Urinary pH and antibiotics, choose carefully. A systematic review.

Uncomplicated urinary tract infection (UTI) is the most common bacterial infection in women. Since 1948, the relationship between urinary pH and antibiotics (ABs) has been established. We aimed to search for the best urinary pH for each family of antibiotics and to assess whether pH changes bacterial susceptibility to them. We included in vitro research and in vivo studies including one or more bacterial species and tested the effect of one or more ABs at different pH values. We also included randomized controlled clinical trials (RCTs) in uncomplicated UTI (EAU guidelines 2019 definition), choosing the ABs based on urinary pH or using an antibiotic plus urinary pH modifiers (L-methionine, vitamin C…) vs. an antibiotic and a placebo. Quadas-2 tool was used as a quality assessment of the studies and PRISMA set of items for systematic reviews. Two authors independently screened and evaluated the papers, while two additional authors individually repeated the search. A fifth researcher acted as an arbiter, and another author collaborated as a hospital pharmaceutical consultant. Alkaline-friendly antibiotics are most fluoroquinolones, aminoglycosides, trimethoprim. Acidic-friendly antibiotics are fosfomycin, tetracycline, nitrofurantoin and some β-lactams. We suggest performing urine cultures with antibiogram tests, in both acidic and alkaline media, to define the bacterial susceptibility profile. There is insufficient in vivo evidence to support whether choosing an antibiotic based on a patient's urinary pH or adding urinary pH modifiers will lead to a higher cure rate.