Co-resistance between oral antibiotics for pyelonephritis and those for simple urinary tract infections – Applying an Escalation Antibiogram Model to local community data
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Objectives
The objective of this study was to apply an escalation antibiogram (EA) to community urine data to assess how presumptive resistance (treatment failure or recent microbiological samples) to first-line antibiotics for simple urinary tract infections (UTIs) affects resistance to antibiotics used to treat pyelonephritis. Furthermore, we examined how this varies with age or in instances of recurrent UTI.
Methods
We extracted susceptibility data from Escherichia coli isolates grown from urine samples sent from general practice from a 5-year period (2019–2023) in a region served by three NHS hospital trusts. All female patients over 18 years old were included giving a total of 130,514 isolates. We applied a Bayesian model to estimate antibiotic resistance rates for oral pyelonephritis antibiotics, when presuming resistance to each of the first-line antibiotics used to treat simple UTIs. The model estimates the probability of resistance with 95% credible intervals and was applied to a variety of patient groups based on age and history of recurrent UTIs. The uncertainty in these estimates increases for smaller patient groups.
Results
Resistance to first-line UTI antibiotics has a marked effect on the probability of resistance to oral antibiotics used to treat pyelonephritis. In particular amoxicillin-clavulanate should be avoided for pyelonephritis if resistance to pivmecillinam is presumed in UTI because resistant rates may exceed 50%. For patients with presumed resistance to nitrofurantoin or trimethoprim in UTI, the optimal pyelonephritis antibiotic depends on both age group and history of past infections. For example, for patients under 50 with recurrent UTIs, amoxicillin-clavulanate has the lowest estimated resistance rate, but for women over 65 with recurrent UTIs, ciprofloxacin is optimal for pyelonephritis, where there is presumed nitrofurantoin resistance in UTI, but cefalexin is superior if trimethoprim resistance is presumed.
Conclusions
EA analysis informed by our Bayesian model is a useful tool to support empiric antibiotic prescribing for pyelonephritis. It provides an estimate of local resistances rates and a comparison of antibiotic options with a measure of the uncertainty in the data.
