Carbapenem-resistant bacteria in the environment.

Carbapenem-resistant bacteria (CRB) pose a significant threat to public health due to their resistance to last-resort antibiotics. Even though they are widely studied in clinical settings, much less is known about their presence in environmental compartments with multiple pathways contributing to their dissemination, which raises a growing concern. The aim of this narrative review is to summarise the current knowledge about the occurrence, isolation, and characterisation of CRB in hospital and natural environments and to highlight their clinical relevance and environmental reservoirs. The CRB species pathogenic for humans - Acinetobacter baumannii, Klebsiella pneumoniae, and Pseudomonas aeruginosa - are often identified in hospital and urban sewage, wastewater treatment plants, water bodies, sediments, soil, animals, and plants. Their presence in these environments is largely attributed to anthropogenic factors such as the discharge of untreated or partially treated effluent from wastewater treatment plants. Suitable methods for CRB isolation include selective media, phenotypic assays, and molecular tools for species identification and resistance gene detection. This review also addresses the One Health approach, which stems from the interconnectedness of humans, animals, and environment in the spread of CRB. While the species-level transmission within the One Health framework is well-documented, further research is needed to establish strain-level dissemination patterns. Understanding the mechanisms of CRB persistence and transmission in diverse environments is crucial for developing effective mitigation strategies to curb their spread.