Caracterização fenotípica e genotípica de Escherichia coli isolada de infecções urinárias e de corrente sanguínea adquiridas na comunidade

Abstract

INTRODUCTION: Escherichia coli is a major cause of community-acquired infections, associated with significant clinical impact and healthcare burden. The increasing prevalence of antimicrobial resistance has further complicated their management. This study compared clinical features, antimicrobial resistance, phylogenetic groups, virulence traits, and clonal profiles of E. coli isolates from community-acquired (CA) urinary tract infections (UTI) and bloodstream infections (BSI). METHODS: The isolates were obtained from two cross-sectional studies: CA-UTI isolates collected between April 2019 and January 2022, and CA-BSI isolates collected between March 2015 and May 2019. Clinical and demographic data were obtained through patient interviews and medical records. Antimicrobial susceptibility was assessed by disk diffusion or Vitek® 2 methods, following CLSI guidelines. β-lactamase genes, phylogenetic groups, and virulence factors were identified by PCR, and molecular typing was performed by MLST. RESULTS: A total of 167 E. coli isolates were analyzed, including 98 from CA-UTIs and 69 from CA-BSIs. CA-UTI mainly affected younger women (95.5%; median age 48 years), while CA-BSI predominated in elderly patients (median age 68 years), with lethality reaching 15.9%, particularly in septic shock cases. Most CA-BSI (71.2%) were secondary to prior UTI. High resistance to ampicillin (≥50%) and trimethoprim-sulfamethoxazole (>30%) was observed in both groups, while fluoroquinolone resistance was higher among CA-UTIs (33.7% vs. 18.8%). Multidrug resistant (MDR) (24.5% vs. 17.4%) and ESBL (6.1% vs. 5.8%) rates were comparable. Phylogroup B2 predominated and included the most virulent strains, whereas phylogroup A showed the greatest proportion of MDR strains. CA-BSIs isolates carried more virulence genes, particularly those related to capsules (kpsM), siderophores (iroN, iutA, and aer), P-fimbriae (papC), serum resistance (traT), and pathogenicity island PAI ICFT073. ST1193 and ST73 were the most prevalent lineages, followed by ST95 and ST131. ST1193 was mainly associated with MDR in CA-UTIs, whereas ST73 and ST95 were restricted to highly virulent strains, with ST95 significantly more frequent in CA-BSIs. CONCLUSION: CA-BSI isolates exhibited greater virulence potential compared to those from CA-UTIs, although resistance profiles were similar. The emergence and detection of high-risk clones, particularly ST1193, underscores the need for continuous molecular surveillance and resistance monitoring in community settings, with implications for clinical practice and control strategies.