Currently, antibiotics such as trimethoprim, sulfamethoxazole, ciprofloxacin, and ampicillin are the most commonly recommended drugs for treating UTIs.11 However, increasing rates of antibiotic resistance and high recurrence rates are steadily increasing the burden on our healthcare systems.
Antibiotic resistance has been well documented for members of the family Enterobacteriaceae, including E. coli and K. pneumoniae. Both pathogens have acquired plasmids encoding extended-spectrum β-lactamases (ESBLs). These plasmids rapidly spread resistance to third-generation cephalosporins among other antibiotics. Other Enterobacteriaceae produce the class C β-lactamases (AmpC enzymes), enzymes that work against cephamycin and third-generation cephalosporins; they are also resistant to β-lactamase inhibitors. The expression of AmpC enzymes is also linked to carbapenem resistance in K. pneumoniae strains.
Multidrug resistance is also common among enterococci, which are naturally resistant to trimethoprim, clindamycin, cephalosporins, and penicillins. Enterococcus species have also developed a high-level resistance to glycopeptides, including vancomycin, one of the last lines of defense against multidrug-resistant organisms.4, 6, 12, 15, 31, 32
Even though antibiotic resistance in S. saprophyticus is uncommon, methicillin-resistance has been found in ~1–8% of urine isolates and appears to be due to the acquisition of a penicillin-binding protein that has low β-lactam affinity encoded by the mecA gene. The majority of S. aureus UTI isolates, which are more common in pregnant women and catheterized individuals, are methicillin-resistant.17, 18, 22, 24, 28
Antibiotic resistance is a global problem that is one of the biggest health challenges facing medicine today. In March 2020, the Center for Disease Control (CDC) and Prevention launched a National Action Plan to slow the emergence and spread of resistant bacteria (Tables 2 & 3). This multi-strategic plan includes heightened surveillance, education, and preventive measures, the development of new therapeutics such as vaccines, as well as the development and use of rapid and innovative diagnostic tests to identify and characterize resistant bacteria. Improved diagnostic accuracy and characterization of antibiotic resistance of common UTI pathogens is an important strategy that will reduce the overuse of antimicrobial prescriptions and slow the emergence of resistant pathogens.
Table 2 – Examples of CDC-based approaches to reducing antimicrobial resistant UTI pathogens
Table 3 – CDC’s Antibiotic Resistance Threats in the United States, 20195