Aeromonas spp. diversity in U.S. mid-Atlantic surface and reclaimed water, seasonal dynamics, virulence gene patterns and attachment to lettuce

Aeromonas, an opportunistic pathogen present in wastewater in Tulancingo, Mexico

Wastewater is free in the environment and is an important source of contamination. One of the microorganisms that is present in aquatic environments is Aeromonas, so the objective of this study was to identify the presence of Aeromonas in the Tulancingo River. A total of 55 presumptive isolates of Aeromonas spp. were obtained by means of phenotypic characteristics; of these, 80% (44/55) were positive for the gcat gene, and 100% (44/44) of those were confirmed to be Aeromonas spp. by means of the rpoD gene, where Aeromonas caviae was identified in 43.2%, Aeromonas media in 29.5%, Aeromonas hydrophila in 11.3%, Aeromonas salmonicida in 9.1%, and Aeromonas allosaccharophila, Aeromonas lusitana, and Aeromonas veronii in 2.3% each. The genus Aeromonas is capable of causing infections in humans. Aeromonad wastewater can resist treatment processes if not done correctly, which represents a potential route of contamination. Therefore, its presence should not be underestimated, and it should be considered to be a true gastrointestinal pathogen. In addition, specific actions must be taken, mainly with the use of wastewater treatment plants. All of this will ensure the quality of treated water and its reuse for the irrigation of agricultural growing areas, thus mitigating potential health threats.

Antibacterial activity and mechanism of rose essential oil against Aeromonas veronii isolated from Northern snakehead (Channa argus)

AIMS

To investigate and identify the antibacterial action and mechanism of rose essential oil (REO) against Aeromonas veronii isolated from Northern snakehead for the first time by the phenotypic and metabolic analysis.

METHODS AND RESULTS

The 2-fold broth microdilution and spread-plate method identified that the minimum inhibitory concentration and minimum bactericidal concentration of REO against A. veronii were 1.25 μl ml-1 and REO impaired the growth in a concentration-dependent manner, indicating that REO possessed a significant bacteriostatic activity. Electron microscopy and live-dead cell staining found that REO caused a severe disruption of cellular morphology and increased the membrane permeability. Additionally, REO treatment induced the leakage of intracellular biomolecules such as proteins and nucleic acids from the bacteria. Metabolomics analysis showed that compared with the control, the REO treatment group exhibited a total of 190 differential metabolites (118 down-regulated and 72 up-regulated), which involved in the main metabolic pathways such as biotin metabolism, arginine biosynthesis, glutathione metabolism, lysine degradation, and histidine metabolism and the TCA cycle. These results verified that REO disturbed the metabolic processes of A. veronii to achieve the bacteriostatic effect.

CONCLUSION

The rose essential oil exhibited the effective antibacterial activity against A. veronii via breaking the cellular structure, increasing the membrane permeation and disrupting the metabolic processes.

Isolation, identification and characterization of Aeromonas jandaei from diseased Chinese soft-shell turtles

Aeromonas jandaei is a gram-negative bacterium commonly found in aquatic environments and can induce illnesses in amphibians, reptiles and aquatic animals. In this study, a strain of bacteria was isolated from the diseased Chinese soft-shell turtle (Pelodiscus sinensis), then named strain JDP-FX. This isolate was identified as A. jandaei after analysis of morphological, physiological and biochemical characteristics, as well as 16S rRNA and gyrB gene sequences. Virulence genetic testing further detected temperature-sensitive protease (eprCAI), type III secretion system (TTSS) (ascv), nuclease (nuc), cytotonic enterotoxin (alt) and serine proteinase (ser) in JDP-FX. Compared with healthy Chinese soft-shell turtle, the serum levels of total protein (TP), albumin (ALB) and globulin (GLB) were significantly decreased in the diseased Chinese soft-shell turtle, while, the levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST) and alkaline phosphatase (ALP) were significantly increased. Histopathological observations showed that multiple tissues, including intestinal mucosa, liver and kidney, were severely damaged in the diseased Chinese soft-shell turtle. Moreover, the diseased Chinese soft-shell turtle had significant cell degeneration, necrosis, sloughing and interstitial inflammatory cell infiltration. The pathogenicity of JDP-FX was tested via artificial infection. The median lethal dosage (LD50 ) of the strain was 1.05 × 105 colony forming units (CFU/g) per weight of Chinese soft-shell turtle. Drug susceptibility analysis revealed that JDP-FX was susceptible to ceftazidime, minocycline, cefoperazone, ceftriaxone and piperacillin. In addition, JDP-FX was resistant to doxycycline, florfenicol, sulfonamides, gentamicin, ampicillin and neomycin. Therefore, this study may provide guidance for further research into the diagnosis, prevention and treatment of JDP-FX infection.

Nosocomial infections by diverse carbapenemase-producing Aeromonas hydrophila associated with combination of plumbing issues and heat waves

BACKGROUND

Aquatic opportunistic pathogen Aeromonas hydrophila, known to persist in low-nutrient chlorinated waters, can cause life-threatening infections. Two intensive care units experienced a cluster of Aeromonas infections following outdoor temperature spikes coinciding with recurrent plumbing issues, with fatalities due to severe underlying comorbidities co-occurring with extensively-drug resistant (XDR) Aeromonas.

METHODS

We investigated this cluster using whole genome sequencing to assess genetic relatedness of isolates and identify antimicrobial resistance determinants. Three A. hydrophila were isolated from patients staying in or adjacent to rooms with plumbing issues during or immediately after periods of elevated outdoor temperatures. Sinks and faucets were swabbed for culture.

RESULTS

All A. hydrophila clinical isolates exhibited carbapenem resistance but were not genetically related. Diverse resistance determinants corresponding to extensively-drug resistant were found, including co-occurring KPC-3 and VIM-2, OXA-232, and chromosomal CphA-like carbapenemase genes, contributing to major treatment challenges. All 3 patients were treated with multiple antibiotic regimens to overcome various carbapenemase classes and expired due to underlying comorbidities. Environmental culture yielded no Aeromonas.

CONCLUSIONS

While the investigation revealed no singular source of contamination, it supports a possible link between plumbing issues, elevated outdoor temperatures and incidence of nosocomial Aeromonas infections. The diversity of carbapenemase genes detected in these wastewater-derived Aeromonas warrants heightened infection prevention precautions during periods of plumbing problems especially with heat waves.

Aeromonas spp. in drinking water and food: Occurrence, virulence potential and antimicrobial resistance

Aeromonas sp. is a Gram-negative, non-spore-forming, rod-shaped, oxidase-positive, facultative anaerobic bacterium and a natural contaminant found in aquatic environments. Some species can invade, colonize, and damage host cells due to the presence of virulence factors, such as flagella, elastase, hemolysins, aerolysins, adhesins, enterotoxins, phospholipases and lipases, that lead to pathogenic activities. Consequently, can cause many health disorders that range from gastrointestinal problems, enteric infections, and ulcers to hemorrhagic septicemia. Aeromonas has been isolated and identified from a variety of sources, including drinking water and ready-to-eat foods (fish, meat, fresh vegetables, dairy products, and others). Some species of this opportunistic pathogen are resistant to several commercial antibiotics, including some used as a last resort for treatment, which represents a major challenge in the clinical segment. Antimicrobial resistance can be attributed to the indiscriminate use of antibiotics by society in aquaculture and horticulture. In addition, antibiotic resistance is attributed to plasmid transfer between microorganisms and horizontal gene transfer. This review aimed to (i) verify the occurrence of Aeromonas species in water and food intended for human consumption; (ii) identify the methods used to detect Aeromonas species; (iii) report on the virulence genes carried by different species; and (iv) report on the antimicrobial resistance of this genus in the last 5 years of research. Additionally, we present the existence of Aeromonas spp. resistant to antimicrobials in food and drinking water represents a potential threat to public health.

Effect of aquaponic water and substratum material on biofilm formation by Aeromonas hydrophila

Aeromonas hydrophila is a zoonotic pathogen causing illness in fish and susceptible humans. This emerging pathogen has been isolated within aquaponic systems and could cause disease in fish and a hazard to humans consuming aquaponic produce. This study determined whether A. hydrophila from an aquaponic farm could form biofilms in aquaponic water and on materials used in these systems. A. hydrophila biofilm biomass and cell density in aquaponic water were evaluated by crystal violet staining and culture-based enumeration. Biofilm biomass and biofilm cell density were affected by the water source and A. hydrophila isolate (P < 0.05). A. hydrophila formed the most biomass from the beginning of deep-water culture (BDWC) water (OD570 0.202 ± 0.066) and the least from the end of deep-water culture (EDWC) water (OD570 0.140 ± 0.036; P < 0.05). Enumerated A. hydrophila from the biofilm varied among water sources; the fish tank water supported the greatest cell density (7.04 ± 0.71 log CFU/mL) while the EDWC supported the lowest cell density (6.76 ± 0.83 log CFU/mL). Biofilm formation was also evaluated on aquaponic materials such as nylon, polyvinyl chloride, polyethylene liner, bead filter, and foam. Biofilm formation on the liner had the greatest population (2.39 ± 0.022 log CFU/cm2), and the bead had the least (0.64 ± 0.039 log CFU/cm2; P < 0.05). Pathogenic organisms, such as A. hydrophila, may pose a greater risk to produce harvested from the BDWC and MDWC due to greater biofilm formation.

Quantitative models and potential surrogates for rapid evaluation and surveillance of chlorine disinfection efficacy in reclaimed water

Chlorine disinfection has become the most widely applied and indispensable technology in wastewater treatment and reuse to mitigate microbial risk and guarantee water safety. However, owing to complexities and high concentrations of contaminants in reclaimed water, rapid evaluation of chlorine disinfection efficacy is a crucial but challenging issue. Based on intensive experimental and statistical analyses, this study has established kinetic models and potential surrogates for rapid indication of the inactivation of microbial indicators and opportunistic pathogens during chlorine disinfection in different reclaimed waters. Overall, the constructed Selleck models performed very well to simulate log removal values (LRVs) of fecal coliforms, Pseudomonas aeruginosa and heterotrophic plate counts in all reclaimed water samples (R² = 0.877-0.990). Moreover, total and Peak A fluorescence intensity as well as fluorescence integral intensities in Regions II and IV were found to have high response sensitivities during the chlorination process. Nevertheless, their effectiveness to act as potential surrogates of LRVs of microbial indicators needs to be further validated. The results from this study can provide valuable information on microbial safety surveillance of disinfection toward sustainable and long-term water reuse.

Contribution of flagellar cap gene in virulence and pathogenicity of Aeromonas veronii

Aeromonas veronii is an important zoonotic and aquatic pathogen that causes a number of illnesses in both humans and animals. It is related to gastroenteritis, skin and soft tissue infections and bacteremia in humans, as well as causing significant economic losses in aquaculture owing to fish sepsis. Here, we constructed the flagellar cap gene (fliD) mutant strain of A. veronii by suicide plasmid-mediated homologous recombination system and analysed its characteristics. It was found that the deletion of fliD had no effect on growth and biochemical properties and could be inherited stably. However, the motility of A. veronii ΔfliD was significantly reduced, the flagellum was defective and the biofilm formation was attenuated compared with that of A. veronii wild-type strain. In vivo experiments revealed that the colonization capacity of ΔfliD was significantly lower than that of the wild-type strain in the period of first 24 h, and the median lethal dose (LD₅₀ ) was 56 times higher than that of the wild-type strain. The Cyprinus carpio infected with the wild-type strain indicated faster death speed and more severe clinical signs compared to ΔfliD strain. These results suggest that fliD is closely related to the virulence of A. veronii and plays an important role in pathogenicity, providing the foundation for pathogenic mechanism studies of A. veronii.

Potential Exposure to Respiratory and Enteric Bacterial Pathogens among Wastewater Treatment Plant Workers, South Africa

Wastewater handling has been associated with an increased risk of developing adverse health effects, including respiratory and gastrointestinal illnesses. However, there is a paucity of information in the literature, and occupational health risks are not well quantified. Grab influent samples were analysed using Illumina Miseq 16S amplicon sequencing to assess potential worker exposure to bacterial pathogens occurring in five municipal wastewater treatment plants (WWTPs). The most predominant phyla were Bacteroidota, Campilobacterota, Proteobacteria, Firmicutes, and Desulfobacterota, accounting for 85.4% of the total bacterial community. Taxonomic analysis showed a relatively low diversity of bacterial composition of the predominant genera across all WWTPs, indicating a high degree of bacterial community stability in the influent source. Pathogenic bacterial genera of human health concern included Mycobacterium, Coxiella, Escherichia/Shigella, Arcobacter, Acinetobacter, Streptococcus, Treponema, and Aeromonas. Furthermore, WHO-listed inherently resistant opportunistic bacterial genera were identified. These results suggest that WWTP workers may be occupationally exposed to several bacterial genera classified as hazardous biological agents for humans. Therefore, there is a need for comprehensive risk assessments to ascertain the actual risks and health outcomes among WWTP workers and inform effective intervention strategies to reduce worker exposure.

Prevalence and genetic diversity of Aeromonas veronii isolated from aquaculture systems in the Poyang Lake area, China

The area around Poyang Lake is the main aquaculture area in Jiangxi Province, China, and an important base for the supply of freshwater aquatic products. Aquaculture in the Poyang Lake area is severely threatened by diseases caused by bacterial pathogens, and Aeromonas veronii has been the main pathogen in recent years. In this paper, ERIC-PCR genotyping, virulence gene and antimicrobial resistance gene detection, and drug susceptibility tests were carried out on 46 A. veronii isolates obtained from aquaculture systems in the Poyang Lake area from 2016 to 2020. The results showed that the A. veronii strains in the Poyang Lake area had high genetic diversity, and 46 strains produced 36 ERIC genotypes. There were no geographical and temporal differences in the cluster analysis results and no dominant clones. All 13 virulence genes tested were detected, and all isolates had harbored 2 or more virulence genes, with a maximum of 12 virulence genes detected. Among the 22 antimicrobial resistance genes selected, 15 were detected; 97.8% of the isolates contained 2 or more antimicrobial resistance genes, with a maximum of 9 antimicrobial resistance genes. Drug susceptibility tests showed that some strains were resistant to a variety of traditionally effective drugs for Aeromomas, such as enrofloxacin and florfenicol. This study provides a reference for exploring the impact of aquaculture in the Poyang Lake area on public health.

Variations in Bacterial Communities and Antibiotic Resistance Genes Across Diverse Recycled and Surface Water Irrigation Sources in the Mid-Atlantic and Southwest United States: A CONSERVE Two-Year Field Study

Reduced availability of agricultural water has spurred increased interest in using recycled irrigation water for U.S. food crop production. However, there are significant knowledge gaps concerning the microbiological quality of these water sources. To address these gaps, we used 16S rRNA gene and metagenomic sequencing to characterize taxonomic and functional variations (e.g., antimicrobial resistance) in bacterial communities across diverse recycled and surface water irrigation sources. We collected 1 L water samples (n = 410) between 2016 and 2018 from the Mid-Atlantic (12 sites) and Southwest (10 sites) U.S. Samples were filtered, and DNA was extracted. The V3-V4 regions of the 16S rRNA gene were then PCR amplified and sequenced. Metagenomic sequencing was also performed to characterize antibiotic, metal, and biocide resistance genes. Bacterial alpha and beta diversities were significantly different (p < 0.001) across water types and seasons. Pathogenic bacteria, such as Salmonella enterica, Staphylococcus aureus, and Aeromonas hydrophilia were observed across sample types. The most common antibiotic resistance genes identified coded against macrolides/lincosamides/streptogramins, aminoglycosides, rifampin and elfamycins, and their read counts fluctuated across seasons. We also observed multi-metal and multi-biocide resistance across all water types. To our knowledge, this is the most comprehensive longitudinal study to date of U.S. recycled water and surface water used for irrigation. Our findings improve understanding of the potential differences in the risk of exposure to bacterial pathogens and antibiotic resistance genes originating from diverse irrigation water sources across seasons and U.S. regions.

Factors Driving Microbial Community Dynamics and Potential Health Effects of Bacterial Pathogen on Landscape Lakes with Reclaimed Water Replenishment in Beijing, PR China

Assessing the bacteria pathogens in the lakes with reclaimed water as major influents are important for public health. This study investigated microbial communities of five landscape lakes replenished by reclaimed water, then analyzed driven factors and identified health effects of bacterial pathogens. 16S rRNA gene sequence analysis demonstrated that Proteobacteria, Actinobacteria, Cyanobacteria, Firmicutes, and Verrucomicrobia were the most dominant phyla in five landscape lakes. The microbial community diversities were higher in June and July than that in other months. Temperature, total nitrogen and phosphorus were the main drivers of the dominant microbial from the Redundancy analysis (RDA) results. Various potential bacterial pathogens were identified, including Pseudomonas, GKS98_freshwater_group, Sporosarcina, Pseudochrobactrum, Streptomyces and Bacillus, etc, some of which are easily infectious to human. The microbial network analysis showed that some potential pathogens were nodes that had significant health effects. The work provides a basis for understanding the microbial community dynamics and safety issues for health effects in landscape lakes replenished by reclaimed water.

The effects of reclaimed water irrigation on the soil characteristics and microbial populations of plant rhizosphere

In this paper, the effects of irrigation with different water qualities on the soil characteristics of 8 kinds of garden plants were analyzed. The results showed that soil pH (ranging at 7.76-8.73) had no significant difference in different soils compared with the contrast treatment. Under the reclaimed water irrigation, the content of soil total salinity, chloride ions, and water soluble sodium in soil of most plants was averagely 160.3%, 83.3%, and 67.5% higher than that of tap water, respectively. The influences of reclaimed water irrigation on soil nutrients were changed with the types of plants. The content of soil organic matter and the available potassium showed no significant differences in most plants. Compared with the tap water irrigation, the content of alkaline nitrogen in 5 plants increased (averagely 25.8%) after 5-year irrigation with reclaimed water. In terms of soil microorganism, the increase of soil microbial population, including bacteria, fungus and actinomycetes, has been promoted by different levels of reclaimed water irrigation, which is closely related with soil nutrients.

Molecular Epidemiology, Virulence Traits and Antimicrobial Resistance Signatures of Aeromonas spp. in the Critically Endangered Iberochondrostoma lusitanicum Follow Geographical and Seasonal Patterns

Despite the fact that freshwater fish populations are experiencing severe declines worldwide, our knowledge on the interaction between endangered populations and pathogenic agents remains scarce. In this study, we investigated the prevalence and structure of Aeromonas communities isolated from the critically endangered Iberochondrostoma lusitanicum, a model species for threatened Iberian leuciscids, as well as health parameters in this species. Additionally, we evaluated the virulence profiles, antimicrobial resistance signatures and genomic relationships of the Aeromonas isolates. Lesion prevalence, extension and body condition were deeply affected by location and seasonality, with poorer performances in the dry season. Aeromonas composition shifted among seasons and was also different across river streams. The pathogenic potential of the isolates significantly increased during the dry season. Additionally, isolates displaying clinically relevant antimicrobial resistance phenotypes (carbapenem and fluroquinolone resistance) were detected. As it inhabits intermittent rivers, often reduced to disconnected pools during the summer, the dry season is a critical period for I. lusitanicum, with lower general health status and a higher potential of infection by Aeromonas spp. Habitat quality seems a determining factor on the sustainable development of this fish species. Also, these individuals act as reservoirs of important antimicrobial resistant bacteria with potential implications for public health.