Urinary pH levels vary broadly (pH 4.5–8) and can be easily modified by diet or medications. Modification of the urinary pH could play an important role both in the treatment and in the prevention of UTIs since pH is an essential factor in the colonization and proliferation of uropathogenic bacteria and modifies the efficacy of antibiotics. Moreover, urine composition is a crucial host factor that can alter the risk of a UTI; a pH of less than 5, organic acids, and high urea content make the environment less ideal for bacterial growth. The study evaluated the effect of urine pH on the efficacy of antibiotics against Escherichia coli, Proteus mirabilis, and Klebsiella pneumoniae. The results show that erythromycin had no antibacterial effect at pH 5 and 6. At pH 7 and 8, significant activity was observed on sensitive E. coli and K. pneumoniae strains. Erythromycin prevented the growth of tested bacteria most effectively in an alkaline environment. Ampicillin showed potent antibacterial activity at pH 5–7. pH dependence was also detected for Ciprofloxacin showing higher antibacterial activity at pH 7-8. Gentamicin was the most active antibiotic at alkaline pH.

There is other research which reviews the efficacy of Fosfomycin, the recommended treatment for uncomplicated urinary tract infections, and reported a better efficacy at acidic urine pH. Therefore, the activity of antimicrobial drugs is pH dependent. The regulation of urinary pH contributes to more effective therapy of urinary tract infections, especially in cases of infections caused by multidrug-resistant bacteria.

Urinary tract infections (UTIs) are also frequent the pediatric patients. The estimated prevalence of urinary infections among febrile infants aged 0 to 24 months is 7.5 and 7.8% among children aged 0 to 19 years. The first task in the diagnosis is to rule out a cause that can be a risk factor for infections such as neurogenic bladder, or vesicoureteral reflux. The study evaluates the relation between urine pH and microbiological patterns including the results of 5201 pediatric patients with urinary tract infections. Urine analysis, 6348 were positive in urine culture. Proteus mirabilis or Pseudomonas aeruginosa were more commonly isolated in cases of the least acidic urine pH (pH 6.72 and 6.62, respectively). Whereas urine with Escherichia coli or Klebsiella pneumoniae was more common in the case of the most acidic pH (pH 6.21 and 6.18, respectively). After stratifying the urine samples by their pH range (<6, 6-6.9, 7-7.9,>8) the prevalence of Proteus mirabilis increased significantly across increasing pH categories.

The results may be related to Proteus mirabilis and also Pseudomonas aeruginosa are bacteria that can produce urease. Urease hydrolyzes urea in urine into CO2 and ammonia, which causes the pH of urine to increase. Among children, UTI caused by the Proteus species is one of the most common presenting signs of urolithiasis. The results suggest that pH must be taken into account in children with infections and pH modification always needs to be evaluated.

According to pH, urine can be defined as acid (4.5 to 5.5), average (5.5 to 6.5), or alkaline (6.5 to 8). Several studies have proposed that an acidic urine pH may be protective against recurrent urinary tract infections. The present study focused on postmenopausal women with recurrent urinary tract infections analyzing the effect of changes in urinary pH incidence of infections. The study was carried out in 26 women during a follow-up period of 2 weeks and 65% reported a urine pH variation greater than 1 unit. Beta-carotene and total dietary sugar intake were associated with a decrease in urine pH, whereas monounsaturated fatty acids and protein were associated with an increase in urine pH. Moreover, the authors showed the urine pH changes along the day and a postprandial increase in urine pH is described.

There is growing evidence that the effect of urine pH has an important effect on patients with recurrent infections and it must be evaluated as a therapeutical tool. Authors conclude with this sentence: “Future research may identify if regulating urine pH toward a more acidic range via diet modifications can in-fluence the rate of RUTIs among postmenopausal women”.