Camila Maria Piñeiro Silva

Klebsiella pneumoniae poses a significant public health threat, but the relationship between community-acquired (CA) infections and environmental isolates remains poorly understood. Therefore, this study aimed to assess whether K. pneumoniae from CA infections share microbiological and molecular features with isolates recovered from an urban river in Salvador, Brazil. A total of 115 isolates, including 65 from CA infections and 50 from river water, were analyzed using antimicrobial susceptibility testing, β-lactamase and virulence gene detection, and multilocus sequence typing (MLST). Resistance rates were similar between groups, including multidrug resistance (24.6% vs. 22.0%; p > 0.05) and carbapenem resistance (4.6% vs. 4.0%; p > 0.05). β-lactamase gene detection was consistent with observed resistance patterns, with bla _CTX−M detected in 18.5% of CA isolates and 12.0% of river isolates, while bla _KPC−2 (3.1% vs. 2.0%) and bla _NDM−1 (1.5% vs. 2.0%) occurred at comparable frequencies. However, hypervirulent K. pneumoniae isolates were identified only among CA infections (4.6%). MLST revealed high clonal diversity, with 88 sequence types (STs), including 14 novel STs, with most STs being singletons. Four STs were shared between groups, including the high-risk lineages ST11 and ST307. These findings indicate that clinically relevant K. pneumoniae lineages, including high-risk, occur beyond healthcare settings, with urban aquatic environments serving as potential environmental reservoirs.