Urinary tract infection (UTI) afflicts millions of patients globally each year. While the majority of UTIs are successfully treated with orally administered antibiotics, the impact of oral antibiotics on the host microbiota is under close research scrutiny and the potential for dysbiosis is a cause for concern. Optimal treatment of UTI relies upon the selection of an agent which displays appropriate pharmacokinetic-pharmacodynamic (PK-PD) properties that will deliver appropriately high concentrations in the urinary tract after oral administration. Alternatively, high local concentrations of antibiotic at the urothelial surface can be achieved by direct instillation into the urinary tract. For antibiotics with the appropriate physicochemical properties, this can be of critical importance in cases for which an intracellular urothelial bacterial reservoir is suspected. In this review, we summarise the underpinning biopharmaceutical barriers to effective treatment of UTI and provide an overview of the evidence for the deployment of the intravesical administration route for antibiotics.

Nearly 150 million cases of urinary tract infections (UTIs) are reported each year, of which uncomplicated cystitis triggers > 25% of outpatient prescriptions of oral antimicrobial treatment (OAT). OAT aids immune cells infiltrating the urothelium in eliminating uropathogens capable of invading the urothelium and surviving hyperosmotic urine. This self-evident adaptability of uropathogens and the short interval between the introduction of Penicillin and the first report of antimicrobial resistance (AMR) implicate AMR as an evolutionary conserved heritable trait of mutant strains selected by the Darwinian principle to survive environmental threats through exponential proliferation. Therefore, AMR can only be countered by antimicrobial stewardship (AMS) following the principle of the five Ds—drug, dose, duration, drug route, and de-escalation. While convenient to administer, the onset of the minimum inhibitory concentration (MIC) for OAT in urine leaves a window of opportunity for uropathogens to survive the first contact with an antimicrobial and arm their descendant colonies with AMR for surviving subsequent higher urine antimicrobial levels. Meanwhile, the initial dose of intravesical antimicrobial treatment (IAT) may be well above the MIC. Therefore, the widespread clinical use of OAT for cystitis warrants an analysis of the strengths, weaknesses, opportunity, and threats (SWOTs) and a root cause analysis of the AMR associated with OAT and IAT.

Out of a worldwide annual incidence of ~150 million cases for urinary tract infection (UTI), >25% of outpatient prescriptions of oral antimicrobial treatment (OAT) are for cystitis not complicated by sepsis. OAT aids the immune cells infiltrating urothelium to eliminate uropathogens attaching and invading urothelium amidst hyperosmotic urine. This adaptability of uropathogens and the short interval between Penicillin sale and the first antimicrobial resistance (AMR) report suggests that AMR is a 3.8 billion years old evolutionary conserved heritable trait of surviving environmental threats through exponential proliferation of mutant strains selected by Darwinian principle. Therefore, OAT success with minimal AMR can be ensured by antimicrobial stewardship (AMS) following the principle of 5Ds -drug, dose, duration, drug-route, and de-escalation. While convenient to administer, the onset of minimum inhibitory concentration (MIC) for OAT in urine is a window of opportunity for uropathogens to survive the first contact with OAT and the descendant colonies armed with AMR are likely to survive subsequent higher urine OAT levels. Meanwhile, intravesical antimicrobial treatment (IAT) delivers the first strike well above MIC. The root cause analysis of AMR dovetails with the strengths, weaknesses, opportunity, and threat (SWOT) analysis of OAT in this interdisciplinary review.