Gram-positive bacteria are a common cause of urinary-tract infection (UTI), particularly among individuals who are elderly, pregnant, or who have other risk factors for UTI. Here we review the epidemiology, virulence mechanisms, and host response to the most frequently isolated Gram-positive uropathogens: Staphylococcus saprophyticus, Enterococcus faecalis, and Streptococcus agalactiae. We also review several emerging, rare, misclassified, and otherwise underreported Gram-positive pathogens of the urinary tract including Aerococcus, Corynebacterium, Actinobaculum, and Gardnerella. The literature strongly suggests that urologic diseases involving Gram-positive bacteria may be easily overlooked due to limited culture-based assays typically utilized for urine in hospital microbiology laboratories. Some UTIs are polymicrobial in nature, often involving one or more Gram-positive bacteria. We herein review the risk factors and recent evidence for mechanisms of bacterial synergy in experimental models of polymicrobial UTI. Recent experimental data has demonstrated that, despite being cleared quickly from the bladder, some Gram-positive bacteria can impact pathogenic outcomes of co-infecting organisms. When taken together, the available evidence argues that Gram-positive bacteria are important uropathogens in their own right, but that some can be easily overlooked because they are missed by routine diagnostic methods. Finally, a growing body of evidence demonstrates that a surprising variety of fastidious Gram-positive bacteria may either reside in or be regularly exposed to the urinary tract and further suggests that their presence is widespread among women, as well as men. Experimental studies in this area are needed; however, there is a growing appreciation that the composition of bacteria found in the bladder could be a potentially important determinant in urologic disease, including susceptibility to UTI.

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Gram-Positive Uropathogens, Polymicrobial Urinary Tract Infection, and the Emerging Microbiota of the Urinary Tract

Koch's postulates dictate the use of experimental models to illustrate features of human disease and provide evidence for a singular organism as the cause. The underlying cause(s) of bacterial vaginosis (BV) has been debated in the literature for over half a century. In 1955, it was first reported that a bacterium now known as Gardnerella vaginalis may be the cause of a condition (BV) resulting in higher vaginal pH, thin discharge, a fishy odor, and the presence of epithelial cells covered in bacteria. Here we review contemporary and historical studies on BV with a focus on reports of experimental infections in human or animal models using Gardnerella vaginalis. We evaluate experimental evidence for the hypothesis that G. vaginalis is sufficient to trigger clinical features of BV or relevant health complications associated with the condition. Additionally, we evaluate in vivo models of co-infection employing G. vaginalis together with other bacterial species to investigate evidence for the hypothesis that G. vaginalis may encourage colonization or virulence of other potential pathogens. Together, these studies paint a complex picture in which G. vaginalis has both direct and indirect roles in the features, health complications, and co-infections associated with BV. We briefly review the current taxonomic landscape and genetic diversity pertinent to Gardnerella and note the limitations of sequence-based studies using different marker genes and priming sites. Although much more study is needed to refine our understanding of how BV develops and persists within the human host, applications of the experimental aspects of Koch's postulates have provided an important glimpse into some of the causal relationships that may govern this condition in vivo.

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Gardnerella vaginalis as a Cause of Bacterial Vaginosis: Appraisal of the Evidence From in vivo Models

The current paradigm of urinary tract infection (UTI) pathogenesis takes into account the contamination of the periurethral space by specific uropathogens residing in the gut, which is followed by urethral colonization and pathogen ascension to the urinary bladder. Consequently, studying the relationship between gut microbiota and the subsequent development of bacteriuria and UTI represents an important field of research. However, the well-established diagnostic and therapeutic paradigm for urinary tract infections (UTIs) has come into question with the discovery of a multifaceted, symbiotic microbiome in the healthy urogenital tract. More specifically, emerging data suggest that vaginal dysbiosis may result in Escherichia coli colonization and prompt recurrent UTIs, while urinary microbiome perturbations may precede the development of UTIs and other pathologic conditions of the urinary system. The question is whether these findings can be exploited for risk reduction and treatment purposes. This review aimed to appraise the three aforementioned specific microbiomes regarding their potential influence on UTI development by focusing on the recent studies in the field and assessing the potential linkages between these different niches, as well as evaluating the state of translational research for novel therapeutic and preventative approaches.

The Role of Gut, Vaginal, and Urinary Microbiome in Urinary Tract Infections: From Bench to Bedside.

RF-magnetron sputter deposited hydroxyapatite-based composite & multilayer coatings: A systematic review from mechanical, corrosion, and biological points of view

Mounting evidence indicates that the vagina can harbor uropathogenic bacteria. Here, we consider three roles played by the vagina and its bacterial inhabitants in urinary tract infection (UTI) and urinary health. First, the vagina can serve as a reservoir for Escherichia coli, the most common cause of UTI, and other recognized uropathogens. Second, several vaginal bacterial species are frequently detected upon urine culture but are underappreciated as uropathogens, and other vaginal species are likely under-reported because of their fastidious nature. Third, some vaginal bacteria that are not widely viewed as uropathogens can transit briefly in the urinary tract, cause injury or immunomodulation, and shift the balance of host-pathogen interactions to influence the outcomes of uropathogenesis. This chapter describes the current literature in these three areas and summarizes the impact of the vaginal microbiota on susceptibility to UTI and other urologic conditions.

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Roles of the vagina and the vaginal microbiota in urinary tract infection: evidence from clinical correlations and experimental models.

Despite the differences between the organisms that cause vaginitis and urinary tract infections (UTI), it is possible that women with vaginitis develop UTI. The main objective of the study was to find the association of the common types of infectious vaginitis with UTI. Cross sectional study was conducted for six months in a referral hospital at Lalitpur, Nepal. Three hundred and sixmid-stream urine samples and high vaginal swabs (HVS) collected from non pregnant women were investigated by standard microbiological techniques. Among the women with bacterial vaginosis (BV), 75% also had UTI. Similarly, 46% and 13% of those with vaginal candidiasis and trichomoniasis respectively had concurrent UTI. Considering this strong association of UTI and vaginitis, women with either of these conditions should be tested for the other.

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Urinary tract infection in vaginitis: a condition often overlooked.

Urinary tract infection (UTI) is the commonest bacterial infection occurring in renal disorder patients and is associated with significant morbidity. Resistance to antibiotics is highly prevalent in bacterial isolates and is an emerging problem in UTI. A hospital based cross sectional study was conducted from April 2011 to September 2011 to determine the frequency and bacterial profile of urinary tract infections in the patients with renal disorders visiting KIST Hospital along with their antimicrobial susceptibility pattern. Urine samples were collected from 300 clinically-suspected cases of UTI among renal disorder patients and investigated by conventional semi-quantitative culture technique, microscopy and antibiotic susceptibility test. Significant bacteriuria were detected in 34% of the total subjects, mostly from patients with Chronic Kidney Disease. Incidence of bacteriuria was found higher in females (40.40%) than in males (27.52%) and mostly occurred in elderly patients. Escherichia coli (62.75%) was the predominant isolate followed by Klebsiella pneumoniae (10.78%), Staphylococcus aureus (9.80%), Coagulase negative Staphylococcus aureus (CoNS) (5.88%), Enterococcus spp (3.92%), Klebsiella oxytoca (2.00%), Pseudomonas aeruginosa (2.00%), Proteus mirabilis (2.00%) and Proteus vulgaris (1.00%). Multidrug resistance was observed in 68.82% of the total bacterial isolates.

B M S Karki

Papers

Urinary tract infection in vaginitis: a condition often overlooked.

Spectrum of bacterial pathogens and their antibiogram from cases of urinary tract infection among renal disorder patients.