Antibiotic and heavy metal resistance in bacteria isolated from the Eastern Mediterranean Sea coast

Antibiotic resistance profile of facultative deep-sea psychro-piezophile bacteria from the Arabian Sea and their relation with physicochemical factors

Antibiotic resistance (ABR) is a significant global challenge, with antibiotics from various sources ending up in the ocean and affecting marine life. Profiling ABR in deep-sea bacteria is crucial for understanding the spread of ABR from environmental microbes to clinical pathogen and vice-versa. We evaluated facultative psychro-piezophile deep-sea bacteria from different depths of the Arabian Sea for their resistance to 20 commercial antibiotics. Bacteria from Zone 5 (2000-3000 m) exhibited the highest multiple antibiotic resistance (MAR) index (0.90), identifying it as a significant reservoir of ABR. Zone 1 (5-100 m) isolates (average 20 %) showed the highest resistance to synthetic antibiotics. Zone 3 (500-1000 m) isolates were highly resistant to diverse classes of antibiotics, separating upper (zone 1 and 2 (100-500 m) and deeper sea zones (zone 4 (1000-2000 m) and 5). The identified isolates belong to Bacillus, Niallia, Escherichia, Cytobacillus, and Pseudomonas genera. Additionally, antibiotic resistance genes (ARGs) such as StrB (2 isolates) and SXT integrase (1 isolate) were detected only in Zone 5 isolates. The SulII gene (19 isolates) was present across all zones. PCA analysis revealed a negative correlation between resistance and physicochemical factors (macronutrients like phosphate (PO43-), nitrate (NO3-), nitrite (NO2-), and ammonia (NH3); micronutrient and heavy metals like (iron (Fe), manganese (Mn), zinc (Zn), copper (Cu), nickel (Ni)), aluminium (Al), cadmium (Cd), and chromium (Cr)), except for Phosphate (0.65). Overall, this study is the first to provide valuable insights into the prevalence of ABR using culture-dependent methods and its correlation with physicochemical factors in the deep-sea environments of the Arabian Sea.

Integrated assessment of mucilage impact on human health using the One Health approach: Prevalence and antimicrobial resistance profiles of Escherichia coli and Clostridium perfringens in the Marmara Sea, Türkiye

This study employed a One Health approach to assess the potential impact of mucilage on human health by characterizing the prevalence and antimicrobial resistance (AMR) profiles of Escherichia coli and Clostridium perfringens strains isolated during the 2021 mucilage event in the Marmara Sea, Türkiye. Mucilage, a gelatinous organic substance exacerbated by climate change, disrupts marine ecosystems by depleting oxygen, threatening biodiversity, and serving as a reservoir for pathogenic microorganisms. Surface and benthic mucilage samples collected from the Marmara Sea were analysed for AMR profiles using genome analysis, the BD Phoenix™ 100 automated system, and E-test methods. The study identified 13 E. coli and one C. perfringens strain, harboring 244 and six AMR genes from 21 and eight drug classes, respectively, along with multiple virulence factors (VFs). The E. coli strains exhibited four distinct serotypes (O138:H28 [Mu-3], O18:H49 [Mu-4], O128:H12 [Mu-35] and O101:H10 [Mu-125]), reported for the first time from Türkiye and mucilage. Notably, anaerobic microorganisms like C. perfringens thrived in mucilage, underscoring their ecological significance. Seasonal and climatic factors influencing mucilage formation amplify its role in transmitting antimicrobial-resistant pathogens, posing significant risks to public and environmental health. The findings highlight the urgent need for continuous monitoring and mitigation strategies for mucilage-related hazards.

Assessment and characterization of heavy metals resistance bacteria isolated in Southwestern Mediterranean coastal waters (Bou-Ismail Bay): Impacts of anthropogenic activities

Bacteria present in the marine environment can cause ecological risks and seriously impact human health through direct contact or the food chain. This paper examines bacterial resistance to heavy metals and anthropogenic inputs' influence in four Bou-Ismail Bay regions (Algerian coast). The study was conducted from May to October 2018. High levels of resistance of total flora and total coliform were observed respectively for zinc (29.5 %, 30.5 %), copper (26.2 %, 20.7 %), mercury (17.4 %, 17.2 %), lead (16.9 %, 14.2 %), and cadmium (8.9 %, 0 %). A total 118 metal resistant bacteria were identified. All isolates were tested against 5 heavy metals and 7 antibiotics. The isolates showed tolerance to different concentrations of heavy metals ranging from 12.5 to 6400 μg/ml and exposed a co-resistance to the other heavy metals. The majority of strains were multi-resistant to heavy metals and antibiotics. Therefore, the bacteria isolated from Bou-Ismail Bay are highly resistant to heavy metals and antibiotics.

Multiple mechanisms collectively mediate tungsten homeostasis and resistance in Citrobacter sp. Lzp2

Tungsten (W) is an emerging contaminant, and current knowledge on W resistance profiles of microorganisms remains scarce and fragmentary. This study aimed to explore the physiological responses of bacteria under W stress and to resolve genes and metabolic pathways involved in W resistance using a transcriptome expression profiling assay. The results showed that the bacterium Citrobacter sp. Lzp2, screened from W-contaminated soil, could tolerate hundreds of mM W(VI) with a 50% inhibiting concentration of ∼110 mM. To cope with W stress, Citrobacter sp. Lzp2 secreted large amounts of proteins through the type VI secretory system (T6SS) to chelate W oxoanions via carboxylic groups in extracellular polymeric substances (EPS), and could transport cytosolic W outside via the multidrug efflux pumps (mdtABC and acrD). Intracellular W is probably bound by chaperone proteins and metal-binding pterin (tungstopterin) through the sulfur relay system. We propose that tetrathionate respiration is a new metabolic pathway for cellular W detoxification likely producing thio-tungstate. We conclude that multiple mechanisms collectively mediate W homeostasis and resistance in Citrobacter sp. Lzp2. Our results have important implications not only for understanding the intricate regulatory network of W homeostasis in microbes but also for bio-recovery and bioremediation of W in contaminated environments.

Anthropogenic impact and antibiotic resistance among the indicator and pathogenic bacteria from several industrial and sewage discharge points along the coast from Pydibhimavaram to Tuni, East Coast of India

Increasing urbanisation and industrialisation of the Visakhapatnam region have brought domestic sewage and industrial wastewater discharge into the coastal ocean. This study examines the indicator and pathogenic bacteria's quantitative abundance and antibiotic susceptibility. This study collected surface and subsurface water samples from ten different regions (147 stations; 294 samples), including 12 industrial discharge points, surrounding stations and two harbours from the coast of Pydibheemavaram to Tuni. Physicochemical parameters like salinity, temperature, fluorescence, pH, total suspended matter, nutrients, chlorophyll-a and dissolved oxygen showed a difference between regions. We noticed the presence of indicator (Escherichia coli and Enterococcus faecalis) and pathogenic (Aeromonas hydrophila, Klebsiella pneumoniae, Proteus mirabilis, Pseudomonas aeruginosa, Salmonella and Shigella, Vibrio cholera and Vibrio parahaemolyticus) bacteria among the samples. Waters from the near harbour and Visakhapatnam steel plant showed lower bacterial load with no direct input from industries to the coastal water. Samples collected during the industrial discharge period had a higher bacterial load, including E. coli. Enteric bacteria were found in higher numbers at most stations. Some isolates were resistant to multiple antibiotics with higher antibiotic resistance and multiple antibiotic resistance indexes compared with the other coastal water habitats in the Bay of Bengal. The occurrence of these bacteria above the standard limits and with multiple antibiotic resistance in the study region may pose a potential threat to the local inhabitants. It can create an alarming situation in the coastal waters in the study region.

Ecological risk assessment of heavy metals in the sediments and their impacts on bacterial community structure: A case study of Bamen Bay in China

Heavy metal pollution associated with human activity is of big concern in tropical bays. Microorganisms may be highly sensitive to heavy metals. Nonetheless, little is known about effects of heavy metals on microbial structure in tropical bay sediments. In this study, 16S rRNA gene sequencing and potential ecological risk index analysis were used to analyze the relationships between nine metals (arsenic, lead, cadmium, cobalt, chromium, copper, zinc, manganese, and nickel) and bacterial communities in the sediments of Bamen Bay, China. Our results showed that Bamen Bay was under a considerable ecological risk and cadmium had the highest monomial potential ecological risk. In addition, individual metal contamination correlated with bacterial community composition but not with bacterial α-diversity. Arsenic was the metal influencing bacterial community structure the most. Our findings provide a novel insight into the monitoring and remediation of heavy metal pollution in tropical bays.

The Emergence of Colistin- and Imipenem-Associated Multidrug Resistance in Escherichia coli Isolates from Retail Meat

To determine the prevalence of Escherichia coli and their drug resistance profiles in fresh pork sold at two retail outlets (open-air market and closed retail stores) in Alice, South Africa. Retail meat samples (n = 176) collected from four shops (two from open-air markets and two from closed stores) were analyzed by conventional biochemical and PCR-based molecular confirmatory tests. The confirmed isolates were profiled for antimicrobial susceptibility to a panel of 12 commercial antibiotics: tetracycline, ampicillin, sulphamethoxazole trimethoprim, erythromycin, gentamycin, colistin sulphate, cefotaxime, chloramphenicol, norfloxacin, ciprofloxacin, cefuroxime, and imipenem. Colistin, ampicillin, and erythromycin resistance genes were profiled with the gene-specific primers. Multidrug resistance (MDR) and the association of imipenem and colistin in the MDR profile were determined. A total of 68 (39.08%) E. coli isolates were confirmed by PCR analysis. Resistance was most common to erythromycin (100%), followed by cefotaxime (95.58%), ampicillin (88.23%), cefuroxime (88.23%), trimethoprim-sulphamethoxazole (88.23%), and tetracycline (60.29%). Overall, 27/68 (39.70%) were MDR (≥ 3antibiotics classes). MDR E. coli isolates associated with imipenem resistance (50.00%) and colistin resistance (33.82%) were detected. The resistance genes were detected among the isolates though not in all the phenotypically resistant isolates. The detection of colistin resistance among MDR E. coli isolates from retail meat is troubling as the drug is a last resort antibiotic. Overall, the epidemiological implications of the findings are of public health importance.

Ingestion of remediated lead-contaminated soils affects the fecal microbiome of mice

The relationship between ingestion of diets amended with a Pb-contaminated soil and the composition of the fecal microbiome was examined in a mouse model. Mice consumed diets amended with a Pb-contaminated soil in its native (untreated) state or after treatment for remediation with phosphoric acid or triple superphosphate alone or in combination with iron-waste material or biosolids compost. Subacute dietary exposure of mice receiving treated soil resulted in modulation of the fecal intestinal flora, which coincided with reduced relative Pb bioavailability in the bone, blood and kidney and differences in Pb speciation compared to untreated soil. Shifts in the relative abundance of several phyla including Verrucomicrobia, Tenericutes, Firmicutes, Proteobacteria, and TM7 (Candidatus Saccharibacteria) were observed. Because the phyla persist in the presence of Pb, it is probable that they are resistant to Pb. This may enable members of the phyla to bind and limit Pb uptake in the intestine. Families Ruminococcaceae, Lachnospiraceae, Erysipelotrichaceae, Verrucomicrobiaceae, Prevotellaceae, Lactobacilaceae, and Bacteroidaceae, which have been linked to health or disease, also were modulated. This study is the first to explore the relationship between the murine fecal microbiome and ingested Pb contaminated soils treated with different remediation options designed to reduce bioavailability. Identifying commonalities in the microbiome that are correlated with more positive health outcomes may serve as biomarkers to assist in the selection of remediation approaches that are more effective and pose less risk.

Biogeographic patterns of benthic microbial communities in metal(loid)-contaminated semi-enclosed bay

Anthropogenic activities can adversely impact biogeochemical processes essential for maintaining ecosystem health in semi-enclosed bays. However, the influence of anthropogenic contaminants such as potentially toxic elements on microbial communities that regulate biogeochemical cycles in semi-enclosed bays is poorly understood. We determined the concentrations of four potentially toxic elements (Cu, Zn, Pb, and As) in sediments from a typical tropical semi-enclosed bay in Guangdong, China. Source apportionment using Pearson's correlation analysis revealed that aquaculture activities were probably the primary source of Cu, Zn, and Pb. Using high-throughput sediment DNA sequencing, we found that Proteobacteria was the dominant phylum in sediments. There was no evidence suggesting site-specific variation in microbial function even though sediments adjacent to aquaculture discharge points had higher microbial diversity. In contrast, pollutant-specific variations were observed; for example, Zn and Pd showed potential adverse effects on the environmental information processing function, while As showed a negative correlation with metabolic function. Based on different environmental characteristics, future research should consider the impact of multiple factors on the bacterial community in aquaculture systems.

Heavy metal resistance of marine bacteria on the sediments of the Black Sea

The Black Sea is unfortunately globally established as a highly polluted sea, with contaminants from various sources polluting its marine sediments. This study aimed at analyzing heavy metal resistance levels by heterotrophic bacteria colonizing marine sediments across Black Sea shores within Turkey. Twenty-nine bacterial samples from marine sediments were investigated through exposure to sixteen heavy metal salts using the microdilution method. The minimum inhibitory concentration values for bacterial colonies within such marine sediment samples ranged from <0.97 mM/L to >1000 mM/L. Trough and peak minimum inhibitory concentration values were determined at <0.17 mg/mL and > 331 mg/mL. Peak tolerated and peak toxic heavy metals were identified as iron and cadmium, respectively. Resistance ratios were also obtained in this study. Bacillus wiedmannii was identified as the most resistant bacterial population when exposed to heavy metal salts. This study shows occurrence of heavy metal resistant bacteria within Black Sea sediments.

Analysis of antibiotic resistance genes reveals their important roles in influencing the community structure of ocean microbiome

Antibiotic resistance gene (ARG) content is a well-established driver of microbial abundance and diversity in an environment. By reanalyzing 132 metagenomic datasets from the Tara Oceans project, we aim to unveil the associations between environmental factors, the ocean microbial community structure and ARG contents. We first investigated the structural patterns of microbial communities including both prokaryotes such as bacteria and eukaryotes such as protists. Additionally, several ARG-dominant horizontal gene transfer events between Protist and Prokaryote have been identified, indicating the potential roles of ARG in shaping the ocean microbial communities. For a deeper insight into the role of ARGs in ocean microbial communities on a global scale, we identified 1926 unique types of ARGs and discovered that the ARGs are more abundant and diverse in the mesopelagic zone than other water layers, potentially caused by limited resources. Finally, we found that ARG-enriched genera were often more abundant compared to their ARG-less neighbors in the same environment (e.g. coastal oceans). A deeper understanding of the ARG-microbiome relationships could help in the conservation of the oceanic ecosystem.

The role of bacterial signaling networks in antibiotics response and resistance regulation

Excessive use of antibiotics poses a threat to public health and the environment. In ecosystems, such as the marine environment, antibiotic contamination has led to an increase in bacterial resistance. Therefore, the study of bacterial response to antibiotics and the regulation of resistance formation have become an important research field. Traditionally, the processes related to antibiotic responses and resistance regulation have mainly included the activation of efflux pumps, mutation of antibiotic targets, production of biofilms, and production of inactivated or passivation enzymes. In recent years, studies have shown that bacterial signaling networks can affect antibiotic responses and resistance regulation. Signaling systems mostly alter resistance by regulating biofilms, efflux pumps, and mobile genetic elements. Here we provide an overview of how bacterial intraspecific and interspecific signaling networks affect the response to environmental antibiotics. In doing so, this review provides theoretical support for inhibiting bacterial antibiotic resistance and alleviating health and ecological problems caused by antibiotic contamination.

The High Risk of Bivalve Farming in Coastal Areas With Heavy Metal Pollution and Antibiotic-Resistant Bacteria: A Chilean Perspective

Anthropogenic pollution has a huge impact on the water quality of marine ecosystems. Heavy metals and antibiotics are anthropogenic stressors that have a major effect on the health of the marine organisms. Although heavy metals are also associate with volcanic eruptions, wind erosion or evaporation, most of them come from industrial and urban waste. Such contamination, coupled to the use and subsequent misuse of antimicrobials in aquatic environments, is an important stress factor capable of affecting the marine communities in the ecosystem. Bivalves are important ecological components of the oceanic environments and can bioaccumulate pollutants during their feeding through water filtration, acting as environmental sentinels. However, heavy metals and antibiotics pollution can affect several of their physiologic and immunological processes, including their microbiome. In fact, heavy metals and antibiotics have the potential to select resistance genes in bacteria, including those that are part of the microbiota of bivalves, such as Vibrio spp. Worryingly, antibiotic-resistant phenotypes have been shown to be more tolerant to heavy metals, and vice versa, which probably occurs through co- and cross-resistance pathways. In this regard, a crucial role of heavy metal resistance genes in the spread of mobile element-mediated antibiotic resistance has been suggested. Thus, it might be expected that antibiotic resistance of Vibrio spp. associated with bivalves would be higher in contaminated environments. In this review, we focused on co-occurrence of heavy metal and antibiotic resistance in Vibrio spp. In addition, we explore the Chilean situation with respect to the contaminants described above, focusing on the main bivalves-producing region for human consumption, considering bivalves as potential vehicles of antibiotic resistance genes to humans through the ingestion of contaminated seafood.

Identification and Genome Analysis of an Arsenic-Metabolizing Strain of Citrobacter youngae IITK SM2 in Middle Indo-Gangetic Plain Groundwater

Whole-genome sequencing (WGS) data of a bacterial strain IITK SM2 isolated from an aquifer located in the middle Indo-Gangetic plain is reported here, along with its physiological, morphological, biochemical, and redox-transformation characteristics in the presence of dissolved arsenic (As). The aquifer exhibits oxidizing conditions relative to As speciation. Analyses based on 16S rRNA and recN sequences indicate that IITK SM2 was clustered with C. youngae NCTC 13708T and C. pasteuri NCTC UMH17T. However, WGS analyses using the digital DNA-DNA hybridization and Rapid Annotations using Subsystems Technology suggest that IITK SM2 belongs to a strain of C. youngae. This strain can effectively reduce As(V) to As(III) but cannot oxidize As(III) to As(V). It exhibited high resistance to As(V) [32,000 mg L-1] and As(III) [1,100 mg L-1], along with certain other heavy metals typically found in contaminated groundwater. WGS analysis also indicates the presence of As-metabolizing genes such as arsC, arsB, arsA, arsD, arsR, and arsH in this strain. Although these genes have been identified in several As(V)-reducers, the clustering of these genes in the forms of arsACBADR, arsCBRH, and an independent arsC gene has not been observed in any other Citrobacter species or other selected As(V)-reducing strains of Enterobacteriaceae family. Moreover, there were differences in the number of genes corresponding to membrane transporters, virulence and defense, motility, protein metabolism, phages, prophages, and transposable elements in IITK SM2 when compared to other strains. This genomic dataset will facilitate subsequent molecular and biochemical analyses of strain IITK SM2 to identify the reasons for high arsenic resistance in Citrobacter youngae and understand its role in As mobilization in middle Indo-Gangetic plain aquifers.

Occurrence of Antibiotic Resistance in the Mediterranean Sea

Seawater could be considered a reservoir of antibiotic-resistant bacteria and antibiotic resistance genes. In this communication, we evaluated the presence of bacterial strains in seawater collected from different coasts of Sicily by combining microbiological and molecular methods. Specifically, we isolated viable bacteria that were tested for their antibiotic resistance profile and detected both antibiotic and heavy metal resistance genes. Both antibiotic-resistant Gram-negative bacteria, Vibrio and Aeromonas, and specific antibiotic resistance genes were found in the seawater samples. Alarming levels of resistance were determined towards cefazolin, streptomycin, amoxicillin/clavulanic acid, ceftriaxone, and sulfamethoxazole/trimethoprim, and mainly genes conferring resistance to β-lactamic and sulfonamide antibiotics were detected. This survey, on the one hand, presents a picture of the actual situation, showing the pollution status of the Tyrrhenian coast of Sicily, and, on the other hand, can be considered as a baseline to be used as a reference time for future analysis.

Heavy metals in a typical city-river-reservoir system of East China: Multi-phase distribution, microbial response and ecological risk

The rapid construction of artificial reservoirs in metropolises has promoted the emergence of city-river-reservoir systems worldwide. This study investigated the environmental behaviors and risks of heavy metals in the aquatic environment of a typical system composed of main watersheds in Suzhou and Jinze Reservoir in Shanghai. Results shown that Mn, Zn and Cu were the dominant metals detected in multiple phases. Cd, Mn and Zn were mainly presented in exchangeable fraction and exhibited high bioavailability. Great proportion and high mobility of metals were found in suspended particulate matter (SPM), suggesting that SPM can greatly affect metal multi-phase distribution process. Spatially, city system (CiS) exhibited more serious metal pollution and higher ecological risk than river system (RiS) and reservoir system (ReS) owing to the diverse emission sources. CiS and ReS were regarded as critical pollution source and sink, respectively, while RiS was a vital transportation aisle. Microbial community in sediments exhibited evident spatial variation and obviously modified by exchangeable metals and nutrients. In particular, Bacteroidetes and Firmicutes presented significant positive correlations with most exchangeable metals. Risk assessment implied that As, Sb and Ni in water may pose potential carcinogenic risk to human health. Nevertheless, ReS was in a fairly safe state. Hg was the main risk contributor in SPM, while Cu, Zn, Ni and Sb showed moderate risk in sediments. Overall, Hg, Sb and CiS were screened out as priority metals and system, respectively. More attention should be paid to these priority issues to promote the sustainable development of the watershed.

Comparative proteomics and secretomics revealed virulence, and coresistance-related factors in non O1/O139 Vibrio cholerae recovered from 16 species of consumable aquatic animals

Vibrio cholerae can cause pandemic cholera in humans. The bacterium resides in aquatic environments worldwide. Identification of risk factors of V. cholerae in aquatic products is imperative for assuming food safety. In this study, we determined virulence-associated genes, cross-resistance between antibiotics and heavy metals, and genome fingerprinting profiles of non O1/O139 V. cholerae isolates (n = 20) recovered from 16 species of consumable aquatic animals. Secretomes and proteomes of V. cholerae with distinct genotypes and phenotypes were obtained by using two-dimensional gel electrophoresis (2D-GE) and/or liquid chromatography-tandem mass spectrometry (LC-MS/MS) techniques. Comparative secretomic analysis revealed 4 common and 45 differential extracellular proteins among 20 V. cholerae strains, including 13 virulence- and 8 resistance-associated proteins. A total of 21,972 intracellular proteins were identified, and comparative proteomic analysis revealed 215 common and 913 differential intracellular proteins, including 22 virulence- and 8 resistance-associated proteins. Additionally, different secretomes and proteomes were observed between V. cholerae isolates of fish and shellfish origins. A number of novel proteins with unknown function and strain-specific proteins were also discovered in the V. cholerae isolates. SIGNIFICANCE: V. cholerae can cause pandemic cholera in humans. The bacterium is distributed in aquatic environments worldwide. Identification of risk factors of V. cholerae in aquatic products is imperative for assuming food safety. Non-O1/O139 V. cholerae has been reported to cause sporadic cholera-like diarrhea and bacteremia diseases, which indicates virulence factors rather than the major cholera toxin (CT) exist. This study for the first time investigated proteomes and secretomes of non-O1/O139 V. cholerae originating from aquatic animals. This resulted in the identification of a number of virulence and coresistance-related factors, as well as novel proteins and strain-specific proteins in V. cholerae isolates recovered from 16 species of consumable aquatic animals. These results fill gaps for better understanding of pathogenesis and resistance of V. cholerae, and also support the increasing need for novel diagnosis and vaccine targets against the leading waterborne pathogen worldwide.

Antibiotic resistance development and human health risks during wastewater reuse and biosolids application in agriculture

The reuse of treated wastewater (TWW) and sewage sludge are considered as solutions to the limited water resource and sludge disposal issues, respectively. The associated environmental and human health risks need to be analyzed to assess whether they are safe solutions or not. This paper discusses issues that relate to the accumulation of antibiotics and antibiotic resistance (AR) determinants in agricultural lands and crops, following TWW irrigation and biosolid amendment. Exposure assessment and dose-response assessment are the two important aspects of risk assessment discussed in this paper. Finally, research gaps in current knowledge that are relevant to a comprehensive and quantitative AR risk assessment were identified which includes: 1.) Studies on soil conditions that increase the frequency of horizontal gene transfer (HGT) between native soil resistome and pathogenic microbes in biosolids and TWW 2.) Holistic studies that examine the accumulation or dissipation of antibiotics, antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) from the irrigation/biosolids application stage to crop consumption stage 3.) The influences of soil environmental conditions (e.g. salinity, nutrients) on the fate of ARB and ARGs in soil and translocation in edible plants 4.) The development of dose-response models that explicitly incorporate the potential for ARGs transfer between microbes when quantifying the risks of infection due to ARB.

Virulence, resistance, and genetic diversity of Vibrio parahaemolyticus recovered from commonly consumed aquatic products in Shanghai, China

Vibrio parahaemolyticus can cause severe gastroenteritis, septicaemia and even death in humans. Continuous monitoring of V. parahaemolyticus contamination in aquatic products is imperative for ensuring food safety. In this study, we isolated and characterized 561 V. parahaemolyticus strains recovered from 23 species of commonly consumed shellfish, crustaceans, and fish collected in July and August of 2017 in Shanghai, China. The bacterium was not isolated from two fish species Carassius auratus and Parabramis pekinensis. The results revealed a very low occurrence of pathogenic V. parahaemolyticus carrying the toxin genes trh (0.2%) and tdh (0.0%). However, high percentages of resistance to the antimicrobial agents ampicillin (93.0%), rifampin (82.9%), streptomycin (75.4%) and kanamycin (50.1%) were found. A high incidence of tolerance to the heavy metals Hg²⁺ (74.7%) and Zn²⁺ (56.2%) was also observed in the isolates. ERIC-PCR-based fingerprinting of MDR isolates (77.5%) revealed 428 ERIC-genotypes, demonstrating remarkable genetic variation among the isolates. The results of this study support the urgent need for food safety risk assessment of aquatic products.

Patterns of antimicrobial resistance observed in the Middle East: Environmental and health care retrospectives

Antimicrobial resistance is one of the biggest worldwide challenging problems that associates with high morbidity and mortality rates. The resistance of bacteria to various antibiotic classes results in difficulties in the treatment of infectious diseases caused by those bacteria. This paper highlights and provides a critical overview of observational and experimental studies investigating the presence of antibiotic resistant bacteria in different environments in Middle East countries and the mechanisms by which bacteria acquire and spread resistance. The data of this research considered the published papers within the last ten years (2010-2020) and was carried out using PubMed. A total of 66 articles were selected in this review. This review covered studies done on antibiotic resistant bacteria found in a wide range of environments including foods, animals, groundwater, aquatic environments as well as industrial and hospital wastewater. They acquire and achieve their resistance through several mechanisms such as antibiotic resistant genes, efflux pumps and enzymatic reactions. However, the dissemination and spread of antibiotic resistant bacteria is affected by several factors like anthropogenic, domestic, inappropriate use of antibiotics and the expulsion of wastewater containing antibiotic residues to the environments. Therefore, it is important to increase the awareness regarding these activities and their effect on the environment and eventually on health.

Structural Characterization of an Exopolysaccharide Isolated from Enterococcus faecalis, and Study on its Antioxidant Activity, and Cytotoxicity Against HeLa Cells

An exopolysaccharide (EPS-I) having the molecular weight ~ 2.6 × 10⁵ Da, was isolated from a Zinc resistant strain of Enterococcus faecalis from costal area. The exopolysaccharide consists of D-mannose, D-glucose, and L-fucose in molar ratio of 9:4:1. The monosaccharide units in the EPS-1 were determined through chemical (total acid hydrolysis and methylation analysis) and spectroscopic (FTIR and ¹H NMR experiment) analysis. The mannose-rich EPS-1 showed total antioxidant activity (1 mg mL^-1 of EPS-I as functional as approximately to 500 ± 5.2 µM of ascorbic acid) and Fe²⁺ metal ion chelation activity (EC₅₀ = 405.6 µg mL^-1) and hydroxyl radical scavenging activity (EC₅₀ = 219.5 µg mL^-1). The in vitro cytotoxicity experiment of EPS-I against cervical carcinoma cell line, HeLa cells showed strong cytotoxic effect (LC₅₀ = 267.3 µg mL^-1) and at that concentration, it found almost nontoxic against normal healthy cells (HEK-293).

Fluoroquinolone Resistance and Virulence Properties Among Wastewater Aeromonas caviae Isolates

The study provides data on antibiotic resistance as well as the virulence characteristics of Aeromonas caviae isolated from raw and treated wastewater. The isolates were identified as A. caviae by 16S rRNA gene sequencing. In the analyzed strains, high frequency for the following genes was observed: aac(6')-Ib-cr, qnrB, and qnrD. The presence of qnrA and ogxB genes was not found in any strain. The higher frequency of the investigated genes was observed in strains from raw wastewater (RW). The strains of A. caviae showed multiple antibiotic resistance evaluated by the disk diffusion method. Multiple antibiotic resistance indices ranged from 0.36 to 0.69. Susceptibility to six heavy metals (Cd⁺², Zn⁺², Cu⁺², Co⁺², Mn⁺², and Ni⁺²) was recorded for all the isolates. The order of metal resistance of A. caviae was Co > Cu > Zn > Cd > Ni > Mn. All the strains of A. caviae showed β-hemolytic activity. Enzymes of amylase, cellulase, and lipase were produced by all isolates. Only the strains from RW had the ability to form biofilms and showed motility. The obtained results indicate that wastewater is a potential source and/or reservoir of virulent and multidrug-resistant A. caviae as "high-risk isolates."

Advances in characterizing microbial community change and resistance upon exposure to lead contamination: Implications for ecological risk assessment

Recent advancement in molecular techniques has spurred waves of studies on responses of microorganisms to lead contamination exposure, leveraging detailed phylogenetic analyses and functional gene identification to discern the effects of lead toxicity on microbial communities. This work provides a comprehensive review of recent research on (1) microbial community changes in contaminated aquatic sediments and terrestrial soils; (2) lead resistance mechanisms; and (3) using lead resistance genes for lead biosensor development. Sufficient evidence in the literature, including both in vitro and in situ studies, indicates that exposure to lead contamination inhibits microbial activity resulting in reduced respiration, suppressed metabolism, and reduced biomass as well as altered microbial community structure. Even at sites where microbial communities do not vary compositionally with contamination levels due to extremely long periods of exposure, functional differences between microbial communities are evident, indicating that some microorganisms are susceptible to lead toxicity as others develop resistance mechanisms to survive in lead contaminated environments. The main mechanisms of lead resistance involve extracellular and intracellular biosorption, precipitation, complexation, and/or efflux pumps. These lead resistance mechanisms are associated with suites of genes responsible for specific lead resistance mechanisms and may serving as indicators of lead contamination in association with dominance of certain phyla. This allows for development of several lead biosensors in environmental biotechnology. To promote applications of these advanced understandings, molecular techniques, and lead biosensor technology, perspectives of future work on using microbial indicators for site ecological assessment is presented.

Virulence, antimicrobial and heavy metal tolerance, and genetic diversity of Vibrio cholerae recovered from commonly consumed freshwater fish

Vibrio cholerae is a leading waterborne pathogen worldwide. Continuous monitoring of V. cholerae contamination in aquatic products and identification of risk factors are crucial for assuring food safety. In this study, we determined the virulence, antimicrobial susceptibility, heavy metal tolerance, and genetic diversity of 400 V. cholerae isolates recovered from commonly consumed freshwater fish (Aristichthys nobilis, Carassius auratus, Ctenopharyngodon idellus, and Parabramis pekinensis) collected in July and August of 2017 in Shanghai, China. V. cholerae has not been previously detected in the half of these fish species. The results revealed an extremely low occurrence of pathogenic V. cholerae carrying the major virulence genes ctxAB (0.0%), tcpA (0.0%), ace (0.0%), and zot (0.0%). However, high incidence of virulence-associated genes was observed, including the RTX toxin gene cluster (rtxA-D) (83.0-97.0%), hlyA (87.8%), hapA (95.0%), and tlh (76.0%). Meanwhile, high percentages of resistance to antimicrobial agents streptomycin (65.3%), ampicillin (44.5%), and rifampicin (24.0%) were observed. Approximately 30.5% of the isolates displayed multidrug resistant (MDR) phenotypes with 42 resistance profiles, which were significantly different among the four fish species (MARI, P = 0.001). Additionally, tolerance of isolates to heavy metals Hg²⁺ (49.3%), Zn²⁺ (30.3%), and Pb²⁺ (12.0%) was observed. The enterobacterial repetitive intergenic consensus-polymerase chain reaction (ERIC-PCR)-based fingerprinting of the 400 V. cholerae isolates revealed 328 ERIC-genotypes, which demonstrated a large degree of genomic variation among the isolates. Overall, the results of this study support the need for food safety risk assessment of aquatic products.

Copper tolerance and antibiotic resistance in soil bacteria from olive tree agricultural fields routinely treated with copper compounds

BACKGROUND

Heavy metal pollution may act as persistent selective pressure that favors the spread of antimicrobial resistance in natural environments. The aim of this study was to isolate and identify metal-tolerant bacteria from soils in olive tree fields routinely treated with copper-derived compounds and to evaluate the tolerance of bacterial strains to other metals and their resistance to clinically relevant antibiotics.

RESULTS

Five hundred and ninety-five bacterial isolates from 45 olive tree agricultural fields were studied. Minimum inhibitory concentrations (MICs) ≥ 16 mmol L^-1 were detected for copper (57% of isolates), zinc (37%) and lead (62%), while only 3% had MICs ≥ 12 mmol L^-1 for nickel. Ninety-six metal-tolerant strains were selected for identification and antibiotic resistance determination. Most isolates belonged to the genera Pseudomonas (37%), Bacillus (23%) and Chryseobacterium (20%), while 6% were identified as Variovorax, 4% as Stenotrophomonas and 2% as Serratia or Burkholderia. Highest copper tolerance was detected among Pseudomonas. Over 75% of the strains with high copper tolerance were also resistant to vancomycin, 50% to ampicillin and 40% to erythromycin or trimethoprim/sulfamethoxazole.

CONCLUSION

Bacteria from olive soils are tolerant to metals, mainly copper, but also zinc and lead, as well as resistant to clinically important antibiotics, which could be a troublesome issue in clinical settings. © 2019 Society of Chemical Industry.

Integrative and Conjugative Elements-Positive Vibrio parahaemolyticus Isolated From Aquaculture Shrimp in Jiangsu, China

The development of multidrug- and toxin-resistant bacteria as a result of increasing industrialization and sustained and intense antimicrobial use in aquaculture results in human health problems through increased incidence of food-borne illnesses. Integrative and conjugative elements (ICEs) are self-transmissible mobile genetic elements that allow bacteria to acquire complex new traits through horizontal gene transfer and encode a wide variety of genetic information, including resistance to antibiotics and heavy metals; however, there is a lack of studies of ICEs of environmental origin in Asia. Here, we determined the prevalence, genotypes, heavy metal resistance and antimicrobial susceptibility of 997 presumptive strains of Vibrio parahaemolyticus (tlh⁺, tdh^–), a Gram-negative bacterium that causes gastrointestinal illness in humans, isolated from four species of aquaculture shrimp in Jiangsu, China. We found that 59 of the 997 isolates (5.9%) were ICE-positive, and of these, 9 isolates tested positive for all resistance genes. BLAST analysis showed that similarity for the eight strains to V. parahaemolyticus was 99%. Tracing the V. parahaemolyticus genotypes, showed no significant relevance of genotype among the antimicrobial resistance strains bearing the ICEs or not. Thus, in aquaculture, ICEs are not the major transmission mediators of resistance to antibiotics or heavy metals. We suggest future research to elucidate mechanisms that drive transmission of resistance determinants in V. parahaemolyticus.

Inherent bacterial community response to multiple heavy metals in sediment from river-lake systems in the Poyang Lake, China

Sediment is the one of most important storage of heavy metal. Microbiotas in sediment can be used as the effective indicators of heavy metals. The goal of this study was to understand the bacterial communities responding to heavy metal enrichment in sediments and prioritize some factors that affected significantly to bacterial community. Sediments were sampled from five river-lake systems in the Poyang Lake in dry season, and the bacterial community was analyzed using Illumina high-throughput sequencing. Relationships between sediment environment and the diversity and structure of bacterial communities were determined by correlation analysis and redundancy analysis (RDA). The result indicated that Cd and Sb were identified as the heavy metals of the great risk in sediments. Sediments from five river-lake systems shared 31.83% core operational taxonomic units (OTUs) of bacterial communities. Proteobacteria (33.54% of total sequences) and Actinobacteria (15.04%) were the dominant phyla across all sites. High enrichment of heavy metals (MRI and mC_d) resulted in low diversity of bacterial communities (Simpson index). The RDA revealed pH, OC, mCd, and Efs of As, Pb, Cd were major factors related to bacterial community structure changes. The dominant phylum Actinobacteria was regarded as tolerant bacteria, while the dominant phylum Proteobacteria was named as resistant bacteria in sediment with high anthropogenic Cd enrichment.

Mathematical model for the transport of fluoroquinolone and its resistant bacteria in aquatic environment

Development of antibiotic resistance in environmental bacteria is a direct threat to public health. Therefore, it becomes necessary to understand the fate and transport of antibiotic and its resistant bacteria. This paper presents a mathematical model for spatial and temporal transport of fluoroquinolone and its resistant bacteria in the aquatic environment of the river. The model includes state variables for organic matter, fluoroquinolone, heavy metals, and susceptible and resistant bacteria in the water column and sediment bed. Resistant gene is the factor which makes bacteria resistant to a particular antibiotic and is majorly carried on plasmids. Plasmid-mediated resistance genes are transferable between different bacterial species through conjugation (horizontal resistance transfer). This model includes plasmid dynamics between susceptible and resistant bacteria by considering the rate of horizontal resistance gene transfer among bacteria and the rate of losing resistance (segregation). The model describes processes which comprise of advection, dispersion, degradation, adsorption, diffusion, settling, resuspension, microbial growth, segregation, and transfer of resistance genes. The mathematical equations were solved by using numerical methods (implicit-explicit scheme) with appropriate boundary conditions. The development of the present model was motivated by the fact that the Musi River is heavily impacted by antibiotic pollution which led to the development of antibiotic resistance in its aquatic environment. The model was simulated for hypothetical pollution scenarios to predict the future conditions under various pollution management alternatives. The simulation results of the model for different cases show that the concentration of antibiotic, the concentration of organic matter, segregation rate, and horizontal transfer rate are the governing factors in the variation of population density of resistant bacteria. The treatment of effluents for antibiotics might be costly for the bulk drug manufacturing industries, but the guidelines can be made to reduce the organic matter which can limit the growth rate of microbes and reduce the total microbial population in the river. The reduction in antibiotic concentration can reduce the selection pressure on bacteria and can limit the population of resistant culture and its influence zone in the river stretch; however, complete removal of antibiotics may not result in complete elimination of antibiotic-resistant bacteria.

Bioremediation of Mercury by Vibrio fluvialis Screened from Industrial Effluents

Thirty-one mercury-resistant bacterial strains were isolated from the effluent discharge sites of the SIPCOT industrial area. Among them, only one strain (CASKS5) was selected for further investigation due to its high minimum inhibitory concentration of mercury and low antibiotic susceptibility. In accordance with 16S ribosomal RNA gene sequences, the strain CASKS5 was identified as Vibrio fluvialis. The mercury-removal capacity of V. fluvialis was analyzed at four different concentrations (100, 150, 200, and 250 μg/ml). Efficient bioremediation was observed at a level of 250 μg/ml with the removal of 60% of mercury ions. The interesting outcome of this study was that the strain V. fluvialis had a high bioremediation efficiency but had a low antibiotic resistance. Hence, V. fluvialis could be successfully used as a strain for the ecofriendly removal of mercury.

Diversity and Distribution of Heavy Metal-Resistant Bacteria in Polluted Sediments of the Araça Bay, São Sebastião (SP), and the Relationship Between Heavy Metals and Organic Matter Concentrations

Heavy metals influence the population size, diversity, and metabolic activity of bacteria. In turn, bacteria can develop heavy metal resistance mechanisms, and this can be used in bioremediation of contaminated areas. The purpose of the present study was to understand how heavy metals concentration influence on diversity and distribution of heavy metal-resistant bacteria in Araça Bay, São Sebastião, on the São Paulo coast of Brazil. The hypothesis is that activities that contribute for heavy metal disposal and the increase of metals concentrations in environment can influence in density, diversity, and distribution of heavy metal-resistant bacteria. Only 12 % of the isolated bacteria were sensitive to all of the metals tested. We observed that the highest percentage of resistant strains were in areas closest to the São Sebastião channel, where port activity occurs and have bigger heavy metals concentrations. Bacterial isolated were most resistant to Cr, followed by Zn, Cd, and Cu. Few strains resisted to Cd levels greater than 200 mg L(-1). In respect to Cr, 36 % of the strains were able to grow in the presence of as much as 3200 mg L(-1). Few strains were able to grow at concentrations of Zn and Cu as high as 1600 mg L(-1), and none grew at the highest concentration of 3200 mg L(-1). Bacillus sp. was most frequently isolated and may be the dominant genus in heavy metal-polluted areas. Staphylococcus sp., Planococcus maritimus, and Vibrio aginolyticus were also isolated, suggesting their potential in bioremediation of contaminated sites.

Virulence and Antibiotic and Heavy Metal Resistance of Vibrio parahaemolyticus Isolated from Crustaceans and Shellfish in Shanghai, China

Vibrio parahaemolyticus can cause serious human seafoodborne gastroenteritis and even death. In this study, we isolated and characterized 208 V. parahaemolyticus strains from 10 species of commonly consumed crustaceans and shellfish available in fish markets in Shanghai, People's Republic of China, in 2014. Most of these aquatic species had not been detected previously. The results revealed an extremely low occurrence of pathogenic V. parahaemolyticus carrying the toxin gene trh (1.9%). However, a high level of resistance to the antibiotics ampicillin (94.2%), rifampin (93.3%), and streptomycin (77.9%) was found. Approximately 74.5% of the isolates had multidrug-resistant phenotypes. Tolerance to the heavy metals Cu(2+), Pb(2+), and Cd(2+) was detected in the majority of antibiotic resistant isolates. The resistance patterns differed depending on the tested samples. The crustaceans Penaeus monodon and Marsupenaeus japonicus harbored more antibiotic-resistant bacteria, whereas the isolates from the crustacean Litopenaeus vannamei and the shellfish Busycon canaliculatus had high tolerance to eight heavy metals tested. In contrast to the wide distribution of multidrug resistance and tolerance to heavy metals, lower percentages of plasmid DNA (22.6%) and SXT/R391-like integrative and conjugative elements (4.8%) were detected in the isolates, suggesting that V. parahaemolyticus in these aquatic species may have adopted some other molecular mechanisms that mediated the high prevalence of resistance determinants. The results of this study support the need for food safety risk assessment of aquatic products.

Antibiotic and heavy-metal resistance of Vibrio parahaemolyticus isolated from fresh shrimps in Shanghai fish markets, China

Vibrio parahaemolyticus is a causative agent of human serious seafood-borne gastroenteritis disease and even death. Shrimps, often eaten raw or undercooked, are an important reservoir of the bacterium. In this study, we isolated and characterized a total of 400 V. parahaemolyticus strains from commonly consumed fresh shrimps (Litopenaeus vannamei, Macrobrachium rosenbergii, Penaeus monodon, and Exopalaemon carinicauda) in Shanghai fish markets, China in 2013-2014. The results revealed an extremely low occurrence of pathogenic V. parahaemolyticus carrying two major toxic genes (tdh and trh, 0.0 and 0.5 %). However, high incidences of antibiotic resistance were observed among the strains against ampicillin (99 %), streptomycin (45.25 %), rifampicin (38.25 %), and spectinomycin (25.50 %). Approximately 24 % of the strains derived from the P. monodon sample displayed multidrug resistant (MDR) phenotypes, followed by 19, 12, and 6 % from the E. carinicauda, L. vannamei, and M. rosenbergii samples, respectively. Moreover, tolerance to heavy metals of Cr(3+) and Zn(2+) was observed in 90 antibiotic resistant strains, the majority of which also displayed resistance to Cu(2+) (93.3 %), Pb(2+) (87.8 %), and Cd(2+)(73.3 %). The pulsed-field gel electrophoresis (PFGE)-based genotyping of these strains revealed a total of 71 distinct pulsotypes, demonstrating a large degree of genomic variation among the isolates. The wide distribution of MDR and heavy-metal resistance isolates in the PFGE clusters suggested the co-existence of a number of resistant determinants in V. parahaemolyticus population in the detected samples. This study provided data in support of aquatic animal health management and food safety risk assessment in aquaculture industry.

Detection and characterization of integrative and conjugative elements (ICEs)-positive Vibrio cholerae isolates from aquacultured shrimp and the environment in Shanghai, China

Increasing industrialization and use of antimicrobial agents in aquaculture production, have led to heavy metals and multidrug resistant (MDR) pathogens becoming serious problems. These resistances are conferred in two ways: intrinsic and transfer via conjugation, or transformation by the major transmission mediators. Integrative and conjugative elements (ICEs) are one of the major mediators; however, few studies on ICEs of environmental origin have been reported in Asia. Herein, we determined the prevalence, antimicrobial susceptibility, heavy metal resistance and genotypes of 126 strains of Vibrio cholerae isolated from aquatic products and the environment in Shanghai, China. 92.3% of isolates were ICEs-positive from aquaculture water and 89.3% of isolates from shrimp showed MDR. Tracing the V. cholerae genotypes, showed no significant relevance of genotype among the antimicrobial resistance strains bearing the ICEs or not. Thus, in aquaculture, ICEs are not the major transmission mediators of resistance to antibiotics or heavy metals.

Occurrence of antibiotic resistance genes in culturable bacteria isolated from Turkish trout farms and their local aquatic environment

Antibiotic resistance and presence of the resistance genes were investigated in the bacteria isolated from water, sediment, and fish in trout farms. A total of 9 bacterial species, particularly Escherichia coli, were isolated from the water and sediment samples, and 12 species were isolated from fish. The antimicrobial test indicated the highest resistance against sulfamethoxazole and ampicillin in coliform bacteria, and against sulfamethoxazole, imipenem, and aztreonam in known pathogenic bacteria isolated from fish. The most effective antibiotics were rifampicin, chloramphenicol, and tetracycline. The multiple antibiotic resistance index was above the critical limit for almost all of the bacteria isolated. The most common antibiotic resistance gene was ampC, followed by tetA, sul2, blaCTX-M1, and blaTEM in the coliform bacteria. At least one resistance gene was found in 70.8% of the bacteria, and 66.6% of the bacteria had 2 or more resistance genes. Approximately 36.54% of the bacteria that contain plasmids were able to transfer them to other bacteria. The plasmid-mediated transferable resistance genes were ampC, blaCTX-M1, tetA, sul2, and blaTEM. These results indicate that the aquatic environment could play an important role in the development of antibiotic resistance and the dissemination of resistance genes among bacteria.

Development and validation of an HPLC method for determination of Amikacin in water samples by solid phase extraction and pre-column derivatization

This work presents a rapid and sensitive high performance liquid chromatography method for the determination of amikacin in water samples with solid phase extraction and pre-column derivatization. Amikacin residue was extracted from water samples with solid phase extraction cartridge. Then the extraction solution was derivatized with 4-chloro-3,5-dinitrobenzotrifluoride in the presence of triethylamine at 70°C in 20 min. The amikacin derivative was separated on a C18 column and detected by application of UV detection at 238 nm. The limit of detection is 0.2 μg/L with a signal-to-noise ratio of 3 and linearity is established over the concentration range from 0 to 500.0 μg/L. Recoveries of the amikacin in three types of water samples are from 87.5 % to 99.6 % and RSDs are 2.1 %-4.5 %. This method can be used for the quantification of amikacin residues in water samples.

Simultaneous removal of cadmium and sulfamethoxazole from aqueous solution by rice straw biochar

The simultaneous sorption behavior and characteristics of cadmium (Cd) and sulfamethoxazole (SMX) on rice straw biochar were investigated. Isotherms of Cd and SMX were well modeled by the Langmuir equation (R(2)>0.95). The calculated maximum adsorption parameter (Q) of Cd was similar in single and binary systems (34129.69 and 35919.54 mg/kg, respectively). However, the Q of SMX in a binary system (9182.74 mg/kg) was much higher than that in a single system (1827.82 mg/kg). The presence of Cd significantly promoted the sorption of SMX on rice straw biochar. When the pH ranged from 3 to 7.5, the sorption of Cd had the characteristics of a parabola pattern with maximum adsorption at pH 5, while the adsorption quantity of SMX decreased with increasing pH, with maximum adsorption at pH 3. The amount of SMX adsorbed on biochar was positively correlated with the surface area of the biochar, and the maximum adsorption occurred with d 250 biochar (biochar with a diameter of 150-250 μm). Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) showed that the removal of Cd and SMX by rice straw biochar may be attributed to precipitation and the formation of surface complexes between Cd or SMX and carboxyl or hydroxyl groups. The results of this study indicate that rice straw biochar has the potential for simultaneous removal of Cd and SMX from co-contaminated water.