Widespread Distribution of Carbapenem-Resistant Klebsiella spp. in Clinical and Environmental Settings

<b>Background/Objectives:</b><i>Klebsiella</i> spp., particularly <i>K</i>. <i>pneumoniae</i>, are major opportunistic pathogens in healthcare settings driven by carbapenemase- and ESBL-producing strains. We assessed antimicrobial resistance and biofilm formation abilities in <i>Klebsiella</i> spp. from a Brazilian tertiary hospital and related environments and characterized capsular types. <b>Methods</b>: Over six months (July-December 2023), 303 carbapenem-resistant <i>Klebsiella</i> spp. were collected from clinical specimens (<i>n</i> = 198), ICU/non-ICU surfaces (<i>n</i> = 79), hospital sewage (<i>n</i> = 22), and stream water (<i>n</i> = 4). Species were identified by MALDI-TOF. Susceptibility testing covered eight antibiotic classes, focusing on carbapenems and polymyxin B. Biofilm formation was quantified by crystal violet, and capsular typing used <i>wzi</i>/K-locus approaches. <b>Results</b>: Most isolates (70.95%) had meropenem MICs ≥ 128 μg/mL, while 77.6% (<i>n</i> = 235) remained susceptible to polymyxin B. Resistance profiles largely consisted of extensive drug resistance (95.4%), with 1.3% exhibiting pandrug resistance, including isolates from bed rails. Biofilm formation was detected in 96.7% of isolates, mainly weak (67.6%) or moderate (28%), with 4.4% being strong producers. Among the <i>Klebsiella</i> isolates analyzed, 21 K types were identified with an uneven distribution dominated by K64, followed by K24, K173, and K50. K75 was the only K type detected across all sources-clinical isolates, bed-rail surfaces (non-ICU), wastewater, and fluvial water. <b>Conclusions</b>: Carbapenem-resistant <i>Klebsiella</i> spp. exhibited widespread resistance, with residual susceptibility to aminoglycosides, ceftazidime-avibactam, and polymyxins. Environmental reservoirs-hospital surfaces, sewage, and stream water-harbored resistant biofilm producers, reinforcing their role in persistence and dissemination. K-typing revealed concentrated distribution (predominantly K64) and cross-source K75. These findings underscore the urgency of integrated strategies combining molecular surveillance, antimicrobial stewardship, and environmental control.