![\"AnaPEREIRA\"](\"https:\/\/veterinarska-stanica-journal.hr\/wp-content\/uploads\/2024\/06\/AnaPEREIRA.jpg\")
<\/p>\n<\/p>\n
A. Pereira<\/strong>*, C. Jota Baptista<\/strong>, P. A. Oliveira<\/strong> and A. C. Coelho<\/strong><\/p>\n <\/a><\/p>\n <\/a> ▲<\/a><\/p>\n The urinary tract infection (UTI) is a common disease in dogs and cats, and it can occur as isolated infections or recurrently. Recurrent cases are particularly common in cases with underlying health conditions. The diagnosis of UTIs in dogs and cats generally involves an integrated interpretation of clinical signs, urinalysis, and bacterial cultures. Diagnostic imaging can also help assessing or discarding anatomical lesions. One of the many microorganisms that can cause UTIs is Escherichia coli<\/em>. Females, geriatric patients, and animals with comorbidities usually have an increased risk of UTI. Antimicrobial prescription is common for the treatment of UTIs in companion animals. However, nowadays, there is a growing concern about antimicrobial resistance due to over-prescription driving selection for resistance. Therefore, correct prescription and appropriate patient management are essential. This review aims to provide a summary of the clinical and epidemiological aspects of UTIs, contributing to improving veterinary practices and antibiotic prescription in the context of UTIs in companion animals.<\/p>\n Key words:<\/strong> Cats; Clinical signs; Dogs; Epidemiology; Urinary tract infections<\/em><\/p><\/blockquote>\n <\/a> ▲<\/a><\/p>\n Urinary tract infections (UTIs) occur frequently in veterinary practice and are among the most common reasons for antibiotic prescription (Sykes and Westropp, 2014; Hernando et al<\/em>., 2021). A wide variety of pathogens can cause UTIs, even though bacteria are the most frequent (Olin and Bartges, 2015; Koc\u00farekov\u00e1 et al<\/em>., 2021). These agents may cause a lower UTI, affecting the bladder (cystitis) and\/or the urethra (urethritis); or upper TI, affecting renal pelvis (pyelonephritis) and\/or ureters (ureteritis) (Kogika and Waki, 2015; Olin and Bartges, 2015; Teh, 2022). Frequently, an etiological diagnosis is not performed due to financial constraints of the owner (Fonseca et al<\/em>., 2021), and the empirical treatment antibiotic is initiated. Notwithstanding, antimicrobial drug treatment without knowing the responsible agent may lead to recurrent infection and treatment failure (Sykes and Westropp, 2014). Improper therapy has consequences for the patient (e.g., prolonged pain), economic concerns for the owner (as additional costs) and a public health impact (as the possibility of zoonotic transmission of resistant bacteria) (Weese et al<\/em>., 2019; Yudhanto et al<\/em>., 2022).<\/p>\n Previous studies have described patterns of antimicrobial prescriptions in companion animals in different countries. <\/a> ▲<\/a><\/p>\n The urinary tract (UT) is sterile, with the exception of the distal urethra and external genitalia, where commensal microbiota is present (Lanzi et al<\/em>., 2022). In a few words, UTIs are more often caused by agents that belong to this microbiota or to the intestine\u2019s commensal microbiota (ascending infection) (Rodriguez, 2016) (Figure 1).<\/p>\n Less commonly, an infectious agent can reach the UT from the kidney, through a descending route or, in other words, via hematogenous spread (Littman, 2011; Sykes and Westropp, 2014). Basically, for a UTI, two conditions must occur: 1) temporary or permanent failure in host\u2019s immunity, and 2) pathogens must be present in sufficient quantity and with specific virulence (Kogika and Waki, 2015; Koc\u00farekov\u00e1 et al<\/em>., 2021).<\/p>\n A wide variety of infectious agents can cause UTIs. Fungal infections, including Candida<\/em> spp., have been described in cases of immunosuppression, chronic UT conditions, and animals receiving concomitant antibiotic therapy (Reagan et al<\/em>., 2019; Dowling, 2023). However, recent data reported that viral, fungal, and parasitic infections represent less than 1% of UTIs cases (Kogika and Waki, 2015; Dorsch et al<\/em>., 2019).<\/p>\n In general, UTIs bacterial agents are similar between the two species in small animal practice (Labato, 2009). Escherichia coli<\/em> (E. coli<\/em>) is the most frequently isolated agent in canines, felines, and even humans (Koc\u00farekov\u00e1 et al<\/em>., 2021; Weese et al<\/em>., 2019), representing 33-55% of the isolated pathogens (Lima et al<\/em>., 2021; DiBartola and Westropp, 2023). Bacteria such as Enterococcus<\/em> spp., Staphylococcus<\/em> spp., Streptococcus<\/em> spp., Enterobacter<\/em> spp., Proteus<\/em> spp., Klebsiella<\/em> spp., Pseudomonas<\/em> spp., Pasteurella<\/em> spp., and Corynebacterium<\/em> spp. are also commonly isolated (Sykes and Westropp, 2014; Byron, 2019; Lanzi et al<\/em>., 2022). UTIs usually involve a single microorganism. <\/a> ▲<\/a><\/p>\n Bacterial UTIs are estimated to affect about 14% to 15% of dogs over their lifetime (Dowling, 2023; Rodriguez, 2016). Females are more affected (Furini et al<\/em>., 2013; Hall et al<\/em>., 2013; Lima et al<\/em>., 2021), with a higher prevalence in spayed and matured animals (7 to 8 years old) (Sykes and Westropp, 2014; Lanzi et al<\/em>., 2022; Llido et al<\/em>., 2020).<\/p>\n In cats, lower UT diseases are normally approached as a disease complex, called the feline lower UT disease (FLUD). Idiopathic cystitis and UT inflammatory disease without the presence of an infectious agent, is far more than bacterial UTIs in this species (Kovarikova, 2020; Heseltine, 2022). In fact, according to Rodriguez (2016) and Heseltine (2022), less than 10% of cats with urinary clinical signs have a positive urine culture. Unlike dogs, cats seem to have an innate resistance to bacteria (Bartges, 2012). Nevertheless, similarly to dogs, positive urine cultures are more easily found in female cats. The incidence tends to increase with age, and it is especially higher after 10 years old (Dorsch et al<\/em>., 2019; Kovarikova et al<\/em>., 2020; Leckcharoensuk et al<\/em>., 2001), neutered females and\/or in cases with comorbidities (DiBartola and Westropp, 2023). Studies performed by S\u00e6vik et al<\/em>. (2011) in Norway have also shown a predisposition in purebred cats, being the Abyssinian (Gerber, 2007; Dorsch et al<\/em>., 2019) and the Persian breeds the most susceptible (Sykes and Westropp, 2014).<\/p>\n <\/a> ▲<\/a><\/p>\n In ascending infections, the resident microbiota present in the distal urethra, genitalia (Figure 1), and in the intestine become causes of disease (Rodriguez, 2016; Lanzi et al<\/em>., 2022). Several studies have shown that, in dogs, at the time of infection, the pathogens which colonize the urinary bladder are the same that are predominant in the gastrointestinal tract (Low et al<\/em>., 1988; Ball et al<\/em>., 2008; Johnson et al<\/em>., 2008). Although infrequent, UTIs can also occur through hematogenous spread. Non-pathogenic bacteria in a normal animal can become pathogenic in immunosuppressed patients (Pressler and Bartges, 2010). The development of UTI depends on the balance between the host\u2019s defense mechanisms and the virulence factors of the pathogen (Dorsch et al<\/em>., 2019; Kovarikova et al<\/em>., 2020).<\/p>\n Normal urine storage and voiding<\/strong> Dogs with intervertebral disc disease often present urinary retention and abnormal urination, conditions that predispose them to UTI (Baigi et al<\/em>., 2017; Teh, 2022). Antimicrobial properties of urine<\/strong> Anatomic structures<\/strong> Mucosal defense barriers<\/strong> Local and systemic immune competence<\/strong> A retrospective study involving 101 dogs with DM, HD, or both concluded that 41.6% developed UTI (Smee et al<\/em>., 2013a). Another retrospective study in cats reported bacterial UTI in 17-30% of cats with CKD, 12-13% with DM, and 12-22% with HT (Smee et al<\/em>., 2013a). Mayer et al<\/em>. (2007) and Baillif et al<\/em>. (2008) found positive cultures in 17% and 22% of cats with CKD and 22% and 12% with HT, respectively. Dogs treated with immunosuppressive drugs for long periods showed a high prevalence of positive urine cultures (Torres et al<\/em>., 2005; Senior, 2007).<\/p>\n UTI leads to the expression of microbial virulence factors (VF), which are responsible for adherence, colonization, and invasion in the urinary tissue (Kogika and Waki, 2015; Dorsch et al<\/em>., 2019; Raheema, 2021). For example, Proteus<\/em> spp., C. urealyticum<\/em>, Staphylococcus<\/em> spp., and Klebsiella<\/em> spp. can hydrolyze urease, converting it into ammonia (Senior, 2011). This compound not only induces direct damage to the epithelium but also facilitates bacterial invasion and its persistence (Litster et al<\/em>., 2011; Byron, 2019), as it increases pH and promotes crystalluria (Litster et al<\/em>., 2011). <\/a> ▲<\/a><\/p>\n The clinical signs depend on the site of infection, duration of disease, presence or absence of predisposing causes, compensatory response of the animal, virulence, and the quantity of uropathogenic agents (Smee, 2020). Inflammation of the lower UT often results in polyuria, stranguria, dysuria, inappropriate urination, and hematuria (Dorsch et al<\/em>., 2019; Smee, 2020). Pain, retention, or even urinary incontinence may arise because of vesicourethral inflammation (Senior, 2011; Rodriguez, 2016). Animals with involvement of the upper UT may present polyuria, polydipsia, pain in the lumbodorsal region, vomiting, hyperthermia, lethargy, and anorexia (Rodriguez, 2016).<\/p>\n <\/a> ▲<\/a><\/p>\n Clinical signs of UTI are not specific or pathognomonic (Hernando et al<\/em>., 2021). Urinalysis is an important clinical diagnostic tool in these patients (Yadav et al<\/em>., 2020). The physical properties of urine (color, odor, turbidity, and density) should be evaluated and interpreted macroscopically (Smee et al<\/em>., 2013b; Yadav et al<\/em>., 2020). Chemical properties can be assessed using urine test strips, providing information such as pH (whose value changes in the presence of urease-positive bacteria) (Nelson and Couto, 2009), the presence of blood, protein, and glucose (Yadav et al<\/em>., 2020). A recent study by Farris et al<\/em>. (2022) reported that leukocytes in urine strips predicts pyuria, but nitrites do not confirm infection. Examination of the sediment allows the determination of the presence of epithelial cells, red blood cells (hematuria), inflammatory cells (pyuria), and\/or bacteria (Smee et al<\/em>., 2013b; Yadav et al<\/em>., 2020). In the presence of bacteriuria, Gram staining may be advantageous (Soares et al<\/em>., 2024). Bacteriuria has moderate sensitivity and high specificity in predicting bacterial growth, but this relationship decreases in urines with low urinary densities (urine specific gravity (USG) \u22641.012) (Torre et al<\/em>., 2022). Therefore, isosthenuric or hyposthenuric urines should always be subjected to culture (Rodriguez, 2016). The presence of hematuria, pyuria, and proteinuria may indicate UTI, but not its cause or location (Lloyd, 1987; DiBartola and Westropp, 2023). Therefore, ideally, urine should be subjected to a microbiological culture in aerobic conditions before treatment to confirm the presence and type of bacteria (Pressler and Bartges, 2010; Smee et al<\/em>., 2013b; Dorsch et al<\/em>., 2019; Lanzi et al<\/em>., 2022; Lien and Wang, 2023). Urine collection for culture should, whenever possible, be performed by cystocentesis to prevent contamination by bacteria inhabiting the distal urethra, prepuce, or vulva (DiBartola and Westropp, 2023). Other collection methods (catheterization or spontaneous micturition) should only be used when cystocentesis is contraindicated (e.g., suspicion of transitional cell carcinoma of the bladder or pyoderma on the ventral abdomen) (Smee et al<\/em>., 2013b) or when it is not feasible (animals with severe clinical signs of UTI) (Pressler and Bartges, 2010). Van Duijkeren et al<\/em>. (2004) demonstrated that while urine culture was negative in 79% of samples collected by cystocentesis, this value decreased to 55% when collected by catheterization, and only 17% when collected by midstream voiding.<\/p>\n Diagnostic imaging (radiography, ultrasound, or cystoscopy) can help finding concomitant lesions (Mazda et al<\/em>., 2022). <\/a> ▲<\/a><\/p>\n Treating UTIs in dogs and cats requires a comprehensive approach, including appropriate antibiotics, addressing underlying causes, and providing supportive care (Sykes and Westropp, 2014). A retrospective study in dogs shows that the prescription of antibiotics is not usually preceded by proper diagnostic testing, potentially leading to over-treatment with antibiotics (S\u00f8rensen et al<\/em>., 2018). The empirical treatment and the overuse (or misuse) of antibiotics may promote selection pressure and the emergence of resistant bacteria (Schwarz et al<\/em>., 2017; McEwen and Collignon, 2018; Richter et al<\/em>., 2020). In fact, a single dose of antibiotic can be sufficient for an entire bacterial population to gain resistance (Nelson and Couto, 2009). The risk is more significant as the number of antibiotics used increases (McEwen and Collignon, 2018). Currently, numerous studies demonstrate the transmission of microorganisms and multidrug-resistant (MDR) strains between humans and their companion animals (Johnson & Clabots 2006; Eggertsd\u00f3ttir et al<\/em>., 2007; Johnson et al<\/em>., 2008; Pomba et al<\/em>., 2017; Schwarz et al<\/em>., 2017; Derakhshandeh et al<\/em>., 2018; Fernandes et al<\/em>., 2018; Gr\u00f6nthal, et al<\/em>., 2018; Rampacci et al<\/em>., 2018; Belas et al<\/em>., 2021). Table 1 summarizes the reasons for antibiotic treatment failure.<\/p>\n The UT of dogs is the most common extraintestinal site to find MDR E. coli<\/em> and Enterobacter<\/em> spp. with 62% and 58% of isolates, respectively (Smee et al<\/em>., 2013b; Hutton et al<\/em>., 2018). In a multicenter study in Europe conducted by Marques et al<\/em>. (2016), it was found that Southern countries had higher levels of resistance to antibiotics for all urinary bacteria compared to Northern countries. Moreover, the prevalence of multidrug-resistant E. coli<\/em> was also higher in these countries. Studies in Australia (Scarborough et al<\/em>., 2020), Africa (Qekwana et al<\/em>., 2018), central Italy (Smoglica et al<\/em>., 2022), the United Kingdom (Fonseca et al<\/em>., 2021), and even Portugal (Garc\u00eas et al<\/em>., 2022) have found increasingly higher prevalences of MDR E. coli<\/em>.<\/p>\n Because of this phenomenon, the World Health Organization (WHO) has classified antimicrobials based on their importance in human medicine (McEwen and Collignon, 2018), and it restricted the treatment options in veterinary medicine. <\/a> ▲<\/a><\/p>\n In a healthy animal, i.e<\/em>. patients with normal anatomy and without associated comorbidities, sporadic bacterial infections are more frequent. The occurrence of three or more episodes in a year excludes a bladder infection from this group (DiBartola and Westropp, 2023; Weese et al<\/em>., 2019). Diagnosis is based on clinical signs compatible with UTI, urinalysis (pyuria and bacteriuria increase suspicion of infection), and urine culture with an antibiotic susceptibility test (AST) (Weese et al<\/em>., 2019). Nonsteroidal anti-inflammatory drugs (NSAIDs) (such as carprofen, ketoprofen, meloxicam, piroxicam and robenacoxib) or tramadol may be initiated for three to four days to minimize the animal\u2019s discomfort until a microbiological result is obtained (He et al<\/em>., 2022; Sykes and Westropp 2014).<\/p>\n Empirical antimicrobial treatment can be initiated, especially in animals with clinical signs and no previous antibiotics exposure. However, empirically antibiotherapy should be adjusted to the type of pathogen and resistance patterns (Weese et al<\/em>., 2011). Amoxicillin (11-15 mg\/kg orally every 8 hours) or trimethoprim sulfamethoxazole (15 mg\/kg orally every 12 hours) can be used as a first-line antibiotic therapy (DiBartola and Westropp, 2023). The guidelines proposed by ISCAID recommend a short-term therapy of 3 to 5 days in dogs and cats, as in humans (Weese et al<\/em>., 2019). The antibiotic should not be changed if there is a clinical improvement, even if antimicrobial susceptibility testing indicates resistance (Weese et al<\/em>., 2019). If there is no clinical response within 48 hours, clinicians should look for factors that can be impairing antimicrobial\u2019s effectiveness, before changing the antibiotic (DiBartola and Westropp, 2023).<\/p>\n Animals that have three or more episodes of bacterial cystitis within a year, or at least two in the past six months are included in this group. Recurrent infections may result from relapse, persistent infection, re-infection, super-infection, as summarized in Table 2.<\/p>\n Recurrent infections have been reported in 0.3% of hospitalized dogs, with spayed females being the most represented for this type of infection (Teh, 2022). For long-term treatments, urine cultures should be done 5-7 days after the day 1, and 5-7 days after the end of the treatment. When urine cultures are positive, predisposing factors and associated comorbidities should be investigated before the antibiotic is changed. The presence of bacteriuria in an animal without clinical signs should be treated as subclinical bacteriuria, as discussed in the next section (Weese et al<\/em>., 2019).<\/p>\n If the animal shows a positive urine culture without clinical signs, it should be diagnosed as subclinical bacteriuria. The presence of bacteria and inflammatory cells in urinary sediment does not always indicate UTI. Therefore, the diagnosis of subclinical bacteriuria should be based on urine culture (Lien and Wang, 2023; O\u2019Neil et al<\/em>., 2013; McGhie et al<\/em>., 2014; Weese et al<\/em>., 2019; Torre et al<\/em>., 2022). For both species, DM (McGuire et al<\/em>., 2002; Bailiff et al<\/em>., 2006; Nelson et al<\/em>., 2023) as well as long-term administration of corticosteroids (Torres et al<\/em>., 2005) were predisposing factors for subclinical bacteriuria. Baigi et al<\/em>. (2017) found similar results in chronically paralyzed dogs. The same happened for White et al<\/em>. (2013) for cats with chronic kidney disease. Moreover, Harrer et al<\/em>. (2022) found a high prevalence of positive urine cultures in animals receiving antineoplastic drugs. In contrast, Peterson et al<\/em>. (2020) did not observe a relationship between positive urine culture and hyperthyroidism in cats. Notwithstanding, ISCAID generally advises against performing urine cultures in animals without clinical signs of UTI, unless there are particular comorbidities.<\/p>\n The bacterial strains involved in subclinical bacteriuria often have few virulence factors or low bacterial counts (Smee et al<\/em>., 2013b). Treating subclinical bacteriuria cases with low bacterial counts can contribute to antibiotic resistance and may result in secondary colonization by more pathogenic strains. Most pyelonephritis are caused by Enterobacteriaceae<\/em>, ascending from the lower UT (Wong et al<\/em>., 2015). Diagnosis is based on clinical signs, blood and urine tests, and diagnostic imaging (William
\nAna PEREIRA<\/strong>*, DVM, MSc, (Corresponding author, e-mail: anafilipalp@gmail.com), Department of Veterinary Sciences, University of Tr\u00e1s-os-Montes e Alto Douro (UTAD), Vila Real, Portugal; Catarina JOTA BAPTISTA<\/strong>, DVM, MSc, Portugal Centre for the Research and Technology of Agro-Environmental and Biological Sciences (CITAB), UTAD, Egas Moniz Center for Interdisciplinary Research (CiiEM), Egas Moniz School of Health & Science, Almada, Portugal; Paula Alexandra OLIVEIRA<\/strong>, DVM, MSc, PhD, Department of Veterinary Sciences, UTAD, Vila Real, Portugal Centre for the Research and Technology of Agro-Environmental and Biological Sciences (CITAB), UTAD, Portugal; Ana Cl\u00e1udia COELHO<\/strong>, DVM, MSc, PhD, Department of Veterinary Sciences (ECAV), Animal and Veterinary Research Centre (CECAV), UTAD, Vila Real, Portugal<\/div>\n![\"\"](\"https:\/\/veterinarska-stanica-journal.hr\/wp-content\/uploads\/2021\/03\/pdf.png\")
<\/a>https:\/\/doi.org\/10.46419\/vs.55.6.8<\/a><\/div>\n<\/p>\n\nAbstract<\/a>Introduction<\/a>Etiology of Urinary Tract Infections (UTIs)<\/a>Epidemiology<\/a>Pathogenesis<\/a>Clinical signs<\/a>Diagnosis<\/a>Treatment<\/a>Classification of UT infection and its clinical management<\/a>Prevention and prophylaxis<\/a>Conclusions<\/a>Funding<\/a>References<\/a>Sa\u017eetak<\/a><\/span><\/div>\n<\/div>\n\n
Abstract<\/h2>\n
\nIntroduction<\/h2>\n
\n
\nIn some cases, bacterial agents may also colonize surrounding tissues, such as the prostate (prostatitis) or vagina (vaginitis) (Olin and Bartges, 2015; Koc\u00farekov\u00e1 et al<\/em>., 2021). In some cases, animals may reveal no clinical signs or mild discomfort while urinating, leading to signs of dysuria and pollakiuria that usually disappear with pharmacological treatment. Nevertheless, in severe cases, intravenous fluids, hospitalization, or surgery may be necessary (Weese et al<\/em>., 2019).<\/p>\n
\nIn this review, the 2019 ISCAID (International Society for Companion Animal Infectious Diseases) guidelines have been considered. Our aim is providing a brief review about the clinical and epidemiological aspects of UTIs, to improve veterinary practices, especially in antibiotic treatment.<\/p>\nEtiology of Urinary Tract Infections (UTIs)<\/h2>\n
\n![\"figure01-urinary-tract\"](\"https:\/\/veterinarska-stanica-journal.hr\/wp-content\/uploads\/2024\/06\/figure01-urinary-tract.jpg\")
\nHowever, mixed infections, with two or more microorganisms, may also be involved (Nelson and Couto, 2009). According to Smee, (2020), 75% of dog isolates are single bacteria, 20% are caused by a combination of two species, and 5% by three or more species. A similar frequency was found for cat patients (Pressler and Bartges, 2010). Mixed infections are more frequent cases of prolonged use of urinary catheters or other comorbidities (Dorsch et al<\/em>., 2016).<\/p>\nEpidemiology<\/h2>\n
\nPathogenesis<\/h2>\n
\n
\nProvenances of these bacteria bacterial endocarditis or extension from infected tissues surrounding the UT, such as prostate gland (Smee et al<\/em>., 2013a; DiBartola and Westropp, 2023).<\/p>\nNatural Host Defense Mechanism<\/h3>\n
\nThe mechanical and unidirectional elimination that occurs in normal urination is responsible for eliminating 95% of non-adherent bacteria that reach the urinary bladder (DiBartola and Westropp, 2023). Complete emptying of the urinary bladder minimizes the agent\u2019s exposure time, reducing the probability of colonization (Teh, 2022; DiBartola and Westropp, 2023). Urinary obstruction (tumors, hypertrophic lesions, or urethral stenosis) as well as incomplete emptying of the urinary bladder (due to spinal cord injury or congenital\/acquired bladder atony) increases bacterial proliferation and consequent infections (Smee et al<\/em>., 2013; Teh, 2022).<\/p>\n
\nStudies have shown that 38% of dogs undergoing spinal disc surgery develop UTI within three postoperative months (Olby et al<\/em>., 2010). Moreover, the presence of bacteriuria has also been documented in 74% of dogs paralyzed for more than three months (Baigi et al<\/em>., 2017).<\/p>\n
\nThe combination of a low pH, high concentrations of urea and organic acids, and higher osmolarity makes the UT inhospitable for bacterial growth (Teh, 2022). According to several authors, animals with more diluted urine are more susceptible to bacterial growth (Senior, 2007; Litster et al<\/em>., 2009; Ruzafa et al<\/em>., 2012). However, these results do not seem consistent with other studies (Baillif et al<\/em>., 2008; Dorsch et al<\/em>., 2019; DiBartola and Westropp, 2023). A study conducted by Teh (2022) also found a higher prevalence of UTI in dogs that received diuretics.<\/p>\n
\nThe high pressure and the peristaltic contractions at the level of the urethra, help prevent the ascent of commensal bacteria (Teh, 2022; DiBartola and Westropp, 2023). The length of the urethra and prostatic secretions in males contribute to a lower incidence of UTI in male dogs (Smee, 2020). The vesicoureteral valve, created by the oblique passage of the ureters through the bladder wall, prevents vesicoureteral reflux (Confer and Panciera, 1998; Teh, 2022). Congenital or acquired abnormalities, such as ectopic ureters, are associated with ascending UTIs, especially pyelonephritis (Smee et al<\/em>., 2013a). Furthermore, persistent urachus is associated with chronic UTI, and hypoplasia or vulvar atresia is related to recurrent UTIs (Lightner et al<\/em>., 2001; Smee, 2020). Animals undergoing urethrostomy often present chronic UTIs (Senior, 2007, Kogika and Waki, 2015). Additionally, the presence of skin folds near the vulva often results in located dermatitis, which increases the likelihood of bacterial ascent through the urethra. Episioplasty (excision of skin folds) in animals with this dermatitis usually solves the clinical signs of chronic UTI (Lightner et al<\/em>., 2001).<\/p>\n
\nThe UT has several defense mechanisms. The commensal microbiota occupies most of the epithelial receptors, produces bacteriocins, and competes for the same nutrients as pathogenic bacteria (Kogika and Waki, 2015; DiBartola and Westropp, 2023). The epithelial cells in the bladder form an impermeable barrier.
\nIn case of infection, bacteria can induce cellular apoptosis, resulting in the exfoliation of these cells (Smee et al<\/em>., 2013a).
\nMoreover, the urothelium produces and releases glycosaminoglycans (GAGs) and proteoglycans, which prevent the adherence of pathogens and crystals to the epithelium (Smee, 2020). As well as the local production of Immunoglobulins A and G (IgA, IgG) (Kogika and Waki, 2015; Teh, 2022; DiBartola and Westropp, 2023).
\nThus, mucosal injury due to urolithiasis, catheterization trauma, neoplasia, or cyclophosphamide-induced injury induces secondary UTI (Kogika and Waki, 2015; Smee, 2020). A previous study suggests that ovariectomized animals may have a higher risk of UTI because the amount of GAG produced is lower (Senior, 2011).
\nIn a study conducted by Budreckis et al<\/em>. (2015), 55% of dogs with transitional cell carcinoma showed positive urine cultures.<\/p>\n
\nImmunosuppressive conditions, such as chronic kidney disease (CKD), diabetes mellitus (DM), hyperadrenocorticism (HD), hyperthyroidism (HT) and a prolonged administration of corticosteroids (CE), have been related to UTI (Hall et al<\/em>., 2013; Smee, 2020). In addition to immunosuppression, glycosuria and low urinary osmolality are associated with some of these conditions, which also increase the susceptibility to UTIs (Teh, 2022).<\/p>\nMicrobial factors<\/h3>\n
\nOther species have intrinsic mobility and can undergo retrograde migration, i.e., against the urinary flow (Senior, 2006), while others can thrive in hypertonic environments such as the renal medulla and bladder where leukocyte migration and phagocytosis are compromised (Nelson and Couto, 2009). Some enzymes, like beta-lactamases, allow them to resist the action of antimicrobials such as penicillins and cephalosporins (Kogika and Waki, 2015). E. coli<\/em> presents a high number of virulence factors (Tramuta et al<\/em>., 2011; Kern et al<\/em>., 2018; Gunathilake et al<\/em>., 2023; Liang et al<\/em>., 2023).<\/p>\nClinical signs<\/h2>\n
\nDiagnosis<\/h2>\n
\n
\nOn the other hand, distinguishing bacterial from idiopathic cystitis or subclinical bacteriuria represents a challenge. A complete urinalysis with a positive culture is crucial for a reliable diagnostic (Dorsh et al<\/em>., 2019).<\/p>\n
\nCultures in anaerobic conditions are only necessary when there is a suspicion of emphysematous cystitis (Littman, 2011). Recent and promising studies have utilized rapid immunoassay tests (RIA; Rapid Bac) to detect bacteriuria, showing high specificity and sensitivity. Moreover, it represents an inexpensive, fast, and easy-to-perform technique (Grant et al<\/em>., 2021; Sutter et al<\/em>., 2023).<\/p>\n
\nFigure 2 summarizes the general diagnostic approach to UTIs.<\/p>\n![\"figure02-urinary-tract\"](\"https:\/\/veterinarska-stanica-journal.hr\/wp-content\/uploads\/2024\/06\/figure02-urinary-tract.jpg\")
(Pressler and Bartges 2010; Littman 2011; Papich 2013; Richter et al<\/em>., 2019; Weese et al<\/em>., 2019; Llido et al<\/em>., 2020; Lanzi et al<\/em>., 2022; Lien and Wang, 2023).<\/figcaption><\/figure>\nTreatment<\/h2>\n
\n![\"table01-urinary-tract\"](\"https:\/\/veterinarska-stanica-journal.hr\/wp-content\/uploads\/2024\/06\/table01-urinary-tract.png\")
\nAntimicrobials such as third generation cephalosporins, carbapenems, and fluoroquinolones should not be used in veterinary medicine or only used under rare circumstances (Dorsh v., 2019; McEwen and Collignon, 2018). The chosen antimicrobial agent should be based on susceptibility testing of uropathogen (Olin and Bartges, 2015). When this is not possible, the empirical treatment should be based on the variation in bacterial prevalence rates and antimicrobial resistance patterns across different regions (consulting guidelines studies, local studies, national databases, or surveillance systems (McEwen and Collignon, 2018; Hernando, 2021).<\/p>\nClassification of UT infection and its clinical management<\/h2>\n
\nSporadic bacterial cystitis<\/h3>\n
Recurrent bacterial cystitis<\/h3>\n
![\"table02-urinary-tract\"](\"https:\/\/veterinarska-stanica-journal.hr\/wp-content\/uploads\/2024\/06\/table02-urinary-tract.png\")
\nMicroorganisms such as Enterococcus<\/em> spp. and Pseudomonas<\/em> spp. are rarely found in sporadic cystitis, but their prevalence increases in animals with recurrent UTIs (Thompson et al<\/em>., 2011). Diagnosis should always be based on urine culture. Furthermore, searching for underlying causes is imperative, especially if the identified pathogen differs from the initial one (Weese et al<\/em>., 2029). In severe cases, empirical treatment can be started and should follow the lines of sporadic cystitis. Regardless of the AST result, the antibiotic is only changed if there is no clinical response to empirical treatment. A shortterm treatment (3-5 days) is suggested, mainly if it is a reinfection. Longer treatments (7-14 days) are only recommended for persistent or recurrent infections, and when there are anatomical lesions (Weese et al<\/em>., 2019).<\/p>\nSubclinical bacteriuria<\/h3>\n
\nThe prevalence of this is low (2-12%) in healthy dogs, but increases to 15-74% in obese animals or in presence of comorbidities (Eggertsd\u00f3ttir et al<\/em>., 2011; O`Neil et al<\/em>., 2013; McGhie et al<\/em>, 2014; Olin and Bartges, 2015). In cats, this prevalence appears to be lower than in dogs (Puchot et al<\/em>., 2017), and it is higher in matured and geriatric females (DiBartola and Westropp, 2023).<\/p>\n
\nMoreover, the treatment of bacteriuria in humans has been questioned due to the induced resistance, and because it is normally ineffective (Dorsch et al<\/em>., 2019; Freitag, 2011). According to Weese et al<\/em>. (2019), treatment of subclinical bacteriuria in veterinary medicine should only be performed in three situations: (a) when there is a high risk of bacterial ascension or systemic infection (e.g., immunocompromised patients, renal abnormalities), (b) animals that are subjected to surgical or endoscopic procedures of the UT, (c) when the bladder is secondary infected by extra-UT bacteria (Weese et al<\/em>., 2011; Westropp et al<\/em>., 2011; Dorsch et al<\/em>., 2019).<\/p>\nPyelonephritis<\/h3>\n