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Urinary Tract Infection

The antibiotic I was given for cystitis doesn't seem to be working. Is that common?

Common enough that the most frequently prescribed option now fails in roughly two cases out of five in Korea. Which antibiotic you were given matters more than how long you take it.

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Answer

Antibiotics failing in cystitis is common in Korea: in the 2023 national surveillance of 885 patients with uncomplicated cystitis, only 58.4 percent of the organisms were susceptible to ciprofloxacin — the fluoroquinolone most often prescribed first — against 94.9 percent for fosfomycin and 90.5 percent for nitrofurantoin, and fluoroquinolone resistance reached 59.8 percent among patients with recurrent cystitis and 44.9 percent among postmenopausal patients, so a course that fails is more likely to mean the wrong drug than an unusual infection.

Key takeaways

  • In Korean national surveillance for 2023, 58.4 percent of cystitis organisms were susceptible to ciprofloxacin.
  • Susceptibility was 94.9 percent to fosfomycin and 90.5 percent to nitrofurantoin in the same survey.
  • Fluoroquinolone resistance was 59.8 percent among patients with recurrent cystitis.
  • It was 44.9 percent among postmenopausal patients and 47.4 percent in tertiary hospitals.
  • Escherichia coli caused 75.1 percent of the infections.
  • Recurrent cystitis carried an odds ratio of 2.37 for fluoroquinolone resistance, and postmenopausal status 1.96.
  • A urine culture identifies which antibiotic will work, which is why it is worth asking for when a first course fails.

The usual assumption when cystitis does not settle is that the infection is stubborn. In Korea the more likely explanation is that the antibiotic was chosen by habit rather than by what the organisms in this country are still susceptible to.

58.4%

of cystitis organisms in Korean national surveillance for 2023 were susceptible to ciprofloxacinYu SH et al., Investigative and Clinical Urology, 2025

Which drugs still work

In the same 885 patients, fosfomycin was effective against 94.9 percent of organisms and nitrofurantoin against 90.5 percent. Both are oral, both are narrow-spectrum, and both were designed for exactly this infection. So this is not a situation with no options — it is a situation where the ranking of the options has changed and prescribing habits have not caught up.

If you have had cystitis before, the odds are worse

What to ask for

A urine culture with sensitivity testing answers the question directly rather than by guesswork, and it is the reasonable request when a first course has not worked. If you have had cystitis more than once, it is worth saying so before the prescription is written rather than after — that single fact more than doubles the chance the standard choice will fail.

One caution on reading the figure. 58.4 percent is a national average across participating centres, weighted towards hospitals where resistance runs highest. Your own infection is not 58.4 percent susceptible; it is either susceptible or it is not, and a culture is what distinguishes them.

Sources

  1. 1

    Yu SH, Jung SI, Lee SJ, Oh MM, Choi JB, Choi CI, Kim YJ, Park DJ, Bae S, Min SK

    Nationwide surveillance of antimicrobial resistance for uncomplicated cystitis in 2023: Conducted by the Korean Association of Urogenital Tract Infection and Inflammation

    Investigative and Clinical Urology 2025;66(2):161-171

    doi:10.4111/icu.20240302 · PMID:40047130

    https://doi.org/10.4111/icu.20240302