximately 30% of all septic patients the infectious focus is localized in the urogenital tract, mainly due to obstructions at various levels, such as ureteral stones. Urosepsis may also occur after operations in the urogenital tract. In urosepsis, complete bacteria and components of the bacterial cell wall from the urogenital tract trigger the host inflammatory event and act as exogenous pyrogens on eukaryotic target cells of patients. A burst of second messenger molecules leads to several different stages of the septic process, from hyperactivity to immunosuppression. As pyelonephritis is the most frequent cause for urosepsis, the kidney function is therefore most important in terms of cause and as a target organ for dysfunction in the course of the sepsis.Since effective antimicrobial therapy must be initiated early during sepsis, the empiric intravenous therapy should be initiated immediately after microbiological sampling. For the selection of appropriate antimicrobials, it is important to know risk factors for resistant organisms and whether the sepsis is primary or secondary and community or nosocomially acquired. In addition, the preceding antimicrobial therapies should be recorded as precisely as possible. Resistance surveillance should, in any case, be performed locally to adjust for the best suitable empiric treatment. Treatment challenges arise from the rapid increase of antibiotic resistance in Gram-negative bacteria, especially extended-spectrum β-lactamase (ESBL)-producing bacteria. Treatment of urosepsis comprises four basic strategies I) supportive therapy (stabilizing and maintaining blood pressure), II) antimicrobial therapy, III) control or elimination of the complicating factor, and IV) specific sepsis therapy.

Inflammasomes in the urinary tract: a disease-based review

Inflammasomes are supramolecular structures that sense molecular patterns from pathogenic organisms or damaged cells and trigger an innate immune response, most commonly through production of the proinflammatory cytokines IL-1β and IL-18, but also through less understood mechanisms independent of these cytokines. Great strides have been made in understanding these structures and their dysfunction in various inflammatory diseases, lending new insights into urological and renal problems. From a clinical perspective, benign urinary pathology almost universally involves the inflammatory process, and understanding how inflammasomes translate etiological conditions (diabetes, obstruction, stones, urinary tract infections, etc.) into acute and chronic inflammatory responses is critical to understanding these diseases at a molecular level. To date, inflammasome components have been found in the bladder, prostate, and kidney and have been shown to be activated in response to several infectious and noninfectious insults. In this review, we summarize what is known regarding inflammasomes in both the upper and lower urinary tract and describe several common disease states where they potentially play critical roles.

The NACHT, LRR and PYD Domains-Containing Protein 3 (NLRP3) Inflammasome Mediates Inflammation and Voiding Dysfunction in a Lipopolysaccharide-Induced Rat Model of Cystitis

OBJECTIVE

NOD-like receptors (NLRs) sense sterile and non-sterile signals and form inflammasomes which trigger an inflammatory response through the activation of caspase-1 and release of IL-1β. Recently we have shown the presence of several NLRs in the bladder urothelia and demonstrated the importance of NLRP3 in bladder outlet obstruction and cyclophosphamide-induced cystitis, both models of sterile inflammation. In this study we explore a role for NLRP3 in mediating the response to LPS, a key antigen of uropathogenic bacteria.

METHOD

In order to bypass the protective glycosaminoglycan layer lining the urothelium, LPS was directly injected into the bladder wall of Sprague-Dawley rats. Glyburide (a NLRP3 inhibitor) or vehicle was administered orally prior to and after injection. Rats were analyzed 24 h later. Inflammasome activity (caspase-1 activity, IL-1β release) and inflammation (Evan's Blue extravasation, bladder weight) were assessed, as was physiological bladder function (urodynamics).

RESULTS

Injection of LPS stimulated inflammasome activation (caspase-1 activity) and the release of IL-1β into the urine which was prevented by glyburide. Likewise, LPS increased inflammation, (bladder weight and the extravasation of Evan's blue dye), and this was reversed by glyburide. Functionally, animals injected with saline alone demonstrated decreased voiding volume as measured by urodynamics. In the presence of LPS, additional urinary dysfunction was evident with decreased voiding pressures and threshold pressures. The decrease in voiding pressure was blocked by glyburide but the decrease in threshold pressure was not, suggesting that LPS has significant effects mediated by inflammasome-dependent and -independent mechanisms.

CONCLUSION

Overall, the results demonstrate the potential importance of inflammasomes in bacterial cystitis as well as the ability of the bladder wall injection technique to isolate the in vivo effects of specific inflammasome ligands to the physiological changes associated with cystitis.

In Vitro Models for the Study of the Intracellular Activity of Antibiotics

Intracellular bacteria are poorly responsive to antibiotic treatment. Pharmacological studies are thus needed to determine which antibiotics are most potent or effective against intracellular bacteria as well as to explore the reasons for poor bacterial responsiveness. An in vitro pharmacodynamic model is described, consisting of (1) phagocytosis of pre-opsonized bacteria by eukaryotic cells; (2) elimination of non-internalized bacteria with gentamicin; (3) incubation of infected cells with antibiotics; and (4) determination of surviving bacteria by viable cell counting and normalization of the counts based on sample protein content.

The potential repertoire of the innate immune system in the bladder: expression of pattern recognition receptors in the rat bladder and a rat urothelial cell line (MYP3 cells)

PURPOSE

The urothelium is a frontline sensor of the lower urinary tract, sampling the bladder lumen and stimulating an immune response to infectious and noxious agents. Pattern recognition receptors (PRRs) recognize such agents and coordinate the innate response, often by forming inflammasomes that activate caspase-1 and the release of interleukin-1. We have shown the presence of one PRR (NLRP3) in the urothelia and its central role in the inflammatory response to cyclophosphamide. The purpose of this study was to (1) assess the likely range of the PPR response by assessing the repertoire present in the rat bladder and (2) determine the utility of the MYP3 rat urothelia cell line for in vitro studies by assessing its PPR repertoire and functional responsiveness.

METHODS

Immunohistochemistry was performed for seven PPRs (NLRP1, NLRP3, NLRP6, NLRP7, NLRP12, NLRC4 and AIM2) on bladder sections and MYP3 cells. For functionality, MYP3 cells were challenged with the quintessential NLRP3 activator ATP and assessed for caspase-1 activation.

RESULTS

All PPRs examined were expressed in the bladder and localized to the urothelial layer with several also in the detrusor (none in the interstitia). MYP3 cells also expressed all PRRs with a variable intracellular location. ATP-stimulated caspase-1 activity in MYP3 cells in a dose-dependent manner was reduced by knockdown of NLRP3 expression.

CONCLUSION

The results suggest that the bladder possesses the capacity to initiate an innate immune response to a wide array of uropathological agents and the MYP3 cells will provide an excellent investigational tool for this field.

The yin-yang driving urinary tract infection and how proteomics can enhance research, diagnostics, and treatment

Bacterial urinary tract infections (UTIs) afflict millions of people worldwide both in the community and the hospital setting. The onset, duration, and severity of infection depend on the characteristics of the invading pathogen (yin), as well as the immune response elicited by the infected individual (yang). Uropathogenic Escherichia coli (UPEC) account for the majority of UTIs, and extensive investigations by many scientific groups have elucidated an elaborate pathogenic UPEC life cycle, involving the occupation of extracellular and intracellular niches and the expression of an arsenal of virulence factors that facilitate niche occupation. This review will summarize the current knowledge on UPEC pathogenesis; the host immune responses elicited to combat infection; and it will describe proteomics approaches used to understand UPEC pathogenesis, as well as drive diagnostics and treatment options. Finally, new strategies are highlighted that could be applied toward furthering our knowledge regarding host-bacterial interactions during UTI.

Pathogenesis of human diffusely adhering Escherichia coli expressing Afa/Dr adhesins (Afa/Dr DAEC): current insights and future challenges

The pathogenicity and clinical pertinence of diffusely adhering Escherichia coli expressing the Afa/Dr adhesins (Afa/Dr DAEC) in urinary tract infections (UTIs) and pregnancy complications are well established. In contrast, the implication of intestinal Afa/Dr DAEC in diarrhea is still under debate. These strains are age dependently involved in diarrhea in children, are apparently not involved in diarrhea in adults, and can also be asymptomatic intestinal microbiota strains in children and adult. This comprehensive review analyzes the epidemiology and diagnosis and highlights recent progress which has improved the understanding of Afa/Dr DAEC pathogenesis. Here, I summarize the roles of Afa/Dr DAEC virulence factors, including Afa/Dr adhesins, flagella, Sat toxin, and pks island products, in the development of specific mechanisms of pathogenicity. In intestinal epithelial polarized cells, the Afa/Dr adhesins trigger cell membrane receptor clustering and activation of the linked cell signaling pathways, promote structural and functional cell lesions and injuries in intestinal barrier, induce proinflammatory responses, create angiogenesis, instigate epithelial-mesenchymal transition-like events, and lead to pks-dependent DNA damage. UTI-associated Afa/Dr DAEC strains, following adhesin-membrane receptor cell interactions and activation of associated lipid raft-dependent cell signaling pathways, internalize in a microtubule-dependent manner within urinary tract epithelial cells, develop a particular intracellular lifestyle, and trigger a toxin-dependent cell detachment. In response to Afa/Dr DAEC infection, the host epithelial cells generate antibacterial defense responses. Finally, I discuss a hypothetical role of intestinal Afa/Dr DAEC strains that can act as "silent pathogens" with the capacity to emerge as "pathobionts" for the development of inflammatory bowel disease and intestinal carcinogenesis.

Enterococcus faecalis infection activates phosphatidylinositol 3-kinase signaling to block apoptotic cell death in macrophages

Apoptosis is an intrinsic immune defense mechanism in the host response to microbial infection. Not surprisingly, many pathogens have evolved various strategies to manipulate this important pathway to benefit their own survival and dissemination in the host during infection. To our knowledge, no attempts have been made to explore the host cell survival signals modulated by the bacterium Enterococcus faecalis. Here, we show for the first time that during early stages of infection, internalized enterococci can prevent host cell (RAW264.7 cells, primary macrophages, and mouse embryonic fibroblasts [MEFs]) apoptosis induced by a wide spectrum of proapoptotic stimuli. Activation of caspase 3 and cleavage of the caspase 3 substrate poly(ADP-ribose) polymerase were inhibited in E. faecalis-infected cells, indicating that E. faecalis protects macrophages from apoptosis by inhibiting caspase 3 activation. This antiapoptotic activity in E. faecalis-infected cells was dependent on the activation of the phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway, which resulted in the increased expression of the antiapoptotic factor Bcl-2 and decreased expression of the proapoptotic factor Bax. Further analysis revealed that active E. faecalis physiology was important for inhibition of host cell apoptosis, and this feature seemed to be a strain-independent trait among E. faecalis isolates. Employing a mouse peritonitis model, we also determined that cells collected from the peritoneal lavage fluid of E. faecalis-infected mice showed reduced levels of apoptosis compared to cells from uninfected mice. These results show early modulation of apoptosis during infection and have important implications for enterococcal pathogenesis.

Cranberry and recurrent cystitis: more than marketing?

Epidemiologic studies indicate that millions of people suffer from recurrent cystitis, a pathology requiring antibiotic prophylaxis and entailing high social costs. Cranberry is a traditional folk remedy for cystitis and, which, in the form of a variety of products and formulations has over several decades undergone extensive evaluation for the management of urinary tract infections (UTI). The aim of this retrospective study is to summarize and review the most relevant and recent preclinical and clinical studies on cranberries for the treatment of UTIs. The scientific literature selected for this review was identified by searches of Medline via PubMed. A variety of recent experimental evidence has shed light on the mechanism underlying the anti-adhesive properties of proanthrocyanidins, their structure-activity relationships, and pharmacokinetics. Analysis of clinical studies and evaluation of the cranberry efficacy/safety ratio in the prevention of UTIs strongly support the use of cranberry in the prophylaxis of recurrent UTIs in young and middle-aged women. However, evidence of its clinical use among other patients remains controversial.

Biofilm and fluoroquinolone resistance of canine Escherichia coli uropathogenic isolates

Background

Escherichia coli is the most common uropathogen involved in urinary tract infection (UTI). Virulence of strains may differ, and may be enhanced by antimicrobial resistance and biofilm formation, resulting in increased morbidity and recurrent infections. The aim of this study was to evaluate the in vitro biofilm forming capacity of E. coli isolates from dogs with UTI, by using fluorescent in situ hybridization, and its association with virulence genes and antimicrobial resistance.

Findings

The proportion of biofilm-producing isolates significantly increased with the length of incubation time (P < 0.05). Biofilm production was significantly associated with fluoroquinolone resistance at all incubation time points and was independent of the media used (P < 0.05). Biofilm production was not associated with cnf1, hly, pap and sfa genes (P > 0.05), but was significantly associated with afa, aer and the β-lactamase genes (P < 0.05).

Conclusions

To the best of our knowledge, this is the first report showing significant association between biofilm production and fluoroquinolone resistance in E. coli isolates from dogs with UTI. Biofilm formation may contribute to UTI treatment failure in dogs, through the development of bacterial reservoirs inside bladder cells, allowing them to overcome host immune defenses and to establish recurrent infections.

Recurrent urinary tract infections in healthy and nonpregnant women

Recurrent urinary tract infections (RUTI) are prevalent and pose significant clinical challenges. Although the term RUTI has long been vaguely defined, a consensus definition has emerged in recent years. The exact etiology behind RUTI remains under debate, with valid arguments for both ascending reinfections as well as persistent infection inside the bladder. These persistent infections exist in the form of quiescent intracellular reservoirs in the mouse model and may represent a novel concept to explain UTI recurrence in humans. Manageable risk factors such as behavioral patterns alongside nonmanageable risk factors including genetic susceptibility are growing fields of investigation. Acute UTI have been studied through two model bacterial strains: Escherichia coli UTI89 and CFT073. However, the clinical relevance to RUTI of these two strains has not been firmly established. Current treatment strategies for RUTI are limited and remain dominated by antibiotic usage despite variable efficacy. The majority of studies in humans have focused on younger groups of women with little information available about the postmenopausal population despite a heightened risk of RUTI in this age group.

Enterococcus faecalis subverts and invades the host urothelium in patients with chronic urinary tract infection

Bacterial urinary tract infections (UTI) are a major growing concern worldwide. Uropathogenic Escherichia coli has been shown to invade the urothelium during acute UTI in mice and humans, forming intracellular reservoirs that can evade antibiotics and the immune response, allowing recurrence at a later date. Other bacterial species, such as Staphylococcus saprophyticus, Klebsiella pneumonia and Salmonella enterica have also been shown to be invasive in acute UTI. However, the role of intracellular infection in chronic UTI causing more subtle lower urinary tract symptoms (LUTS), a particular problem in the elderly population, is poorly understood. Moreover, the species of bacteria involved remains largely unknown. A previous study of a large cohort of non-acute LUTS patients found that Enterococcus faecalis was frequently found in urine specimens. E. faecalis accounts for a significant proportion of chronic bladder infections worldwide, although the invasive lifestyle of this uropathogen has yet to be reported. Here, we wanted to explore this question in more detail. We harvested urothelial cells shed in response to inflammation and, using advanced imaging techniques, inspected them for signs of bacterial pathology and invasion. We found strong evidence of intracellular E. faecalis harboured within urothelial cells shed from the bladder of LUTS patients. Furthermore, using a culture model system, these patient-isolated strains of E. faecalis were able to invade a transitional carcinoma cell line. In contrast, we found no evidence of cellular invasion by E. coli in the patient cells or the culture model system. Our data show that E. faecalis is highly competent to invade in this context; therefore, these results have implications for both the diagnosis and treatment of chronic LUTS.

Spectrum of bacterial colonization associated with urothelial cells from patients with chronic lower urinary tract symptoms

Chronic lower urinary tract symptoms (LUTS), such as urgency and incontinence, are common, especially among the elderly, but their etiology is often obscure. Recent studies of acute urinary tract infections implicated invasion by Escherichia coli into the cytoplasm of urothelial cells, with persistence of long-term bacterial reservoirs, but the role of infection in chronic LUTS is unknown. We conducted a large prospective study with eligible patients with LUTS and controls over a 3-year period, comparing routine urine cultures of planktonic bacteria with cultures of shed urothelial cells concentrated in centrifuged urinary sediments. This comparison revealed large numbers of bacteria undetected by routine cultures. Next, we typed the bacterial species cultured from patient and control sediments under both aerobic and anaerobic conditions, and we found that the two groups had complex but significantly distinct profiles of bacteria associated with their shed bladder epithelial cells. Strikingly, E. coli, the organism most responsible for acute urinary tract infections, was not the only or even the main offending pathogen in this more-chronic condition. Antibiotic protection assays with shed patient cells and in vitro infection studies using patient-derived strains in cell culture suggested that LUTS-associated bacteria are within or extremely closely associated with shed epithelial cells, which explains how routine cultures might fail to detect them. These data have strong implications for the need to rethink our common diagnoses and treatments of chronic urinary tract symptoms.

Bacterial biofilms: development, dispersal, and therapeutic strategies in the dawn of the postantibiotic era

Biofilm formation constitutes an alternative lifestyle in which microorganisms adopt a multicellular behavior that facilitates and/or prolongs survival in diverse environmental niches. Biofilms form on biotic and abiotic surfaces both in the environment and in the healthcare setting. In hospital wards, the formation of biofilms on vents and medical equipment enables pathogens to persist as reservoirs that can readily spread to patients. Inside the host, biofilms allow pathogens to subvert innate immune defenses and are thus associated with long-term persistence. Here we provide a general review of the steps leading to biofilm formation on surfaces and within eukaryotic cells, highlighting several medically important pathogens, and discuss recent advances on novel strategies aimed at biofilm prevention and/or dissolution.

Biofilm-specific antibiotic resistance

Bacterial biofilms are the basis of many persistent diseases. The persistence of these infections is primarily attributed to the increased antibiotic resistance exhibited by the cells within the biofilms. This resistance is multifactorial; there are multiple mechanisms of resistance that act together in order to provide an increased overall level of resistance to the biofilm. These mechanisms are based on the function of wild-type genes and are not the result of mutations. This article reviews the known mechanisms of resistance, including the ability of the biofilm matrix to prevent antibiotics from reaching the cells and the function of individual genes that are preferentially expressed in biofilms. Evidence suggests that these mechanisms have been developed as a general stress response of biofilms that enables the cells in the biofilm to respond to all of the changes in the environment that they may encounter.

Vaccination with recombinant FimH fused with flagellin enhances cellular and humoral immunity against urinary tract infection in mice

Urinary tract infection (UTI) caused by Uropathogenic Escherichia coli (UPEC) is one of the most common infections in the world. Despite extensive efforts, a vaccine that confers protection against UTIs in human is currently lacking. In this study, the ability of flagellin (FliC), a Toll-like receptor 5 (TLR5) agonist of UPEC strain, and the conventional adjuvant Montanide ISA 206 to enhance the protective immune responses of FimH against urinary tract infection have been compared. Mice immunized with the fused FimH.FliC protein induced significantly higher humoral (IgG1 and IgG2a) and cellular (IFN-γ and IL-4) immune responses than with FimH alone or FimH admixed with FliC. The immune responses of Montanide formulations were comparable to that of the fusion protein and were significantly higher than that of FimH alone. Our results showed that based on the IgG1/IgG2a ratios, FliC directed the anti-FimH responses preferentially toward Th2 and Montanide toward Th1. The FimH.FliC fusion and FimH admixed with FliC and Montanide formulations gave the best results in protection of bladder colonization, compared to the control mice. The results propose new promising vaccine formulation based on the adjuvant properties of FliC and Montanide against UTI caused by UPEC strains.

Assessment of immune responses of the flagellin (FliC) fused to FimH adhesin of Uropathogenic Escherichia coli

Urinary tract infection (UTI) caused by Uropathogenic Escherichia coli (UPEC) is one of the most common infectious diseases in the world. Despite extensive efforts, a vaccine that protects humans against UTI is currently missing. In this study, the immunogenicity of flagellin (FliC) of UPEC strain in different vaccine combinations with FimH antigen of UPEC and conventional adjuvant Montanide ISA 206 was assessed. Finally, efficacy of the immune responses was evaluated for protection of the bladder and kidney of challenged immunized mice. Mice immunized with the fusion FimH·FliC induced significantly higher anti-FliC humoral (IgG1) and cellular (Th1 and Th2) immune responses than with FliC alone or FliC admixed with FimH. The Montanide enhanced the immune responses of FliC antigen and directed the anti-FliC responses preferentially toward Th1. The FliC vaccine combinations reduced bladder infection as compared to control mice. The fusion FimH·FliC and FliC admixed with FimH and Montanide combinations gave the best results in protection of kidney infection, compared to the control mice. The results of this study propose new promising vaccine combinations based on the FliC antigen and Montanide against UTI caused by UPEC.

Transposon mutagenesis identifies uropathogenic Escherichia coli biofilm factors

Uropathogenic Escherichia coli (UPEC), which accounts for 85% of urinary tract infections (UTI), assembles biofilms in diverse environments, including the host. Besides forming biofilms on biotic surfaces and catheters, UPEC has evolved an intracellular pathogenic cascade that culminates in the formation of biofilm-like intracellular bacterial communities (IBCs) within bladder epithelial cells. Rapid bacterial replication during IBC formation augments a build-up in bacterial numbers and persistence within the host. Relatively little is known about factors mediating UPEC biofilm formation and how these overlap with IBC formation. To address this gap, we screened a UPEC transposon mutant library in three in vitro biofilm conditions: Luria broth (LB)-polyvinyl chloride (PVC), YESCA (yeast extract-Casamino Acids)-PVC, and YESCA-pellicle that are dependent on type 1 pili (LB) and curli (YESCA), respectively. Flagella are important in all three conditions. Mutants were identified that had biofilm defects in all three conditions but had no significant effects on the expression of type 1 pili, curli, or flagella. Thus, this approach uncovered a comprehensive inventory of novel effectors and regulators that are involved in UPEC biofilm formation under multiple conditions. A subset of these mutants was found to be dramatically attenuated and unable to form IBCs in a murine model of UTI. Collectively, this study expands our insights into UPEC multicellular behavior that may provide insights into IBC formation and virulence.

In vitro biofilm formation by uropathogenic Escherichia coli and their antimicrobial susceptibility pattern

OBJECTIVE

To detect in vitro biofilm formation of uropathogenic Escherichia coli (E. coli) (UPEC) strains isolated from urine specimens and also to determine their antimicrobial susceptibility pattern using 13 commonly used antibiotics.

METHODS

The present study comprised of 166 urine specimens collected from tertiary care hospitals in and around Coimbatore, South India. All the specimens were subjected to gram staining, bacterial culture and the E. coli strains were screened for biofilm formation using Tube Method (TM), Congo Red Agar (CRA) and Tissue Culture Plate method (TCP) respectively. Subsequently, the antimicrobial susceptibility test was performed by Kirby Bauer-disk diffusion method for the biofilm and non-biofilm producing E. coli strains.

RESULTS

Of the 100 (60.2 %) E. coli strains, 72 strains displayed a biofilm positive phenotype under the optimized conditions in the Tube Method and the strains were classified as highly positive (17, 23.6%), moderate positive (19, 26.3 %) and weakly positive (36, 50.0 %), similarly under the optimized conditions on Congo Red agar medium, biofilm positive phenotype strains were classified as highly positive (23, 23 %), moderate positive (37, 37 %) and weakly positive (40, 40%). While in TCP method, the biofilm positive phenotype strains were also classified as highly positive (6, 6 %), moderate positive (80, 80 %) and weakly positive (14, 14 %), it didn't not correlate well with the tube method for detecting biofilm formation in E. coli. The rates of antibiotic resistance of biofilm producing E. coli were found to be 100 % for chloramphenicol and amoxyclav (amoxicillin and clavulanic acid), 86% for gentamicin and cefotaxime, 84% for ceftazidime, 83% for cotrimoxazole and piperacillin/tazobactam, 75% for tetracycline and 70% for amikacin.

CONCLUSIONS

This study reveals the prevalence and antimicrobial susceptibility pattern of biofilm and non-biofilm producing uropathogenic E. coli strains.

Broad identification of bacterial type in urinary tract infection using (1)h NMR spectroscopy

To address the shortcomings of urine culture for the rapid identification of urinary tract infection (UTI), we applied (1)H-nuclear magnetic resonance (NMR) spectroscopy as a surrogate method for fast screening of microorganisms. Study includes 682 urine samples from suspected UTI patients, 50 healthy volunteers, and commercially available standard strains of gram negative bacilli (GNB) (Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumonia, Enterobacter, Acinetobacter, Proteus mirabilis, Citrobacter frundii) and gram positive cocci (GPC) (Enterococcus faecalis, Streptococcus group B, Staphylococcus saprophyticus). Acetate, lactate, ethanol, succinate, creatinine, trimethylamine (TMA), citrate, trimethylamin-N-oxide, glycine, urea, and hippurate were measured by (1)H NMR spectroscopy. All urine specimens were evaluated with culture method. Multivariate discriminant function analysis (DFA) reveals that acetate, lactate, succinate, and formate were able to differentiate, with high accuracy (99.5%), healthy controls from UTI patients. This statistical analysis was also able to classify GNB to GPC infected urine samples with high accuracy (96%). This technique appears to be a promising, rapid, and noninvasive approach to probing GNB and GPC infected urine specimens with its distinguishing metabolic profile. The determination of infection will be very important for rapidly and efficiently measuring the efficacy of a tailored treatment, leading to prompt and appropriate care of UTI patients.

Multi-species bacterial biofilm and intracellular infection in otitis media

Background

Bacteria which are metabolically active yet unable to be cultured and eradicated by antibiotic treatment are present in the middle ear effusion of children with chronic otitis media with effusion (COME) and recurrent acute otitis media (rAOM). These observations are suggestive of biofilm presence or intracellular sequestration of bacteria and may play a role in OM pathogenesis. The aim of this project is to provide evidence for the presence of otopathogenic bacteria intracellularly or within biofilm in the middle ear mucosa of children with COME or rAOM.

Methods

Middle ear mucosal biopsies from 20 children with COME or rAOM were examined for otopathogenic bacteria (either in biofilm or located intracellularly) using transmission electron microscopy (TEM) or species specific fluorescent in situ hybridisation (FISH) and confocal laser scanning microscopy (CLSM). One healthy control biopsy from a child undergoing cochlear implant surgery was also examined.

Results

No bacteria were observed in the healthy control sample. In 2 of the 3 biopsies imaged using TEM, bacteria were observed in mucus containing vacuoles within epithelial cells. Bacterial species within these could not be identified and biofilm was not observed. Using FISH with CLSM, bacteria were seen in 15 of the 17 otitis media mucosal specimens. In this group, 11 (65%) of the 17 middle ear mucosal biopsies showed evidence of bacterial biofilm and 12 demonstrated intracellular bacteria. 52% of biopsies were positive for both biofilm and intracellular bacteria. At least one otopathogen was identified in 13 of the 15 samples where bacteria were present. No differences were observed between biopsies from children with COME and those with rAOM.

Conclusion

Using FISH and CLSM, bacterial biofilm and intracellular infection with known otopathogens are demonstrated on/in the middle ear mucosa of children with COME and/or rAOM. While their role in disease pathogenesis remains to be determined, this previously undescribed infection pattern may help explain the ineffectiveness of current treatment strategies at preventing or resolving COME or rAOM.

Urosepsis--from the view of the urologist

Urosepsis accounts for approximately 25% of all sepsis cases and may develop from a community-or nosocomial-acquired urinary tract infection (UTI). The underlying UTI is almost exclusively a complicated one with involvement of parenchymatous urogenital organs (e.g. kidneys, prostate). In urosepsis, as in other types of sepsis, the severity of sepsis depends mostly upon the host response. The urological management of urosepsis comprises early diagnosis, early fluid and oxygen treatment, early antibiotic therapy and early control of the complicating factor in the urinary tract. Time from admission to therapy is critical. The shorter the time to effective treatment, the higher is the success rate. This aspect has to become incorporated into the organisational process, including urologists, radiologists and intensive care specialists amongst others. Adequate initial antibiotic therapy has to be insured. This goal implies, however, a wide array of measures over time to ensure a rational antibiotic policy, including microbiologists and clinical pharmacologists. Dosage of an antibiotic in the septic patient generally has to be high to ensure adequate pharmacological exposure in the individual patient.

Dynamin2- and endothelial nitric oxide synthase-regulated invasion of bladder epithelial cells by uropathogenic Escherichia coli

Invasion of bladder epithelial cells by uropathogenic Escherichia coli (UPEC) contributes to antibiotic-resistant and recurrent urinary tract infections (UTIs), but this process is incompletely understood. In this paper, we provide evidence that the large guanosine triphosphatase dynamin2 and its partner, endothelial nitric oxide (NO) synthase (NOS [eNOS]), mediate bacterial entry. Overexpression of dynamin2 or treatment with the NO donor S-nitrosothiols increases, whereas targeted reduction of endogenous dynamin2 or eNOS expression with ribonucleic acid interference impairs, bacterial invasion. Exposure of mouse bladder to small molecule NOS inhibitors abrogates infection of the uroepithelium by E. coli, and, concordantly, bacteria more efficiently invade uroepithelia isolated from wild-type compared with eNOS(-/-) mice. E. coli internalization promotes rapid phosphorylation of host cell eNOS and NO generation, and dynamin2 S-nitrosylation, a posttranslational modification required for the bacterial entry, also increases during E. coli invasion. These findings suggest that UPEC escape urinary flushing and immune cell surveillance by means of eNOS-dependent dynamin2 S-nitrosylation and invasion of host cells to cause recurrent UTIs.

Urinary tract infections in women

Urinary tract infection (UTI) is the most common extraintestinal infectious disease entity in women worldwide, and perhaps one of the most formidable challenges in clinical practice given its high prevalence, frequent recurrence, and myriad associated morbidities in the setting of rapidly evolving antimicrobial resistance. Achieving timely symptom relief and infection control and preventing morbidity, growth of resistant organisms, and recurrent infection are often difficult. This article reviews epidemiology and pathogenesis of urinary tract infection in women; characterizes common patterns of infection, clinical red flags, and appropriate laboratory testing and imaging; explores emerging patterns of antimicrobial resistance; and reviews the updated guidelines for the treatment of uncomplicated UTI in women.

Different types of cell death induced by enterotoxins

The infection of bacterial organisms generally causes cell death to facilitate microbial invasion and immune escape, both of which are involved in the pathogenesis of infectious diseases. In addition to the intercellular infectious processes, pathogen-produced/secreted enterotoxins (mostly exotoxins) are the major weapons that kill host cells and cause diseases by inducing different types of cell death, particularly apoptosis and necrosis. Blocking these enterotoxins with synthetic drugs and vaccines is important for treating patients with infectious diseases. Studies of enterotoxin-induced apoptotic and necrotic mechanisms have helped us to create efficient strategies to use against these well-characterized cytopathic toxins. In this article, we review the induction of the different types of cell death from various bacterial enterotoxins, such as staphylococcal enterotoxin B, staphylococcal alpha-toxin, Panton-Valentine leukocidin, alpha-hemolysin of Escherichia coli, Shiga toxins, cytotoxic necrotizing factor 1, heat-labile enterotoxins, and the cholera toxin, Vibrio cholerae. In addition, necrosis caused by pore-forming toxins, apoptotic signaling through cross-talk pathways involving mitochondrial damage, endoplasmic reticulum stress, and lysosomal injury is discussed.