Revisiting the Frequency and Antimicrobial Resistance Patterns of Bacteria Implicated in Community Urinary Tract Infections

Abstract

Urinary tract infections (UTIs) are one of the most common infectious diseases at the community level. The continue misuse of antimicrobials is leading to an increase in bacterial resistance, which is a worldwide problem. The objective of this work was to study the incidence and pattern of antimicrobial resistance of the main bacteria responsible for UTI in the community of central and northern Portugal, and establish an appropriate empirical treatment. The urine samples were collected in Avelab—Laboratório Médico de Análises Clínicas over a period of 5 years (2015–2019). The urine cultures were classified as positive when bacterial growth was equal to or higher than 105 CFU/mL, and only for these cases, an antimicrobial susceptibility test was performed. Of the 106,019 samples analyzed, 15,439 had a urinary infection. Urinary infections were more frequent in females (79.6%) than in males (20.4%), affecting more elderly patients (56.9%). Escherichia coli (70.1%) was the most frequent uropathogen, followed by Klebsiella pneumoniae (8.9%). The bacteria responsible for UTI varied according to the patient’s sex, with the greatest differences being observed for Enterococcus faecalis and Pseudomonas aeruginosa, these being more prevalent in men. In general, there was a growth in bacterial resistance as the age of the patients increased. The resistance of bacteria in male patients was, in most cases, statistically different (Chi-Square test, p < 0.05) from that observed for bacteria isolated from female patients, showing, in general, higher resistance in male patients. Although E. coli was the most responsible uropathogen for UTI, it was among the bacteria most susceptible to antibiotics. The isolates of K. pneumoniae, Proteus vulgaris and Enterobacter showed high resistance to the tested antimicrobials. The most common multidrug-resistant (MDR) bacteria implicated in UTI were K. pneumoniae (40.4%) and P. aeruginosa (34.7%), but E. coli, the most responsible bacteria for UTI, showed a MDR of 23.3%. When we compared our results with the results from 10 years ago for the same region, in general, an increase in bacterial resistance was observed. The results of this study confirmed that urinary tract infections are a very common illness, caused frequently by resistant uropathogens, for which the antibiotic resistance profile has varied over a short time, even within a specific region. This indicates that periodically monitoring the microbial resistance of each region is essential in order to select the best empirical antibiotic therapy against these infections, and prevent or decrease the resistance among uropathogenic strains.