Urinary tract infections are among the most common bacterial infections encountered in older adults and represent a major reason for antimicrobial prescribing in community, emergency, and inpatient settings. The incidence and complexity of UTI increase with advancing age because of multiple interacting anatomical, functional, immunological, and healthcare-related factors [1-3].

Older adults frequently have conditions that predispose them to urinary infection, including diabetes mellitus, benign prostatic enlargement, post-void residual urine, urinary incontinence, neurogenic bladder, urolithiasis, chronic kidney disease, pelvic-organ prolapse, recurrent UTI, and previous urinary instrumentation. Functional dependency, recurrent hospitalization, long-term-care residence, and repeated antimicrobial exposure further increase the likelihood of colonization or infection with resistant microorganisms [2,3].

Interpretation of microbiological findings is particularly challenging in this population because asymptomatic bacteriuria becomes increasingly prevalent with age. A positive urine culture alone does not establish symptomatic UTI, and unnecessary antimicrobial treatment of asymptomatic bacteriuria contributes to avoidable antimicrobial exposure and selection pressure [3]. Consequently, studies evaluating resistance in elderly populations must be interpreted in relation to symptoms, clinical setting, culture indication, and case definition.

Despite these complexities, Escherichia coli continues to be the predominant cause of UTI in older adults. Nevertheless, the microbiological distribution becomes broader with increasing age and healthcare exposure, with higher representation of Klebsiella pneumoniae, Proteus mirabilis, Enterococcus spp., Pseudomonas aeruginosa, and polymicrobial infections [4-15].

Of particular concern is the increasing frequency of antimicrobial resistance. Fluoroquinolones, trimethoprim-sulfamethoxazole, aminopenicillins, and cephalosporins have historically played important roles in empirical UTI treatment. However, resistance to these agents has increased substantially in many settings. The burden is further complicated by ESBL-producing Enterobacterales and MDR organisms.

The clinical importance of resistance extends beyond microbiological surveillance. Inappropriate initial therapy may delay effective treatment, especially in older individuals presenting with pyelonephritis, bacteremia, sepsis, or multiple comorbidities. Madrazo et al. demonstrated that MDR community-acquired UTI in hospitalized older adults was associated with substantially higher rates of inadequate empirical antimicrobial therapy and longer hospitalization [10].

Resistance patterns cannot, however, be universally generalized. Fagan et al. found relatively low ciprofloxacin resistance among elderly patients in Norway [4], whereas Leoni et al. reported ciprofloxacin resistance exceeding 50% in E. coli isolates from community-acquired UTI among older adults in Argentina [7]. These variations underscore the importance of local and population-specific resistance surveillance.

A systematic synthesis focused specifically on the elderly population is therefore clinically relevant. Understanding organism distribution, resistance to commonly used agents, MDR and ESBL prevalence, predictors of resistant infection, and associated clinical outcomes can support more rational empirical treatment and antimicrobial stewardship.

1.1 Aim

To systematically evaluate antimicrobial resistance, antimicrobial susceptibility patterns, and clinical outcomes associated with community-acquired urinary tract infections among older adults.

1.2 Objectives

1. To identify the principal bacterial pathogens responsible for community-acquired or community-onset UTI among adults aged >=65 years.
2. To evaluate resistance and susceptibility to commonly used antimicrobial agents.
3. To examine the prevalence and clinical relevance of MDR and ESBL-producing organisms.
4. To identify patient characteristics associated with antimicrobial-resistant UTI.
5. To assess relationships between antimicrobial resistance and inadequate empirical therapy, recurrence, hospitalization, length of stay, bacteremia, recovery, and mortality.
6. To describe geographical and setting-specific variations in resistance patterns.

2.1 Study Design and Reporting This systematic review was structured in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 statement [1]. The review addressed the following question: Among adults aged 65 years or older with community-acquired or community-onset UTI, what bacterial pathogens and antimicrobial resistance patterns are reported, which factors are associated with resistant infection, and what clinical outcomes are associated with antimicrobial resistance? 2.2 Information Sources and Search Strategy Electronic literature searches were structured for PubMed/MEDLINE, Embase, Scopus, Web of Science, and CINAHL. Reference lists of potentially eligible articles were also screened to identify additional studies. The search incorporated combinations of Medical Subject Headings and free-text terms related to UTI, older adults, community acquisition, antimicrobial resistance, and clinical outcomes. A representative strategy was: ("urinary tract infection" OR UTI OR "urinary infection" OR cystitis OR pyelonephritis) AND (elderly OR geriatric OR aged OR "older adult*" OR "older patient*") AND ("community acquired" OR "community-acquired" OR "community onset" OR outpatient OR "primary care") AND ("antimicrobial resistance" OR "antibiotic resistance" OR susceptibility OR MDR OR "multidrug resistant" OR ESBL OR "extended-spectrum beta-lactamase"). Additional combinations included individual antimicrobial agents, recurrent UTI, bacteremia, sepsis, hospital admission, treatment failure, recurrence, and mortality. 2.3 Eligibility Criteria Inclusion Criteria 1. Adults aged >=65 years, or studies providing independently extractable older-adult data. 2. Community-acquired, community-onset, or community-managed UTI. 3. Clinically diagnosed, symptomatic, or microbiologically confirmed UTI. 4. Reporting bacterial etiology, antimicrobial susceptibility, antimicrobial resistance, MDR status, ESBL production, or relevant clinical outcomes. 5. Cohort, case-control, cross-sectional, surveillance, longitudinal observational, or other primary research design. 6. Sufficient microbiological or clinical data for extraction. Exclusion Criteria 1. Pediatric or predominantly younger populations without extractable elderly data. 2. Exclusively hospital-acquired UTI without a separable community-acquired component. 3. Exclusive focus on asymptomatic bacteriuria. 4. No antimicrobial susceptibility, resistance, bacterial etiology, or relevant clinical outcome. 5. Narrative reviews, systematic reviews, editorials, letters without primary data, conference abstracts with insufficient information, or protocols. 6. Duplicate or substantially overlapping datasets without additional relevant outcomes. 2.4 Study Selection A total of 1,842 records were identified through database and supplementary searching. Following removal of 463 duplicate records, 1,379 records underwent title and abstract screening. A total of 1,248 records were excluded at this stage, and 131 reports were sought for retrieval. Three reports could not be retrieved, leaving 128 full-text reports for eligibility assessment. Of these, 116 were excluded, leaving 12 studies for qualitative synthesis. Reasons for full-text exclusion were: wrong population or age group (n=28); older-adult data not separately extractable (n=17); hospital-acquired UTI only (n=16); asymptomatic bacteriuria without symptomatic UTI data (n=12); no antimicrobial-resistance or susceptibility outcome (n=18); ineligible study design (n=11); review/editorial/commentary/protocol (n=7); duplicate or overlapping population (n=4); and insufficient microbiological or clinical outcome data (n=3). Figure 1. PRISMA 2020 flow diagram of study selection. 2.5 Data Extraction Data were organized using a predefined extraction framework including author and year, country, study design, clinical setting, definition of older age, sample size, UTI definition, community-acquired/community-onset status, bacterial pathogens, antimicrobial susceptibility, resistance percentages, MDR prevalence, ESBL prevalence, previous antimicrobial exposure, recurrent UTI, long-term-care residence, urinary instrumentation, diabetes and other comorbidities, empirical treatment adequacy, recurrence, hospital stay, bacteremia, recovery, and mortality. 2.6 Definitions and Outcomes Where reported by individual studies, MDR was interpreted according to accepted international definitions broadly corresponding to non-susceptibility to at least one agent in three or more antimicrobial categories [16]. Primary review outcomes were organism distribution, antimicrobial resistance and susceptibility, and MDR/ESBL prevalence. Secondary outcomes were risk factors for resistant infection, inadequate empirical therapy, recurrence, length of hospitalization, bacteremia or sepsis, clinical recovery, and mortality. 2.7 Risk-of-Bias Assessment Study-level risk of bias was evaluated using domains adapted from Joanna Briggs Institute principles for observational research and modified for the objectives of this review. D1 assessed selection and UTI case definition; D2 assessed antimicrobial-resistance measurement; D3 assessed confounding and comparability; and D4 assessed outcome measurement and completeness. Risk was categorized as low risk (+), some concerns/moderate risk (-), or high risk (X). 2.8 Data Synthesis Substantial heterogeneity was anticipated across UTI definitions, study settings, patient comorbidity, age thresholds, antimicrobial susceptibility panels, laboratory breakpoints, definitions of resistance, clinical severity, and outcome measures. Accordingly, findings were synthesized narratively. A pooled prevalence or pooled treatment-effect estimate was not calculated because such pooling could produce clinically misleading summary estimates.

3.1 PRISMA Study Selection

The final qualitative synthesis included 12 primary studies. No study was included in a quantitative meta-analysis because substantial clinical and methodological heterogeneity precluded meaningful pooling.

3.2 Characteristics of Included Studies

The 12 included studies represented Norway, the Netherlands, England, Argentina, Spain, France, Germany, Saudi Arabia, Iraq, Ethiopia, and a multinational primary-care population from Norway, Sweden, Poland, and the Netherlands. Study designs included cross-sectional studies, retrospective observational studies, prospective cohorts, population-based surveillance, and longitudinal cohort studies. Study populations ranged from focused samples of symptomatic older adults to large laboratory-surveillance databases.

Table 1. Characteristics of Included Studies

3.3 Microbiological Etiology

Escherichia coli

67. coli was consistently the most frequent uropathogen. Fagan et al. reported E. coli in approximately 64% of positive urine cultures from both community-dwelling and nursing-home elderly patients [4]. Leoni et al. identified E. coli in 67.7% of positive cultures in older adults with CA-UTI [7]. Taha reported E. coli in 57.26% of symptomatic CA-UTIs [13]. In the multinational recurrent-UTI cohort reported by Heltveit-Olsen et al., E. coli was detected in 60% of cultures obtained during acute symptomatic UTI episodes [15].

Klebsiella species

15. pneumoniae was generally the second or one of the principal secondary Gram-negative pathogens. Leoni et al. reported K. pneumoniae in approximately 12% of infections [7], while Taha reported 15.32% [13]. Heltveit-Olsen et al. detected Klebsiella spp. in 14% of cultures during acute recurrent UTI episodes among women aged >=70 years [15].

Other uropathogens

Other clinically important isolates included Proteus mirabilis, Enterococcus faecalis, Enterococcus faecium, Pseudomonas aeruginosa, Aerococcus spp., Citrobacter spp., and Enterobacter spp. Their relative contribution was generally greater among males, recurrent infections, patients with urinary devices, long-term-care residents, and populations with greater healthcare exposure.

3.4 Polymicrobial UTI

Polymicrobial infection was an important feature in selected elderly cohorts. Taha found polymicrobial CA-UTI in 69 of 427 patients (16.16%) [13]. Diabetes mellitus, antimicrobial use during the previous 30 days, and recurrent UTI were significantly associated with polymicrobial infection. Heltveit-Olsen et al. reported mixed flora in approximately 10% of cultures collected during acute UTI episodes in older women with recurrent UTI [15].

3.5 Resistance to Fluoroquinolones

Fluoroquinolone resistance varied markedly by geography and clinical population. Mulder et al. reported ciprofloxacin resistance in 10.2% of 1,080 E. coli isolates obtained from an elderly Dutch community cohort [5]. By contrast, Leoni et al. reported ciprofloxacin resistance of 51.9% among E. coli isolates and 60.8% among K. pneumoniae isolates in older adults with CA-UTI in Argentina [7]. These differences indicate that fluoroquinolone susceptibility cannot be assumed across settings and that local antibiograms are particularly important when considering empirical therapy.

3.6 Trimethoprim and Trimethoprim-Sulfamethoxazole

Resistance to trimethoprim-based therapy was substantial in several studies. Leoni et al. reported trimethoprim-sulfamethoxazole resistance of 45.7% among E. coli isolates [7]. In the 2026 multinational recurrent-UTI study, E. coli resistance to trimethoprim was 22% during acute UTI episodes, compared with 16% in baseline cultures [15]. Fagan et al. similarly reported E. coli trimethoprim resistance exceeding 20% in both nursing-home and community-dwelling groups in Norway [4].

3.7 Aminopenicillins and Beta-Lactam/Beta-Lactamase Inhibitor Combinations

High resistance to aminopenicillins was consistently observed. Fagan et al. found E. coli resistance exceeding 20% to ampicillin among elderly Norwegian patients [4]. Leoni et al. reported 52.7% resistance to ampicillin/sulbactam among E. coli isolates [7]. Taha demonstrated 49.89% resistance to amoxicillin-clavulanate among Gram-negative uropathogens [13]. Heltveit-Olsen et al. found E. coli resistance during acute recurrent UTI episodes of 43% to amoxicillin and 16% to amoxicillin-clavulanate [15].

3.8 Nitrofurantoin and Fosfomycin

Several included studies suggested comparatively preserved susceptibility to nitrofurantoin and/or fosfomycin, particularly among E. coli isolates. Their microbiological activity must be interpreted in relation to infection location and patient characteristics. An agent showing good urinary susceptibility is not necessarily appropriate for pyelonephritis, bacteremia, prostatitis, or severe systemic infection. Renal function is another important consideration in older adults.

3.9 Carbapenems and Broad-Spectrum Agents

Carbapenem resistance was lower than resistance to many conventional oral agents in several datasets. Taha reported 7.19% resistance to imipenem among Gram-negative organisms [13]. Alebachew et al. similarly found meropenem among the most active agents against urinary isolates [14]. These findings should not encourage indiscriminate empirical carbapenem use; stewardship remains essential to reduce selection pressure for carbapenem-resistant Enterobacterales.

3.10 MDR Organisms

The strongest direct evidence concerning MDR community-acquired UTI came from Madrazo et al. [10]. Among 348 adults aged >=65 years hospitalized with community-acquired UTI, MDR organisms caused 41.4% of cases and XDR organisms caused 7.8%. Previous antimicrobial therapy and nursing-home residence were independent risk factors for MDR infection.

3.11 ESBL-Producing Organisms

Artero et al. evaluated 310 elderly adults admitted with E. coli UTI and identified ESBL-producing E. coli in 85/310 (27.4%) overall [8]. ESBL prevalence differed markedly according to exposure: 8.9% in strictly community-acquired UTI and 43.9% in healthcare-associated UTI. This distinction is clinically important because infections presenting from the community may still carry a healthcare-associated resistance phenotype if patients have recent hospital contact, antimicrobial exposure, long-term-care residence, or urinary instrumentation.

3.12 Risk Factors for Antimicrobial Resistance

Previous Antimicrobial Exposure

Previous antimicrobial use was among the most consistent risk factors. Mulder et al. found that repeated prior fluoroquinolone prescriptions were strongly associated with ciprofloxacin-resistant E. coli [5]. Madrazo et al. identified previous antimicrobial therapy as an independent predictor of MDR UTI [10]. Taha similarly identified antimicrobial use during the previous 30 days as a risk factor for polymicrobial infection [13].

Long-Term-Care Residence

Long-term-care or nursing-home residence was associated with greater resistance in several studies [6,9,10]. Madrazo et al. specifically identified nursing-home residence as an independent predictor of MDR community-acquired UTI requiring hospitalization [10]. However, Fagan et al. observed relatively modest differences between nursing-home and community-dwelling older adults in Norway [4], demonstrating that the effect of residential setting depends on local epidemiology.

Recurrent UTI

Recurrent infection was associated with more complex microbiology and greater antimicrobial exposure. Taha found recurrent UTI significantly associated with polymicrobial CA-UTI [13]. Al Qahtani et al. demonstrated that recurrence itself was common in elderly patients, occurring in 43.5% of older adults with UTI during longitudinal follow-up [12].

Diabetes Mellitus

Diabetes was associated with UTI recurrence or polymicrobial infection in multiple studies. Taha demonstrated an association between diabetes and polymicrobial infection [13], while Al Qahtani et al. identified diabetes among the risk factors for recurrent UTI [12].

Urinary Instrumentation

Older adults frequently use urinary devices. Manseck et al. found indwelling devices in 30.3% of patients aged >=75 years compared with 6.0% among younger patients [11]. Urinary catheterization and instrumentation may facilitate colonization, biofilm formation, polymicrobial infection, and antimicrobial-resistant organisms.

3.13 Clinical Outcomes

Inadequate Empirical Antimicrobial Therapy

Madrazo et al. reported inadequate empirical antimicrobial treatment in 23.3% of the total cohort [10]. The proportion differed significantly according to resistance status: 33.3% in MDR infection versus 16.2% in non-MDR infection (p<0.001). Thus, MDR infection approximately doubled the probability that the initial antimicrobial regimen would be microbiologically inadequate.

Length of Hospital Stay

Median hospital stay in Madrazo et al. was longer among patients infected with MDR organisms: 6 days (IQR 4-8) versus 5 days (IQR 4-7) in non-MDR infection (p=0.029) [10].

Recurrence

Al Qahtani et al. followed 1,123 patients, including 560 adults aged >=65 years [12]. Among the older cohort, UTI incidence over follow-up was 38.0%, complete recovery 44.6%, recurrent UTI 43.5%, and antibiotic-resistant UTI 11.7%. Compared with younger patients, older adults demonstrated significantly more recurrence and antimicrobial resistance and less frequent complete recovery.

Mortality

In Madrazo et al., hospital mortality was 8.6% [10]. Despite greater inadequate empirical treatment and longer hospitalization among MDR infections, mortality did not significantly differ between MDR and non-MDR groups. Outcome is likely influenced by severity of illness, sepsis, bacteremia, comorbidities, source control, physiological reserve, and timeliness of effective therapy.

3.14 Risk-of-Bias Assessment

Table 2. Study-Level Risk-of-Bias Assessment

Legend: + = low risk; - = some concerns/moderate risk; X = high risk. D1 = selection/case definition; D2 = antimicrobial-resistance measurement; D3 = confounding/comparability; D4 = outcome assessment/completeness.

Figure 2. Traffic-light plot of study-level risk of bias. Green (+) indicates low risk, yellow (-) indicates some concerns or moderate risk, and red (X) indicates high risk. No included study was rated as high risk overall.

3.15 Summary of Risk of Bias

Among the 12 included studies, 3/12 (25.0%) were classified as low overall risk, 6/12 (50.0%) as low-to-moderate risk/some concerns, and 3/12 (25.0%) as moderate risk. No study was classified as high risk. D1 was low risk in 7/12 (58.3%) and showed some concerns in 5/12 (41.7%); D2 was low risk in all 12 studies (100%); D3 was low risk in 5/12 (41.7%) and showed some concerns in 7/12 (58.3%); D4 was low risk in 9/12 (75.0%) and showed some concerns in 3/12 (25.0%).

4.1 Principal Findings This systematic review demonstrates that antimicrobial resistance has become an important determinant of management in community-acquired and community-onset UTI among older adults. Several consistent findings emerged. First, E. coli remains the predominant uropathogen, generally accounting for approximately one-half to two-thirds of microbiologically documented infections. Second, substantial resistance to historically common empirical agents was documented. Third, multidrug resistance was common in older adults requiring hospitalization for community-acquired infection. Fourth, resistance had clinically measurable consequences, especially a higher probability of inadequate empirical therapy and longer hospitalization. Fifth, resistant infection was not simply an age phenomenon; previous antimicrobial therapy, long-term-care residence, recurrent UTI, diabetes, urinary devices, and previous healthcare exposure repeatedly modified risk. 4.2 Microbiological Diversity in Older Adults Although E. coli remained dominant, increasing representation of Klebsiella, Proteus, Enterococcus, and Pseudomonas was evident. This diversification is biologically plausible because older adults have greater rates of urinary obstruction, retention, instrumentation, catheter use, structural abnormalities, prior antibiotic exposure, and healthcare contact. Fagan et al. further demonstrated sex-related differences, with E. coli more common among women and Enterococcus faecalis contributing a greater proportion among men [4]. 4.3 Fluoroquinolone Resistance and Empirical Therapy One of the most clinically important observations was the large geographical variation in fluoroquinolone resistance. Mulder et al. documented ciprofloxacin resistance of 10.2% in elderly Dutch patients with community-acquired E. coli UTI [5], whereas Leoni et al. found 51.9% resistance among E. coli isolates in Argentina [7]. Such variation has direct implications for empirical prescribing. Repeated previous fluoroquinolone exposure further increases resistance probability, making individual antimicrobial history important alongside institutional and regional antibiograms. 4.4 Beta-Lactam Resistance Resistance to aminopenicillins and selected beta-lactam/beta-lactamase inhibitor combinations was substantial. Taha reported approximately 50% resistance to amoxicillin-clavulanate among Gram-negative uropathogens [13], while Leoni et al. observed high resistance to ampicillin/sulbactam [7]. ESBL production further complicates beta-lactam therapy. Artero et al. showed a marked contrast between strictly community-acquired and healthcare-associated infection, with ESBL rates of 8.9% and 43.9%, respectively [8]. 4.5 Nitrofurantoin and Fosfomycin Nitrofurantoin and fosfomycin frequently demonstrated comparatively favorable activity against E. coli in community settings. However, in-vitro susceptibility should not be equated with universal clinical appropriateness. Renal function, anatomical site of infection, severity of illness, and suspected bacteremia must accompany susceptibility data when selecting treatment in older adults. 4.6 MDR Infection and Empirical-Treatment Failure The study by Madrazo et al. provides particularly important outcome data [10]. One-third of patients with MDR UTI received inadequate initial therapy compared with approximately one-sixth of those with non-MDR infections. Older adults may be especially vulnerable to delayed appropriate treatment because of lower physiological reserve, multiple comorbidities, atypical presentation, and greater risk of sepsis. Nevertheless, mortality was not increased in the MDR group, suggesting that subsequent effective treatment and host factors also influence outcome. 4.7 Long-Term-Care Residence Several population studies identified a higher resistance burden among nursing-home residents [6,9], and nursing-home residence was independently associated with MDR UTI in Madrazo et al. [10]. However, Fagan et al. reported relatively small differences between nursing-home and community-dwelling older adults in Norway [4]. Long-term-care residence should therefore be regarded as a potential risk marker rather than a universally deterministic predictor of resistance. 4.8 Recurrent UTI Recurrent UTI represents an important clinical problem in older adults. Al Qahtani et al. reported recurrence in 43.5% of older patients who developed UTI [12]. Recurrent disease may accumulate additional resistance risk because of repeated antibiotic exposure and healthcare contact. Heltveit-Olsen et al. nevertheless demonstrated that narrow-spectrum treatment remained widely used in European primary care and that resistance to several commonly used agents was not uniformly high [15]. 4.9 Asymptomatic Bacteriuria and Diagnostic Stewardship Asymptomatic bacteriuria is common in older adults, particularly women, long-term-care residents, and patients with urinary abnormalities [3]. Heltveit-Olsen et al. found significant bacterial findings in 29% of baseline urine samples collected during asymptomatic periods from older women with recurrent UTI [15]. A positive urine culture in an older adult with nonspecific symptoms should therefore not automatically be attributed to symptomatic UTI. Diagnostic stewardship is an essential component of antimicrobial stewardship. 4.10 Clinical Implications Empirical antimicrobial therapy should incorporate infection severity, previous urine-culture results, recent antimicrobial use, previous MDR/ESBL organisms, recurrent UTI, recent hospitalization or healthcare contact, long-term-care residence, urinary catheterization or instrumentation, structural urinary tract disease, sex and possible prostatic involvement, renal function, and local susceptibility patterns. For severe infection, culture acquisition before antimicrobial therapy, where this does not cause clinically important delay, is particularly valuable. Once susceptibility results become available, empirical broad-spectrum treatment should be reviewed and narrowed whenever appropriate. 4.11 Antimicrobial Stewardship Urine cultures should be requested when clinically indicated rather than as a routine response to nonspecific symptoms. Previous microbiology should be actively reviewed before empirical therapy in patients with recurrent infection, unnecessary broad-spectrum treatment should be avoided, and local antibiograms should ideally stratify susceptibility by community versus hospital onset, age, sex, long-term-care residence, and prior healthcare exposure. 4.12 Strengths of the Review This review focuses specifically on older adults, integrates microbiological and clinical outcomes, includes geographically diverse settings, considers community-dwelling and community-onset infections with differing healthcare exposure, and includes study-level risk-of-bias assessment across clinically relevant methodological domains. 4.13 Limitations Several limitations must be acknowledged. Definitions of community-acquired, community-onset, and healthcare-associated infection differed between studies. Age thresholds varied. Some laboratory surveillance studies relied primarily on positive urine cultures and could not definitively distinguish symptomatic infection from asymptomatic bacteriuria. Susceptibility methods, antimicrobial panels, breakpoints, and periods of data collection also differed. Resistance is highly geographically dependent, and some included studies compared community residents with nursing-home populations rather than exclusively enrolling patients with strictly defined symptomatic CA-UTI. Only a limited number of studies directly evaluated the clinical consequences of antimicrobial resistance. Because of substantial methodological and clinical heterogeneity, meta-analysis was not considered appropriate. 5. Overall Quality of Evidence Overall, the available literature provides moderate-quality observational evidence that antimicrobial resistance is common and clinically important in community-acquired and community-onset UTI among older adults. Confidence is greatest for organism distribution, antimicrobial susceptibility, the association between previous antimicrobial exposure and resistance, and increased resistance among selected healthcare-exposed elderly populations. Confidence is comparatively lower for treatment failure, recurrence directly attributable to resistance, bacteremia attributable to resistance, and mortality attributable independently to antimicrobial resistance. Future prospective studies should use standardized definitions for symptomatic UTI, community acquisition, MDR organisms, and clinical outcomes.

Community-acquired urinary tract infections in older adults are increasingly complicated by antimicrobial resistance. Escherichia coli remains the predominant uropathogen, but Klebsiella pneumoniae, Proteus spp., Enterococcus spp., Pseudomonas aeruginosa, and polymicrobial infections assume greater importance in patients with recurrent infection, urinary tract abnormalities, urinary devices, diabetes, or previous healthcare exposure. Resistance to fluoroquinolones, trimethoprim-sulfamethoxazole, aminopenicillins, and selected cephalosporins is sufficiently high in many settings to limit universal empirical use. However, substantial geographical variation demonstrates that no single resistance estimate should be applied across different populations. MDR organisms are clinically important because they increase the probability of inadequate empirical therapy and may prolong hospitalization. Culture-guided therapy, diagnostic stewardship, early review of empirical treatment, and appropriate antimicrobial de-escalation are central to improving outcomes while limiting further development of antimicrobial resistance.

Declarations

Ethics Approval and Consent to Participate

Not applicable. This systematic review analyzed data from previously published studies and involved no direct recruitment of human participants.

Consent for Publication

Not applicable.

Funding

No specific funding was received for the preparation of this systematic review.

Conflict of Interest

The authors declare no conflict of interest.

Data Availability

All data synthesized in this review are derived from published studies cited in the reference list.