Carbapenem-resistant bacteria in the environment

Abstract

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.

Keywords: One Health approach; antibiotici; antibiotics; bolnički okoliš; hospital environment; koncept jednog zdravlja; natural environment; prirodni okoliš; resistance; rezistencija.

Figure 1

Carbapenem-resistant bacterial species from river sediment cultured on CHROMagar Acinetobacter. Red – Acinetobacter spp., Pseudomonas sp., and Stenotrophomonas sp. (similar to Acinetobacter but of different morphology). Blue – Enterobacterales

Figure 2

Recommended protocol for the detection and characterisation of CRB from the environment

Figure 3

Mechanisms of carbapenem resistance in environmental isolates (drawing created with bioRender). 1) overexpression of the efflux pump; 2) reduced porin activity; 3) carbapenemase-catalysed reactions (carbapenem hydrolysis)

Figure 4

Possible transmission routes and reservoirs of CRB in the natural environment (drawing created with bioRender). 1) discharge of untreated hospital and urban sewage; 2) hospital and urban sewage that goes through WWTP but is released as partially treated effluent; 3) transmission of CRB through animals and ready-to eat-vegetables