Shelf life extension of Pacific white shrimp (Litopenaeus vannamei) using chitosan and ε-polylysine during cold storage.

In this study, we examined the effects of an ε-polylysine (PL) and chitosan (CH) coating on the quality of shrimp under refrigeration. Pacific white shrimp (Litopenaeus vannamei) were coated with PL, CH, or CH + PL and stored at 4 °C for 15 days. The quality of shrimp was measured by observing changes in microbiota, pH, total volatile basic nitrogen (TVB-N), and sensory characteristics. Among the coating films, the CH + PL coating most effectively inhibited the growth of mesophilic and psychrotrophic bacteria, Pseudomonas spp., and H2S-producing bacteria. This coating increased the shelf life of shrimp by decreasing the amount of mesophilic and psychrotrophic bacteria, with inhibition greater than three log cycles on the ninth day of storage. In addition, the CH and CH + PL coatings effectively suppressed the formation of TVB-N compared with that in the control by 43% and 30%, respectively. The pH of all treated samples increased slowly compared with that of the control, but no significant difference was observed. Sensory quality was similar to microbial and physicochemical properties, and the acceptability of all treated samples gradually decreased.

Middle Ear Prosthesis with Bactericidal Efficacy-In Vitro Investigation.

Materials used in ossicular replacement prostheses must possess appropriate biological properties, such as biocompatibility, stability, no cytotoxicity. Due to the risk of infection (otitis media and chronic otitis media), it is desirable to use an antibacterial agent for illness prevention during the ossicular reconstruction. The goal of this work was to observe biological properties of a new composite prosthesis made of ABS containing silver nanoparticles (AgNPs 45T). Samples for biological tests and then a prototype of middle ear prosthesis were prepared using injection moulding and extrusion techniques. In vitro experiments were carried out to assess bactericidal efficacy against Staphylococcus aureus and Pseudomona aeruginosa standard strains, cell proliferation, viability and cytotoxicity, using Hs680.Tr. fibroblast cells. Surface parameters of the samples were evaluated, including roughness and wettability. The silver ions were continually released from the polymer in aqueous solution. The silver ions release was measured as increasing with time and concentration of the silver nanoparticles in the polymer matrix. No cytotoxicity effect was observed, while bactericidal efficacy was noticed for silver nanoparticles. The roughness studies showed an increase in roughness for the samples with silver nanoparticles. All polymer and composite materials containing silver nanoparticles showed hydrophilic properties. The composites were found to release silver ions at a concentration level capable of rendering the antimicrobial efficacy even with the lowest concentration of silver nanoparticles in the material. Our results demonstrate that middle ear prosthesis made of polymer and silver nanoparticles may eliminate bacteria during inflammation in the middle ear.

Viable bacterial population and persistence of foodborne pathogens on the pear carpoplane.

BACKGROUND: Knowledge on the culturable bacteria and foodborne pathogen presence on pears is important for understanding the impact of postharvest practices on food safety assurance. Pear fruit bacteria were investigated from the point of harvest, following chlorine drenching and after controlled atmosphere (CA) storage to assess the impact on natural bacterial populations and potential foodborne pathogens. RESULTS: Salmonella spp. and Listeria monocytogenes were detected on freshly harvested fruit in season one. During season one, chemical drenching and CA storage did not have a significant effect on the bacterial load of orchard pears, except for two farms where the populations were lower 'after CA storage'. During season two, bacterial populations of orchard pears from three of the four farms increased significantly following drenching; however, the bacterial load decreased 'after CA storage'. Bacteria isolated following enumeration included Enterobacteriaceae, Microbacteriaceae, Pseudomonadaceae and Bacillaceae, with richness decreasing 'after drench' and 'after CA storage'. CONCLUSION: Salmonella spp. and L. monocytogenes were not detected after postharvest practices. Postharvest practices resulted in decreased bacterial species richness. Understanding how postharvest practices have an impact on the viable bacterial populations of pear fruit will contribute to the development of crop-specific management systems for food safety assurance. © 2016 Society of Chemical Industry.

Detection and molecular characterization of ß-lactamase genes in clinical isolates of Gram-negative bacteria in Southern Ecuador.

This work performed a phenotypic and genotypic characterization of 79 clinical isolates of Enterobacteriaceae and Pseudomonadaceae collected in hospitals of Southern Ecuadorin 2013. Our results showed a high incidence of ß-lactamases and ESBLs with blaTEM and blaCTX-M as the prevalent genes, respectively. By direct sequencing of PCR amplicons, the different ß-lactamases and variants of the genes were also distinguished. Our results revealed a predominance of TEM-1 ß-lactamase and the presence of different CTX-M variants with a prevalence of CTX-M-15. Two infrequent CTX-M variants in South America were also identified. To the best of our knowledge, this is one of the first studies describing the genetic characteristics of ß-lactamases in Ecuador.

Antibiotic Resistance Patterns of Gram-Negative Psychrotrophic Bacteria from Bulk Tank Milk.

Bacterial resistance to antibiotics is a major global health problem and resistance of Pseudomonadaceae and Enterobacteriaceae is a serious concern. We investigated the prevalence of drug-resistance in a total of 80 psychrotrophic strains from bulk milk belonging to Pseudomonas genus (n. 63) and Enterobacteriaceae group (n. 17). All the strains were tested against 16 antibiotics. Pseudomonas were further investigated for their sensitivity against 12 additional antibiotics. Pseudomonas showed a high susceptibility toward fluoroquinolones, aminoglycosides, and piperacillin and, to a lesser extent, to imipenem, ceftazidime, cefepime. Thirty-five out of 63 Pseudomonas strains were susceptible to meropenem, while among antibiotics for which recommended breakpoints are not yet available, 55% of Pseudomonas strains had no inhibition halo in presence of nitrofurantoin, highlighting a resistance toward this drug. The results obtained in this study indicate a high efficiency of fluoroquinolones, chloramphenicol (94%), and kanamycin (76%) for Enterobacteriaceae while a high prevalence of resistant strains was found to ampicillin (13/17). Serratia marcescens is highly susceptible to fluoroquinolones, chloramphenicol, and kanamycin. Moreover, mupirocin seems to be the new antibiotic with the less efficacy for Enterobacteriaceae, with 41% of strains without halo, pointing out an important resistance. Further knowledge on resistance to known and new antibiotics among Pseudomonas species and Enterobacteriaceae of milk origin was acquired.

Composition of epiphytic bacterial communities differs on petals and leaves.

The epiphytic bacterial communities colonising roots and leaves have been described for many plant species. In contrast, microbiologists have rarely considered flowers of naturally growing plants. We identified bacteria isolated from the surface of petals and leaves of two plant species, Saponaria officinalis (Caryophyllaceae) and Lotus corniculatus (Fabaceae). The bacterial diversity was much lower on petals than on leaves of the same plants. Moreover, the bacterial communities differed strongly in composition: while Pseudomonadaceae and Microbacteriaceae were the most abundant families on leaves, Enterobacteriaceae dominated the floral communities. We hypothesise that antibacterial floral volatiles trigger the low diversity on petals, which is supported by agar diffusion assays using substances emitted by flowers and leaves of S. officinalis. These results suggest that bacteria should be included in the interpretation of floral traits, and possible effects of bacteria on pollination are proposed and discussed.

Isolation and characterization of halophilic bacteria from Urmia Lake in Iran.

Urmia Lake is one of the most permanent hypersaline lakes in the world which is threatened by hypersalinity and serious dryness. In spite of its importance no paper has been published regarding bacterial community of this lake. Accordingly, the present study aimed to investigate the halophilic bacteria in the aforementioned lake. In so doing, thirty seven strains were isolated on six different culture media. The isolated strains were characterized using phenotypic and genotypic methods. Growth of the strains occurred at 2535 degrees C, pH 6-9 and 7 to 20% (w/v) NaCl indicating that most of the isolates were moderately halophiles. Catalase, oxidase and urease activities were found to be positive for the majority of the isolates. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the isolated bacteria belonged to two major taxa: Gammaproteobacteria (92%, including Salicola [46%], Pseudomonas [13.5%], Marinobacter [ 11%], Idiomarina [11%], and Halomonas [8%]) and Firmicutes (8%, including Bacillus [5%] and Halobacillus [3%]). In addition, a novel bacterium whose 16S rRNA gene sequence showed almost 98% sequence identity with the taxonomically troubled DSM 3050T, Halovibrio denitrificans HGD 3T and Halospina denitrificans HGD 1-3T, each, was isolated. 16S rRNA gene similarity levels along with phenotypic characteristics suggest that some of the isolated strains could be regarded as potential type strain for novel species, on which further studies are recommended.

Environmental toxicity testing of contaminated soil based on microcalorimetry.

Contaminated site assessment and monitoring requires efficient risk-management tools including innovative environmental toxicity tests. The first application of microcalorimetry for toxicity testing draw the attention to a possible new tool to increase sensitivity, to eliminate matrix effect and to study effect-mechanism. A Thermal Activity Monitor (TAM) microcalorimeter was used for measuring the heat production of various test organisms when getting in contact with sterile toxic soils. Well known bacterial (Azomonas agilis), animal (Folsomia candida) and plant test organisms (Sinapis alba) were tested for heat production. The heat response of selected testorganisms was measured in case of metal (Cu and Zn) and organic pollutant (Diesel oil, DBNPA and PCP) contaminated soils. In addition to the quantitative determination of the heat production, the mechanism of the toxic effect can be characterized from the shape of the power-time curve (slope of the curve, height and time of the maximum). In certain concentration ranges the higher the pollutant concentration of the soil the lower the maximum of the time-heat curve. At low pollutant concentrations an increased heat production was measured in case of A. agile and 20 and 200 mg Zn kg(-1) soil. The microcalorimetric testing was more sensitive in all cases than the traditional test methods. Our results showed that the microcalorimetric test method offers a new and sensitive option in environmental toxicology, both for research and routine testing.

Comparison of bioassays by testing whole soil and their water extract from contaminated sites.

The harmful effects of contaminants on the ecosystems and humans are characterised by their environmental toxicity. The aim of this study was to assess applicability and reliability of several environmental toxicity tests, comparing the result of the whole soils and their water extracts. In the study real contaminated soils were applied from three different inherited contaminated sites of organic and inorganic pollutants. The measured endpoints were the bioluminescence inhibition of Vibrio fischeri (bacterium), the dehydrogenase activity inhibition of Azomonas agilis (bacterium), the reproduction inhibition of Tetrahymena pyriformis (protozoon), and Panagrellus redivivus (nematode), the mortality of Folsomia candida (springtail), the root and shoot elongation inhibition of Sinapis alba (plant: white mustard) and the nitrification activity inhibition of an uncontaminated garden soil used as "test organism". Besides the standardised or widely used methods some new, direct contact ecotoxicity tests have been developed and introduced, which are useful for characterisation of the risk of contaminated soils due to their interactive nature. Soil no. 1 derived from a site polluted with transformer oil (PCB-free); Soil no. 2 originated from a site contaminated with mazout; Soil no. 3 was contaminated with toxic metals (Zn, Cd, Cu, Pb, As). In most cases, the interactive ecotoxicity tests indicated more harmful effect of the contaminated soil than the tests using soil extracts. The direct contact environmental toxicity tests are able to meet the requirements of environmental toxicology: reliability, sensibility, reproducibility, rapidity and low cost.

Effect of fluorescent pseudomonades and Trichoderma sp. and their combination with two chemicals on Penicillium digitatum caused agent of citrus green mold.

Citrus green mold (Penicillium digitatum) causes economic losses. Chemical fungicides such as imazalil provide the primary means for controlling green mold decay of citrus fruits. Continuous use of fungicides has faced two major obstacles- increasing public concern regarding contamination of perishables with fungicidal residues, and proliferation of resistance in the pathogen populations. The aim of this research was to determine if the attacks of green mold on orange could be reduced by usage of biocontrol agent alone or in combination with low dosage of imazalil or sodium bicarbonate. Pseudomonas fluorescens isolate PN, P. fluorescens isolate PS and Trichoderma virens isolate TE were evaluated as potential biological agents for control of green mold of oranges caused by P. digitatum. Increasing concentration of SB decreased spore germination of P. digitatum. In laboratory tests, a cell suspension (10(8) cells per ml.) of bacterial strains reduced the incidence of green mold. On fruits surface biocontrol activity of antagonistic isolates was significantly increased when combined with low dosage of imazalil (500ppm) or sodium carbonate (5%). Effect of Trichoderma virens on controlling P. digitatum was better than others with or without these chemicals.

Use of electrospray ionization mass spectrometry for profiling of crude oil effects on the phospholipid molecular species of two marine bacteria.

We investigated the membrane lipid composition of two hydrocarbon-degrading gram-negative bacterial strains (Pseudomonas nautica IP 617 and Marinobacter hydrocarbonoclasticus) initially cultured on a soluble substrate, then on petroleum hydrocarbons, and finally taken back onto the soluble substrate. For the two strains, the growth on petroleum and the return to the initial medium showed major, but comparable, qualitative and quantitative modifications of the intact phospholipid molecular species (IPMS) composition. Furthermore, since bacterial membranes are mainly made up of phospholipids, these modifications reflected hydrocarbon assimilation, restoration abilities and membrane fluidity adaptation. The electrospray ionization mass spectrometry (ESI-MS) analysis of intact phospholipid provided some new information (e.g. sn fatty acyl chain distribution) that could not be assessed by the classical fatty acid analysis. Moreover, such information should be particularly helpful with regards to bacterial taxonomy and xenobiotic toxicity studies.

Calibration and deployment of custom-designed bioreporters for protecting biological remediation consortia from toxic shock.

We have previously described the development of a panel of site-specific lux-based bioreporters from an industrial wastewater treatment system remediating coking effluents. The Pseudomonad strains carry a stable chromosomal copy of the luxCDABE operon from Photorhabdus luminescens and display proportional responses in bioluminescence decay with increasing phenol concentration up to 800 mg l-1. In this work we describe their deployment to provide a strategic sensing network for protecting bacterial communities involved in the biological breakdown of coking effluents. This evaluation demonstrated the utility of strategic placement of reporters around heavy industry treatment systems and the reliability of the reporter strains under normal operational conditions. Mono-phenol or total phenolic variation within the treatment system accounted for>65-80% of the luminescence response. The reporters exhibited stable luminescence output during normal operations with maximum standard deviations of luminescence over time of c. 5-15% depending on the treatment compartment. Furthermore, deployment of the bioreporters over a 5-month period allowed the determination of an operational range (OR) for each reporter for effluent samples from each compartment. The OR allowed a convenient measure of toxicity effects between treatment compartments and accurately reflected a specific pollution event occurring within compartments of the treatment system. This work demonstrates the utility of genetic modification to provide ecologically relevant bioreporters, extends the sensing capabilities currently obtained through marine derived biosensors and significantly enhances the potential for in situ deployment of reporting agents.

Molecular diversity in the bacterial community and the fluorescent pseudomonads group in natural and chlorobenzoate-stressed peat-forest soil.

Bacterial community shifts in a soil microcosm spiked with 3-chlorobenzoate or 2,5-dichlorobenzoate were monitored. The V6-V8 variable regions of soil bacterial 16S rRNA and rDNA were amplified and separated by temperature gradient gel electrophoresis (TGGE) profiling. Culturing in the presence of 2.5 mM chlorinated benzoates suppressed 10 to 100 fold the total aerobic bacterial community but had no effect on the diversity within the group of fluorescent pseudomonads. In contrast, the uncultured bacterial community showed a decrease in the number of bands in the TGGE profiles of the chlorobenzoate-spiked treatments. Accordingly, the Shannon's diversity and equitability indices of these treatments reflected a decreasing trend in time. The approach allowed a direct assessment of community shifts upon contamination of soil.

Halogenated metabolites from the new Okinawan red alga Laurencia yonaguniensis.

A novel brominated diterpene based on the rare neoirieane skeleton, named neoirietetraol (1), has been isolated along with a halogenated C15 acetogenin, (3Z)-laurenyne (2), from a new Laurencia species, L.yonaguniensis Masuda et Abe, species inedita, collected at Yonaguni Island, Okinawa Prefecture, Japan. The structures of these metabolites were elucidated by spectroscopic data (IR, 1H NMR, 13C NMR, 2D NMR, and MS). Neoirietetraol (1) was toxic to the brine shrimp (Altemia salina; LC50, 40.1 microM) and also showed weak antibacterial activities against two marine bacteria, Alcaligenes aquamarinus and Escherichia coli.

Use of Etests with carbapenems for Gram-negative rods producing beta-lactamases.

The in vitro activity of imipenem and meropenem on strains of Gram-negative rods producing extended-spectrum beta-lactamase (ESBL) and inducible beta-lactamase (IBL) was studied using the Etest. In all, 185 strains from the surgical intensive care units of four different hospitals were looked at over 2 years. Of these, 94 were ESBL producers and 91 were IBL positive. The in vitro sensitivities of imipenem and meropenem were 89.7 and 95.1%, respectively, against all strains. The imipenem and meropenem sensitivities of Klebsiella spp. were 98.4 and 100%, respectively, but imipenem resistance (21.6%) in Pseudomonas aeruginosa strains was higher than that of meropenem (10.8%).

In vitro activity of newer broad spectrum beta-lactam antibiotics against enterobacteriaceae and non-fermenters: a report from Austrian intensive care units. Austrian Carbapenem Susceptibility Surveillance Group.

We compared the in vitro activity of broad spectrum beta-lactam antibiotics against 573 gram-negative isolates (enterobacteriaceae and non-fermenters) collected between November 1996 and May 1997 from 9 laboratories serving intensive care units throughout Austria. MIC's (Minimal Inhibitory Concentration) were obtained with the E-test for meropenem, imipenem, ceftazidime, cefepime, cefpirome and piperacillin/tazobactam. Pseudomonas aeruginosa was the most frequently isolated organism (22%), followed by E. coli (19%), Klebsiella spp. (16%), and Enterobacter spp. (14%). Acinetobacter spp., Proteus spp., Serratia spp., Stenotrophomonas maltophilia, Citrobacter spp., Morganella morganii, Burkholderia cepacia and Salmonella enteritidis were isolated less frequently. Overall meropenem, imipenem and ceftazidime were the most active compounds in vitro, inhibiting 90%, 89%, and 87% of the isolates, respectively. Pseudomonas aeruginosa was inhibited by piperacillin/tazobactam in 89%, by cefepime in 87% and by ceftazidime in 85%. Imipenem, meropenem and cefpirome were less active (79%, 75% and 69% respectively). All E. coli strains were inhibited by meropenem, 99% were inhibited by imipenem, cefepime and cefpirome. Ceftazidime was active against 95% and piperacillin/tazobactam against 92% of E. coli. All Klebsiella spp. were inhibited by meropenem, cefepime and cefpirome. Imipenem inhibited 99% and ceftazidime 98% of the Klebsiella isolates. Piperacillin/tazobactam was active against 95% of Klebsiella spp. In vitro carbapenems are still the most active of all antibiotics tested. The relatively high resistance of Pseudomonas spp. and Acinetobacter spp. to carbapenems reflects the wide use of carbapenems during the last years. However, most bacterial isolates are still sensitive to the tested broad spectrum beta-lactams.

Susceptibility testing of Stenotrophomonas maltophilia to carbapenems.

The susceptibility of 20 clinical isolates of Stenotrophomonas maltophilia to the carbapenems imipenem and meropenem was investigated by various methods. S. maltophilia appeared sensitive to meropenem but resistant to imipenem by disc testing in Iso-sensitest agar. Agar dilution MICs were performed using Iso-sensitest agar and with incubation under three sets of atmospheric conditions. MICs of meropenem were considerably lower than those of imipenem; this effect was maximal after incubation in 5% CO2 when the MIC of meropenem was approximately 64 times less than that of imipenem. Induction experiments showed that both carbapenems could induce production of the L1 carbapenemase. However, disc approximation tests showed that imipenem could induced resistance to meropenem. Partially stably derepressed mutants were readily selected in vitro. We conclude that, although S. maltophilia may give large zones of inhibition to meropenem on disc testing, resistant mutants are readily selected and therefore standard sensitivity tests may be poorly predictive of clinical outcome of treatment of S. maltophilia infections with meropenem.

Multiple antibiotic resistance in Stenotrophomonas maltophilia.

A cryptic multidrug resistance (MDR) system in Stenotrophomonas maltophilia, the expression of which is selectable by tetracycline, is described. Tetracycline resistance was the consequence of active efflux of the antibiotic, and it was associated with resistance to quinolones and chloramphenicol, but not to aminoglycosides or beta-lactam antibiotics. MDR is linked to the expression of an outer membrane protein (OMP54) both in a model system and in multidrug-resistant clinical isolates.