Introductory Chapter: Urinary Tract Infections (UTIs)

1. Introduction

Urinary tract infections (UTIs) are a prevalent bacterial infection in humans, accounting for about 40% of all hospital-acquired infections [1, 2]. The occurrence of UTIs has increased by 60% in the last three decades between 1990 and 2019, highlighting the significant public health issue they pose [3]. The UTIs symptoms commonly include bacteriuria along with suprapubic discomfort, urgency, urinary frequency, and dysuria [4]. UTIs are classified into two types: uncomplicated UTIs, also known as cystitis, affect only the bladder and can be resolved with simple antibiotic treatments. While the disseminated infections to the upper urinary tract are referred as complicated UTIs, that require more aggressive antibiotic treatments for longer periods. Furthermore, complicated UTIs are associated with higher rates of sepsis, recurrent infection, treatment failure, and significant morbidity and mortality [4, 5, 6, 7]. Uncomplicated UTIs affect 40–60% of females, at least once in their lifetime, on the other hand, all UTIs in males are usually considered complicated [8, 9, 10]. Recurrent UTIs are characterized by the occurrence of at least two acute UTI episodes within a span of 10 months or three episodes within a 12-month period, with a higher incidence in females than males [11, 12]. The UTIs can be self-infected, community-acquired, or nosocomial. Community-acquired infections typically result from low sanitary precautions, poor personal hygiene, or multiple sexual partners [7, 11]. The risk of self-infections often occurs in immunocompromised individuals as commensal inhabitants from the periurethral, vaginal, or rectal flora usually cause it [13, 14].

2. Risk factors

However, UTIs are recurrently encountered in healthcare amenities, the high infection rates could be associated with some risk factors. The gender, females are usually at high risk; it is expected that 40–60% of females will get UTIs at least once in their life, and half of them will suffer from recurrency within 1 year [9, 11, 12]. In males, the incidence of UTIs is lower than in females (10–15%), and even lower in circumcised males [10].

Females are at a higher risk of UTIs for various reasons; first of all, their shorter urethra eases the spread of bacteria to the bladder establishing infection [15]. Additionally, anatomical differences between males and females make self-infection from perineal flora more likely in females [9]. Hormonal changes during menopause, which reduce estrogen levels, also increase the risk of infection by making urogenital skin thinner and reducing the presence of protective Lactobacilli, as the lactic acid production by Lactobacilli renders the vaginal pH more acidic that does not encourage the growth of invading bacteria conferring a protective barrier against pathogenic infections [16]. Furthermore, the immunocompromised individuals including geriatrics and pregnant women are at high risk [17, 18, 19, 20]. In diabetic patients, nephropathy, glycosuria, and reduced immunity contribute to the higher incidence of complicated UTIs [3, 21, 22, 23]. Other factors that increase the risk of UTIs comprise anatomical abnormalities of the urinary tract, kidney stones, and the use of physical interventions such as spermicides, contraceptive diaphragms, intrauterine devices, catheters, and frequent pelvic examinations [10, 14].

3. Bacterial and fungal etiology of UTIs

The bacterial etiology of UTIs involves a variety of Gram-positive and -negative bacteria as well as the most common fungal infections by Candida spp., mainly C. albicans (Figure 1) [2]. Typically, the infections are mostly originated from the normal flora of the urogenital system, vaginal, and rectum besides the intestinal microbiota serving as the main reservoir of infections [4, 9]. Escherichia coli is the most frequently identified urinary tract pathogen, responsible for 65% of complicated UTIs and 75% of uncomplicated UTIs [24]. Klebsiella pneumoniae is the second most frequent cause of UTIs, accounting for 6–8% of cases, while C. albicans and Enterococcus faecalis are significant causes of complicated UTIs, causing 7% and 11% of UTIs, respectively [14]. Other less commonly identified causative agents include Staphylococcus saprophyticus, Staphylococcus aureus, Staphylococcus epidermidis, group B Streptococcus, Proteus mirabilis, Acinetobacter baumannii, and Pseudomonas aeruginosa [14, 25].

Figure 1.

The most common uropathogens (adopted from Lila et al. [2]). UTIs are caused by a wide range of Gram-positive and -negative bacterial pathogens and fungal pathogens mainly Candida spp.

4. Pathogenesis of UTIs

The bacterial ability to breach the urethral sphincter muscle, the natural barrier against pathogens, initiates pathogenesis employing bacterial fimbriae and adhesin to adhere to the urethral epithelium [26, 27]. Then, bacteria ascend the urethra and colonize the urinary bladder, where they express numerous virulence factors that promote necrosis of tissues and facilitate invasion, resulting in cystitis [4, 14, 28]. UTIs symptoms extend to include fever, suprapubic pain, lower abdominal pain, blisters, and ulcers in the urogenital area besides bacteriuria, dysuria, urgency, urinary frequency, pyuria, itching, and burning sensation during urination [29, 30].

5. Catheter-associated urinary tract infections (CAUTIs)

CAUTIs are the most frequent hospital-acquired infections and account for nearly 40% of all infections [3, 21]. Urinary catheters are foreign bodies that induce local mechanical stress, causing various inflammatory responses such as mucosal lesions edema, and exfoliation [21]. Insufficient use of aseptic techniques while inserting a catheter can cause contamination, which in turn can result in CAUTIs. The probability of developing UTIs is notably high when catheterization is prolonged (beyond 7 days) because the surface of urinary catheters provides an optimal environment for bacterial growth and attachment [21, 31]. Additionally, the deposited fibrinogen lubricates the catheter surface and serves as a nutrient source providing an ideal niche for bacterial attachment [23].

6. Biofilm formation

Biofilm formation constitutes the cornerstone in the UTIs pathogenesis playing the main role in CAUTIs [32, 33, 34]. Moreover, the formation of biofilms is regarded as a crucial factor contributing to the frequent recurrence of UTIs. In Refs. [23, 32], and antimicrobial resistance [34, 35, 36, 37]. These biofilms are anchored in the place by an extracellular polymer matrix that is secreted by the bacteria themselves, which constitute an obstacle against antibiotics to attack bacteria [2, 26, 38]. The behavior of bacteria in biofilms is different from that of planktonic bacteria, they prioritize fortifying their establishment plan over motility and metabolic activities to conserve nutrients and energy [26, 39, 40]. They upregulate extracellular toxins to cause maximum tissue damage, releasing nutrients and cementing the biofilm in place [41, 42]. The biofilm sheds daughter planktonic cells that persistently disseminate the infection and create new biofilms. These biofilms are difficult to eradicate and can lead to chronic and recurrent infections [13, 26].

7. Objectives of UTIs book

UTIs are a common health issue that affects millions of people around the world every year, resulting in discomfort and pain that have a significant impact on a person’s quality of life, and if left untreated, can lead to more serious complications. This book aims to provide a comprehensive guide to understanding UTIs, their causes, symptoms, and treatment options. Through this book, readers will gain a better understanding of the risk factors associated with UTIs, as well as ways to prevent and manage them. The book will cover both conventional and alternative treatments, as well as lifestyle changes that can help prevent UTIs from occurring. In addition to providing valuable information for those who have already experienced UTIs, this book will also serve as a valuable resource for healthcare professionals who treat patients with UTIs. By presenting the latest research and evidence-based recommendations, this book will help healthcare providers make informed decisions about diagnosis and treatment.