The Causative Organism of Urinary Tract Infections UTI: a Cross-sectional Study from a Tertiary Hospital In Saudi Arabia

Introduction

Urinary tract infections (UTIs) are a common disease, accounting for 20-25% of all infections and representing 150 million diagnosed cases annually [1-3]. The incidence of such infections differs in relation to age and gender. In adult women, for instance, the lifetime incidence of UTI is greater than 50% [2], while urosepsis is the second-most common cause of sepsis among the elderly popu- lation [4,5]. It has been estimated that UTIs cost approximately $800,000 annually in a local study [6]. As such, the burden of the disease and its relatively high prevalence mandate revisiting this infection and exploring it in greater depth.

There are several predispositions to the develop- ment of UTI beyond the anatomical and physiolog- ical factors, including sexual activity, immunosup- pression, and the use of Foley catheters. Therapeutic use of Foley catheters, for instance, increases the risk for UTI by 10% for every day the catheter is in situ [7,8]. Meanwhile, immunosuppression promotes the development of UTI due to the loss of the body’s defense system [9]. This is seen among people with diabetes, chronic kidney disease, organ transplants, and patients on active chemotherapy. Those with diabetes appear to be affected more than the others. In Saudi Arabia, for example, the prevalence of UTI is around one quarter in those with diabetes mellitus [10], making it the most prevalent infection in this cohort [11,12].

Furthermore, the organisms that cause UTI vary depending on the patients’ comorbidities, previous infections, the use of Foley catheters and instrumen- tation, and prior surgeries. Classically, Escherichia coli is the most common organism, followed by Klebsiella pneumoniae [13,14]. The former remains the most common irrespective of whether the patient is immunocompromised or immunocompetent [9]. In addition, other organisms, including Enterococ- cus species, Candida, Staphylococcus aureus, Pro- teus mirabilis, Pseudomonas aeruginosa, and group B Streptococcus (GBS), were also cultured [13].

The prevalence of these organisms in immuno- competent and immunocompromised patients in Saudi Arabia needs further elucidation. Further- more, an updated exploration of the topic is neces- sary, primarily for physicians working under acute conditions who treat patients empirically before obtaining culture results. We therefore aim, in this study, to explore the organisms causing UTI in emergency patients and inpatients of a tertiary hospital in Saudi Arabia. In addition, we aim to determine whether the type of organism causing the UTI can be predicted on the basis of the patient’s demographic or immune status.

Methods

This is a cross-sectional analysis reviewing the charts of patients visiting the emergency department and those admitted during the month of July-August 2021. We tracked patients from the E.D., inpatients in the internal medicine and oncology wards, and those in the intensive care unit. Our sample was selected from a large tertiary hospital in the capital of Saudi Arabia, with a capacity of 1,200 beds.

We estimated a sample size of 200 patients us- ing Raosoft@ online sample size calculator (95% Confidence interval and 6.33% margin of error). Using only information from the medical records, we obtained the demographic details, urine cul- ture method, and whether a clean catch or via a Foley catheter. We also noted any comorbidities, and whether the patient was known to have cancer and was on chemotherapy. Patients were labelled as immunocompromised if they had diabetes, chronic kidney disease/end-stage renal disease, or were on active chemotherapy.

In our analysis, we used the mean and the stan- dard deviation to report the patients’ age, and used proportions to register other demographic details. We used Fisher’s exact test to explore the presence of a nonrandom association between the organisms causing UTI and the patients’ demographics or immune status. We used STATA ® to analyse the results, with a p<0.05 threshold for statistically significant findings. The IRB board approves this study, with IRB registration number 00010471

Results

Demographics: The total number of participants was 199. The mean age of the patients was 55.8 years (SD=20.02), ranging from 14 to 97 years. The patients’ demo- graphic details are illustrated in Table 1. 61.8% of the patients were immunocompromised, and one- third were from the oncology wards. 40.7% (n=81) were diabetic, and 8.54% (n=17) had chronic kidney disease or end-stage renal disease. Most of the urine samples were obtained via clean catch, with 12% via a Foley catheter.

Organisms causing UTI: Most UTIs were caused by mixed gram-negative bacteria, as seen in 40.20% (n=80) of the sample, followed by Candida, in 16.1% (n=32), and then mixed gram-positive bacteria, in 14.57% (n=29). Escherichia coli was cultured in 7.04% (n=14) of the patients. Other organisms are illustrated in Table 2. In oncology patients, the most common organisms causing UTI were mixed gram-negative bacteria, in 45.8% (n=22) of patients, followed by Candida and mixed gram-positive bacteria, both seen in 12.5% (n=6). The proportions of the various organisms in oncology patients are illustrated in Table 3.

Similarly, the most common organisms among immunocompromised patients were mixed gram- negative bacteria, representing 42.3% (n=52) of total infections in this patient cohort. Candida caused 21.1% (n=26) of UTI in this stratum, followed by mixed gram-positive bacteria, at 12.2% (n=15). Table 4 illustrates the prevalence of these organisms according to a subgroup analysis of immunocom- promised and immunocompetent patients.

Conclusion

This study demonstrates that patients’ immune status is the main determinant of the causative organism of UTIs. As such, the treatment threshold for Candida in diabetic patients and those with CKD/ESRD should be lower, especially when they require admission. Emergency physicians should provide antibiotics that cover gram-negative bacteria for patients in general, Candida for immunocom- promised patients, and gram-positive bacteria for immunocompetent patients.