The Korean Antimicrobial Resistance Monitoring System for Complicated Urinary Tract Infections: A Prospective Multicenter Observational Study Conducted by the Korean Association of Urogenital Tract Infection and Inflammation

Article information

Urogenit Tract Infect. 2026;21(1):15-25

Publication date (electronic) : 2026 April 30

doi : https://doi.org/10.14777/uti.2550040020

Seong Hyeon Yu¹, Seung Il Jung^,1, Donghoon Lim², Jeong Woo Lee³, Seung-Ju Lee⁴, Hong Chung⁵, Mi-Mi Oh⁶, Jing Bong Choi⁷, Jae Hung Jung⁸, Hee Jo Yang⁹, KAUTII Investigators

¹Department of Urology, Chonnam National University Medical School, Gwangju, Korea

²Department of Urology, College of Medicine, Chosun University, Gwangju, Korea

³Department of Urology, Kyung Hee University Hospital, Kyung Hee University College of Medicine, Seoul, Korea

⁴Department of Urology, St. Vincent’s Hospital, College of Medicine, The Catholic University of Korea, Suwon, Korea

⁵Department of Urology, Wonju Severance Christian Hospital, Yonsei University Wonju College of Medicine, Wonju, Korea

⁶Department of Urology, Korea University Guro Hospital, Seoul, Korea

⁷Department of Urology, Bucheon St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, Bucheon, Korea

⁸Department of Urology, Yonsei University Wonju College of Medicine, Wonju, Korea

⁹Department of Urology, Soonchunhyang University Medical School, Soonchunhyang University Cheonan Hospital, Cheonan, Korea

Corresponding author: Seung Il Jung Department of Urology, Chonnam National University Hwasun Hospital, 322 Seoyang-ro, Hwasun-eup, Hwasun 58128, Korea Email: drjsi51@gmail.com

Received 2025 November 17; Revised 2026 February 7; Accepted 2026 March 4.

Abstract

HIGHLIGHTS

The antimicrobial resistance (AMR) of complicated urinary tract infection (cUTI) in South Korea has reached a serious level, not only fluoroquinolone and 3rd generation cephalosporin, even in piperacillin/tazobactam. In addition, AMR of cUTI was especially higher in healthcare-associated UTI.

INTRODUCTION

Urinary tract infection (UTI) is one of the most common bacterial infections worldwide [1]. Clinically, UTIs are categorized as uncomplicated or complicated based on clinical presentation, anatomical involvement, and infection severity [2,3]. Uncomplicated cystitis accounts for the majority of UTIs and typically presents with localized symptoms such as dysuria, urgency, frequency, and a sensation of incomplete bladder emptying [4]. In contrast, complicated UTI (cUTI) is often accompanied by systemic symptoms, including fever, chills, and costovertebral angle pain or tenderness, and is associated with higher morbidity and mortality due to the possibility of secondary bloodstream infection [2,5]. cUTIs are generally linked to specific anatomical or functional urinary tract abnormalities or compromised host defenses, making them more difficult to eradicate than uncomplicated UTIs [6].

The primary treatment for cUTI is antimicrobial therapy, along with appropriate management of the underlying anatomical or functional abnormalities. Optimal antibiotic selection depends on infection severity, host factors, and local microbiological patterns. However, cUTIs occur in a heterogeneous patient population with diverse comorbidities, resulting in a broader range of causative microorganisms compared to uncomplicated infections. Additionally, the global emergence and rapid spread of multidrug-resistant organisms, including extended-spectrum β-lactamase (ESBL)-producing Escherichia coli and carbapenem-resistant Enterobacterales, has made treatment increasingly challenging and represents a significant public health concern [7,8]. The prevalence of antimicrobial resistance (AMR) in cUTI is particularly high in Asian regions, including South Korea [9,10], contributing to substantial clinical and socioeconomic burdens through increased morbidity and mortality [2]. Therefore, continuous surveillance of AMR is essential to obtain accurate information on pathogen distribution, microbiological characteristics, and antimicrobial susceptibility patterns in the community, which is crucial for optimizing cUTI treatment strategies.

In response to these needs, the Korean Association of Urogenital Tract Infection and Inflammation (KAUTII) established the Korean Antimicrobial Resistance Monitoring System (KARMS) in 2023 to facilitate nationwide surveillance of AMR. KARMS for UTIs is a web-based monitoring program (https://uti.karms.kr/main-page, accessed from 1 January 2023) that operates through collaboration with medical centers throughout South Korea. To date, KARMS provides continuously updated national data on AMR in UTIs [1,3]. The present study aimed to provide an interim report for the prevalence and AMR patterns of representative uropathogens in patients with cUTI.

MATERIALS AND METHODS

RESULTS

1. Baseline Characteristics

A total of 698 patients with cUTI were eligible for inclusion in the present study from the KARMS database. The baseline characteristics of the study population are summarized in Table 1. The mean age was 68.94±15.95 years, and 449 patients (64.3%) were female. The numbers of patients treated at primary, secondary, and tertiary medical centers were 4 (0.6%), 126 (18.0%), and 568 (81.4%), respectively. With respect to geographic distribution, the largest proportion of patients were from Gangwon-do province (n=228, 32.7%), followed by Jeolla-do (n=143, 20.5%), Gyeonggi-do (n=121, 17.3%), Seoul (n=114, 16.3%), Chungcheong-do (n=84, 12.0%), and Gyeongsang-do (n=8, 1.2%). A total of 171 patients (24.5%) had healthcare-associated UTI and 240 (34.4%) had recurrent UTI. Regarding UTI classification, 66 (9.5%) had acute prostatitis, 86 (12.3%) had catheter-associated UTI, 8 (1.1%) had chronic prostatitis, 252 (36.1%) had cystitis, 136 (19.5%) had pyelonephritis, and 32 (4.6%) had urosepsis. Data without any UTI classification were considered as unknown (n=76, 10.9%). ESBL positivity was identified as 45.2% (166 of 367). E. coli was the most frequently identified uropathogen (n=356, 51.1%), followed by Enterococcus species (n=80, 11.5%) and Klebsiella pneumoniae (n=76, 10.9%). In addition, other pathogens accounted for approximately 9% of isolates, as shown in Fig. 1.

Table 1.

Demographic characteristics of patients with complicated urinary tract infection (N=698)

Fig. 1.

Distribution of uropathogens in patients with complicated urinary tract infection.

2. Antimicrobial Susceptibility to Antibiotics

The antimicrobial susceptibility patterns of isolates obtained from patients with cUTI are presented in Table 2. Overall, susceptibility rates were 47.2% (296 of 627) for ciprofloxacin, 63.3% (210 of 332) for cefotaxime, 92.9% (118 of 127) for fosfomycin, 75.5% (333 of 441) for nitrofurantoin, 92.7% (455 of 491) for amikacin, 70.7% (205 of 290) for amoxicillin/clavulanate, 60.2% (247 of 410) for trimethoprim/sulfamethoxazole, 80.6% (441 of 547) for piperacillin/tazobactam, and 98.8% (508 of 514) for ertapenem. In summary, the resistance rates to ciprofloxacin and cefotaxime were 52.8% and 36.7%, respectively.

Table 2.

Antimicrobial susceptibility patterns in patients with complicated urinary tract infection

3. AMR According to Clinical Factors

Rates of ESBL positivity, fluoroquinolone resistance, third-generation cephalosporin resistance, and piperacillin/tazobactam resistance were compared according to clinical characteristics, including sex, hospital type, UTI classification, infection association, and recurrence status. Detailed subgroup analyses are presented in Fig. 2A–E. ESBL positivity was significantly higher in patients with pyelonephritis and urosepsis (acute prostatitis, 32.6%; catheter-associated UTI, 38.0%; cystitis, 37.1%; pyelonephritis, 62.3%; urosepsis, 62.5%; p=0.002), in healthcare-associated UTI (community-acquired, 41.6%; healthcare-associated, 58.6%; hospital-acquired, 44.4%; p=0.040), and in recurrent cUTI (nonrecurrent, 40.9%; recurrent, 53.2%; p=0.028). Fluoroquinolone resistance was significantly higher in female patients (male, 42.0%; female, 49.1%; p=0.021) and in healthcare-associated UTI (community-acquired, 41.7%; healthcare-associated, 57.9%; hospital-acquired, 48.4%; p=0.014). Piperacillin/tazobactam resistance was significantly higher in patients with urosepsis (acute prostatitis, 10.0%; catheter-associated UTI, 13.9%; cystitis, 9.1%; pyelonephritis, 18.6%; urosepsis, 37.0%; p=0.004), in tertiary hospitals (secondary, 8.2%; tertiary, 17.2%; p=0.019), and in healthcare-associated UTI (community-acquired, 12.0%; healthcare-associated, 26.4%; hospital-acquired, 16.7%; p=0.001). Additionally, third-generation cephalosporin resistance was significantly higher in secondary hospitals compared with tertiary hospitals (43.5% vs. 33.3%, p=0.041).

Fig. 2.

Extended-spectrum β-lactamase (ESBL) positivity, fluoroquinolone resistance, third-generation cephalosporin resistance, and piperacillin/tazobactam resistance in complicated urinary tract infection according to clinical factors: urinary tract infection (UTI) classification (A), sex (B), hospital type (C), UTI association (D), and recurrence of infection (E).

DISCUSSION

Antimicrobial agents remain the cornerstone of treatment for UTIs. However, AMR has risen rapidly in recent years and is now considered a global public health con-cern [7,8]. Major international public health organizations, including the World Health Organization, World Economic Forum, Centers for Disease Control and Prevention, and Infectious Diseases Society of America, have identified AMR as one of the most urgent threats to global health [14,15]. In response to this growing challenge, the Korean Association of Urogenital Tract Infection and Inflammation (KAUTII) established a nationwide AMR surveillance system, the KARMS for UTI. KARMS is a webbased, prospective, multicenter, national observational program implemented through collaboration among medical centers throughout South Korea (https://uti. karms.kr/main-page, accessed from 1 January 2023). This structure enables continuous and efficient AMR monitoring with reduced time and resource requirements, and more than 2000 clinical entries have been recorded to date. In the present analysis of cUTI cases within the KARMS database, E. coli was the most frequently identified uropathogen, and AMR rates among cUTI isolates had reached concerning levels, particularly with respect to fluoroquinolones, third-generation cephalosporins, and piperacillin/tazobactam. AMR rates were especially elevated among patients with healthcare-associated cUTI.

cUTI is not uncommon and frequently occurs in individuals with host-related risk factors, such as diabetes or immunosuppression, or in those with anatomical or functional abnormalities of the urinary tract, such as obstruction or impaired bladder emptying associated with detrusor dysfunction [5]. As with uncomplicated UTI, cUTI may be caused by gram-negative or gram-positive bacteria, although E. coli remains the most prevalent uropathogen, followed by Enterococcus species, Klebsiella species, Pseudomonas aeruginosa, and Proteus mirabilis [9,10,16]. Previous studies have reported that E. coli accounts for approximately 40% to 60% of cUTI cases, a proportion generally lower than that observed in uncomplicated UTI, likely due to the greater clinical heterogeneity and broader range of predisposing conditions in cUTI populations [9,10,16]. In the present study, E. coli accounted for 51.1% of cases, followed by Enterococcus species (11.5%), Klebsiella pneumoniae (10.9%), and Pseudomonas aeruginosa (4.7%), consistent with prior data. Additionally, ESBL positivity was 45.2%, and was significantly higher among patients with pyelonephritis and urosepsis (acute prostatitis, 32.6%; catheter-associated UTI, 38.0%; cystitis, 37.1%; pyelonephritis, 62.3%; urosepsis, 62.5%; p=0.002), in healthcareassociated UTI (community-acquired, 41.6%; healthcareassociated, 58.6%; hospital-acquired, 44.4%; p=0.040), and in recurrent cUTI (nonrecurrence, 40.9%; recurrence, 53.2%; p=0.028). ESBL-producing gram-negative organisms are resistant to most β-lactam antibiotics, including extended-spectrum cephalosporins and monobactams, and their global prevalence continues to rise [17]. The elevated ESBL rate observed in this study may reflect the distribution of patient populations with differing socio-environmental exposures, anatomical or functional urinary tract abnormalities, and underlying comorbidities [18].

The primary therapeutic approach for patients with cUTI is the use of antimicrobial agents. However, cUTI typically presents with systemic symptoms such as fever, chills, and costovertebral angle pain or tenderness, and is often associated with risk factors that increase the likelihood of a more complicated clinical course and reduce treatment success [2,5,6]. Furthermore, AMR in cUTI is generally higher than in uncomplicated UTI across most antimicrobial agents [16,19] and is associated with increased morbidity and mortality.

In the present study, resistance rates to ciprofloxacin and cefotaxime among patients with cUTI were 52.8% and 36.7%, respectively. These rates were higher than those reported for uncomplicated cystitis in the KARMS database, which demonstrated 41.6% resistance to fluoroquinolones and 16.4% resistance to third-generation cephalosporins [3]. Compared with a South Korean nationwide cUTI registry study conducted in 2008, the current resistance rates represent increases of approximately 10% for ciprofloxacin and 35% for cefotaxime [16]. Third-generation cephalosporin resistance among cUTI pathogens in South Korea has therefore reached a critical level. Clinicians should take this into consideration when selecting empiric antimicrobial therapy, and unnecessary or nonjudicious use of third-generation cephalosporins should be avoided. In addition, the resistance rate to piperacillin/tazobactam was 19.4% in the present study. Piperacillin/tazobactam is a combination of an extended-spectrum penicillin and a β-lactamase inhibitor used to treat a wide range of serious bacterial infections and is active against many gram-positive and gram-negative organisms, including Pseudomonas aeruginosa [20]. However, if the upward trend in resistance continues, resistance to piperacillin/tazobactam may also reach clinically concerning levels. On the other hand, fosfomycin has shown a high susceptibility of over 90% for cUTI. Although fosfomycin is mainly recommended for acute uncomplicated cystitis, it may have a possibility in the treatment of cUTI, particularly in the outpatient settings.

The present study also evaluated differences in AMR to fluoroquinolones, third-generation cephalosporins, and piperacillin/tazobactam according to clinical factors such as sex, hospital type, UTI classification, infection association, and recurrence status. In detailed analysis, healthcare-associated UTI showed higher resistance rates to fluoroquinolones (community-acquired, 41.7%; healthcare-associated, 57.9%; hospital-acquired, 48.4%; p=0.014) and piperacillin/tazobactam (community-acquired, 12.0%; healthcare-associated, 26.4%; hospital-acquired, 16.7%; p=0.001). Third-generation cephalosporin resistance was 34%. When compared with previous reports of healthcare-associated UTI, the current AMR rates have not changed substantially over the past decade (ciprofloxacin, 50%, cephalosporins, 35%– 50% [9]; ciprofloxacin, 54.9%, cephalosporins, 42% [10]) However, in the present study, resistance to fluoroquinolones and piperacillin/tazobactam in healthcare-associated UTI was significantly higher than in hospital-acquired UTI. Several factors may contribute to these findings, but inappropriate antibiotic use without adherence to local, national, or international stewardship guidelines is likely the most significant. For example, a nationwide registry study of UTI management in South Korea reported that 28% of urologists did not obtain a urine culture before initiating treatment, and 54% did not obtain a urine culture even in cases of initial treatment failure [21]. Prolonged misuse of antimicrobials can lead to the development of multidrug-resistant organisms by gradually altering normal gastrointestinal and vaginal microbiota [18]. In addition, the number of healthcare institutions in South Korea has increased rapidly due to socio-environmental changes, including population aging and the rising prevalence of chronic medical diseases [22]. These facilities frequently care for elderly patients who may have impairments in communication, mobility, or cooperation due to conditions such as dementia, cerebral infarction, Parkinson disease, and spinal cord injuries [23,24]. Although these patients often present with various urologic problems, they may not receive appropriate management due to limited access to certified urologists and insufficient nursing staff trained in antimicrobial stewardship principles [25]. Therefore, clinicians and healthcare providers working in these settings must prioritize efforts to address the growing AMR burden in healthcare-associated UTI.

AMR in patients with cUTI in South Korea has already reached a critical level, particularly among healthcare-associated cases. Although the benefits of antibiotics in reducing mortality and prolonging life expectancy are undeniable, the indiscriminate and prolonged use of these agents has substantially contributed to the rise of AMR [26]. Therefore, comprehensive antimicrobial stewardship programs are urgently required to optimize clinical outcomes, ensure cost-effective therapy, and minimize the unintended consequences of inappropriate antibiotic use [27]. Antimicrobial stewardship encompasses a series of coordinated interventions designed to promote the appropriate use of antimicrobials. These include regular training of healthcare staff in the optimal application of antimicrobial agents; strict adherence to local, national, and international treatment guidelines; systematic audits of adherence and treatment outcomes; ongoing monitoring and feedback to prescribers; and the evaluation of local pathogen resistance trends [28]. Despite the global emphasis on such initiatives, South Korea currently lacks an official nationwide antimicrobial stewardship program. Consequently, establishing a robust stewardship framework in conjunction with the ongoing AMR surveillance system is essential to address this growing threat effectively.

This study has several limitations. First, although it was a web-based, prospective, multicenter, and nationwide observational study, potential selection bias may exist due to regional and institutional disparities in patient inclusion and UTI classification. As a result, standardization and quality control of data could not be fully ensured. Second, methodologies for pathogen identification and antimicrobial susceptibility testing were not uniform across all institutions. Nonetheless, all laboratories adhered to their respective microbial standards, and susceptibility results were interpreted according to the CLSI breakpoints [13]. Third, because data entry relied on multiple investigators within a web-based system, inter-investigator variability may have influenced the dataset. In fact, geographic distribution is imbalanced due to differences in participating hospitals, regional demographics, or data-entry profiles. Consequently, the lack of centralized verification is a limitation of this study. Fourth, several possible confounders (e.g., outpatient antibiotic exposure, device status, prior hospitalization and relevant comorbidities) are unmeasured in this study. This might contribute to the results of subgroup analysis. Therefore, further investigations including these possible confounders are needed.

Despite these limitations, the present study provides valuable and timely insights into the distribution of uropathogens and the current status of AMR in cUTI within South Korea during the ongoing global AMR crisis. The KARMS initiative for UTI continues to collect and monitor nationwide data, enabling the identification of emerging resistance patterns and temporal trends. Such continuous surveillance will be instrumental in reducing AMR through evidence-based prescribing and the avoidance of unnecessary antibiotic use.

CONCLUSIONS

In the context of the ongoing global AMR crisis, continuous surveillance is essential to guide the selection of optimal antibiotics based on accurate susceptibility data. To address this critical need, the KARMS was established for the nationwide surveillance of AMR in UTIs and is officially endorsed by the KAUTII. In the present study focusing on cUTI, the resistance rates to ciprofloxacin and cefotaxime were found to have reached an alarming level, and resistance to piperacillin/tazobactam remains particularly concerning. These findings underscore the urgent need for continuous monitoring and systematic data accumulation to curb the escalation of AMR. In this regard, the KARMS system provides contemporary nationwide surveillance data on AMR patterns in cUTI and may support evidence-based empirical antibiotic selection in South Korea.

Article information Continued