Prevalence of MDR and XDR in Uropathogenic E. coli
Multidrug-resistant (MDR) UPEC prevalence ranges from 7-68% depending on geographic location and patient population, while extensively drug-resistant (XDR) UPEC occurs in approximately 16% of cases, with the high-risk O25b/ST131 clone showing MDR rates of 41% and XDR rates of 16% in pediatric complicated UTIs.
Overall MDR Prevalence in UPEC
The prevalence of MDR UPEC varies substantially by geographic region, patient setting, and time period:
United States (2000): MDR prevalence was 7.1% among urinary isolates, with higher rates in males (10.4%) versus females (6.6%), elderly patients >65 years (8.7%) versus younger age groups, and inpatients (7.6%) versus outpatients (6.9%) 1
United States (2016-2021): More recent data shows MDR prevalence of 12% overall in outpatient uncomplicated UTIs, with a slight decreasing trend over time from 13% to 12% 2
Iran (2012-2013): Dramatically higher MDR rates of 68% in inpatients and 61% in outpatients were documented, reflecting significant geographic variation in resistance patterns 3
Egypt (2017): Among fluoroquinolone-resistant isolates specifically, 60.9% belonged to the high-risk ST131-O25b/O16 subgroups, indicating clustering of resistance in particular clones 4
XDR Prevalence in UPEC
Extensively drug-resistant UPEC is less common but clinically significant, with a documented prevalence of 15.87% among O25b strains causing complicated UTIs in hospitalized children 5. This represents a concerning subset of already multidrug-resistant organisms with even more limited treatment options.
Prevalence in the O25b/ST131 Clone
The O25b/ST131 clone represents a particularly problematic subset with enhanced resistance profiles:
MDR prevalence: 41.27% of O25b strains from pediatric complicated UTIs demonstrated multidrug resistance 5
XDR prevalence: 15.87% of these same O25b strains showed extensive drug resistance 5
Virulence characteristics: These strains harbor multiple virulence genes including fimH (95.23%), csgA (91.26%), papGII (80.95%), and chuA (95.23%), with 64.28% producing extended-spectrum β-lactamases 5
Phylogenetic associations: ST131 (63.63%) was primarily associated with phylogenetic group B2, known for enhanced virulence and extraintestinal pathogenicity 5
Common Resistance Patterns
The most prevalent resistance phenotypes involve specific antibiotic combinations:
Classic MDR pattern: Resistance to ampicillin, cephalothin, and trimethoprim-sulfamethoxazole represents 57.9% of all MDR isolates 1
Penicillin-TMP-SMX coresistance: This combination occurs in 12% of isolates, with an additional 10% showing MDR involving these two classes plus at least one additional class 2
Preserved susceptibility: Carbapenems (meropenem) maintain excellent activity with no resistance detected in multiple studies 3, 4, while nitrofurantoin (85.9% sensitivity), amikacin (89.1%), and gentamicin (82.4%) show relatively preserved activity 3
Clinical Implications and Caveats
Geographic variation is substantial, with developing regions showing MDR rates up to 10-fold higher than developed countries, necessitating reliance on local antibiogram data rather than generalized prevalence figures 3, 1, 2.
Patient population matters significantly: Complicated UTIs in hospitalized children show much higher MDR (41%) and XDR (16%) rates compared to community-acquired uncomplicated UTIs in adults (12% MDR) 5, 2.
The ST131 clone deserves special attention as it combines high-level antimicrobial resistance with enhanced virulence factors and accounts for a disproportionate share of fluoroquinolone-resistant infections 5, 4.