Battle against superbugs: E. coli resistance in UTIs shows slight decline

By Bhavana KunkalikarReviewed by Benedette Cuffari, M.Sc.May 30 2023

In a recent study published in the Open Forum Infectious Diseases, researchers assess the resistance of uropathogenic Escherichia coli (UPEC) over time in adults who received uncomplicated urinary tract infections (uUTIs) outpatient care.

Study: Multi-drug resistance of Escherichia coli from outpatient uncomplicated urinary tract infections in a large U.S. integrated health care organization. Image Credit: 220 Selfmade studio / Shutterstock.com

Drug resistance and UTIs

UPEC is responsible for 80% of UTIs. UTI treatment has become more complicated in recent years due to the rise of multi-drug resistant UPEC strains.

Between 2000 to 2010, there were notable rises in UPEC resistance to ciprofloxacin and trimethoprim-sulfamethoxazole (TMP-SMX), according to outpatient data from the U.S. Surveillance Network. Extended-spectrum beta-lactamase (ESBL)-bearing strains with multiple drug resistance pose a challenge for treatment due to the limited options available since they are likely to carry other resistance genes.

Recent data on the multi-drug resistance of UPEC are limited, despite recent rises in multi-drug resistance and altering resistance trends in UPEC in the last two decades.

About the study

A retrospective cohort study was performed to assess antibiotic resistance patterns in E. coli and compare resistance trends in virtual and in-person care settings. The study was conducted between 2016 and 2021 at Kaiser Permanente Southern California (KPSC), which includes 15 medical centers along with 236 medical offices situated in Southern California.

The KPSC electronic health records (EHR) system comprehensively records members' health information, covering their demographic details, diagnoses, laboratory examinations, and medicines from all care settings.

The study included individuals aged 18 years or older with an outpatient uUTI who had been continuous members of KPSC for at least one year before their first uUTI was documented between January 1, 2016, and December 31, 2021. The identification of uUTIs involved the use of specific criteria, including the presence of a UTI diagnosis code accompanied by an antibiotic prescription given within at least three days of the code date, a positive urine sample with an antibiotic prescription given within three days of the culture date, or a positive urine culture with a diagnosis code given at about seven days of culture date. The occurrences of UTI were classified into two categories of uUTI and complicated (cUTI).

For the detected E. coli isolates, the team obtained susceptibility information from EHR on carbapenems, aminoglycosides, fluoroquinolones, cephalosporins, nitrofurantoin, fosfomycin, TMP-SMX, penicillins, and other UTI-related antibiotics.

Study findings

A total of 777,817 adults who were members of KPSC for at least one year before the index date had experienced at least one UTI event. The cohort consisted of 475,013 individuals. After exclusions were considered, 233,974 were identified as outpatient uUTIs. On average, each person experienced 1.3 UTI events.

The group consisted of 92% women and 46% Hispanics, with an average age of 52 years. Out of the 88,679 individuals who were not resistant to any of the tested antibiotics, 14,467 reported diabetes and 7,688 reported a Charlson comorbidity index score of four or more while 14,156 were born outside the United States, and 36,860 reported being Hispanic. Additionally, 12,535 had 20 or more outpatient encounters, and 247 had four or more inpatient encounters in the year before the index date.

No variations were noted based on the care environment. UPEC was most prevalent in individuals aged 60 to 69 years who provided a urine culture, followed by those aged 50-59 years and 18-29 years. Furthermore, it was least common in individuals aged 80 years or older.

UPEC resistance reduced over time and was comparable in both virtual and in-person care settings. The most prevalent types of class-specific resistance were resistance to TMP-SMX or penicillins.

The study period was associated with a decline in resistance for penicillins, cephalosporins, and TMP-SMX across all care settings. The percentage of multi-drug resistant UPEC isolates declined from 13% to 12% from 2016 to 2021. This was observed in virtual and in-person settings among female participants. However, there was no significant change in the number of multi-drug resistant UPEC isolates among male participants.

The most common antibiotic resistance identified among multi-drug resistant UPEC samples were penicillins overall, as well as co-resistance to TMP-SMX and penicillins. The prevalence of multi-drug resistance, which includes resistance to penicillins and TMP-SMX, along with at least one other antibiotic class, was also common.

Almost 12% of all resistance patterns observed were due to multi-drug resistance, including for penicillins. Approximately 19% of UPEC isolates were resistant to one antibiotic class, while 17% exhibited co-resistance to two antibiotic classes. Additionally, 8% of isolates were resistant to three, and 4% of isolates were resistant to four antibiotic classes.

Half of the tested antibiotics showed no resistance, while only 1% of isolates exhibited resistance to five or more antibiotic classes. Consistent patterns were observed across different care settings.

Conclusions

The prevalence of antimicrobial resistance in outpatient uUTIs caused by UPEC at KPSC has decreased slightly between 2016 and 2021 in both in-person and virtual settings. However, this reduction was generally small in magnitude. Resistance to penicillin, TMP-SMX, and fluoroquinolones was common.

The occurrence and types of resistance in UPEC were similar across different care settings, including both single-class and multi-drug resistance. Virtual healthcare could provide wider access to UTI treatment without the added risk of multi-drug resistance.

Continued monitoring of nearby resistance trends and microbial prevalence is necessary to assist in prescribing appropriate empirical therapy for UTIs.