A nationwide genomic study has found that multidrug-resistant Klebsiella pneumoniae is spreading widely in community settings across the United States, raising concerns about treatment options for common infections such as urinary tract infections (UTIs).
The study, published in Nature Communications, analyzed more than 2,000 antibiotic-resistant Klebsiella isolates collected from 10 regional diagnostic laboratories between July 2023 and July 2024. The samples originated from 42 states and were obtained primarily from outpatients.
Most isolates came from UTIs, and the majority were recovered from older adults and women. Researchers found that all isolates were resistant to multiple classes of antibiotics, including several agents commonly used to treat UTIs in outpatient settings.
Among isolates tested against four commonly prescribed oral antibiotics, nearly 70 percent were resistant to all four drugs. Resistance to carbapenems – often considered last-line therapies – was less common but still present in a subset of isolates.
Genomic analysis showed that much of this resistance was linked to a gene known as blaCTX-M-15, which enables bacteria to produce an extended-spectrum β-lactamase (ESBL) enzyme. This enzyme can inactivate many commonly used antibiotics, including third-generation cephalosporins.
The researchers found that the resistance gene was frequently carried on mobile DNA elements known as plasmids. Because plasmids can move between bacteria, they can facilitate the spread of resistance within and between bacterial populations.
The study also identified evidence of ongoing transmission in the community. More than half of the isolates belonged to genetic clusters consistent with recent spread, and several clusters were detected across multiple states. These findings suggest that multidrug-resistant K pneumoniae is no longer limited to isolated healthcare-associated outbreaks but is becoming established in community settings.
The findings underscore the importance of accurate identification and antimicrobial susceptibility testing. The high rates of resistance observed in this study suggest that empiric treatment choices may become increasingly challenging, particularly for UTIs.
The authors also highlighted the value of genomic surveillance for tracking emerging resistant strains and monitoring the movement of resistance genes. They noted substantial regional differences in resistance patterns, emphasizing the need for local susceptibility data to support clinical decision-making and antimicrobial stewardship efforts.
Although the study did not include antibiotic-susceptible comparison isolates and lacked detailed patient information, the authors conclude that continued genomic surveillance will be important for understanding and responding to the growing spread of multidrug-resistant K pneumoniae in both community and healthcare settings.
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