Multifunctional polymeric guanidine and hydantoin halamines with broad biocidal activity.

Prolonged and excessive use of biocides during the coronavirus disease era calls for incorporating new antiviral polymers that enhance the surface design and functionality for existing and potential future pandemics. Herein, we investigated previously unexplored polyamines with nucleophilic biguanide, guanidine, and hydantoin groups that all can be halogenated leading to high contents of oxidizing halogen that enables enhancement of the biocidal activity. Primary amino groups can be used to attach poly(N-vinylguanidine) (PVG) and poly(allylamine-co-4-aminopyridine-co-5-(4-hydroxybenzylidene)hydantoin) (PAH) as well as a broad-spectrum commercial biocide poly(hexamethylene biguanide) (PHMB) onto a solid support. Halogenation of polymer suspensions was conducted through in situ generation of excess hypobromous acid (HBrO) from bromine and sodium hydroxide or by sodium hypochlorite in aqueous solutions, resulting in N-halamines with high contents of active > N-Br or > N-Cl groups. The virucidal activity of the polymers against human respiratory coronavirus HCoV-229E increased dramatically with their halogenation. Brominated PHMB-Br showed activation activity value > 5 even at 1 mg/L, and complete virus inhibition was observed with either PHMB-Br or PAH-Br at 10 mg/mL. Brominated PVG-Br and PAH-Br possessed fungicidal activity against C. albicans, while PHMB was fungistatic. PHMB, PHMB-Br and PAH polymers demonstrated excellent bactericidal activity against the methicillin-resistant S. aureus and vancomycin-resistant E. faecium. Brominated polymers (PHMB-Br, PVG-Br, PAH-Br) were not toxic to the HeLa monolayers, indicating acceptable biocompatibility to cultured human cells. With these features, the N-halamine polymers of the present study are a worthwhile addition to the arsenal of biocides and are promising candidates for development of non-leaching coatings.

Chlorhexidine residues in sludge from municipal wastewater treatment plants: analytical determination and toxicity evaluation.

In this work, a procedure for the sensitive and selective determination of chlorhexidine in sludge from municipal sewage treatment plants (STPs) based on matrix solid-phase dispersion (MSPD) and liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) was optimized and validated. Analysis of sewage sludge samples, obtained from different STPs in Northwest Spain from 2018 to 2021, showed that chlorhexidine was ubiquitous in this environmental compartment with concentrations between 0.3 and 16 µg g-1. The toxicity of this pollutant was assessed in in vitro assays considering three different model organisms: Candida albicans, Escherichia coli, and Staphylococcus aureus. C. albicans was the most sensitive of the tested microorganisms to chlorhexidine with a lethal threshold concentration of 0.1 mg L-1. Thus, the lowest observed sludge residue was 3 times higher than the acute toxicity threshold measured for C. albicans. Moreover, E. coli and S. aureus were also affected at chlorhexidine concentrations around 1.8 mg L-1 and 0.5 mg L-1, respectively. So, chlorhexidine residues might affect the population of microorganisms existing in STPs. In addition, the potential phytotoxicity of the compound was evaluated with germination experiments using different model seeds. At the evaluated dose (10 µg g-1 dried soil), chlorhexidine did not affect the germination of Sorghum saccharatum, Lepidium sativum, or Sinapis alba seeds. Thus, amending agriculture soils with chlorhexidine containing sludge is unlikely to affect the germination of plants.

Effect of Bivalent Vaccines against Vibrio anguillarum and Aeromonas salmonicida Subspecie achromogenes on Health and Survival of Turbot.

The efficacy of intraperitoneal injection of an oil-based bivalent autogenous vaccine and the commercial vaccine AlphaJect 3000 (Pharmaq AS) to prevent atypical furunculosis and vibriosis in turbot was analyzed. The effect of both vaccines on health parameters and survival of fish after challenge with V. anguillarum and A. salmonicida subsp. achromogenes was tested. The autogenous vaccine conferred high levels of protection and long-lasting immunity against both pathogens with a single dose. However, severe side effects were observed in turbot injected with this autovaccine and minor negative effects with the AlphaJect 3000 vaccine and the adjuvant Montanide or Eolane. All vaccinated fish showed remarkable antibody agglutination titers, higher than those of control fish, which were maintained 160 d after vaccination. In conclusion, the autogenous bivalent vaccine induces long-lasting protection against atypical furunculosis and vibriosis in turbot, after administration of a single dose, at the cost of high side effects in fish. Therefore, the development of new vaccines should focus on autovaccines and the use of liquid paraffin adjuvants that increase protection with reduced or no side effects.

Development of a real-time PCR assay for detection and quantification of Streptococcus iniae using the lactate permease gene.

The aim of this study is the development and evaluation of a rapid and accurate quantitative PCR (qPCR)-based protocol for detection of zoonotic pathogen Streptococcus iniae in bacterial cultures and tissues of diseased fish. For this purpose, the lactate permease-encoding (lldY) gene was selected as a target for the design of S. iniae-specific primers based on comparative genomic analysis using 45 sequences retrieved from NCBI genome database. Specificity and applicability of these primers were tested using 115 bacterial strains and fish tissues infected with S. iniae. Sensitivity, reproducibility and efficiency of qPCR assay were also determined. The developed qPCR assay showed 100% specificity with pure bacterial cultures or DNA extracted from S. iniae or tissues of fish infected with the bacterium. The method has high sensitivity with a detection limit of 1.12 × 101 amplicon copies per assay (equivalent to 2 × 10-9  ng/µl) using bacterial DNA and of 1.44 × 101 gene copies in tissues of fish infected with S. iniae. In conclusion, this qPCR protocol provides an accurate and sensitive alternative for the identification of S. iniae and its detection on fish tissues that can be implemented as a routine tool in microbiological laboratories.

Usefulness of matrix-assisted laser desorption ionization/time of flight mass spectrometry for the identification of Streptococcus mutans.

This study evaluated the reliability of MALDI-TOF MS coupled with statistical tools for the identification of Streptococcus mutans in comparison with PCR-based techniques. Bacterial isolates were identified and serotyped by conventional PCR, using S. mutans species and serotype-specific primers. For bacterial identification, mass spectra data from S. mutans and other streptococci were compared with Biotyper V 3.1 database and the mass peak lists were examined by cluster and principal component (PCA) analysis. Identification of potential biomarkers was performed using UniProtKB/Swiss-Prot and UniProtKB/TrEMBL databases and BLAST tool of the NCBI database. PCR identified 100% of the isolates as S. mutans. S. mutans strains were typed as serotypes c (85.6%), e (8.6%), k (4.8%), and f (0.9%). Although only the 70% of the strains tested were identified at species level by the Biotyper database, PCA and cluster analysis of mass peaks allowed the identification of 100% S. mutans isolates and its differentiation from the other oral and non-oral streptococci. One mass peak at m/z value of 9572.73 was identified as species-specific biomarker for S. mutans. No biomarkers were identified for S. mutans serotypes. KEY POINTS: • MALDI-TOF MS coupled with statistical tools for the identification of S. mutans. • Detection of species identifying biomarkers by MALDI-TOF MS. • PCR identification and serotyping of S. mutans from saliva samples.

Comparative genomics of Streptococcus parauberis: new target for molecular identification of serotype III.

This paper describes the predicted structure for the cps loci involved in capsule biosynthesis for Streptococcus parauberis serotypes III, IV, and V. Based on the specific serotype regions I, II, and III, a multiplex PCR protocol (mPCR) was designed to differentiate the main serotypes causing fish diseases. A real-time PCR method (qPCR) is also described to identify S. parauberis of serotype III in bacterial cultures and fish tissues. In silico and in vitro analyses revealed that both methods have a 100% specificity. The mPCR assay was optimized for the detection of S. parauberis strains of subtypes Ia (amplicon size 213 bp), subtypes Ib and Ic (both amplicon size 303 bp), serotype II (amplicon size 403 bp), and serotype III (amplicon size 130 bp) from bacterial cultures. The qPCR assay was optimized for the identification and quantification of S. parauberis serotype III strains in bacterial cultures and fish tissues. This assay achieved a sensitivity of 2.67 × 102 gene copies (equivalent to 3.8 × 10-9 ng/µl) using pure bacterial cultures of S. parauberis serotype III and 1.76 × 102 gene copies in fish tissues experimentally and naturally infected with S. parauberis of the serotype III. The specificity and sensitivity of the protocols described in this study suggest that these methods could be used for diagnostic and/or epidemiological purposes in clinical diagnostic laboratories. KEY POINTS: • Structure of loci cps for S. parauberis of serotypes III, IV and V was described. • mPCR to differentiate S. parauberis serotypes causing disease in fish was optimized. • qPCR assay to quantify strains of S. parauberis serotype III in fish tissues.

Molecular and serological typing of Streptococcus mutans strains isolated from young Galician population: relationship with the oral health status.

The aim of this study was to determine the prevalence of Streptococcus mutans and its serotypes in samples from oral cavity of young Galician population and their relationship with the oral health state. The variables generally associated with dental caries, such as salivary flow rate, buffering capacity, eating habits, and lifestyle, were also analysed. No relationship was found between the variables studied and the presence of S. mutans in the oral cavity or the existence of dental caries. Presumptive strains of S. mutans were isolated from saliva samples from 48% of the analysed population. The use of conventional microbiological methods, API 20 Strep system, and species-specific polymerase chain reaction (PCR) allowed to substantiate the identity of the strains as S. mutans. Multiplex PCR protocols, developed in this study for the simultaneous detection of S. mutans and serotypes c, e, and f and for detection of S. mutans and serotype k, also confirmed this result and demonstrated that serotype c was predominant in the studied young Galician population (86%). Serotypes e (8%), k (3%), and f (2%) were also detected. Serotype c was detected in carious and caries-free subjects, while the remaining serotypes were only found in subjects with caries.

Phenotypic and Molecular Characterization of Lacinutrix venerupis Isolated from Atlantic Horse Mackerel Trachurus trachurus.

The aim of the present study was to characterize two gram-negative bacterial strains that were isolated from diseased Atlantic Horse Mackerel Trachurus trachurus in 2017. Based on the results obtained from the biochemical and chemotaxonomic characterization, the isolates were identified as Lacinutrix spp. The highest similarity of the 16S rRNA gene sequences was obtained with the strain L. venerupis CECT 8573T (99.1%), while other species showed similarities of 98% (L. jangbogonensis) and 97% (L. algicola and L. mariniflava). Molecular characterization by repetitive element (REP)-PCR and enterobacterial repetitive intergenic consensus (ERIC)-PCR, as well as proteomic characterization by matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF-MS), demonstrated heterogeneity between the strains from the Atlantic Horse Mackerel and the type strain, CECT 8573T . The virulence of one of the isolates for Turbot Scophthalmus maximus, European Sea Bass Dicentrarchus labrax, Senegalese Sole Solea senegalensis, and Rainbow Trout Oncorhynchus mykiss was assessed under experimental conditions. No mortalities were recorded after intraperitoneal injections with high doses of bacteria (1 × 109  CFU/mL). Thus, further studies are necessary to elucidate the impact of this bacterial species as a fish pathogen.

High-throughput identification and quantification of Vagococcus salmoninarum by SYBR Green I-based real-time PCR combined with melting curve analysis.

This work describes a primer pair and a high-throughput SYBR Green I-based real-time PCR protocol combined with melting curve analysis for identification and quantification of Vagococcus salmoninarum in bacterial cultures and infected fish tissues. The 16S rRNA gene was selected for the design of the primer pair (SalF and SalR). The sensitivity and specificity of this primer pair were compared with other previously designed for conventional PCR. Although both primer pairs showed 100% specificity using pure bacterial cultures or DNA extracted from bacteria or fish tissues, the primer pairs designed in this study showed the highest sensitivity with a detection limit of 0.034 × 100 amplicon copies per assay (equivalent to 2 × 10-11  ng/µl, Cq value of 30.49 ± 1.71). The developed qPCR protocol allowed the detection of V. salmoninarum in non-lethal and lethal fish samples with detection levels of 0.17 × 100 gene copies in tissues artificially infected and 0.02 × 100 in tissues of fish experimentally infected with V. salmoninarum. The high sensitivity of the developed method suggests that it could be considered as a useful tool for diagnosis of vagococcosis and the detection of V. salmoninarum in asymptomatic or carrier fish.

Identification and typing of Vagococcus salmoninarum using genomic and proteomic techniques.

This study reports on the characterization of Vagococcus salmoninarum using phenotypic, serological, antigenic, genetic and proteomic methods. All strains of V. salmoninarum were resistant to most of the antimicrobials tested, and only 10% of strains were sensitive to florfenicol. Serological analysis demonstrated a high antigenic homogeneity within the species. No cross-reaction was detected with other fish pathogenic species causing streptococcosis (Lactococcus garvieae, Streptococcus parauberis, Streptococcus iniae, Streptococcus agalactiae, Carnobacterium maltaromaticum) using serum against V. salmoninarum CECT 5810. Electrophoretic analysis of cell surface proteins and immunoblot supported the antigenic homogeneity within V. salmoninarum strains. Moreover, limited diversity was detected using genomic (RAPD, ERIC-PCR and REP-PCR) and MALDI-TOF-MS analyses. The phenotypic, genomic and proteomic methods tested allowed the rapid differentiation of V. salmoninarum from the other species causing streptococcosis. However, MALDI-TOF-MS is the most promising method for typing and characterization of V. salmoninarum.

Identification and typing of fish pathogenic species of the genus Tenacibaculum.

Tenacibaculosis is a major bacterial disease that causes severe fish outbreaks and losses and limits the culture of a variety of commercially valuable anadromous and marine fish species in Europe, America, Asia and Oceania. Fish affected by tenacibaculosis have external lesions and necrosis that affect different areas of the body surface, reducing their commercial value. Several species of Tenacibaculum have been identified as the causal agent of tenacibaculosis in fish, including Tenacibaculum maritimum, Tenacibaculum soleae, Tenacibaculum discolor, Tenacibaculum gallaicum, Tenacibaculum dicentrarchi and "Tenacibaculum finnmarkense" (quotations marks denote species that have not been validly published). Diagnosis of tenacibaculosis is usually based on culture-dependent detection and identification techniques which are time-consuming and do not allow to differentiate closely related species. The development of reliable techniques for studying the relationships between members of the genus Tenacibaculum and for distinguishing fish-pathogenic species of Tenacibaculum genus is, therefore, a key step in understanding the diversity and incidence of tenacibaculosis in global aquaculture, designing effective prevention strategies and early implementation of infection control measures. In this review, recent advances in molecular, serological, proteomic and chemotaxonomic techniques developed for the identification and differentiation of Tenacibaculum species, as well as for the analysis of their genetic and epidemiological relationships are discussed. Key features of current diagnostic methods likely to facilitate control and prevention of tenacibaculosis and to avoid the spread of its aetiological agents are also outlined.

Comparison of serological and molecular typing methods for epidemiological investigation of Tenacibaculum species pathogenic for fish.

In the present study, the potential of serological methods, the repetitive extragenic palindromic PCR (REP-PCR) and the enterobacterial repetitive intergenic consensus sequence PCR (ERIC-PCR) for the typing of the species Tenacibaculum maritimum, Tenacibaculum soleae and Tenacibaculum discolor was evaluated. Moreover, molecular and proteomic techniques were used to assess variability among strains belonging to different serotypes, as well as isolated from different host species and geographical areas. Slide agglutination and dot-blot assays demonstrated the lack of immunological relationships among Tenacibaculum species analyzed. The serotype O1 was predominant within T. maritimum isolates regardless of the fish species or geographical area. Two serotypes were distinguished within T. soleae isolates and at least one within T. discolor strains. Species- and strain-specific profiles were obtained from the analysis of T. maritimum, T. soleae and T. discolor by REP-PCR and ERIC-PCR, demonstrating their potential as diagnostic tools. The genotyping analysis using both techniques showed genetic variability among the strains of each fish pathogenic Tenacibaculum species analysed. However, Tenacibaculum strains isolated from different host species or geographical areas or belonging to different serotypes produced REP and ERIC profiles with high similarity. Analysis by MALDI-TOF-MS of the T. maritimum strains could not detect any serotype-identifying biomarkers. Serotype-specific mass peaks were found for the serotypes O1 and O2 of T. soleae and for the serotype O1 of T. discolor. However, no relationships between the proteomic profiles and the source of isolation of the strains were obtained for any of the Tenacibaculum species analysed in this study.

Use of ribosomal proteins as biomarkers for identification of Flavobacterium psychrophilum by MALDI-TOF mass spectrometry.

Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF-MS) is a rapid methodology for identification of bacteria that is increasingly used in diagnostic laboratories. This work aimed at evaluating the potential of MALDI-TOF-MS for identification of the main serotypes of Flavobacterium psychrophilum isolated from salmonids, and its discrimination from closely related Flavobacterium spp. A mass spectra library was constructed by analysing 70 F. psychrophilum strains representing the serotypes O1, O2a, O2b and O3, including reference and clinical isolates. Peak mass lists were examined using the Mass-Up software for the detection of potential biomarkers, similarity and cluster analysis. Fourteen species-identifying biomarkers were detected in all the F. psychrophilum isolates tested, moreover, sets of serotype-identifying biomarkers ions were selected. F. psychrophilum-specific biomarkers were identified as ribosomal proteins by matching with protein databases. Furthermore, sequence variation corresponding to amino acid exchanges in several biomarker proteins were tentatively assigned. Closely related Flavobacterium species (F. flevense, F. succinicans, F. columnare, F. branchiophilum and F. johnsoniae) could be differentiated from F. psychrophilum by defining species identifying biomarkers and hierarchical cluster analysis. These results demonstrated that MALDI-TOF spectrometry represents a powerful tool for an accurate identification of the fish pathogen F. psychrophilum as well as for epidemiological studies. BIOLOGICAL SIGNIFICANCE: The results obtained in this study demonstrated that MALDI-TOF mass spectrometry represents a powerful tool that can be used by diagnostic laboratories for rapid identification of the fish pathogen Flavobacterium psychrophilum and its differentiation from other Flavobacterium-related species. Analysis of mass peak lists revealed the potential of the MALDI-TOF technique to identify epidemiologically important serotypes affecting salmonid fish. Furthermore, this study revealed the importance of the technique in the early and fast detection of bacterial pathogens, with the subsequent improvement in the health status and animal welfare and food safety in farmed fish.

MALDI-TOF mass spectrometry for rapid differentiation of Tenacibaculum species pathogenic for fish.

Tenacibaculosis is a fish disease that limits the culture of a variety of marine fish species of commercial value in the world. The genus Tenacibaculum includes several species, and their discrimination is of clinical interest in order to improve the management of an outbreak of the disease. In this study, a novel proteomic approach based on matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) analysis was evaluated for the identification and differentiation of Tenacibaculum species. The peak mass lists derived from MALDI-TOF-MS analysis were examined for the detection of potential biomarkers, similarity and cluster analysis and principal component analysis (PCA). Culture media used for bacterial growth did not affect the mass fingerprints. Eight genus-specific peaks were found in all the Tenacibaculum species analysed. Moreover, at least one species-specific peak was found in the species Tenacibaculum maritimum, Tenacibaculum soleae, Tenacibaculum dicentrarchi, Tenacibaculum litoreum and Tenacibaculum ovolyticum. These peaks could serve as biomarkers for the rapid identification of these bacterial fish pathogens. The cluster and PCA clearly separated the species T. maritimum, T. soleae, T. dicentrarchi and T. ovolyticum in different clusters. However, species of Tenacibaculum discolor and Tenacibaculum gallaicum were difficult to distinguish based on their protein fingerprints. To our knowledge, this is the first study that deals with the characterization and determination of biomarkers of Tenacibaculum species by MALDI-TOF mass spectrometry. This approach proved to be an effective and reliable technique for the discrimination of the Tenacibaculum species; therefore, it could be integrated as a routine diagnostic tool in microbiological laboratories.

Development of a SYBR green I real-time PCR assay for specific identification of the fish pathogen Aeromonas salmonicida subspecies salmonicida.

A SYBR Green I real-time polymerase chain reaction protocol for specific detection of the fish pathogen Aeromonas salmonicida subsp. salmonicida was developed and validated for rapid diagnosis of typical furunculosis. The sequence of the aopO gene of A. salmonicida subsp. salmonicida, which encodes for a serine/threonine protein kinase linked to virulence, was chosen for primer design. The selected primers amplified a 119-bp internal fragment of the aopO gene. The specificity test proved that 100 % (40/40) of the A. salmonicida subsp. salmonicida strains tested showed a positive amplification with subspecies-specific melting temperatures (Tm) of 80.75 ± 0.35 °C. Atypical A. salmonicida subspecies and other non-related bacterial fish pathogens did not amplify or showed unspecific melting profiles, except for one strain of A. salmonicida subsp. achromogenes and one strain of A. salmonicida subsp. smithia. The detection sensitivity was 21 fg of purified bacterial DNA per reaction, corresponding to 1-2 bacterial cells and 6-60 bacteria per reaction for seeded kidney and blood. The assay was highly reproducible with low variation coefficient values for intra-run and inter-run assays. The assay also allowed the specific detection of A. salmonicida subsp. salmonicida in tissues of fish naturally and experimentally infected. No amplification was detected when tissues from healthy fish or fish affected by other diseases were tested. The SYBR Green real-time PCR and melt curve analysis developed in this study is a rapid and accurate method for the specific identification of A. salmonicida subsp. salmonicida isolates and its detection on tissues of fish affected by furunculosis.

Design, synthesis and antibacterial study of new potent and selective coumarin-chalcone derivatives for the treatment of tenacibaculosis.

With the aim of finding new chemical entities selective for fish pathogens to avoid drug resistance in humans, a series of coumarin-chalcone hybrid compounds with different patterns of substitution were designed and synthesized. Their antibacterial activity was evaluated against important types of human bacteria strains (Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa) and against a fourteen strains of the marine pathogen Tenacibaculum maritimum, responsible for tenacibaculosis in fish, which is an important disease that causes great economical loss in the aquaculture industry. All the amino derivatives 5-12 presented high activity against different strains of T. maritimum, no activity against any of the three human pathogenic bacteria strains and no toxicity. Compounds 6, 7 and 11 were the most promising molecules. The most sensitive strains to these compounds were LL01 8.3.8 and LL01 8.3.1, being compound 11 up to 20 times more active than enrofloxacin. Therefore these scaffolds are good candidates for aquaculture treatments, avoiding possible drug resistance problems in humans.

In vitro and in vivo evaluation of lactic acid bacteria of aquatic origin as probiotics for turbot (Scophthalmus maximus L.) farming.

Turbot (Scophthalmus maximus L.) is an important commercial marine flatfish. Its production may be affected by bacterial diseases that cause severe economical losses, mainly tenacibaculosis and vibriosis, provoked by Tenacibaculum maritimum and Vibrio splendidus, respectively. An alternative or complementary strategy to chemotherapy and vaccination for the control of these diseases is the use of probiotics. In this work, we report the in vitro and in vivo potential of eight lactic acid bacteria (LAB), previously isolated from fish, seafood and fish products intended for human consumption, as turbot probiotics. Seven out of the eight LAB exerted direct antimicrobial activity against, at least, four strains of T. maritimum and V. splendidus. All LAB survived in seawater at 18 °C for 7 days, and withstood exposure to pH 3.0 and 10% (v/v) turbot bile; however, they differed in cell surface hydrophobicity (8.2-21.7%) and in their ability to adhere to turbot skin (1.2-21.7%) and intestinal (0.7-2.1%) mucus. Most of the tested strains inhibited the binding of turbot pathogens to the mucus. Leuconostoc mesenteroides subsp. cremoris SMM69 and Weissella cibaria P71 were selected based on their strong antimicrobial activity against T. maritimum and V. splendidus, good probiotic properties, and different adhesion ability to skin mucus and capacity to inhibit the adhesion of turbot pathogens to mucus. These two LAB strains were harmless when administered by bath to turbot larvae and juveniles; moreover, real-time PCR on the transcription levels of the immunity-related genes encoding IL-1ß, TNF-α, lysozyme, C3, MHC-Iα and MHC-IIα in five organs (head-kidney, spleen, liver, intestine and skin) revealed the ability of these LAB to stimulate their expression in turbot juveniles, especially the non-specific immunity associated genes in mucosal tissues. Based on our results, Lc. cremoris SMM69 and W. cibaria P71 may be considered as suitable probiotic candidates for turbot farming.

Evaluation of immune response in turbot (Psetta maxima L.) tenacibaculosis: haematological and immunohistochemical studies.

Tenacibaculum maritimum is a Gram-negative bacterium that causes large losses in farmed turbot, Psetta maxima (L.). Main lesions included erosive and ulcerative skin injuries in different locations in the body of the fish. This study was set up to gain insights into the immune response of the turbot against this bacterial infection. To determine the variations in the peripheral blood leukocytes a minimum of 200 leukocytes in blood smears were counted. The presence of immunoglobulin positive (Ig(+)) cells in spleen, kidney, intestine, thymus and skin from turbot experimentally infected with T. maritimum were studied using an immunohistochemical method. In fish challenged with the bacterium the percentage of circulating granulocytes, lymphocytes and trombocytes showed significant differences at different points of sampling. Moreover, the number of Ig(+) cells significantly increased in the spleen, kidney, intestine and thymus. In the skin a strong immunoreactivity was observed in the interstitial liquid in damaged areas. The results obtained in this study indicated that the infection by T. maritimum in turbot induced an immune response that involved changes in the number of peripheral blood leukocytes and in the number and distribution of Ig(+) cells.

Tenacibaculum maritimum infection: pathology and immunohistochemistry in experimentally challenged turbot (Psetta maxima L.).

Tenacibaculum maritimum is the causative agent of tenacibaculosis, a bacterial disease with a worldwide distribution, which causes important losses in the turbot aquaculture. Despite the importance of this bacterium, little is known about pathogenesis of the tenacibaculosis, pattern of lesions and the portal of entry of T. maritimum. Turbots (Psetta maxima) were experimentally infected with T. maritimum using subcutaneous and intraperitoneal routes of inoculation and samples of skin and internal organs were taken throughout the assay. Fish inoculated by both infection routes suffered a septicaemia but only the subcutaneous inoculation reproduces the disease signs described in natural outbreaks. Bacterial antigen was detected by immunohistochemistry in the internal organs 3 h after infection in fish inoculated by subcutaneous route and 6 h after the inoculation of fish by intraperitoneal route. In summary, both routes of inoculation are able to cause an infection and bacteraemia in the fish. However, subcutaneous inoculation route reproduces the disease in a faster and more reliable way than the intraperitoneal route. Moreover, bacterium spreads along the internal organs easily, but needs a gateway to penetrate in the organism and this portal of entry could be skin.

Synthesis and structure-activity relationships of novel amino/nitro substituted 3-arylcoumarins as antibacterial agents.

A new series of amino/nitro-substituted 3-arylcoumarins were synthesized and their antibacterial activity against clinical isolates of Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative) was evaluated. Some of these molecules exhibited antibacterial activity against S. aureus comparable to the standards used (oxolinic acid and ampicillin). The preliminary structure-activity relationship (SAR) study showed that the antibacterial activity against S. aureus depends on the position of the 3-arylcoumarin substitution pattern. With the aim of finding the structural features for the antibacterial activity and selectivity, in the present manuscript different positions of nitro, methyl, methoxy, amino and bromo substituents on the 3-arylcoumarin scaffold were reported.