Occurrence and prevalence of antimicrobial resistance in urban karst groundwater systems based on targeted resistome analysis

Leaching of antibiotic resistance genes and microbial assemblages following poultry litter applications in karst and non-karst landscapes

Antibiotic resistance is increasingly recognized as a critical challenge affecting human, animal, and environmental health. Yet, environmental dynamics and transport of antibiotic resistance genes (ARGs) and microbial communities in karst and non-karst leachate following poultry litter land applications are not well understood. This study investigates impacts of broiler poultry litter application on the proliferation of ARGs (tetW, qnrS, ermB, sulI, and blaCTX-M-32), class 1 integron (intI1 i), and alterations in microbial communities (16S rRNA) within karst derived soils, which are crucial and under-researched systems in the global hydrological cycle, and non-karst landscapes. Using large, intact soil columns (45 cm diam. × 100 cm depth) from karst and non-karst landscapes, the role of preferential flow and ARG transport in leachate was enumerated following surface application of poultry litter and simulated rain events. This research demonstrated that in poultry litter amended karst soils, ARG (i.e., ermB and tetW) abundance in leachate increased 1.5 times compared to non-karst systems (p < 0.05), highlighting the influence of geological factors on ARG proliferation. Notably, microbial communities in karst soil leachate exhibited increased diversity and abundance, suggesting a potential linkage between microbial composition and ARG presence. Further, our correlation and network analyses identified relationships between leachate ARGs, microbial taxa, and physicochemical properties, underscoring the complex interplay in these environmentally sensitive areas. These findings illuminate the critical role of karst systems in shaping ARG abundance and pollutant dispersal and microbial community dynamics, thus emphasizing the need for landscape-specific approaches in managing ARG dissemination to the environment. This study provides a deeper understanding of hydrogeological ARG dynamics but also lays the groundwork for future research and strategies to mitigate ARG dissemination through targeted manure applications across agricultural landscapes.

Discovery of sulfonamide resistance genes in deep groundwater below Patna, India

Global usage of pharmaceuticals has led to the proliferation of bacteria that are resistant to antimicrobial treatments, creating a substantial public health challenge. Here, we investigate the emergence of sulfonamide resistance genes in groundwater and surface water in Patna, a rapidly developing city in Bihar, India. We report the first quantification of three sulfonamide resistance genes (sulI, sulII and sulIII) in groundwater (12-107 m in depth) in India. The mean relative abundance of gene copies was found to be sulI (2.4 × 10-2 copies/16S rRNA gene) > sulII (5.4 × 10-3 copies/16S rRNA gene) > sulIII (2.4 × 10-3 copies/16S rRNA gene) in groundwater (n = 15) and surface water (n = 3). A comparison between antimicrobial resistance (AMR) genes and wastewater indicators, particularly tryptophan:fulvic-like fluorescence, suggests that wastewater was associated with AMR gene prevalence. Urban drainage channels, containing hospital and domestic wastes, are likely a substantial source of antimicrobial resistance in groundwater and surface water, including the Ganges (Ganga) River. This study is a reference point for decision-makers in the fight against antimicrobial resistance because it quantifies and determines potential sources of AMR genes in Indian groundwater.

Prevalence and whole-genome sequencing characterization of Salmonella in urban karst groundwater and predominantly groundwater-fed surface waters for serotypes and antimicrobial resistance

Karst aquifers provide a significant source of drinking water around the world; however, they are prone to bacterial contamination. We investigated the prevalence, serotypes, and antimicrobial resistance genes (ARGs) of Salmonella in urban karst groundwater and groundwater-fed surface waters. Weekly water samples (n = 443) were collected from nine groundwater sites and the Barren River in Bowling Green, KY. Additionally, cross-sectional samples were collected from 45 sites, including groundwaters and two rivers, in Tampa, FL. Salmonella was detected in 14.5% of Bowling Green samples resulting in 176 isolates representing 18 serotypes. Two (4.4%) of the Tampa samples were positive yielding eight isolates representing two serotypes. In Bowling Green, Salmonella prevalence varied by sampling site, week, month, and season, with the highest prevalence in surface water in the month of November and during summer. Salmonella Newport was the most common serotype detected. Nine of the serotypes detected in the study were among the top 20 serotypes commonly associated with human infections in the United States. Isolates were clustered with human clinical isolates, or isolates obtained from food animals, suggesting the importance of humans and agricultural practices as a source of water contamination. ARGs were detected in 12.5% (n = 176) of the Bowling Green isolates; overall, 81.8% (n = 22) of these were multidrug-resistant (resistance to ≥3 antimicrobial classes). Notably, the four Salmonella Agona isolates were resistant to four antimicrobial classes, mercury, and quaternary ammonium compounds. Seasonality and the widespread occurrence of Salmonella both in the groundwater and groundwater-fed surface waters is a potential risk to public health.