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The effect of urinary pH on the activity of antibiotics against uropathogens

It has been established that there are many factors that influence the effectiveness of antibiotics for urinary tract infections (UTIs), and pH is one. Due to the fact that the pH of human urine varies considerably - from acid (pH 4.5) to alkaline (pH 8), and this factor is fairly easy to handle, this can be a significant advantage for better understanding of the role of pH in the effectiveness of antibiotic use for UTI.

The objective of the study published in the September issue of the journal Urology was to determine the effect of pH on the activity of clinically significant antibiotics against the main bacterial uropathogens.

The in vitro study examined the activity of 24 antimicrobials commonly used against bacterial strains belonging to the 6 main uropathogens (Escherichia coli, Klebsiella pneumoniae , Proteus mirabilis, Enterococcus faecalis, Staphylococcus saprophyticus and Staphylococcus epidermidis), at different pH values (from 5 to 8).

To evaluate the activity of antibiotics, the standard disco-diffusion method and the serial micro-dilution method were used.

It turned out that, for 18 of the 24 antibiotics studied, pH played an important role in the overall inhibitory activity of the drug. Although most of the drugs tested showed similar activity against most or almost all pathogens, several antibiotics had pH-dependent activity against certain pathogens.

Fluoroquinolones, cotrimoxazole, aminoglycosides and macrolides were most active in an alkaline environment, while tetracyclines, nitrofurantoin and many beta-lactams exhibited the highest activity in an acidic environment. The activity of sulfamethoxazole, oxacillin, amoxicillin, clavulanic acid, vancomycin, imipenem and clindamycin, did not mainly depend on the pH of the medium.

Thus, clinicians must take into account the urinary pH of their patients in the treatment of urinary tract infections, especially in complicated cases. More clinical studies are needed to study the pH of the urine and the effectiveness of antibiotics, which may be useful in terms of more precise dosing of the drug, determining the optimal duration of therapy and potentially reducing the development of resistance to antibiotics.