Backdrop/UTI

Biofilms and Antibiotic Resistance in Urinary Tract Infections

Urinary tract infection (UTI) is one of the most common infectious human diseases in the world, with some 150 million cases occurring globally per year. It is also the most common cause of hospital-acquired infections in the developed world, accounting for approximately 40% of documented cases in the United States in 2009. On average, UTI accounts for more than 1 million hospitalizations and $1.6 billion in medical expenses each year in the USA alone [1, 2].

Uropathogenic E. coli is the leading cause of UTIs. It is responsible for 80-85% of community-acquired UTIs, whereas for hospital-acquired UTIs other bacteria such as P. Aeruginosa also play a significant role [3]. Among the UTIs acquired in the hospital, about 75% are associated with the use of urinary catheters, tubes inserted into the bladder through the urethra to drain urine which 1 in 4 hospitalized patients end up receiving [4].

Bacteria like to live as sessile communities adhered to surfaces instead of isolated planktonic individuals. These immobilized bacterial communities protect themselves by creating biofilms (what we typically call bacterial slime), jelly-like coatings comprising a mixture of long carbohydrates, proteins, and DNA molecules [5]. In the context of UTIs, such biofilms are responsible for causing inflammation as well as providing a safe haven in which the bacteria can replicate and mature. Biofilms have accumulated within their matrix enzymes that destroy antimicrobials; this helps protect the embedded bacteria against our immune system as well as administered antibiotics [6, 7]. Biofilms associated with UTIs can form readily on both the surface of our living cells and that of the inserted catheters, and result in infections that are largely recurrent and chronic even after antibiotic administration [8].

Given that antibiotic resistance in UTI-causing bacteria is such a significant problem that it warrants even multiple specific mentions in WHO’s recent antimicrobial resistance global report, the administration of prolonged-courses of antibiotics in attempt to treat biofilm-protected UTIs would of course be ill-advised [9]. Clinical resistance towards even last-resort antibiotics like carbapenems and tigecyclines have surfaced, and at present there has yet to be any antibiotics capable of degrading and destroying bacterial biofilms released for clinical use [10].