Antibiotic and metal resistance among hospital and outdoor strains of Pseudomonas aeruginosa

Agricultural Soil as a Reservoir of Pseudomonas aeruginosa with Potential Risk to Public Health

Pseudomonas aeruginosa is an opportunistic pathogen with a high capacity to adapt to different factors. The aim of this study is to analyze the pathogenicity in P. aeruginosa strains and their resistance to heavy metals and antibiotics, in agricultural soil of the state of Tamaulipas, Mexico. Susceptibility to 16 antibiotics was tested using the Kirby-Bauer method (CLSI). Eight virulence factors (FV) and six genes associated with heavy metal resistance were detected by PCR. As a result, P. aeruginosa was detected in 55% of the samples. The eight virulence factors were identified in ≥80% of the strains. The strains showed some level of resistance to only three antibiotics: 32.8% to ticarcillin, 40.8% to ticarcillin/clavulanic acid and 2.4% to aztreonam. The most frequent heavy metal resistance genes were arsC (92.8%) and copA (90.4%). However, copB and arsB genes were also identified in a percentage greater than 80%, and the least frequent genes were merA in 14.4% and czcA in 7.2%. Although P. aeruginosa strains showed a high percentage of factor virulence (potential ability to cause infections), their high levels of susceptibility to antibiotics lead to the assumption that infections are easily curable.

Runoff microbiome quality assessment of a city center rainwater harvesting zone shows a differentiation of pathogen loads according to human mobility patterns

The hygienic quality of urban surfaces can be impaired by multiple sources of microbiological contaminants. These surfaces can trigger the development of multiple bacterial taxa and favor their spread during rain events through the circulation of runoff waters. These runoff waters are commonly directed toward sewer networks, stormwater infiltration systems or detention tanks prior a release into natural water ways. With water scarcity becoming a major worldwide issue, these runoffs are representing an alternative supply for some usage like street cleaning and plant watering. Microbiological hazards associated with these urban runoffs, and surveillance guidelines must be defined to favor these uses. Runoff microbiological quality from a recently implemented city center rainwater harvesting zone was evaluated through classical fecal indicator bacteria (FIB) assays, quantitative PCR and DNA meta-barcoding analyses. The incidence of socio-urbanistic patterns on the organization of these urban microbiomes were investigated. FIB and DNA from Human-specific Bacteroidales and pathogens such as Staphylococcus aureus were detected from most runoffs and showed broad distribution patterns. 16S rRNA DNA meta-barcoding profilings further identified core recurrent taxa of health concerns like Acinetobacter, Mycobacterium, Aeromonas and Pseudomonas, and divided these communities according to two main groups of socio-urbanistic patterns. One of these was highly impacted by heavy traffic, and showed recurrent correlation networks involving bacterial hydrocarbon degraders harboring significant virulence properties. The tpm-based meta-barcoding approach identified some of these taxa at the species level for more than 30 genera. Among these, recurrent pathogens were recorded such as P. aeruginosa, P. paraeruginosa, and Aeromonas caviae. P. aeruginosa and A. caviae tpm reads were found evenly distributed over the study site but those of P. paraeruginosa were higher among sub-catchments impacted by heavy traffic. Health risks associated with these runoff P. paraeruginosa emerging pathogens were high and associated with strong cytotoxicity on A549 lung cells. Recurrent detections of pathogens in runoff waters highlight the need of a microbiological surveillance prior allowing their use. Good microbiological quality can be obtained for certain typologies of sub-catchments with good hygienic practices but not all. A reorganization of Human mobility and behaviors would likely trigger changes in these bacterial diversity patterns and reduce the occurrences of the most hazardous groups.

Heavy Metals as Catalysts in the Evolution of Antimicrobial Resistance and the Mechanisms Underpinning Co-selection

The menace caused by antibiotic resistance in bacteria is acknowledged on a global scale. Concerns over the same are increasing because of the selection pressure exerted by a huge number of different antimicrobial agents, including heavy metals. Heavy metals are non-metabolizable and recalcitrant to degradation, therefore the bacteria can expel the pollutants out of the system and make it less harmful via different mechanisms. The selection of antibiotic-resistant bacteria may be influenced by heavy metals present in environmental reservoirs. Through co-resistance and cross-resistance processes, the presence of heavy metals in the environment can act as co-selecting agents, hence increasing resistance to both heavy metals and antibiotics. The horizontal gene transfer or mutation assists in the selection of mutant bacteria resistant to the polluted environment. Hence, bioremediation and biodegradation are sustainable methods for the natural clean-up of pollutants. This review sheds light on the occurrence of metal and antibiotic resistance in the environment via the co-resistance and cross-resistance mechanisms underpinning co-selection emphasizing the dearth of studies that specifically examine the method of co-selection in clinical settings. Furthermore, it is advised that future research incorporate both culture- and molecular-based methodologies to further our comprehension of the mechanisms underlying bacterial co- and cross-resistance to antibiotics and heavy metals.

Climate warming, environmental degradation and pollution as drivers of antibiotic resistance

Antibiotic resistance is a major challenge to public health, but human-caused environmental changes have not been widely recognized as its drivers. Here, we provide a comprehensive overview of the relationships between environmental degradation and antibiotic resistance, demonstrating that the former can potentially fuel the latter with significant public health outcomes. We describe that (i) global warming favors horizontal gene transfer, bacterial infections, the spread of drug-resistant pathogens due to water scarcity, and the release of resistance genes with wastewater; (ii) pesticide and metal pollution act as co-selectors of antibiotic resistance mechanisms; (iii) microplastics create conditions promoting and spreading antibiotic resistance and resistant bacteria; (iv) changes in land use, deforestation, and environmental pollution reduce microbial diversity, a natural barrier to antibiotic resistance spread. We argue that management of antibiotic resistance must integrate environmental goals, including mitigation of further increases in the Earth's surface temperature, better qualitative and quantitative protection of water resources, strengthening of sewage infrastructure and improving wastewater treatment, counteracting the microbial diversity loss, reduction of pesticide and metal emissions, and plastic use, and improving waste recycling. These actions should be accompanied by restricting antibiotic use only to clinically justified situations, developing novel treatments, and promoting prophylaxis. It is pivotal for health authorities and the medical community to adopt the protection of environmental quality as a part of public health measures, also in the context of antibiotic resistance management.

Patterns of antimicrobial resistance and metal tolerance in environmental Pseudomonas aeruginosa isolates and the genomic characterization of the rare O6/ST900 clone

Pseudomonas aeruginosa can harbor several virulence and antimicrobial resistance genes (ARGs). In this regard, virulent and multidrug-resistant (MDR) P. aeruginosa strains are closely related to severe infections. In addition, this species can also carry metal tolerance genes, selecting mainly antimicrobial-resistant strains. The action of several pollutants on the environment may favor the occurrence of antimicrobial-resistant and metal-tolerant strains. Therefore, the aim of this study was to characterize potentially pathogenic, antimicrobial-resistant, and/or metal-tolerant P. aeruginosa isolates from different environmental samples (waters, soils, sediments, or sands) and to perform a whole-genome sequence-based analysis of a rare clone from residual water. Environmental isolates carried virulence genes related to adherence, invasion, and toxin production, and 79% of the isolates harbored at least five virulence genes. In addition, the isolates were resistant to different antimicrobials, including important antipseudomonal agents, and 51% of them were classified as MDR, but only ARGs associated with aminoglycoside resistance were found. Furthermore, some isolates were tolerant mainly to copper, cadmium, and zinc, and presented metal tolerance genes related to these compounds. Whole-genome characterization of an isolate with unique phenotype with simultaneous resistance to antimicrobials and metals showed nonsynonymous mutations in different antimicrobial resistance determinants and revealed a classification of O6/ST900 clone as rare, potentially pathogenic, and predisposed to acquire multidrug resistance genes. Therefore, these results draw attention to the dissemination of potentially pathogenic, antimicrobial-resistant, and metal-tolerant P. aeruginosa isolates in environmental niches, alerting to a potential risk mainly to human health.

Detection of virulence, antimicrobial resistance, and heavy metal resistance properties in Vibrio anguillarum isolated from mullet (Mugil cephalus) cultured in Korea

In the present study, we identified and characterized 22 strains of V. anguillarum from 145 samples of mullets (Mugill cephallus) cultured in several fish farms in South Korea. They were subjected to pathogenicity tests, antimicrobial susceptibility test, and broth dilution test to detect virulence markers, antimicrobial resistance, and heavy metal resistance properties. All the isolates showed amylase and caseinase activity, followed by gelatinase (90.9%), DNase (45.5%), and hemolysis activities (α = 81.1% and β = 18.2%). The PCR assay revealed that isolates were positive for VAC, ctxAB, AtoxR, tdh, tlh, trh, Vfh, hupO, VPI, and FtoxR virulence genes at different percentages. All the isolates showed multi-drug resistance properties (MAR index ≥ 0.2), while 100% of the isolates were resistant to oxacillin, ticarcillin, streptomycin, and ciprofloxacin. Antimicrobial resistance genes, qnrS (95.5%), qnrB (86.4%), and StrAB (27.3%), were reported. In addition, 40.9% of the isolates were cadmium-tolerant, with the presence of CzcA (86.4%) heavy metal resistance gene. The results revealed potential pathogenicity associated with V. anguillarum in aquaculture and potential health risk associated with consumer health.

State of Knowledge on the Acquisition, Diversity, Interspecies Attribution and Spread of Antimicrobial Resistance between Humans, Animals and the Environment: A Systematic Review

Resistance to antibiotics is considered one of the most urgent global public health concerns. It has considerable impacts on health and the economy, being responsible for the failure to treat infectious diseases, higher morbidity and mortality rates, and rising health costs. In spite of the joint research efforts between different humans, animals and the environment, the key directions and dynamics of the spread of antimicrobial resistance (AMR) still remain unclear. The aim of this systematic review is to examine the current knowledge of AMR acquisition, diversity and the interspecies spread of disease between humans, animals and the environment. Using a systematic literature review, based on a One Health approach, we examined articles investigating AMR bacteria acquisition, diversity, and the interspecies spread between humans, animals and the environment. Water was the environmental sector most often represented. Samples were derived from 51 defined animal species and/or their products A large majority of studies investigated clinical samples of the human population. A large variety of 15 different bacteria genera in three phyla (Proteobacteria, Firmicutes and Actinobacteria) were investigated. The majority of the publications compared the prevalence of pheno- and/or genotypic antibiotic resistance within the different compartments. There is evidence for a certain host or compartment specificity, regarding the occurrence of ARGs/AMR bacteria. This could indicate the rather limited AMR spread between different compartments. Altogether, there remains a very fragmented and incomplete understanding of AMR acquisition, diversity, and the interspecies spread between humans, animals and the environment. Stringent One Health epidemiological study designs are necessary for elucidating the principal routes and dynamics of the spread of AMR bacteria between humans, animals and the environment. This knowledge is an important prerequisite to develop effective public health measures to tackle the alarming AMR situation.

Heavy Metal (Arsenic) Induced Antibiotic Resistance among Extended-Spectrum β-Lactamase (ESBL) Producing Bacteria of Nosocomial Origin

Antimicrobial resistance (AMR) is a leading cause of treatment failure for many infectious diseases worldwide. Improper overdosing and the misuse of antibiotics contributes significantly to the emergence of drug-resistant bacteria. The co-contamination of heavy metals and antibiotic compounds existing in the environment might also be involved in the spread of AMR. The current study was designed to test the efficacy of heavy metals (arsenic) induced AMR patterns in clinically isolated extended-spectrum β-lactamase (ESBL) producing bacteria. A total of 300 clinically isolated ESBL-producing bacteria were collected from a tertiary care hospital in Lahore, Pakistan, with the demographic characteristics of patients. After the collection of bacterial isolates, these were reinoculated on agar media for reidentification purposes. Direct antimicrobial sensitivity testing (AST) for bacterial isolates by disk diffusion methods was used to determine the AST patterns with and without heavy metal. The heavy metal was concentrated in dilutions of 1.25 g/mL. The collected bacterial isolates were isolated from wounds (n = 63, 21%), urine (n = 112, 37.3%), blood (n = 43, 14.3%), pus (n = 49, 16.3%), and aspirate (n = 33, 11%) samples. From the total 300 bacterial isolates, n = 172 were Escherichia coli (57.3%), 57 were Klebsiella spp. (19%), 32 were Pseudomonas aeruginosa (10.6%), 21 were Proteus mirabilis (7%) and 18 were Enterobacter spp. (6%). Most of the antibiotic drugs were found resistant to tested bacteria. Colistin and Polymyxin-B showed the highest sensitivity against all tested bacteria, but when tested with heavy metals, these antibiotics were also found to be significantly resistant. We found that heavy metals induced the resistance capability in bacterial isolates, which leads to higher AMR patterns as compared to without heavy metal tested isolates. The results of the current study explored the heavy metal as an inducer of AMR and may contribute to the formation and spread of AMR in settings that are contaminated with heavy metals.

Occurrence and dissemination of antibiotic resistance genes in mine soil ecosystems

Metal(loid) selection contributes to selection pressure on antibiotic resistance, but to our knowledge, evidence of the dissemination of antibiotic resistance genes (ARGs) induced by metal(loid)s in mine soil ecosystems is rare. In the current study, using a high-throughput sequencing (HTS)-based metagenomic approach, 819 ARG subtypes were identified in a mine soil ecosystem, indicating that these environmental habitats are important reservoirs of ARGs. The results showed that metal(loid)-induced coselection has an important role in the distribution of soil ARGs. Furthermore, metal(loid) selection-induced ARGs were mainly associated with resistance-nodulation-division (RND) antibiotic efflux, which is distinct from what is observed in agricultural soil ecosystems. By using independent genome binning, metal(loid)s were shown impose coselection pressure on multiple ARGs residing on mobile genetic elements (MGEs), which promotes the dissemination of the antibiotic resistome. Interestingly, the current results showed that the density of several MGEs conferring ARGs was considerably higher in organisms most closely related to the priority pathogens Pseudomonas aeruginosa and Escherichia coli. Together, the results of this study indicate that mine soil ecosystems are important reservoirs of ARGs and that metal(loid)-induced coselection plays critical roles in the dissemination of ARGs in this type of soil habitat. KEY POINTS: • Mining soil ecosystem is a reservoir of antibiotic resistance genes (ARGs). • ARGs distribute via bacterial resistance-nodulation-division efflux systems. • Metal(loid)s coselected ARGs residing on mobile genetic elements in P. aeruginosa and E. coli.

Pseudomonas fluorescens Complex and Its Intrinsic, Adaptive, and Acquired Antimicrobial Resistance Mechanisms in Pristine and Human-Impacted Sites

Pseudomonas spp. are ubiquitous microorganisms that exhibit intrinsic and acquired resistance to many antimicrobial agents. Pseudomonas aeruginosa is the most studied species of this genus due to its clinical importance. In contrast, the Pseudomonas fluorescens complex consists of environmental and, in some cases, pathogenic opportunistic microorganisms. The records of antimicrobial-resistant P. fluorescens are quite scattered, which hinders the recognition of patterns. This review compiles published data on antimicrobial resistance in species belonging to the P. fluorescens complex, which were identified through phylogenomic analyses. Additionally, we explored the occurrence of clinically relevant antimicrobial resistance genes in the genomes of the respective species available in the NCBI database. Isolates were organized into two categories: strains isolated from pristine sites and strains isolated from human-impacted or metal-polluted sites. Our review revealed that many reported resistant phenotypes in this complex might be related to intrinsic features, whereas some of them might be ascribed to adaptive mechanisms such as colistin resistance. Moreover, a few studies reported antimicrobial resistance genes (ARGs), mainly β-lactamases. In-silico analysis corroborated the low occurrence of transferable resistance mechanisms in this Pseudomonas complex. Both phenotypic and genotypic assays are necessary to gain insights into the evolutionary aspects of antimicrobial resistance in the P. fluorescens complex and the possible role of these ubiquitous species as reservoirs of clinically important and transmissible ARGs.

Antibiotic and Heavy Metal Susceptibility of Non-Cholera Vibrio Isolated from Marine Sponges and Sea Urchins: Could They Pose a Potential Risk to Public Health?

Vibrio is an important human and animal pathogen that can carry clinically relevant antibiotic resistance genes and is present in different aquatic environments. However, there is a knowledge gap between antibiotic and heavy metal resistance and virulence potential when it is part of the microbiota from marine invertebrates. Here, we aimed to evaluate these characteristics and the occurrence of mobile genetic elements. Of 25 non-cholera Vibrio spp. from marine sponges and sea urchins collected at the coastlines of Brazil and France analyzed in this study, 16 (64%) were non-susceptible to antibiotics, and two (8%) were multidrug-resistant. Beta-lactam resistance (blaSHV) and virulence (vhh) genes were detected in sponge-associated isolates. The resistance gene for copper and silver (cusB) was detected in one sea urchin isolate. Plasmids were found in 11 (44%) of the isolates. This new information allows a better comprehension of antibiotic resistance in aquatic environments, since those invertebrates host resistant Vibrio spp. Thus, Vibrio associated with marine animals may pose a potential risk to public health due to carrying these antibiotic-resistant genes.

Plasmid profiling of multiple antibiotic-resistant Pseudomonas aeruginosa isolated from soil of the industrial area in Chittagong, Bangladesh

Background

Multiple antibiotic-resistant (MAR) Pseudomonas aeruginosa (P. aeruginosa) plays a significant role in triggering nosocomial infection in clinical settings. While P. aeruginosa isolated from the environment is often regarded as non-pathogenic, the progressive development of antibiotic resistance necessitates exploring the MAR patterns and transposable genetic elements like plasmid in the isolates.

Results

Using ecfX gene-based PCR, 32 P. aeruginosa isolates among 48 soil samples collected from the industrial region have been confirmed. The antibiotic susceptibility pattern of those isolates revealed that 5 (15.63%) of them were resistant to a range of antibiotics, and they were categorized as MAR isolates. Nevertheless, all MAR isolates were found resistant to piperacillin and gentamicin, but none of them to ceftazidime, aztreonam, and ciprofloxacin. Moreover, the isolates were also showed resistance to amikacin (60%), tobramycin (80%), netilmicin (80%), imipenem (60%), doripenem (40%), meropenem (60%), and cefixime (40%). Furthermore, 60% of MAR isolates possessed double plasmids of 1000–2000 bp sizes which indicates the distribution of antibiotic resistance genes in MAR P. aeruginosa might be correlated with the presence of those plasmids. The MAR index’s high threshold values (> 0.20) implied that the isolates were from high-risk environmental sites where the presence of numerous antibiotic residues happened.

Conclusions

These findings highlighted the presence of multiple antibiotic resistance in P. aeruginosa of the industrial soil and a considerable prospect of transferring antibiotic resistance genes in the microbial community by plasmids. We recommend taking immediate stringent measures to prohibit the unnecessary and overuse of antibiotics in agricultural, industrial, or other purposes.

In vitro study to evaluate the antimicrobial activity of various multifunctional cosmetic ingredients and chlorphenesin on bacterial species at risk in the cosmetic industry

AIMS

We evaluated the activity of the preservative chlorphenesin and of four antimicrobial cosmetic multifunctional ingredients against various strains of gram-negative and gram-positive human opportunistic pathogens.

METHODS AND RESULTS

Growth kinetics, modelling growth parameters and statistical analyses enabled comparing bacterial behaviour in the presence and in the absence of the compound. Whatever compound tested (i.e. chlorphenesin, phenylpropanol, hexanediol, ethylhexylglycerin, hydroxyacetophenone) and strain origin (i.e. clinical versus industrial), the growth of 42 strains belonging to Acinetobacter spp., Burkholderia cepacia complex and Stenotrophomonas maltophilia, was totally inhibited. On the opposite all of the P. aeruginosa strains (n = 13) as well as 4 and 6 out of 10 strains of Pluralibacter gergoviae grew in the presence of chlorphenesin and ethylhexylglycerin, respectively. Some P. gergoviae and Staphylococcus hominis strains withstand hydroxyacetophenone. Within a species, the different strains show variable latency phase, growth rate (r) and carrying capacity (K). They can be similar, lower or higher than those measured in control conditions.

CONCLUSIONS

Data showed differences in the antimicrobial activity of compounds. Upon exposure, strains differed in their behaviour between and within species. Whatever species and strains, compound sensitivity could not be related to antibiotic resistance.

SIGNIFICANCE AND IMPACT OF THE STUDY

Most multifunctional ingredients showed significant antimicrobial properties against the wide panel of species and strains evaluated. This will help adjusting preservation strategies in the cosmetic industry.

The effect of Quorum sensing inhibitors on the evolution of CRISPR-based phage immunity in Pseudomonas aeruginosa

Quorum sensing controls the expression of a wide range of important traits in the opportunistic pathogen Pseudomonas aeruginosa, including the expression of virulence genes and its CRISPR-cas immune system, which protects from bacteriophage (phage) infection. This finding has led to the speculation that synthetic quorum sensing inhibitors could be used to limit the evolution of CRISPR immunity during phage therapy. Here we use experimental evolution to explore if and how a quorum sensing inhibitor influences the population and evolutionary dynamics of P. aeruginosa upon phage DMS3vir infection. We find that chemical inhibition of quorum sensing decreases phage adsorption rates due to downregulation of the Type IV pilus, which causes delayed lysis of bacterial cultures and favours the evolution of CRISPR immunity. Our data therefore suggest that inhibiting quorum sensing may reduce rather than improve the therapeutic efficacy of pilus-specific phage, and this is likely a general feature when phage receptors are positively regulated by quorum sensing.

Detection of Antimicrobial and Heavy-Metal Resistance Genes in Aeromonas spp. Isolated from Hard-Shelled Mussel (Mytilus Coruscus)

Hard-shelled mussel (Mytilus coruscus) is a popular seafood in South Korea because of its delicacy and high nutritional value. Our study aimed to identify antimicrobial and heavy-metal resistance determinants in Aeromonas isolates from marketed hard-shelled mussel in South Korea. A total of 33 Aeromonas species were isolated, and antimicrobial disk diffusion test was done to observe antimicrobial resistance patterns. In addition, broth microdilution test was performed to determine resistance to heavy-metals. PCR amplification was done to detect resistance genes. High resistance to amoxicillin (100.0%), ampicillin (93.9%), rifampicin (78.8%), and cephalothin (48.5%) was observed where least resistance to other antimicrobials was also detected. In addition, the isolates showed high resistance to cadmium (Cd) (57.6%), and 42.4% and 27.3% were resistant to chromium (Cr) and copper (Cu). The occurrence of antimicrobial resistance genes, such as blaTEM, blaSHV, blaCTX-M, tetB, tetE, and intI1 genes, was observed in 9 (27.3%), 8 (24.2%), 8 (24.2%), 6 (18.2%), 5 (15.2%), and 9 (27.3%) isolates, respectively. Also, heavy-metal resistance genes, czcA, copA, and merA were detected in 17 (51.5%), 11 (33.3%), and 7 (21.2%) of the isolates, respectively. The results suggest that mussels are a reservoir of multidrug and heavy-metal-resistant Aeromonas spp.

Spatio-temporal variations in chemical pollutants found among urban deposits match changes in thiopurine S-methyltransferase-harboring bacteria tracked by the tpm metabarcoding approach

The bTPMT (bacterial thiopurine S-methyltransferase), encoded by the tpm gene, can detoxify metalloid-containing oxyanions and xenobiotics. The hypothesis of significant relationships between tpm distribution patterns and chemical pollutants found in urban deposits was investigated. The tpm gene was found conserved among eight bacterial phyla with no sign of horizontal gene transfers but a predominance among gammaproteobacteria. A DNA metabarcoding approach was designed for tracking tpm-harboring bacteria among polluted urban deposits and sediments recovered for more than six years in a detention basin (DB). This DB recovers runoff waters and sediments from a zone of high commercial activities. The PCR products from DB samples led to more than 540,000 tpm reads after DADA2 or MOTHUR bio-informatic manipulations that were allocated to more than 88 and less than 634 sequence variants per sample. The tpm community patterns were significantly different between the recent urban deposits and those that had accumulated for more than 2 years in the DB, and between those of the DB surface and the DB settling pit. These groups of samples had distinct mixture of priority pollutants. Significant relationships between tpm ordination patterns, sediment accumulation time periods and location, and concentrations in PAH, chlorpyrifos, and 4-nonylphenols (NP) were observed. These correlations matched the higher occurrences of, among others, Aeromonas, Pseudomonas, and Xanthomonas tpm-harboring bacteria in recent urban DB deposits more contaminated with chrysene and alkylphenol ethoxylates. Highly significant drops in tpm reads allocated to Aeromonas species were recorded in the oldest DB sediments accumulating naphthalene and metallic pollutants. Degraders of urban pollutants such as P. aeruginosa and P. putida showed conserved distribution patterns over time but P. syringae phytopathogens were more abundant in the oldest sediments. TPMT-harboring bacteria can be used to assess the incidence of high risk priority pollutants on environmental systems.

River contamination shapes the microbiome and antibiotic resistance in sharpbelly (Hemiculter leucisculus)

Animals living in urban river systems play critical roles in the dissemination of microbiome and antibiotic resistance that poses a strong threat to public health. This study provides a comprehensive profile of microbiota and antibiotic resistance genes (ARGs) of sharpbelly (Hemiculter leucisculus) and the surrounding water from five sites along the Ba River. Results showed Proteobacteria, Firmicutes and Fusobacteria were the dominant bacteria in gut of H. leucisculus. With the aggravation of water pollution, bacterial biomass of fish gut significantly decreased and the proportion of Proteobacteria increased to become the most dominant phylum eventually. To quantify the contributions of influential factors on patterns of gut microbiome with structural equation model (SEM), water bacteria were confirmed to be the most stressors to perturb fish gut microbiome. SourceTracker model indicated that deteriorating living surroundings facilitated the invasion of water pathogens to fish gut eco-environments. Additionally, H. leucisculus gut is an important reservoir of ARGs in Ba River with relative abundance up to 9.86 × 10^-1/copies. Among the ARGs, tetracycline and quinolone resistance genes were detected in dominant abundance. Deterioration of external environments elicited the accumulation of ARGs in fish gut. Intestinal class I integron, environmental heavy metal residues and gut bacteria were identified as key drivers of intestinal ARGs profiles in H. leucisculus. Analysis of SEM and co-occurrence patterns between ARGs and bacterial hosts indicated that class I integron and bacterial community played vital roles in ARGs transmission through water-fish pathway. In general, this study highlighted hazards of water contamination to microbiome and ARGs in aquatic animals and provided a new perspective to better understand the bacteria and ARGs dissemination in urban river ecosystems.

Genomic insights into multidrug-resistant and hypervirulent Klebsiella pneumoniae co-harboring metal resistance genes in aquatic environments

Klebsiella pneumoniae is one of the most important pathogens related to hospital-acquired infections. The incidence of infections by hypervirulent K. pneumoniae (hvKp), especially community-acquired infections, has been increasing in recent decades. The occurrence of multidrug-resistant (MDR) hvKp has been increasingly reported worldwide decreasing the treatment options, which is a concern. Aquatic environments have been considered a reservoir of MDR pathogens, which contribute to the spread of MDR pathogens. Therefore, this study aimed to characterize MDR-hvKp strains obtained from public aquatic environments using whole genome sequencing in Brazil. Resistome analysis showed ARGs to β-lactams, quinolones, tetracyclines, sulfonamides, and fosfomycin as well as several metal resistance genes. Virulome analysis showed several virulence genes. Besides, genomic islands, CRISPR and prophage-related sequences were also detected. MLST analysis revealed the presence of two novel sequences types (STs) belonging to different clonal complexes (CCs) [ST4415 (CC515) and ST4416 (CC2654)], and one already described [ST661 (CC661)]. The presence of MDR-hvKp lineages in water sources belonging to STs and CCs associated with humans and animals shows the ability of these pathogens to spread to different aquatic environments. This study reports for the first time two novel STs of MDR-hvKp as well as the presence of a rare ST661 closely related to outbreaks in aquatic environments, and contributes to surveillance studies and MDR-hvKp monitoring worldwide.

Water as a Source of Antimicrobial Resistance and Healthcare-Associated Infections

Healthcare-associated infections (HAIs) are one of the most common patient complications, affecting 7% of patients in developed countries each year. The rise of antimicrobial resistant (AMR) bacteria has been identified as one of the biggest global health challenges, resulting in an estimated 23,000 deaths in the US annually. Environmental reservoirs for AMR bacteria such as bed rails, light switches and doorknobs have been identified in the past and addressed with infection prevention guidelines. However, water and water-related devices are often overlooked as potential sources of HAI outbreaks. This systematic review examines the role of water and water-related devices in the transmission of AMR bacteria responsible for HAIs, discussing common waterborne devices, pathogens, and surveillance strategies. AMR strains of previously described waterborne pathogens including Pseudomonas aeruginosa, Mycobacterium spp., and Legionella spp. were commonly isolated. However, methicillin-resistant Staphylococcus aureus and carbapenem-resistant Enterobacteriaceae that are not typically associated with water were also isolated. Biofilms were identified as a hot spot for the dissemination of genes responsible for survival functions. A limitation identified was a lack of consistency between environmental screening scope, isolation methodology, and antimicrobial resistance characterization. Broad universal environmental surveillance guidelines must be developed and adopted to monitor AMR pathogens, allowing prediction of future threats before waterborne infection outbreaks occur.

Synthesis, biological evaluation and model membrane studies on metal complexes containing aromatic N,O-chelate ligands

Novel lanthanide (Ln) compounds [Ln(L)₂]Cl^.xH₂O (Ln = La³⁺, Ce³⁺, Sm³⁺) containing aromatic N,O-chelate ligands [HL1 = 4-amino-2-(1H-benzimidazol-2-yl)phenol; HL2 = 5-amino-2-(1H-benzimidazol-2-yl)phenol] have been synthesized and structurally characterized by elemental analysis, NMR and IR spectroscopy, molar conductance measurements, and mass spectrometry (MS). The spectroscopic data suggested that the benzimidazolyl-phenol ligands act as N,O-chelate ligands through the iminic nitrogen and phenolic oxygen atoms. Elemental analysis indicated that lanthanide compounds were formed in a 1:2 stoichiometry (metal:ligand). In vitro biological evaluation was carried out using these complexes, exhibiting moderate cytotoxicity against six different human tumor cell lines (U251, human glioblastoma; HCT-15, colorectal carcinoma; MCF-7, breast epithelial adenocarcinoma; PC-3, prostate cancer; K562, myelogenous leukemia; SKLU-1, lung carcinoma) and lower toxicity against a non-cancerous cell line (COS-7, primate kidney). In addition, the antibacterial activity of the compounds was assessed against two gram-positive strains (Staphylococcus aureus ATCC 25923, Listeria monocytogenes ATCC 19115) and two gram-negative strains (Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27583) using the microdilution method. The results obtained show that the metal complexes exhibit higher biological activity than the free ligands, confirming a synergistic effect. Further benzimidazolyl-phenol derivatives were explored for the detection of bacteria using fluorescence imaging studies. Interestingly, the fluorescent properties of these compounds make them potential candidates to monitor the morphology of bacteria at different compound concentrations. Hence, the interaction of the ligand and complexes with model membranes mimicking those of bacteria was studied by using differential scanning calorimetry (DSC) and molecular dynamics (MD), showing that both compounds decreased the enthalpy of transition in two model membranes as the concentration of the compounds increased. In addition, the main transition temperature was slightly reduced as a result of these interactions.

Potential risks of antibiotic resistant bacteria and genes in bioremediation of petroleum hydrocarbon contaminated soils

Bioremediation represents a sustainable approach to remediating petroleum hydrocarbon contaminated soils. One aspect of sustainability includes the sourcing of nutrients used to stimulate hydrocarbon-degrading microbial populations. Organic nutrients such as animal manure and sewage sludge may be perceived as more sustainable than conventional inorganic fertilizers. However, organic nutrients often contain antibiotic residues and resistant bacteria (along with resistance genes and mobile genetic elements). This is further exacerbated since antibiotic resistant bacteria may become more abundant in contaminated soils due to co-selection pressures from pollutants such as metals and hydrocarbons. We review the issues surrounding bioremediation of petroleum-hydrocarbon contaminated soils, as an example, and consider the potential human-health risks from antibiotic resistant bacteria. While awareness is coming to light, the relationship between contaminated land and antibiotic resistance remains largely under-explored. The risk of horizontal gene transfer between soil microorganisms, commensal bacteria and/or human pathogens needs to be further elucidated, and the environmental triggers for gene transfer need to be better understood. Findings of antibiotic resistance from animal manures are emerging, but even fewer bioremediation studies using sewage sludge have made any reference to antibiotic resistance. Resistance mechanisms, including those to antibiotics, have been considered by some authors to be a positive trait associated with resilience in strains intended for bioremediation. Nevertheless, recognition of the potential risks associated with antibiotic resistant bacteria and genes in contaminated soils appears to be increasing and requires further investigation. Careful selection of bacterial candidates for bioremediation possessing minimal antibiotic resistance as well as pre-treatment of organic wastes to reduce selective pressures (e.g., antibiotic residues) are suggested to prevent environmental contamination with antibiotic-resistant bacteria and genes.

Characterization of an Environmental Multidrug-Resistant Acinetobacter seifertii and Comparative Genomic Analysis Reveals Co-occurrence of Antimicrobial Resistance and Metal Tolerance Determinants

Acinetobacter calcoaceticus-Acinetobacter baumannii complex is considered one of the main causes of hospital-acquired infections. Acinetobacter seifertii was recently characterized within this complex and it has been described as an emergent pathogen associated with bacteremia. The emergence of multidrug-resistant (MDR) bacteria, including Acinetobacter sp., is considered a global public health threat and an environmental problem because MDR bacteria have been spreading from several sources. Therefore, this study aimed to characterize an environmental MDR A. seifertii isolate (SAb133) using whole genome sequencing and a comparative genomic analysis was performed with A. seifertii strains recovered from various sources. The SAb133 isolate was obtained from soil of a corn crop field and presented high MICs for antimicrobials and metals. The comparative genomic analyses revealed ANI values higher than 95% of relatedness with other A. seifertii strains than A. calcoaceticus-A. baumannii complex. Resistome and virulome analyses were also performed and showed different antimicrobial resistance determinants and metal tolerance genes as well as virulence genes related to A. baumannii known virulence genes. In addition, genomic islands, IS elements, plasmids and prophage-related sequences were detected. Comparative genomic analysis showed that MDR A. seifertii SAb133 had a high amount of determinants related to antimicrobial resistance and tolerance to metals, besides the presence of virulence genes. To the best of our knowledge, this is the first report of a whole genome sequence of a MDR A. seifertii isolated from soil. Therefore, this study contributed to a better understanding of the genetic relationship among the few known A. seifertii strains worldwide distributed.

Antibiotic and heavy metal resistance genes in Aeromonas spp. isolated from marketed Manila Clam (Ruditapes philippinarum) in Korea

AIMS

Manila clam (Ruditapes philippinarum) is one of the most popular seafood in Korea, owing to their unique taste and nutritional value. This study aimed to disclose the antibiotic and heavy metal resistance characteristics of Aeromonas spp. isolated from marketed Manila clam in Korea.

METHODS AND RESULTS

A total of 36 Aeromonas spp. strains were isolated and subjected to two tests: an antibiotic disk diffusion test to determine their resistance to antibiotics, and a broth dilution test to determine their resistance to heavy metals. PCR-based amplification was performed to detect the resistance genes. A high level of resistance to ampicillin (100%) and cephalothin (89%) was observed, while 42, 39, 36 and 36% of the isolates were resistant to oxytetracycline, imipenem, nalidixic acid and tetracycline respectively. In addition, among the tested heavy metals, cadmium (Cd) recorded the highest resistance rate (61%), followed by chromium (Cr) (50%), lead (Pb) (47%) and copper (Cu) (37%). However, mercury (Hg) resistance was not observed. PCRs revealed the occurrence of bla_TEM , bla_SHV , bla_CTX-M , qnrS, tetB, tetE, aac(6')-Ib, strA-strB and intI1 genes among 100, 31, 31, 78, 78, 89, 25, 50 and 72% of the isolates respectively. Moreover, heavy metal resistance genes, copA, merA and czcA were detected in 25, 47 and 61% of the isolates respectively.

CONCLUSIONS

The results suggest the importance of multi-drug and heavy metal-resistant aeromonads in Manila clam to assess the consumer safety and public health.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study is the first to elaborate on the importance of multi-drug and heavy metal-resistant aeromonads in Manila clam. Particularly, the presence of extended-spectrum-β-lactamase genes and other antibiotic resistance genes intensifies the possible health risks and may complicate therapeutic treatments upon infection, while heavy metal resistance suggests possible heavy metal exposure.

Heavy metal resistance genes and plasmid-mediated quinolone resistance genes in Arthrobacter sp. isolated from Brazilian soils

Arthrobacter sp. are Gram-positive bacilli commonly obtained from soil and in the hospital environment. These species have been reported to cause several types of infection. Heavy metals are a threat to the ecological system due to their high-levels of toxicity and the fluoroquinolones are antimicrobials widely used for the treatment of different bacterial infections. The aim of this study was to investigate the resistance to fluoroquinolone and heavy metals, the presence of plasmid-mediated resistance (PMQR) genes and heavy metals resistance (HMR) genes and the presence of plasmids in Arthrobacter sp. obtained from Brazilian soils. Bacterial isolation was performed using soil samples from different Brazilian regions. The bacterial identification was performed by 16S rRNA gene sequencing. The resistance profile for fluoroquinolones and heavy metals was determined by MIC. Several PMQR and HMR genes and plasmid families were investigated by PCR. Eight isolates were obtained from soil samples from different cultivations and regions of Brazil. All isolates were resistant to all fluoroquinolones, cadmium, cobalt and zinc and the majority to copper. Among the PMQR genes, the qepA (4) was the most prevalent, followed by qnrS (3), qnrB (3), oqxB (2) and oqxA (1). Among the HMR genes, the copA was detected in all isolates and the czcA in two isolates. The replication origin of the ColE-like plasmid was detected in all isolates; however, no plasmid was detected by extraction. The association of resistance to heavy metals and antimicrobials is a threat to the environmental balance and to human health. There are no studies reporting the association of PMQR and HMR genes in bacteria belonging to the genus Arthrobacter. To the best of our knowledge, this is the first report of qnrB, qepA, oqxA and oqxB in Arthrobacter species.

Plasmids associated with heavy metal resistance and herbicide degradation potential in bacterial isolates obtained from two Brazilian regions

The use of pesticides has been increasing due to the great agricultural production worldwide. The pesticides are used to eradicate pests and weeds; however, these compounds are classified as toxic to non-target organisms. Atrazine and diuron are herbicides widely used to control grassy and broadleaf weeds and weed control in agricultural crops and non-crop areas. Heavy metals are also important environmental contaminants that affect the ecological system. This study aimed to investigate the presence of herbicides-degrading genes and heavy metal resistance genes in bacterial isolates from two different soil samples from two Brazilian regions and to determine the genetic location of these genes. In this study, two isolates were obtained and identified as Escherichia fergusonii and Bacillus sp. Both isolates presented atzA, atzB, atzC, atzD, atzE, atzF, puhA, and copA genes and two plasmids each, being the major with ~ 60 Kb and a smaller with ~ 3.2 Kb. Both isolates presented the atzA-F genes inside the larger plasmid, while the puhA and copA genes were detected in the smaller plasmid. Digestion reactions were performed and showed that the ~ 60-Kb plasmid presented the same restriction profile using different restriction enzymes, suggesting that this plasmid harboring the complete degradation pathway to atrazine was found in both isolates. These results suggest the dispersion of these plasmids and the multi-herbicide degradation potential in both isolates to atrazine and diuron, which are widely used in different culture types worldwide.

Cross-resistance is modular in bacteria-phage interactions

Phages shape the structure of natural bacterial communities and can be effective therapeutic agents. Bacterial resistance to phage infection, however, limits the usefulness of phage therapies and could destabilise community structures, especially if individual resistance mutations provide cross-resistance against multiple phages. We currently understand very little about the evolution of cross-resistance in bacteria–phage interactions. Here we show that the network structure of cross-resistance among spontaneous resistance mutants of Pseudomonas aeruginosa evolved against each of 27 phages is highly modular. The cross-resistance network contained both symmetric (reciprocal) and asymmetric (nonreciprocal) cross-resistance, forming two cross-resistance modules defined by high within- but low between-module cross-resistance. Mutations conferring cross-resistance within modules targeted either lipopolysaccharide or type IV pilus biosynthesis, suggesting that the modularity of cross-resistance was structured by distinct phage receptors. In contrast, between-module cross-resistance was provided by mutations affecting the alternative sigma factor, RpoN, which controls many lifestyle-associated functions, including motility, biofilm formation, and quorum sensing. Broader cross-resistance range was not associated with higher fitness costs or weaker resistance against the focal phage used to select resistance. However, mutations in rpoN, providing between-module cross-resistance, were associated with higher fitness costs than mutations associated with within-module cross-resistance, i.e., in genes encoding either lipopolysaccharide or type IV pilus biosynthesis. The observed structure of cross-resistance predicted both the frequency of resistance mutations and the ability of phage combinations to suppress bacterial growth. These findings suggest that the evolution of cross-resistance is common, is likely to play an important role in the dynamic structure of bacteria–phage communities, and could inform the design principles for phage therapy treatments.

Phage therapy is a promising alternative to antibiotics for treating bacterial infections. Yet as with antibiotics, bacteria readily evolve resistance to phage attack, including cross-resistance that protects against multiple phages at once and so limits the usefulness of phage cocktails. Here we show, using laboratory experimental evolution of resistance against 27 phages in P. aeruginosa, that cross-resistance is common and determines the ability of phage combinations to suppress bacterial growth. Using whole-genome sequencing, we show that cross-resistance is most common against multiple phages that use the same receptor but that global regulator mutations provide generalist resistance, probably by simultaneously affecting the expression of multiple different phage receptors. Future trials should test if these features of cross-resistance evolution translate to more complex in vivo environments and can therefore be exploited to design more effective phage therapies for the clinic.

Quantification of multi-antibiotic resistant opportunistic pathogenic bacteria in bioaerosols in and around a pharmaceutical wastewater treatment plant

Pharmaceutical wastewater treatment plants (WWTPs) are thought to be a "seedbed" and reservoirs for multi-antibiotic resistant pathogenic bacteria which can be transmitted to the air environment through aeration. We quantified airborne multi-antibiotic resistance in a full-scale plant to treat antibiotics-producing wastewater by collecting bioaerosol samples from December 2014 to July 2015. Gram-negative opportunistic pathogenic bacteria (GNOPB) were isolated, and antibiotic susceptibility tests against 18 commonly used antibiotics, including 11 β-lactam antibiotics, 3 aminoglycosides, 2 fluoroquinolones, 1 furan and 1 sulfonamide, were conducted. More than 45% of airborne bacteria isolated from the pharmaceutical WWTP were resistant to three or more antibiotics, and some opportunistic pathogenic strains were resistant to 16 antibiotics, whereas 45.3% and 50.3% of the strains isolated from residential community and municipal WWTP showed resistance to three or more antibiotics. The calculation of the multiple antibiotic resistance (MAR) index demonstrated that the air environment in the pharmaceutical WWTP was highly impacted by antibiotic resistance, while the residential community and municipal WWTP was less impacted by antibiotic resistance. In addition, we determined that the dominant genera of opportunistic pathogenic bacteria isolated from all bioaerosol samples were Acinetobacter, Alcaligenes, Citrobacter, Enterobacter, Escherichia, Klebsiella, Pantoea, Pseudomonas and Sphingomonas. Collectively, these results indicate the proliferations and spread of antibiotic resistance through bioaerosols in WWTP treating cephalosporin-producing wastewater, which imposed a potential health risk for the staff and residents in the neighborhood, calling for administrative measures to minimize the air-transmission hazard.

Resistance to Metals Used in Agricultural Production

Metals and metalloids have been used alongside antibiotics in livestock production for a long time. The potential and acute negative impact on the environment and human health of these livestock feed supplements has prompted lawmakers to ban or discourage the use of some or all of these supplements. This article provides an overview of current use in the European Union and the United States, detected metal resistance determinants, and the proteins and mechanisms responsible for conferring copper and zinc resistance in bacteria. A detailed description of the most common copper and zinc metal resistance determinants is given to illustrate not only the potential danger of coselecting antibiotic resistance genes but also the potential to generate bacterial strains with an increased potential to be pathogenic to humans. For example, the presence of a 20-gene copper pathogenicity island is highlighted since bacteria containing this gene cluster could be readily isolated from copper-fed pigs, and many pathogenic strains, including Escherichia coli O104:H4, contain this potential virulence factor, suggesting a potential link between copper supplements in livestock and the evolution of pathogens.

Complex migration of antibiotic resistance in natural aquatic environments

Antibiotic resistance is a worsening global concern, and the environmental behaviors and migration patterns of antibiotic resistance genes (ARGs) have attracted considerable interest. Understanding the long-range transport of ARG pollution is crucial. In this study, we characterized the dynamics of ARG changes after their release into aquatic environments and demonstrated the importance of traditional chemical contaminants in the transmission mechanisms of ARGs. We hypothesized that the main route of ARG proliferation switches from active transmission to passive transmission. This antibiotic-dominated switch is motivated and affected by non-corresponding contaminants. The effect of anthropogenic activities gradually weakens from inland aquatic environments to ocean environments; however, the effect of changes in environmental conditions is enhanced along this gradient. The insights discussed in this study will help to improve the understanding of the distribution and migration of ARG pollution in various aquatic environments, and provide a modern perspective to reveal the effect of corresponding contaminants and non-corresponding contaminants in the process of antibiotic resistance proliferation.

Antibiotic and metal resistance in a ST395 Pseudomonas aeruginosa environmental isolate: A genomics approach

We analyzed the resistome of Pseudomonas aeruginosa E67, an epiphytic isolate from a metal-contaminated estuary. The aim was to identify genetic determinants of resistance to antibiotics and metals, assessing possible co-selection mechanisms. Identification was based on phylogenetic analysis and average nucleotide identity value calculation. MLST affiliated E67 to ST395, previously described as a high-risk clone. Genome analysis allowed identifying genes probably involved in resistance to antibiotics (e.g. beta-lactams, aminoglycosides and chloramphenicol) and metals (e.g. mercury and copper), consistent with resistance phenotypes. Several genes associated with efflux systems, as well as genetic determinants contributing to gene motility, were identified. Pseudomonas aeruginosa E67 possesses an arsenal of resistance determinants, probably contributing to adaptation to a polluted ecosystem. Association to mobile structures highlights the role of these platforms in multi-drug resistance. Physical links between metal and antibiotic resistance genes were not identified, suggesting a predominance of cross-resistance associated with multidrug efflux pumps.

Co-selection of antibiotic and metal(loid) resistance in gram-negative epiphytic bacteria from contaminated salt marshes

The goal of this study was to investigate co-selection of antibiotic resistance in gram-negative epiphytic bacteria. Halimione portulacoides samples were collected from metal(loid)-contaminated and non-contaminated salt marshes. Bacterial isolates (n=137) affiliated with Vibrio, Pseudomonas, Shewanella, Comamonas, Aeromonas and with Enterobacteriaceae. Vibrio isolates were more frequent in control site while Pseudomonas was common in contaminated sites. Metal(loid) and antibiotic resistance phenotypes varied significantly according to site contamination, and multiresistance was more frequent in contaminated sites. However, differences among sites were not observed in terms of prevalence or diversity of acquired antibiotic resistance genes, integrons and plasmids. Gene merA, encoding mercury resistance, was only detected in isolates from contaminated sites, most of which were multiresistant to antibiotics. Results indicate that metal(loid) contamination selects for antibiotic resistance in plant surfaces. In salt marshes, antibiotic resistance may be subsequently transferred to other environmental compartments, such as estuarine water or animals, with potential human health risks.

Diversity of endophytic Pseudomonas in Halimione portulacoides from metal(loid)-polluted salt marshes

Phytoremediation assisted by bacteria is seen as a promising alternative to reduce metal contamination in the environment. The main goal of this study was to characterize endophytic Pseudomonas isolated from Halimione portulacoides, a metal-accumulator plant, in salt marshes contaminated with metal(loid)s. Phylogenetic analysis based on 16S rRNA and gyrB genes showed that isolates affiliated with P. sabulinigri (n = 16), P. koreensis (n = 10), P. simiae (n = 5), P. seleniipraecipitans (n = 2), P. guineae (n = 2), P. migulae (n = 1), P. fragi (n = 1), P. xanthomarina (n = 1), and Pseudomonas sp. (n = 1). Most of these species have never been described as endophytic. The majority of the isolates were resistant to three or more metal(loid)s. Antibiotic resistance was frequent among the isolates but most likely related to species-intrinsic features. Common acquired antibiotic resistance genes and integrons were not detected. Plasmids were detected in 43.6 % of the isolates. Isolates that affiliated with different species shared the same plasmid profile but attempts to transfer metal resistance to receptor strains were not successful. Phosphate solubilization and IAA production were the most prevalent plant growth promoting traits, and 20 % of the isolates showed activity against phytopathogenic bacteria. Most isolates produced four or more extracellular enzymes. Preliminary results showed that two selected isolates promote Arabidopsis thaliana root elongation. Results highlight the diversity of endophytic Pseudomonas in H. portulacoides from contaminated sites and their potential to assist phytoremediation by acting as plant growth promoters and as environmental detoxifiers.

Heavy metal resistance and virulence profile in Pseudomonas aeruginosa isolated from Brazilian soils

Pseudomonas aeruginosa is an opportunistic pathogen, which can have several virulence factors that confer on it the ability to cause severe, acute and chronic infections. Thus, the simultaneous occurrence of resistance to antibiotics and heavy metals associated with the presence of virulence genes is a potential threat to human health and environmental balance. This study aimed to investigate the resistance profile to heavy metals and the correlation of this phenotype of resistance to antimicrobials and to investigate the pathogenic potential of 46 P. aeruginosa isolates obtained from the soil of five Brazilian regions. The bacteria were evaluating for antimicrobial and heavy metal resistance, as well as the presence of plasmids and virulence genes. The isolates showed resistance to four different antibiotics and the majority (n = 44) had resistance to aztreonam or ticarcillin, furthermore, 32 isolates showed concomitant resistance to both of these antibiotics. A high prevalence of virulence genes was found, which highlights the pathogenic potential of the studied environmental isolates. Moreover, a high frequency of heavy metal resistance genes was also detected, however, the phenotypic results indicated that other genes and/or mechanisms should be related to heavy metal resistance.

Occurrence of Stenotrophomonas maltophilia in agricultural soils and antibiotic resistance properties

The occurrence of Stenotrophomonas maltophilia was monitored in organic amendments and agricultural soils from various sites in France and Tunisia. S. maltophilia was detected in horse and bovine manures, and its abundance ranged from 0.294 (±0.509) × 10(3) to 880 (±33.4) × 10(3) CFU (g drywt)(-1) of sample. S. maltophilia was recovered from most tested soil samples (104/124). Its abundance varied from 0.33 (±0.52) to 414 (±50) × 10(3) CFU (g drywt)(-1) of soil and was not related to soil characteristics. Antibiotic resistance properties of a set of environmental strains were compared to a clinical set, and revealed a high diversity of antibiotic resistance profiles, given both the numbers of resistance and the phenotypes. Manure strains showed resistance phenotypes, with most of the strains resisting between 7 and 9 antibiotics. While French soil strains were sensitive to most antibiotics tested, some Tunisian strains displayed resistance phenotypes close to those of clinical French strains. Screening for metal resistance among 66 soil strains showed a positive relationship between antibiotic and metal resistance. However, the prevalence of antibiotic resistance phenotypes in the studied sites was not related to the metal content in soil samples.

Virulence Attributes and Host Response Assays for Determining Pathogenic Potential of Pseudomonas Strains Used in Biotechnology

Pseudomonas species are opportunistically pathogenic to humans, yet closely related species are used in biotechnology applications. In order to screen for the pathogenic potential of strains considered for biotechnology applications, several Pseudomonas strains (P.aeruginosa (Pa), P.fluorescens (Pf), P.putida (Pp), P.stutzeri (Ps)) were compared using functional virulence and toxicity assays. Most Pa strains and Ps grew at temperatures between 28°C and 42°C. However, Pf and Pp strains were the most antibiotic resistant, with ciprofloxacin and colistin being the most effective of those tested. No strain was haemolytic on sheep blood agar. Almost all Pa, but not other test strains, produced a pyocyanin-like chromophore, and caused cytotoxicity towards cultured human HT29 cells. Murine endotracheal exposures indicated that the laboratory reference strain, PAO1, was most persistent in the lungs. Only Pa strains induced pro-inflammatory and inflammatory responses, as measured by elevated cytokines and pulmonary Gr-1 -positive cells. Serum amyloid A was elevated at ≥ 48 h post-exposure by only some Pa strains. No relationship was observed between strains and levels of peripheral leukocytes. The species designation or isolation source may not accurately reflect pathogenic potential, since the clinical strain Pa10752 was relatively nonvirulent, but the industrial strain Pa31480 showed comparable virulence to PAO1. Functional assays involving microbial growth, cytotoxicity and murine immunological responses may be most useful for identifying problematic Pseudomonas strains being considered for biotechnology applications.

Lack of dissemination of acquired resistance to β-lactams in small wild mammals around an isolated village in the Amazonian forest

In this study, we quantitatively evaluated the spread of resistance to β-lactams and of integrons in small rodents and marsupials living at various distances from a point of antibiotic's use. Rectal swabs from 114 animals were collected in Trois-Sauts, an isolated village in French Guiana, and along a 3 km transect heading through the non-anthropized primary forest. Prevalence of ticarcillin-resistant enterobacteria was 36% (41/114). Klebsiella spp., naturally resistant to ticarcillin, were found in 31.1% (23/73) of animals from the village and in an equal ratio of 31.7% (13/41) of animals trapped along the transect. By contrast Escherichia coli with acquired resistance to ticarcillin were found in 13.7% (10/73) of animals from the village and in only 2.4% (1/41) of those from the transect (600 m from the village). There was a huge diversity of E. coli and Klebsiella pneumoniae strains with very unique and infrequent sequence types. The overall prevalence of class 1 integrons carriage was 19.3% (22/114) homogenously distributed between animals from the village and the transect, which suggests a co-selection by a non-antibiotic environmental factor. Our results indicate that the anthropogenic acquired antibiotic resistance did not disseminate in the wild far from the point of selective pressure.

Pseudomonas aeruginosa and Achromobacter sp. clonal selection leads to successive waves of contamination of water in dental care units

Dental care unit waterlines (DCUWs) consist of complex networks of thin tubes that facilitate the formation of microbial biofilms. Due to the predilection toward a wet environment, strong adhesion, biofilm formation, and resistance to biocides, Pseudomonas aeruginosa, a major human opportunistic pathogen, is adapted to DCUW colonization. Other nonfermentative Gram-negative bacilli, such as members of the genus Achromobacter, are emerging pathogens found in water networks. We reported the 6.5-year dynamics of bacterial contamination of waterlines in a dental health care center with 61 dental care units (DCUs) connected to the same water supply system. The conditions allowed the selection and the emergence of clones of Achromobacter sp. and P. aeruginosa characterized by multilocus sequence typing, multiplex repetitive elements-based PCR, and restriction fragment length polymorphism in pulsed-field gel electrophoresis, biofilm formation, and antimicrobial susceptibility. One clone of P. aeruginosa and 2 clones of Achromobacter sp. colonized successively all of the DCUWs: the last colonization by P. aeruginosa ST309 led to the closing of the dental care center. Successive dominance of species and clones was linked to biocide treatments. Achromobacter strains were weak biofilm producers compared to P. aeruginosa ST309, but the coculture of P. aeruginosa and Achromobacter enhanced P. aeruginosa ST309 biofilm formation. Intraclonal genomic microevolution was observed in the isolates of P. aeruginosa ST309 collected chronologically and in Achromobacter sp. clone A. The contamination control was achieved by a complete reorganization of the dental health care center by removing the connecting tubes between DCUs.

Ellagic acid derivatives from Terminalia chebula Retz. increase the susceptibility of Pseudomonas aeruginosa to stress by inhibiting polyphosphate kinase

AIM

Polyphosphate kinase 1 (PPK1) plays an important role in virulence, antibiotic resistance and survival under stress conditions and, therefore, is an attractive therapeutic target to control infections caused by multiple drug resistant Pseudomonas aeruginosa. This study explores the PPK1 inhibiting activity of ellagic acid derivatives (EADs) from Terminalia chebula Retz. that could increase the susceptibility of Ps. aeruginosa to in vitro stress conditions.

METHODS AND RESULTS

EADs reduced ppk1 gene expression by 93% (P < 0·05) and completely inhibited its activity (P < 0·01) at 0·5 mg ml(-1) . EADs-treated Ps. aeruginosa showed marked reduction in polyphosphate granules in cytosol. Expression of rpoS, the downstream master stress response regulator, was reduced by 94% (P < 0·05) and the sensitivity of Ps. aeruginosa increased many fold to desiccation, oxidative (H2 O2 ) and antibiotic (piperacillin) stresses. PPK-regulated swimming, swarming and twitching motilities and biofilm formation were also reduced significantly (P ≤ 0·05) in MPAO1 and the clinical strains of Ps. aeruginosa.

CONCLUSION

EADs from T. chebula inhibited PPK1 expression and its activity and increased the sensitivity of Ps. aeruginosa to desiccation and oxidative stress while reducing tolerance to piperacillin.

SIGNIFICANCE AND IMPACT OF THE STUDY

The study underlines the potential of EADs as therapeutic agent against Ps. aeruginosa.

Occurrence of multi-antibiotic resistant Pseudomonas spp. in drinking water produced from karstic hydrosystems

Aquatic environments could play a role in the spread of antibiotic resistance genes by enabling antibiotic-resistant bacteria transferred through wastewater inputs to connect with autochthonous bacteria. Consequently, drinking water could be a potential pathway to humans and animals for antibiotic resistance genes. The aim of this study was to investigate occurrences of Escherichia coli and Pseudomonas spp. in drinking water produced from a karst, a vulnerable aquifer with frequent increases in water turbidity after rainfall events and run-offs. Water samples were collected throughout the system from the karstic springs to the drinking water tap during three non-turbid periods and two turbid events. E. coli densities in the springs were 10- to 1000-fold higher during the turbid events than during the non-turbid periods, indicating that, with increased turbidity, surface water had entered the karstic system and contaminated the spring water. However, no E. coli were isolated in the drinking water. In contrast, Pseudomonas spp. were isolated from the drinking water only during turbid events, while the densities in the springs were from 10- to 100-fold higher than in the non-turbid periods. All the 580 Pseudomonas spp. isolates obtained from the sampling periods were resistant (to between 1 and 10 antibiotics), with similar resistance patterns. Among all the Pseudomonas isolated throughout the drinking water production system, between 32% and 86% carried the major resistance pattern: ticarcillin, ticarcillin-clavulanic acid, cefsulodin, and/or aztreonam, and/or sulfamethoxazol-trimethoprim, and/or fosfomycin. Finally, 8 Pseudomonas spp. isolates, related to the Pseudomonas putida and Pseudomonas fluorescens species, were isolated from the drinking water. Thus, Pseudomonas could be involved in the dissemination of antibiotic resistance via drinking water during critical periods.

Aquatic environments polluted with antibiotics and heavy metals: a human health hazard

Aquatic environments often receive wastewater containing pollutants such as antibiotics and heavy metals from hospital sewage, as well as contaminants from soil. The presence of these pollutants can increase the rate of exchange of resistant genes between environmental and pathogenic bacteria, which can make the treatment of various types of bacterial infections in humans and animals difficult, in addition to causing environmental problems such as ecological risk. In this study, two tetracycline-resistant Pseudomonas aeruginosa (EW32 and EW33), isolated from aquatic environments close to industries and a hospital in southeastern Brazil, were investigated regarding the possible association between tetracycline and heavy metal resistance. The isolate EW32 presented a conjugative plasmid with coresistance to tetracycline and copper, reinforcing the concern that antibiotic resistance by acquisition of plasmids can be induced by the selective pressure of heavy metals in the environment.

Characterization of mercury-resistant clinical Aeromonas species

Mercury-resistant Aeromonas strains isolated from diarrhea were studied. Resistance occurs via mercuric ion reduction but merA and merR genes were only detected in some strains using PCR and dot hybridization. Results indicate a high variability in mer operons in Aeromonas. To our knowledge, this is the first report of mercury-resistant clinical Aeromonas strains.

High level of resistance to aztreonam and ticarcillin in Pseudomonas aeruginosa isolated from soil of different crops in Brazil

Pseudomonas aeruginosa can be found in water, soil, plants and, human and animal fecal samples. It is an important nosocomial pathogenic agent characterized by an intrinsic resistance to multiple antimicrobial agents and the ability to develop high-level (acquired) multidrug resistance through some mechanisms, among them, by the acquisition of plasmids and integrons, which are mobile genetic elements. In this study, 40 isolates from Brazilian soil were analyzed for antibiotic resistance, presence of integrons and plasmidial profile. The results demonstrated that the vast majority of the isolates have shown resistance for aztreonam (92.5%, n=37) and ticarcillin (85%, n=34), four isolates presented plasmids and eight isolates possess the class 1 integron. These results demonstrated that environmental isolates of P. aeruginosa possess surprising antibiotic resistance profile to aztreonam and ticarcillin, two antimicrobial agents for clinical treatment of cystic fibrosis patients and other infections occurred by P. aeruginosa.

Diversity among strains of Pseudomonas aeruginosa from manure and soil, evaluated by multiple locus variable number tandem repeat analysis and antibiotic resistance profiles

The results of a multiple locus variable number of tandem repeat (VNTR) analysis (MLVA)-based study designed to understand the genetic diversity of soil and manure-borne Pseudomonas aeruginosa isolates, and the relationship between these isolates and a set of clinical and environmental isolates, are hereby reported. Fifteen described VNTR markers were first selected, and 62 isolates recovered from agricultural and industrial soils in France and Burkina Faso, and from cattle and horse manure, along with 26 snake-related isolates and 17 environmental and clinical isolates from international collections, were genotyped. Following a comparison with previously published 9-marker MLVA schemes, an optimal 13-marker MLVA scheme (MLVA13-Lyon) was identified that was found to be the most efficient, as it showed high typability (90%) and high discriminatory power (0.987). A comparison of MLVA with PFGE for typing of the snake-related isolates confirmed the MLVA13-Lyon scheme to be a robust method for quickly discriminating and inferring genetic relatedness among environmental isolates. The 62 isolates displayed wide diversity, since 41 MLVA types (i.e. MTs) were observed, with 26 MTs clustered in 10 MLVA clonal complexes (MCs). Three and eight MCs were found among soil and manure isolates, respectively. Only one MC contained both soil and manure-borne isolates. No common MC was observed between soil and manure-borne isolates and the snake-related or environmental and clinical isolates. Antibiotic resistance profiles were performed to determine a potential link between resistance properties and the selective pressure that might be present in the various habitats. Except for four soil and manure isolates resistant to ticarcillin and ticarcillin/clavulanic acid and one isolate from a hydrocarbon-contaminated soil resistant to imipenem, all environmental isolates showed wild-type antibiotic profiles.

Antimicrobial efficacy of two surface barrier discharges with air plasma against in vitro biofilms

The treatment of infected wounds is one possible therapeutic aspect of plasma medicine. Chronic wounds are often associated with microbial biofilms which limit the efficacy of antiseptics. The present study investigates two different surface barrier discharges with air plasma to compare their efficacy against microbial biofilms with chlorhexidine digluconate solution (CHX) as representative of an important antibiofilm antiseptic. Pseudomonas aeruginosa SG81 and Staphylococcus epidermidis RP62A were cultivated on polycarbonate discs. The biofilms were treated for 30, 60, 150, 300 or 600 s with plasma or for 600 s with 0.1% CHX, respectively. After treatment, biofilms were dispensed by ultrasound and the antimicrobial effects were determined as difference in the number of the colony forming units by microbial culture. A high antimicrobial efficacy on biofilms of both plasma sources in comparison to CHX treatment was shown. The efficacy differs between the used strains and plasma sources. For illustration, the biofilms were examined under a scanning electron microscope before and after treatment. Additionally, cytotoxicity was determined by the MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay with L929 mouse fibroblast cell line. The cell toxicity of the used plasma limits its applicability on human tissue to maximally 150 s. The emitted UV irradiance was measured to estimate whether UV could limit the application on human tissue at the given parameters. It was found that the UV emission is negligibly low. In conclusion, the results support the assumption that air plasma could be an option for therapy of chronic wounds.