Prevalence of MDR and XDR in Uropathogenic E. coli
The prevalence of multidrug-resistant (MDR) uropathogenic E. coli ranges from 12-68% depending on geographic location and care setting, while extensively drug-resistant (XDR) strains occur in 5-16% of cases, with pediatric populations showing particularly concerning rates.
Geographic and Population Variations
Adult Populations
- In the United States, MDR prevalence among outpatient uncomplicated UTIs decreased from 13% to 12% between 2016-2021, with resistance patterns consistent across both in-person and virtual care settings 1
- In Iran, MDR rates were substantially higher at 68% in hospitalized patients and 61% in outpatients, demonstrating significant geographic variation 2
- The most common resistance pattern in U.S. adults involves penicillins and trimethoprim-sulfamethoxazole (TMP-SMX), with 12% showing co-resistance to both classes 1
Pediatric Populations
Pediatric patients demonstrate notably higher rates of drug resistance compared to adults:
- In Nepal, 64.9% of pediatric UPEC isolates were MDR and 5% were XDR, representing an alarming burden in this population 3
- In Pakistan, pediatric patients showed extensive drug resistance in both E. coli and K. pneumoniae strains, with high resistance to β-lactams, quinolones, and fluoroquinolones 4
- Among hospitalized children with complicated UTIs, 41.27% of O25b strains were MDR and 15.87% were XDR, with 64.28% producing extended-spectrum β-lactamases (ESBLs) 5
Resistance Patterns and Clinical Implications
Most Commonly Affected Antibiotic Classes
The following antibiotics show the highest resistance rates across populations:
- Penicillins (particularly ampicillin): >50% resistance in multiple studies 2, 1
- Cephalosporins (ceftazidime, cefotaxime, ceftriaxone): High resistance especially in pediatric populations 4, 5
- Fluoroquinolones (ciprofloxacin, nalidixic acid, norfloxacin): >50% resistance 2, 4
- Trimethoprim-sulfamethoxazole: >50% resistance 2
Antibiotics Retaining Activity
Despite widespread resistance, certain agents maintain effectiveness:
- Aminoglycosides: Amikacin (89.1% sensitivity) and gentamicin (82.4% sensitivity) show preserved activity 2
- Nitrofurantoin: 85.9% sensitivity in adult populations 2, and retained activity in pediatric populations 4
- Carbapenems: Meropenem showed no resistance in Iranian cohorts 2
- Polymyxins: Polymyxin B and colistin sulphate retained activity against resistant pediatric strains 4
- Fosfomycin and chloramphenicol: Maintained antimicrobial activity in extensively resistant pediatric cases 4
Critical Clinical Pitfalls
The most important caveat is that empirical treatment decisions must be based on local resistance patterns rather than generalized data, as prevalence varies dramatically by geography—from 12% MDR in the U.S. to 68% in Iran 2, 1.
In pediatric populations, clinicians should maintain heightened suspicion for MDR and XDR organisms, particularly in hospitalized children with complicated UTIs where rates approach 41% and 16% respectively 5. The association of UPEC O25b with sequence type ST131 and phylogenetic group B2 represents a particularly virulent and resistant clone requiring aggressive management 5.
Avoid empirical use of ampicillin, first-generation cephalosporins, TMP-SMX, and fluoroquinolones in areas with high resistance rates (>20%), as these agents show >50% resistance in multiple geographic regions 2, 4.