神經性膀胱無症狀菌尿症與一般族群泌尿道感染中大腸桿菌毒力特性之比較分析

^1,2曾義翔、^1,2范玉華、^1,2林志杰、³陳佩琪、^3,4,5高政彥、⁶蔡昀岸、^1,2黃逸修、^1,2顧明軒

¹臺北榮民總醫院泌尿部

²國立陽明交通大學醫學院泌尿學科及書田泌尿科學研究中心

³國立陽明交通大學生命科學院微生物及免疫學研究所

⁴國立陽明交通大學健康創新中心

⁵國立陽明交通大學 微生物體研究中心

⁶臺北榮民總醫院神經醫學中心

Comparative analysis of virulence characteristics in Escherichia coli between asymptomatic bacteriuria in neurogenic bladder and symptomatic UTI in the general population

^1,2I-Hsiang Tseng,^1,2Yu-Hua Fan, ^1,2Chih-Chieh Lin, ³Pek Kee Chen, ^3,4,5Cheng-Yen Kao,

 ⁶Yun-An Tsai, ^1,2Eric Yi-Hsiu Huang, ^1,2Ming-Hsuan Ku

¹Department of Urology, Taipei Veterans General Hospital, Taipei, Taiwan

²Department of Urology, College of Medicine and Shu-Tien Urological

³ Institute of Microbiology and Immunology, College of Life Sciences,

⁴Health Innovation Center, ⁵Microbiota Research Center,

National Yang Ming Chiao Tung University, Taipei, Taiwan

⁶Department of Neurosurgery, Neurological Institute,

Taipei Veterans General Hospital, Taipei, Taiwan

Abstract

Introduction:

Asymptomatic bacteriuria (ASB) is defined as the presence of significant quantitative bacterial growth in a properly collected urine sample from an individual without clinical signs or symptoms of a urinary tract infection (UTI). In patients with neurogenic bladder (NGB), urinary stasis and chronic catheterization often lead to persistent bacterial colonization, with Escherichia coli being the most prevalent pathogen  ADDIN EN.CITE  ADDIN EN.CITE.DATA [1]. We hypothesized that the virulent profiles of E. coli from asymptomatic NGB patients differ from those isolated from symptomatic UTI patients in the general population, the latter of which typically exhibit more aggressive characteristics. This study investigates the genetic determinants of E. coli in these two distinct cohorts to compare the bacterial factors contributing to UTI symptomatology.

Methods

E. coli isolates were obtained from the microbiology laboratory of our institution. Asymptomatic NGB patients and individuals from the general population with uncomplicated UTIs were enrolled. Most isolates from NGB patients were collected via clean intermittent catheterization. Bacteriuria was defined as ≥10⁵ CFU/mL in urine cultures. For the NGB group, asymptomatic status was confirmed by the absence of UTI-related manifestations (e.g., new-onset incontinence, fever, or suprapubic pain) and the absence of symptomatic UTI episodes during a three-month post-collection follow-up period. We isolated symptomatic E. coli from individuals in the general population with uncomplicated UTIs. Uncomplicated UTI was defined as infection in patients with no history of UTI within the past year and no underlying urological abnormalities, such as urolithiasis, malignancy, or prior urological procedures.

Selected Escherichia coli isolates were analyzed for phylogenetic groups, multilocus sequence typing (MLST), virulence genes, antimicrobial susceptibility, and plasmid profiles, and whole-genome sequencing was performed. Patients younger than 20 years of age, those with major genitourinary abnormalities, contaminated urine specimens, recent UTI, or polymicrobial urine cultures were excluded.

When multiple colonies from the same patient showed distinct genetic profiles in RAPD-PCR analysis, they were considered different strains and included separately in subsequent analyses.

Statistical analyses were performed using IBM SPSS Statistics version 25. Categorical variables were compared using the chi-square test or Fisher’s exact test, as appropriate. The Fisher–Freeman–Halton exact test was used for multi-category variables with sparse data. A p value < 0.05 was considered statistically significant.

Results

The study included 36 patients with NGB presenting with ASB and 64 patients from the general population with uncomplicated UTI. The NGB-ASB cohort had a mean age of 44.4 ± 19.5 years (range 18–94) with an equal sex distribution (18 males, 18 females). In contrast, the UTI group was significantly older, with a mean age of 60.6 ± 18.1 years (range 22–92) and predominantly female (93.8%).

From these cohorts, a total of 102 Escherichia coli isolates were analyzed. Within the ASB group, RAPD-PCR identified two distinct strains in two separate patients, resulting in 38 unique isolates. Regarding antimicrobial resistance, no significant differences were observed on the prevalence of ESBL-producing strains (22.2% vs. 17.2%, p = 0.599, chi-square test) or multidrug-resistant (MDR) isolates (13.9% vs. 4.7%, p = 0.132, Fisher’s exact test) between ASB group and the UTI group.

Phylogenetic analysis was evaluated between the ASB group and the UTI group. Although phylogenetic group B2, recognized as the most virulent lineage of E. coli associated with extraintestinal and acute symptomatic UTIs, was the most prevalent in both cohorts, its frequency was lower in the ASB group (42.1%) than in the UTI group (57.8%). Other lineages identified in the ASB group included groups E (10.5%), A (7.9%), F (7.9%), and C (5.3%). In contrast, the UTI group primarily comprises groups E (9.4%), B1 (7.8%), and D (3.1%). A substantial proportion of isolates remained unclassified (26.3% in ASB vs. 20.3% in UTI). Overall, the distribution of phylogenetic groups did not differ significantly between the ASB and UTI groups (Fisher–Freeman–Halton exact test, p = 0.09; Table 1). When isolates were dichotomized into B2 and non-B2 groups, the UTI group exhibited a higher proportion of B2 isolates (57.8% vs. 42.1%); however, this difference did not reach statistical significance (p = 0.14).

Analysis of virulence factors revealed distinct genetic signatures between the two cohorts (Table 2). The prevalence of individual virulence genes was compared using Fisher’s exact test. Among the genes analyzed, cnf1 was significantly more prevalent in the UTI group compared with the ASB group (25.0% vs. 7.9%, p = 0.037). No significant differences were observed for other genes.

Conclusion

Escherichia coli isolates from NGB patients with ASB exhibited greater phylogenetic diversity and a lower prevalence of toxin-associated virulence genes compared to those from symptomatic UTI patients in the general population. These findings support our hypothesis that bacterial determinants are characteristically distinct between these two patient cohorts. Our results suggest that ASB-associated strains likely possess attenuated virulence potential, distinguishing them from the classic uropathogenic E. coli (UPEC) typically responsible for acute infections.

Table 1. Phylogenetic group distribution of Escherichia coli isolates from neurogenic bladder patients with asymptomatic bacteriuria and symptomatic UTI patients in the general population

ASB, asymptomatic bacteriuria; UTI, urinary tract infection; ND, not detected. Data are presented as number (%). The p value represents the overall comparison of phylogenetic group distribution between groups and was calculated using the Fisher–Freeman–Halton exact test.

Table 2. Comparison of virulence gene profiles of Escherichia coli isolates between asymptomatic bacteriuria (ASB) and urinary tract infection (UTI) groups

ASB, asymptomatic bacteriuria; UTI, urinary tract infection; ND, not detected. Data are presented as number (%). P values were calculated using Fisher’s exact test.