Inert Substrata Research Articles

Modulation of Quorum Sensing and Biofilms in Less Investigated Gram-Negative ESKAPE Pathogens.

Pathogenic bacteria have the ability to sense their versatile environment and adapt by behavioral changes both to the external reservoirs and the infected host, which, in response to microbial colonization, mobilizes equally sophisticated anti-infectious strategies. One of the most important adaptive processes is the ability of pathogenic bacteria to turn from the free, floating, or planktonic state to the adherent one and to develop biofilms on alive and inert substrata; this social lifestyle, based on very complex communication networks, namely, the quorum sensing (QS) and response system, confers them an increased phenotypic or behavioral resistance to different stress factors, including host defense mechanisms and antibiotics. As a consequence, biofilm infections can be difficult to diagnose and treat, requiring complex multidrug therapeutic regimens, which often fail to resolve the infection. One of the most promising avenues for discovering novel and efficient antibiofilm strategies is targeting individual cells and their QS mechanisms. A huge amount of data related to the inhibition of QS and biofilm formation in pathogenic bacteria have been obtained using the well-established gram-positive Staphylococcus aureus and gram-negative Pseudomonas aeruginosa models. The purpose of this paper was to revise the progress on the development of antibiofilm and anti-QS strategies in the less investigated gram-negative ESKAPE pathogens Klebsiella pneumoniae, Acinetobacter baumannii, and Enterobacter sp. and identify promising leads for the therapeutic management of these clinically significant and highly resistant opportunistic pathogens.

Chemical Composition, Antipathogenic and Cytotoxic Activity of the Essential Oil Extracted from Amorpha fruticosa Fruits.

The purpose of this paper was to characterize and investigate the antimicrobial potential of Amorpha fruticosa fruits essential oil (EO). The EO was extracted by hydrodistillation, analyzed by GC-MS, and then evaluated for its interaction with microbial and mammalian cells. The antimicrobial activity was assessed against bacterial and fungal strains, in a planktonic and adherent growth state, using qualitative and quantitative assays. The main components identified in A. fruticosa fruits EO were δ-cadinene, γ-muurolene, and α-muurolene. The Gram-positive strains proved to be more susceptible than Gram-negative bacteria and fungal strains. The EO exhibited good antibiofilm activity, inhibiting the microbial adherence to the inert (96-well plates and Foley catheter section) and cellular substrata. The flow cytometry analysis revealed as one of the possible mechanisms of antimicrobial action the alteration of cell membrane hydrophobicity. The cytotoxicity on the L929 cell line occurred at concentrations higher than 0.3 mg/mL. Taken together, our results demonstrate that A. fruticosa fruits EO contains active compounds with selective inhibitory effect on different microbial strains in planktonic and biofilm growth state, explained at least partially by the interference with microbial membranes due to their hydrophobic character.

Distribution of genus Jassa (Amphipoda, Ischyroceridae) in the Bay of Campeche, SW Gulf of Mexico, with a description of a new deepwater species

The genus Jassa includes 36 species distributed mainly in shallow waters as biofoulers on human-made structures or associated with living or inert soft bottom substrata worldwide. During the oceanographic cruise "2013-PEMEX Exploración y Produción, Regiones Marinas" in the southwestern Gulf of Mexico, several benthic amphipods of the genus Jassa were collected in sediments of both the continental shelf and the deep benthic sea. The present study examined the geographic and bathymetric distribution of Jassa in the Campeche Salt Basin, SW Gulf of Mexico, and described a new Jassa species collected below the isobath of 200 m. The species Jassa marmorata and Jassa morinoi were recorded mainly in front of the Usumacinta/Grijalva River Basin and Terminos Lagoon Delta, between 21 and 55 m depth. In contrast, the new species was recorded in the Bay of Campeche and the Campeche Canyon, below 450 m depth. For J. morinoi, it is the first register in the Gulf of Mexico. The new species increased the number of Jassa species documented worldwide to 37, and that of the deep-sea benthic amphipods from the Gulf of Mexico to 19 species.

Antimicrobial Activity of Olea europaea Fatty Oil against Multi-Drug Resistant and Biofilm Forming Microorganisms

The aim of the present study was to investigate the potential antimicrobial activity of Olea europaea fatty oil against a collection of bacterial (Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa) and fungal (Candida albicans) clinical isolates. The antimicrobial and antibiofilm activity were evaluated by broth microdilution method for establishing the minimal inhibitory concentration (MIC) and microtiter assay for determining the minimal biofilm eradication concentration (MBEC). Some of the potential microbial targets of the fatty oil were investigated by flow cytometry (FCM). The results obtained hereby revealed that Olea europaea fatty oil inhibited microbial planktonic growth (MICs values of 5.23-41.8 mg/ mL) and biofilm development on inert substrata (MBEC values of 1.31-20.9 mg/ mL). The FCM measurements confirmed that the analyzed oil induced microbial membrane damages and inhibited microbial efflux pump activity.

Short Communication: First report of Thalamoporella rozieri (Bryozoa: Thalamoporellidae) from Andaman waters with reference to its epibiotic colonization on marine sponges

Naufal M, Jayaraj KA. 2018. Short Communication: First report of Thalamoporella rozieri (Bryozoa: Thalamoporellidae) from Andaman waters with reference to its epibiotic colonization on marine sponges. Biodiversitas 19: 1521-1526. Bryozoans are aquatic, sessile, colonial, fouling invertebrates, which are found in most marine habitats. Considering the ecological and economic consequence due to the biofouling behavior of bryozoans, a far-reaching study has been carried out on it throughout the world. However, Andaman waters are lacking the bryozoan research for last nine decades. A study on the bryozoan distribution in the littoral region in the eastern coasts of the Andaman Islands was carried out during August 2016. This is the first study on the intertidal bryozoans of Andaman Islands and identified a new report of bryozoan Thalamoporella rozieri from Andaman and Nicobar Waters. Tuberosities in the present T. rozieri colonies are large. The minute calcareous spicules are also examined. Our study has also come across an interesting association in which the epibiont bryozoan T. rozieri adhere to the basibiont sponge Placospongia sp on a big rock. The colony of epizoic T. rozieri on the sponge was lengthier and continuous than on other inert host substrata. This may be because of active substrate selection by settling larvae. As both are filter feeders, no deleterious effect was noticed either in the basibiont side of Placospongia or in the epibiont side of T. rozieri.

Phenotypic, Biochemical and Genotypic Charcaterisation of Some Factors Involved in the Virulence and Survival of Bacteria Isolated from Food and Food Processing Surfaces

Species of the Enterobacteriaceae family are frequently involved in various gastrointestinal infectious diseases, including food poisoning that without proper treatment and medical supervision can be fatal for some patients, particularly for those with weak immune systems. Therefore we proposed to characterize the virulence factors of some strains from the Enterobacteriaceae family isolated from food and food processing surfaces at the phenotypic and genotypic level in order to assess the microbiological risk for the public health. The strains were identified using conventional biochemical methods. The expression of virulence soluble markers and the ability of the enterobacterial strains to adhere to the inert and cellular substrate were investigated. At the genetic level the presence of some genes involved in adhesion and virulence was also investigated by PCR. The tested strains revealed a different adherence capacity to the inert and cellular substrata and also ability to develop biofilms. Regarding enzymatic factors, esculin hydrolysis with the production of esculetin as an iron chelating agent and the casein hydrolysing protease were mostly expressed. The results proved that Enterobacteriaceae strains isolated from food could represent a microbiological risk factor for consumers� health, contributing also to the setting up of the reservoir virulence and resistance genes.

Adherence and Biofilm Formation in Candida albicans Strains Isolated from Different Infection Sites in Hospitalized Patients

Adherence of Candida albicans to the cellular and inert substratum contributes to its commensal status, but also plays an essential role in the development of fungal infections, particularly in hospitalized and immunodepressed patients. This study evaluated the adherence capacity and biofilm formation of 109 C. albicans strains isolated from upper respiratory tract secretions, wound secretions, urine culture, blood culture and stool culture taken from patients hospitalized for cardiovascular surgery. The strains were originally identified as C. albicans, based on their morphological characteristics and then confirmed by the Vitek II automatic system. All tested strains adhered to the cellular substratum, the isolates from stool culture, urine and thrush secretion exhibiting the most intensive adhesion capacity, the predominant adherence pattern being the aggregative one. Patient age and gender did not exhibit a significant influence on the adhesion process. The strains with the highest biofilm production capacity were the ones isolated from respiratory tract secretions and urine cultures. Statistically significant correlations could be established among a high number of yeast cells adhered to HeLa cells and i) the aggregative adherence pattern and ii) the moderate to high capacity to form biofilms on the inert substratum. These results could suggest the implication of common fungal structures in the colonization of inert and cellular substrata, while the elucidation of the molecular mechanisms involved in these processes could bring an important benefit to the appropriate management of fungal infections, depending on the isolation source.

Temperature effects on periphyton, epiphyton and epipelon under a nitrogen pulse in low-nutrient experimental freshwater lakes

The ongoing global climate change involves not only increased temperatures but may also produce more frequent extreme events, such as severe rainfall that could trigger a pulse of nutrients to lakes. In shallow lakes, this may affect primary producers through a number of direct and indirect mechanisms. We conducted a six-month mesocosm experiment to elucidate how periphyton (on inert substrata), epiphyton and epipelon biomass responded to a nitrogen (N) pulse, an approximately tenfold enrichment of the NO3-pool, under three contrasting warming scenarios: ambient temperature and ca. +3°C and ca. +4.5°C elevated temperatures (hereafter T1, T2 and T3). After the N pulse, we found a higher periphyton biomass at elevated than at ambient temperatures but no change in epiphyton biomass. Epipelon biomass was lower in T3 than in T1. Both periphyton and epiphyton biomasses correlated negatively with snail biomass, while epiphyton biomass correlated positively with light. Different responses to higher temperatures under short-term extreme nutrient loading conditions may be attributed to differences in the access to nutrient sources and light. Our data suggest that the biomass of periphyton in oligotrophic clear-water lakes will increase significantly under conditions exhibiting short-term extreme nutrient loading in a warmer climate.

Mussel-derived stimulation of benthic filamentous algae: The importance of nutrients and spatial scale

The reoccurrence of benthic filamentous algal (FA) blooms in the Great Lakes, without associated increases in phosphorus loading, has stimulated renewed interest in determining the causes of Great Lakes benthic algal blooms. We investigated the potential roles of invasive mussels and nutrient limitation with experimental substrata within inner Saginaw Bay. FA abundance on live mussel substrata was typically significantly greater than that on inert (empty shell or rock) substrata. Nutrient addition (from an artificial source) significantly increased FA abundance on inert substrata. These results suggest that: 1) mussel nutrient excretion could be a primary stimulatory mechanism; 2) mussel-mediated stimulation may be even stronger in other, more oligotrophic, Great Lakes nearshore zones; and 3) increased nutrient loading to inner Saginaw Bay may exacerbate existing FA blooms. FA abundance on inert substrata was not affected, even in close proximity to mussels, indicating that the observed stimulatory effect of mussel-derived P on live mussels attenuated at very small spatial scales, on the order of centimeters or less.

Effect of substrate on periphyton communities and relationships among food web components in shallow hypertrophic lake

We studied the role of natural (common reed) and artificial substrata (bamboo) in structuring the abundance and taxonomic composition of periphyton assemblages. Investigations were conducted in a shallow, hypertrophic lake situated in the area of Polesie Lubelskie (Eastern Poland). Periphyton communities (algae, ciliates, small metazoa and chironomids) on both types of substratum were sampled monthly, from May to November of 2007. Water samples for chemical analysis were collected together with biological samples. We selected the group of ten environmental variables which are the most important in determining the habitat conditions in highly eutrophic lakes: temperature, Secchi disc visibility, conductivity, dissolved oxygen, periphytic chlorophyll-a, N-NO3, N-NH4, TP, P-PO4 and total organic carbon (TOC). The abundances of periphytic algae, ciliates, metazoa and chironomids were significantly affected by season and substrate. On natural substrata, in all studied months, periphyton communities showed higher abundances. The results of PCA analysis confirmed the distinction between periphyton communities on natural and artificial substrata. The Monte Carlo permutation test showed that the periphyton communities on common reed were the most significantly affected by temperature, N-NO3, Secchi disc visibility and TOC. The communities on artificial substrata were significantly influenced by temperature, P-PO4 and TOC. On natural substrata biomass of periphytic algae was significantly negatively correlated with abundances of all groups of potential grazers (ciliates, metazoa, chironomids). On artificial substrata the relations between components of periphytic food web were stronger; correlation coefficients between algae, protists and chironomids were significant at P<0.01. The results of analysis indicate that periphytic algae can play an important role as food source for higher trophic levels. These interactions are less significant on natural (reed) substrata, where algae during their growth may use nutrients releasing by plants. On inert substrata intensive feeding activity of grazers (ciliates, metazoan, chironomids) can markedly reduce algal biomass and affect their taxonomic composition.

Effect of substrate on periphyton communities and relationships among food web components in shallow hypertrophic lake

We studied the role of natural (common reed) and artificial substrata (bamboo) in structuring the abundance and taxonomic composition of periphyton assemblages. Investigations were conducted in a shallow, hypertrophic lake situated in the area of Polesie Lubelskie (Eastern Poland). Periphyton communities (algae, ciliates, small metazoa and chironomids) on both types of substratum were sampled monthly, from May to November of 2007. Water samples for chemical analysis were collected together with biological samples. We selected the group of ten environmental variables which are the most important in determining the habitat conditions in highly eutrophic lakes: temperature, Secchi disc visibility, conductivity, dissolved oxygen, periphytic chlorophyll-a, N-NO3, N-NH4, TP, P-PO4 and total organic carbon (TOC). The abundances of periphytic algae, ciliates, metazoa and chironomids were significantly affected by season and substrate. On natural substrata, in all studied months, periphyton communities showed higher abundances. The results of PCA analysis confirmed the distinction between periphyton communities on natural and artificial substrata. The Monte Carlo permutation test showed that the periphyton communities on common reed were the most significantly affected by temperature, N-NO3, Secchi disc visibility and TOC. The communities on artificial substrata were significantly influenced by temperature, P-PO4 and TOC. On natural substrata biomass of periphytic algae was significantly negatively correlated with abundances of all groups of potential grazers (ciliates, metazoa, chironomids). On artificial substrata the relations between components of periphytic food web were stronger; correlation coefficients between algae, protists and chironomids were significant at P<0.01. The results of analysis indicate that periphytic algae can play an important role as food source for higher trophic levels. These interactions are less significant on natural (reed) substrata, where algae during their growth may use nutrients releasing by plants. On inert substrata intensive feeding activity of grazers (ciliates, metazoan, chironomids) can markedly reduce algal biomass and affect their taxonomic composition.

Studies on the antimicrobial activity of new compounds containing thiourea function

New 2-((4-methylphenoxy)methyl)-N-(arylcarbamothioyl)benzamides, prepared from 2-(4- methyl-phenoxymethyl)benzoyl chloride via isothiocyanate formation followed by treatment with various substituted amines, were tested for their antimicrobial features. Despite their weak antimicrobial activity, some of the tested derivatives inhibited the microbial biofilm development on the inert substrata, encouraging further studies of their potential application as anti-biofilm agents.

Interaction of bacteria isolated from clinical biofilms with cardiovascular prosthetic devices and eukaryotic cells

Purpose To identify the relationships between some infectious agents implicated in cardiovascular diseases with the cellular substrate and prosthetic devices in the presence of antibiotics. Specific objectives Strains isolation and identification, comparative study of antibiotic resistance of planktonic (disk diffusion, E-test, automatic systems) and sessile (using original experimental models for in vitro development of monospecific biofilms) bacterial cells, virulence assays (adherence and invasion of HeLa cells, slime test, soluble virulence factors expression), dynamic study of biofilm development on inert substrata, under the influence of antibiotics, the influence of cellular and soluble bacterial fractions on HeLa cells (by flow cytometry and real-time PCR). Results The identified strains were isolated from different sources, the etiology being dominated by Gram-negative non-fermentative bacilli, Gram-positive cocci and yeasts, harboring invasion enzymes responsible for development of systemic infections. The isolated strains exhibited a high level of antibiotic resistance to beta-lactams, aminoglycosides and quinolones, and an evident tendency of colonizing the cellular and inert substrate, the degree of colonization depending on the physico-chemical nature of the substrate. By comparison with planktonic ones, the sessile bacterial strains expressed a changed profile of antibiotic resistance, this aspect being very important for the readjustment of the treatment and prevention of infections associated with prosthetic devices. In vitro experiments suggested that different fractions of S. aureus cultures could trigger the release of proinflammatory (TNF-α, IL-1b, IL-6) and anti-inflammatory (IL-8) cytokines and induced apoptosis in HeLa cells.

Virulence factors of Staphylococcus aureus and Pseudomonas aeruginosa strains involved in the etiology of cardiovascular infections

The purpose of tihis study was to investigate by in vitro methods the capacity of adhesion and invasion to cellular and inert substrata, as well as the invasive properties of some Staphylococcus aureus and Pseudomonas aeruginosa strains isolated from various clinical specimens in patients with cardiovascular infections. Strains isolation and identification was performed using API galleries and the automatic Vitek II system. The selected strains have been phenotypically evaluated for the adherence to the cellular substrate represented by HeLa cells, adherence to the inert substrate quantified by slime test and a serios of soluble virulence factors (lechitinase, lipase, amylase, caseinase, gelatinase, DN-ase, haemolysins). The isolated strains exhibited an evident tendency of colonizing the cellular and inert substrate, also harboring enzymes with role in the invasion of host tissues and thus susceptible to produce systemic infections.

Quorum sensing in biofilms – How to destroy the bacterial citadels or their cohesion/power?

Biofilms or microbial communities formed by adherent and cohesive cells on cellular or inert substrata (like medical devices), are involved in ∼60% of all infections and characterized by moderate intensity symptoms, chronic evolution and resistance to antibiotics. Biofilms’ pathogenicity, even of those formed by opportunistic microorganisms, is amplified by two major biofilm characteristics: 1) the increased resistance to antimicrobials; 2) the protection of cells against the host’s defence mechanisms. The studies at the molecular level shown that the biofilms formation is controlled by cell-to-cell signalling mechanisms and the gene regulation during biofilm growth is due to the accumulation of signal molecules. In this regard, quorum sensing mechanism (QS) is defined as a cell-density dependent bacterial intercellular communication, involved in gene expression (e.g. virulence genes for exoenzymes, exopolysaccharides) and the consequent changed behaviour of biofilm’s cells, including the resistance to stress conditions; this resistance is different of well known antibioresistance, being named phenotypical resistance or tolerance. Considering the differences in physiology and susceptibility to antibiotics of biofilm embedded bacteria, as well as their increased power against the host defence responses, there are necessary new strategies for prevention and therapy of biofilm associated infections. The dental plaque is a typical example of biofilm, involved in the ethiology of cariogenesis and periodontal diseases associated with local chronic inflammation and cytokines production. The genetical and phenotypical versatility of the biofilm’s cells represent a challenge for discovering new methods of treatment and prevention of biofilm associated infections. A novel class of antibiofilm and antipathogenic therapeutics which are interfering with a new target – the QS pathway, not based on growth inhibition and called QS inhibitors, natural, with different origins or artificial, are now developing as an alternative to antibiotherapy.

Shortspine thornyhead and rockfish (Scorpaenidae) distribution in response to substratum, biogenic structures and trawling

Learmonth Bank in northern British Columbia sustains an active trawl fishery that returns large bycatches of deep-sea sponges and corals. To examine effects of biogenic structures on the distribution of fish, we examined nearly 30 km of high-definition imagery from a remotely oper- ated vehicle and documented locations of 2770 scorpaenid fish. The 2 local genera have similar abun- dances, averaging about 1.2 individuals 100 m -2 , but have different spatial abundance patterns: shortspine thornyhead Sebastolobus alascanus are randomly distributed on featureless substrata and their abundance increases with depth. Rockfish Sebastes spp. associate with higher seafloor relief nonrandomly and select for sponges and corals over the inert substrata alone; 95% of the rockfish occurred on 27% of the seafloor surveyed. Sponges (Demospongia and Hexactinellida) were abun- dant on the bedrock and boulders of the bank and adjacent moraine and covered 30 to 55% of the seafloor compared with 1% of the sediment and aggregates of the surrounding basin. The majority of rockfish (80%) occurred with sponges ≥50 cm in height, and even beds of short sponges attracted 4 times as many rockfish than did substrata with no large epifauna. While over half of primnoid corals over 30 cm tall had associated rockfish, less than 2% of the seafloor had large coral, and small coral had no associated rockfish. On the adjacent seafloor with past trawling activity, Primnoa pacifica was 13 times less abundant, and large corals and sponges were rare. Thornyhead abundance doubled but rockfish had a 3-fold reduction in numbers. Our study indicates that degradation of biogenic struc- tures is a long-term detriment to rockfish species and, although the mechanism remains unclear, our data suggest it occurs through the destruction of a habitat that is more effective for shelter than rough inert seafloor.

In vitro methods for the study of microbial biofilms

The emergence of microbial biofilm related infections (bacterial and fungal) has a significant impact for the human pathology in the entire world. The understanding of microbial infections related to the biofilm development on tissues or indwelling devices was possible by using different qualitative and quantitative in vitro assays, in continuous and discontinuous systems, as well as in vivo models. A necessary step for obtaining more standardized, reliable and comparable results among different laboratories is the simplification of the available techniques used for investigating the biofilm formation and properties, including the biofilms susceptibility to antibiotics. The aim of the present study was to exemplify a series of available methods for the investigation of in vitro microbial biofilms developed on inert substrata, as well as coated with ferrite nanoparticles, using as experimental model a Sacharomyces cerevisiae strain. Microbial biofilm architecture was directly examined by two microscopy techniques (inverted microscopy and confocal laser microscopy scanning). The in vitro study of the influence of suspended ferrite nanoparticles on planktonic cells growth, adherence and consecutive biofilm development on inert substrata was performed by using a simple microtiter method.

Antifungal activity of some vegetal extracts on Candida biofilms developed on inert substratum

Essential oils extracted from Citrus maxima (epicarp), Anethum graveolens (fruits) and Picea abies (leaves) were investigated for their ability to inhibit the growth and coordinated expression of virulence factors in Candida sp. strains recently isolated from clinical specimens, identified by using Vitek II automatic system and tested for susceptibility to antifungal drugs by E-test method. Plant materials were hydrodistiled in a Neo Clevenger type apparatus. Qualitative screening was performed using killing time curve and an adapted disk diffusion method. The microtiter method was used for establishing the influence of the essential oils on the microbial adherence to inert substrata. Subinhibitory concentrations of the tested essential oils were studied for their interference with the expression of soluble enzymatic virulence factors. All extracts exhibited an inhibitory activity of variable intensity on the microbial growth of planktonic as well as adherent strains, demonstrating the potential effect of the active compounds on the coordinated expression of virulence factors and consequently, on the initiation and progression of a fungal biofilm associated infection.

MICROLEVEL STUDY FOR THE ASSESSMENT OF THE ECONOMIC IMPACT OF RESISTANCE TO DISINFECTANTS USED IN THE HOSPITAL ENVIRONMENT AND EVALUATION OF NEW ALTERNATIVES

Introduction. The emergence of the antibiotic resistance and multi-resistance to antibiotics drives the acute necessity for the developing of new anti-infective strategies and the permanent changes of the disinfectants used in the hospital environment. The purpose of this study was to investigate by adapted disk diffusion techniques the antimicrobial potential of six (6) newly synthesized chemical compounds (derivatives from phenantroline and cooper complexe combinations with dimethylguanidine), 5 usual disinfectants (Oxigenon, Combi instruments, Virkon, Biguacid, Big spray) and 13 newly synthesized chemical compounds with potential disinfectant activity against 100 enterobacterial strains isolated from different surfaces in the hospital environment grown in planktonic and adherent form, in order to select the most appropriate alternative based on a good cost-effectiveness ratio. Methods: The initial qualitative screening of the antimicrobial activity was performed by disk diffusion and the minimal inhibitory concentration (MIC) of the active chemical compounds was established by Mueller Hinton broth microdillution method using 96-multiwell plates. The microbial strains were tested for their adherence capacity and biofilm developing potential on inert substrata (quantified by a simple method consisting in growing the microbial strains in 60-multiwell plates for 24 hours at 37 C degrees and the biofilms formed on the wall was fixed by methanol and stained by violet crystal and the intensity of color was quantified by measuring the absorbance at 490 nm by an ELISA reader). Results: The 100 enterobacterial strains isolated from surfaces in the hospital environment exhibited high resistance rates to cephuroxime (100%), cephtazidime (100%), ampicillin (98%), cefoxitin (98%), ticarcillin (62%), amoxicillin/ clavulanic acid (53%). 36% of these strains were confirmed for the production of ESBLs and 50% exhibited AMPc inducible beta-lactamases. All tested strains also exhibited high level resistance to tetracyclines (46-53%) and trimetoprim/sulphametoxazole. Concerning their susceptibility to usual disinfectants, the tested strains exhibited high resistance to Oxigenon and to Virkon and were susceptible to Biguacid, Big spray and Combi instruments, the last one being the most effective, active at low concentrations against all tested enterobacterial strains. Concerning the newly synthesized compounds, they exhibited a very low antimicrobial activity. The six derivatives from phenantroline and cooper complexe combinations with dimethylguanidine exhibited antimicrobial activity against the majority of the tested strains with MIC values ranging from 18 to 625 g/ml. The subinhibitory concentrations of the tested chemical compounds slightly inhibited the adherence capacity of the tested strains to the inert substratum. Conclusion. Our results are demonstrating that the increasing rates of resistance to antibiotics in enterobacterial strains are correlated with increasing rates of resistance to the disinfectants used in the hospital environment, as a results of adaptation of an existing resistance mechanism to multiple antimicrobial substrates. The phenantroline derivatives could represent a novel strategy for the antimicrobial treatment, besides the bactericidal effect, the subinhibitory concentrations of newly synthesized chemical compounds impairing the microbial adherence capacity to the inert substratum

Nature and role of newly described symbiotic associations between a sea anemone and gastropods at bathyal depths in the NW Atlantic

The hormathiid sea anemone Allantactis parasitica was found living as an epibiont on numerous species of gastropods at depths of 725–1100 m along the continental slope of eastern Canada. The proportion of bathyal gastropods hosting 1–6 sea anemones reached 72.5% in a single trawl. Although A. parasitica was occasionally found on other substrata (i.e. empty shells, pebbles), laboratory trials confirmed that they preferably associate with living gastropods. Settlement of planula larvae occurred significantly more often on the shells of live bathyal gastropods than on all other substrata present in the tanks. Juvenile sea anemones (∼ 1 mm diameter) readily moved from the mud or other inert substrata onto shells of burrowed bathyal gastropods. Conversely, larvae, juveniles and adults of A. parasitica never associated with any shallow-water gastropods when given the opportunity. Trials exposing predatory sea stars ( Leptasterias polaris) from shallow and bathyal depths to bathyal gastropods ( Buccinum undatum) with epibiotic A. parasitica, and to asymbiotic bathyal and shallow-water B. undatum, revealed adaptive behaviours in both prey and predator. Shallow-water gastropods (devoid of epibionts) reacted defensively to L. polaris, whereas bathyal gastropods relied mostly on their epibionts to protect them, thus falling prey to L. polaris when the epibionts were removed. L. polaris from bathyal depths typically ignored symbiotic gastropods, but they consistently preyed on asymbiotic ones, while L. polaris from shallow areas initially attempted to prey on all gastropods, but learned to avoid those harbouring sea anemones. Furthermore, living as epibionts afforded sea anemones a means to escape one of their own predators, the sea star Crossaster papposus. The mutualistic relationship between hormathiid sea anemones and bathyal gastropods from the NW Atlantic may have evolved in response to predation pressure.