7295 elderly hospitalized patients with catheter-associated urinary tract infection: a case-control study

Our study divided the urine pH value into two subgroups based on the critical value judged by the ROC curve Youden index. The results showed that a urine pH value ≥ 6.5 was an independent risk factor for CAUTI. The median urine pH value in the CAUTI group was 7 (6.5, 7.5) and that in the non-CAUTI group was 6 (5.5, 6.5). This is rare in previous studies. We chose the timing of the urine pH study at the initial admission stage and before the indwelling catheter. The main reason is to reduce the research bias of urine results caused by disease treatment and invasive operation. It is well known that an acidic environment is not conducive to bacterial growth [13], and acidic urine also has a certain protective effect on CAUTI, as confirmed in our study. In clinical practice, we can use this conclusion as a guide through high-safety intervention methods to maintain the urinary environment of patients with catheterization in the normal range and pH < 6.5, which is conducive to the prevention of CAUTI.

We found that moderate dependence or severe dependence in the classification of self-care ability was an independent risk factor for CAUTI. The self-care ability grade in this study is that patients are graded by nurses in charge of the Barthel index rating scale at admission, which can truly reflect the patients’ self-care ability. The self-care ability score scale mainly measures the patients’ ability to eat independently, take a bath, go to the toilet, walk and so on. Many previous studies have shown that cerebrovascular disease, paraplegia or dyskinesia are risk factors for CAUTI [4, 14, 15]. This kind of patient has an increased incidence of CAUTI due to the limitation of activity caused by disease, which is consistent with the conclusion of this study.

In addition, our study shows that males are more prone to CAUTI than females, which is different from previous studies [15]. Advanced age, long hospital stay, long indwelling urinary catheter and diabetes have been unanimously recognized as risk factors for CAUTI in many previous studies [16,17,18], which is no exception in our study.However, our research has clarified the time characteristics of CAUTI in elderly individuals.

Malnutrition in the elderly has been shown to be associated with an increased risk of hospitalization and death [19]. In our study, it was shown that it is an independent risk factor for CAUTI, suggesting that nutritional status assessment is a very important issue in the process of diagnosis and treatment. Improving the nutritional status of elderly individuals is one of the strategies to prevent and control infection, and early intervention should be carried out.

In our study, 276 strains of opportunistic pathogens were detected in 182 cases of CAUTI. The distribution of pathogens was mainly gram-negative bacteria, followed by gram-positive bacteria and fungi. The primary pathogen causing CAUTI is E.faecium, followed by E.coli, K.pneumoniae and C.albicans, which differs from some studies [20,21,22]. This is mainly because E.faecium and E.coli are usually parasitic in the human intestinal flora and elderly individuals due to physical function decline, low immunity, many primary diseases and other reasons. This provides an opportunity for bacterial invasion. It is inferred that the occurrence of CAUTI in elderly individuals is closely related to endogenous infection. At the same time, E.faecium was the most common pathogen in this study, which was different from previous reports. We reviewed the history of antimicrobial exposure during hospitalization in this patient population from the first day of admission until the first diagnosis of CAUTI caused by E. coli or E. faecium.We found that patients infected only with E.faecium and with both pathogens had a high probability of receiving antimicrobial therapy, and the time was longer than that of patients infected only with E.coli.There were 31 patients infected only with E.coli, 16 of whom had not received antimicrobial therapy before infection, and 60 patients infected only with E.faecium, 57 of whom had received antimicrobial therapy before infection.The high incidence of E.faecium is related to the history of antimicrobial exposure.We also found that the antimicrobial exposure history of patients infected with E.faecium in this group was mainly third-generation cephalosporins and carbapenems,while Enterococcus was naturally resistant to cephalosporins.When E.coli and E. faecium are both opportunistic intestinal parasitic pathogens, the tendency of clinicians in this hospital to use drugs leads to E.faecium becoming the dominant pathogen, with a higher incidence than E.coli.In addition, the incidence of C.albicans infection is not low, accounting for 10.14%, which is different from the distribution of UTI pathogens in nonelderly patients [23]. It is considered that it is mainly related to many kinds of pathogens in the elderly and the extensive use of broad-spectrum antibiotics. Thus, the treatment of CAUTI in elderly patients should strictly abide by etiological examination before the use of antibiotics to avoid multidrug-resistant organism infections or complex infections caused by the unreasonable use of antibiotics. At the same time, our study provides a reference for the empirical application of antibiotics before etiological examination results.

In addition, we found that 70 of the 182 infected patients had more than one opportunistic pathogen during hospitalization (including 45 had two, 18 had three, and 7 had four or more). A total of 164 pathogens were detected in 70 patients, mainly E.faecium (25.61%), K.pneumoniae (17.68%), E.coli (14.02%), C.albicans (11.59%) and P.aeruginosa (6.71%).Analysis of the patients showed that 53 of the 70 patients with multi-pathogen infection were admitted to the geriatrics, neurology and rehabilitation departments for chronic diseases, and the length of hospitalization was generally long, with a minimum of 7 days and a maximum of 436 days, and the average hospitalization was 37.5 (22,61) days (median). In conclusion, a long hospital stay is the main risk factor for multi-pathogen infection in elderly patients.

Our study was divided into two groups, the CAUTI group and the non-CAUTI group, to investigate the clinical characteristics of elderly patients with indwelling urinary catheters. The results showed that fever was the clinical feature of elderly CAUTI patients, and 70% of the infected people had fever symptoms. It is well known that fever is a nonspecific symptom of infection. The judgment of CAUTI should be combined with clinical symptoms and signs in addition to indwelling urinary catheter time and urine culture results. Patients with indwelling urinary catheters have no obvious feeling of urinary symptoms, such as frequent urination and urgent urination, and most elderly inpatients have varying degrees of unconsciousness, increasing the difficulty of determining CAUTI. If the judgment is wrong, the optimal time for treatment may be missed. Therefore, in clinical diagnosis and treatment, when elderly patients with indwelling urinary catheters have fever symptoms, attention should be given to the identification of other infections that cannot be excluded from CAUTI determination because they are clinically deemed due to another recognized cause.

In addition, the detection of procalcitonin and urinary nitrite is also an auxiliary index commonly used in the diagnosis of CAUTI. Our analysis results show that compared with the group without CAUTI, these two tests are meaningful, but they have more advantages in determining procalcitonin in infection, with an abnormal rate of 83.52%, which can be considered one of the effective indicators for the diagnosis of CAUTI in elderly individuals.

We found that older patients with urinary retention or incontinence were more likely to develop CAUTI than those with normal urination function. Considering the high incidence of urinary retention and incontinence in the elderly [24, 25], it is the main indication for indwelling urinary catheters in elderly patients, and it requires a long duration of indwelling. The degeneration of urinary tract mucosa and the decrease in local antibacterial ability in elderly individuals may increase the risk of CAUTI. Therefore, elderly patients with abnormal urination function should be taken as the key population for infection prevention and control.

Finally, we analysed the prognosis of CAUTI. We found that CAUTI could significantly affect the clinical outcome of patients, including prolonged hospitalization, increased hospitalization costs and increased all-cause mortality, which was consistent with related research conclusions [26, 27]. In recent years, there have been many studies on CAUTI, but few studies have clarified the impact of adverse outcomes based on a large sample size. The results of this study provide a useful supplement to this. Our study showed that compared with the non-CAUTI group, the hospitalization days of the CAUTI group increased by 18 days, the total hospitalization cost increased by ¥18,000, and discharge all-cause mortality increased by 2.314 times. To save national medical resources, improve patient safety and reduce mortality, clinical doctors and nurses should pay more attention to the prevention, control and management of CAUTI. In daily work, guiding suggestions and prevention and control measures in national norms and expert consensus should be implemented.

There are several limitations to this study. First, our study was conducted in a single hospital, which limits the representativeness and extrapolation of results from a single center. Second, our study is a retrospective analysis with limited data, but it points out the direction for our future research. We will carry out a prospective study on this subject.