Design of colorimetric nanostructured sensor phases for simple and fast quantification of low concentrations of acid vapors.

Two colorimetric nanostructured sensor phases (Color-NSPs) for the determination of low concentrations of acid vapors in the atmosphere of paper storage rooms have been designed and characterized. The acid vapor determination is based on the color change that occurs in polyaniline (PANI) in the presence of acids when it goes from its emeraldine base form (blue) to its emeraldine salt form (green). To synthesize the Color-NSPs, two methods have been used, a one-step method performed by grafting polyaniline onto a cellulose membrane (Cellu-PANI) and a two-step method in which in the first step, polyaniline is grafted onto the surface of polymeric nanoparticles (NPs-PANI), and in a second step, NPs-PANI are immobilized into the pores of a nylon membrane (Nylon-NPs PANI). The response of the sensors versus acid vapor was measured by color coordinates with a photographic camera. A linear response range from 1 ppmv to 7 ppmv was found for both sensors, and the detection limits were 0.95 ppmv (1.2 % RSD) and 0.40 ppmv (0.8 % RSD) for Cellu-PANI and Nylon-NPs PANI, respectively. In addition, both sensors showed complete reversibility and a short exposition time (5 min). The potential applicability of the Color-NSPs in the control of the exposure of paper heritage collections to outdoor- and indoor-generated gaseous pollutants was demonstrated by determining acid vapors in museums. The method was validated with an external reference method; the paired test was applied, and p-values greater than 5% were obtained, indicating an excellent correlation and showing that the Color-NSPs reported are simple, fast, and an economical alternative to control and protect cultural heritage materials in indoor environments.

[Microbiological characterization and antimicrobial susceptibility pattern of infections associated with febrile neutropenia in pediatric hemato-oncological patients.] / Caracterización microbiológica y de susceptibilidad antimicrobiana de las infecciones asociadas a neutropenia febril en pacientes hemato-oncológicos pediátricos.

INTRODUCTION: Febrile neutropenia (FN) is the most frequent hemato-oncological emergency, with high morbidi ty and mortality in pediatrics. The objective of the study was the microbiological characterization and antimicrobial susceptibility of infections associated with FN in pediatric hemato-oncological patients. PATIENTS AND METHOD: Retrospective cohort study with patients aged between 1 month and 18 years, with onco-hematological pathology according to ICD-10 codes, hospitalized in a tertiary healthcare center in Bucaramanga, Colombia. Based on the medical records of the period 2013-2017, the episodes of FN were identified, and the isolated microorganisms and their susceptibility pattern were described. Biochemical identification and antimicrobial susceptibility testing were performed with the Dade Behring Microscan« automated system. The resistant microorganism classification was performed based on the Minimum Inhibitory Concentration (MIC) and the interpretation of the laboratory according to the cut-off points of the Clinical and Laboratory Standards Institute recommendations. RESULTS: Of 130 patients, 14.7% of the cultures obtained were positive. Bloods tream infection was observed in 17.5% of the episodes. The isolated microorganisms were mainly Gram-negative bacteria (75.8%). Enterobacteriaceae (EB) were the most frequent, led by Klebsiella pneumoniae, Escherichia coli, followed by Pseudomonas aeruginosa and coagulase-negative Staphylo cocci. Of the EBs, 40.5% showed resistance to Piperacillin/Tazobactam, 33.3% to Cefepime, and 8.2% to Meropenem. According to the antimicrobial resistance pattern, it was observed that 16.4% of the positive EB cultures had an extended-spectrum beta-lactamase pattern and 5% a pattern suggestive of carbapenemases. All Gram-positive cocci were sensitive to Vancomycin. CONCLUSION: In the studied patients, the predominant pathogenic microorganisms were Gram-negative ones with resistance in dices similar to those of developing countries.

Antimicrobial activity of binary combinations of natural and synthetic phenolic antioxidants against Enterococcus faecalis.

This study investigated the antimicrobial activity of 3 natural (thymol, carvacrol, and gallic acid) and 2 synthetic [butylated hydroxyanisole (BHA) and octyl gallate] phenolic compounds, individually and in binary combinations, on 4 dairy isolates of Enterococcus faecalis with different virulence factors (ß-hemolytic, gelatinase, or trypsin activities; acquired resistance to erythromycin or tetracycline; and natural resistance to gentamicin). A checkerboard technique and a microdilution standardized method were used. All compounds individually tested exhibited antimicrobial activity against E. faecalis, with minimal inhibitory concentrations (MIC) ranging from 30 µg/mL (octyl gallate) to 3,150 µg/mL (gallic acid), although no significant differences were detected among strains to each phenolic compound. Carvacrol in combination with thymol or gallic acid, and gallic acid combined with octyl gallate showed partial synergistic inhibition of all E. faecalis strains. The most effective combinations were thymol+carvacrol and gallic acid+octyl gallate, as the MIC for each of these compounds was reduced by 67 to 75% compared with their respective individual MIC. These results highlight the possibility of using combinations of these phenolic compounds to inhibit the growth of potential virulent or spoilage E. faecalis strains by reducing the total amount of additives used in dairy foods.

Characterization of certain bacterial strains for potential use as starter or probiotic cultures in dairy products.

The present work was aimed at characterizing 12 strains of lactic acid bacteria (LAB) to obtain improved potential starter or probiotic cultures that could be used for making dairy products from ewe's milk and cow's milk. Eight strains with antimicrobial properties, isolated from ewe's milk and from cheese made from ewe's and/or cow's milk, were studied. They were identified as Enterococcus faecalis (five strains), Lactococcus lactis subsp. cremoris, Leuconostoc mesenteroides, and Lactobacillus paracasei subsp. paracasei (one strain of each species). Additionally, four strains were obtained from the American Type Culture Collection: Lactobacillus casei 393 (isolated from cheese), L. lactis subsp. lactis 11454 (origin nonspecified and a producer of nisin), and two strains isolated from human feces (L. paracasei subsp. paracasei 27092 and Lactobacillus rhamnosus 53103, antibacterial agent producer). All E. faecalis strains showed at least one virulence factor (either hemolysin or gelatinase), which emphasizes the importance of these studies in this species. Both L. lactis strains and most Lactobacillus spp. were good acidifiers in ewe's milk and cow's milk at 30°C. High ß-galactosidase activity, as well as aminopeptidase activities that favor the development of desirable flavors in cheese, were detected in all Lactobacillus spp. strains. Furthermore, L. rhamnosus ATCC 53103 showed α-fucosidase activity (thought to help colonization of the intestine) and lack of α-glucosidase activity (a trait considered positive for diabetic and obese humans). This last enzymatic activity was also lacking in L. lactis ATCC 11454. L. mesenteroides was the only strain D(2)-lactic acid producer. The selection of any particular strain for probiotic or dairy cultures should be performed according to the technological and/or functional abilities needed.

Phenotypical characteristics of Shiga-like toxin Escherichia coli isolated from sheep dairy products.

AIMS: To analyse phenotypical characteristics of Shiga toxin-producing Escherichia coli (STEC) strains from ovine origin. METHODS AND RESULTS: A total of 13 STEC strains (eight O157 and five non-O157) isolated from sheep dairy products were used in this study. Biochemical traits, motility, haemolytic activity, resistance to tellurite-cefixime, maximum growth temperature and antibiotic resistance were determined. The STEC strains were grouped into nine biochemical and physiological biotypes (five for the O157 and four for the non-O157 strains). All STEC strains showed resistance to bacitracin, cloxacilin, penicillin and tylosin. CONCLUSIONS: Different biotypes and antibiotic resistance patterns of STEC isolated from sheep dairy products were observed. SIGNIFICANCE AND IMPACT OF THE STUDY: This work will be a contribution to the better characterization of STEC isolated from sheep dairy products, which have, to date, been scarcely studied, and to the better understanding of the risks associated with its consumption.

Detection, occurrence, and characterization of Escherichia coli O157:H7 from raw ewe's milk in Spain.

A study was carried out in the Castilla y León region of Spain to investigate the presence of Escherichia coli O157:H7 in raw ewe's milk samples collected from several cheese factories during 1 year. All specimens were examined for E. coli O157:H7 by selective enrichment at 41.5 +/- 1.0 degrees C, after both 6 and 22 h of incubation, and then immunomagnetically separated and plated on cefixime-potassium tellurite-sorbitol MacConkey agar. No growth was obtained in the enrichment broth after a 6-h incubation. Presumptive colonies obtained after 22 h of incubation were screened by a multiplex PCR assay for the presence of rfbO157 and fliCH7 genes. Of all the ewe's milk samples studied, three were positive for E. coli O157:H7. The E. coli O157:H7 strains that were positive for the rfbO157 and fliCH7 genes were then analyzed by multiplex PCR for the presence of virulence genes (stx1, stx2, ehxA, and eaeA). All E. coli O157:H7 isolates were Shiga toxigenic and harbored additional genes related to virulence (ehxA and eaeA). The predominant Stx toxin type was stx2. These results demonstrate that raw ewe's milk used in cheesemaking may be sporadically contaminated with E. coli O157:H7 strains that are potentially pathogenic for humans.

Susceptibility of mosquito and tick cell lines to infection with various flaviviruses.

The genus Flavivirus consists of more than 70 virus species and subtypes, the majority of which are transmitted by mosquitoes or ticks, although some have no known vector (NKV). The ability of these viruses to infect cultured cells derived from mosquito or tick species offers a useful insight into the suitability of such vectors to harbour and replicate particular viruses. We undertook a comparative study of the susceptibility of mammalian Vero cells, a clonal mosquito cell line (C6/36) and recently developed cell lines derived from the ticks (Acari: Ixodidae) Ixodes ricinus (L.) (IRE/CTVM18), I. scapularis (Say) (ISE6), Rhipicephalus appendiculatus (Neumann) (RAE/CTVM1) and Amblyomma variegatum (Fabricius) (AVL/CTVM17) to infection with 13 flaviviruses (and one alphavirus) using immunofluorescence microscopy and plaque assay techniques. The C6/36 mosquito cell line was infected by all the mosquito-borne flaviviruses tested but not by NKV viruses or tick-borne viruses, with the exception of Langat virus (LGTV). The tick cell lines were susceptible to infection by all of the tick-borne viruses tested, as well as two mosquito-borne viruses, West Nile virus (WNV) and the alphavirus, Venezuelan equine encephalitis virus (VEEV), but not other mosquito-borne viruses or NKV viruses.

Epidemiology of rabbit haemorrhagic disease virus in the United Kingdom: evidence for seasonal transmission by both virulent and avirulent modes of infection.

Rabbit haemorrhagic disease virus (RHDV) has killed many millions of wild rabbits in Europe and Australia, but has had little impact in the United Kingdom, despite outbreaks having occurred since 1994. High seroprevalence detected in the absence of associated mortality had suggested the presence of an endemic non-pathogenic strain which may be 'protecting' UK populations. Following the first detailed field study of RHDV epidemiology in the United Kingdom, using mark-recapture with serum sampling, we report that RHDV caused highly prevalent persistent infection in seropositive rabbits in the absence of associated mortality. Furthermore the virus strains responsible could not be distinguished phylogenetically from known pathogenic isolates, and were clearly very different from the only previously identified non-pathogenic strain of RHDV. These findings suggest that many--perhaps most--strains of RHDV may be propagated through both 'pathogenic' and 'non-pathogenic' modes of behaviour. Transmission occurred predominantly during and just after the breeding season.

Characterization of a siberian virus isolated from a patient with progressive chronic tick-borne encephalitis.

A strain of Tick-borne encephalitis virus designated Zausaev (Za) was isolated in Siberia from a patient who died of a progressive (2-year) form of tick-borne encephalitis 10 years after being bitten by a tick. The complete genomic sequence of this virus was determined, and an attempt was made to correlate the sequence with the biological characteristics of the virus. Phylogenetic analysis demonstrated that this virus belongs to the Siberian subtype of Tick-borne encephalitis virus. Comparison of Za virus with two related viruses, a Far Eastern isolate, Sofjin, and a Siberian isolate, Vasilchenko, revealed differences among the three viruses in pathogenicity for Syrian hamsters, cytopathogenicity for PS cells, plaque morphology, and the electrophoretic profiles of virus-specific nonstructural proteins. Comparative amino acid alignments revealed 10 individual amino acid substitutions in the Za virus polyprotein sequence that were different from those of other tick-borne flaviviruses. Notably, the dimeric form of the Za virus NS1 protein migrated in polyacrylamide gels as a heterogeneous group of molecules with a significantly higher electrophoretic mobility than those of the Sofjin and Vasilchenko viruses. Two amino acid substitutions, T(277)-->V and E(279)-->G, within the NS1 dimerization domain are probably responsible for the altered oligomerization of Za virus NS1. These studies suggest that the patient from whom Za virus was isolated died due to increased pathogenicity of the latent virus following spontaneous mutagenesis.

Molecular epidemiology of Rabbit haemorrhagic disease virus.

Millions of domestic and wild European rabbits (Oryctolagus cuniculus) have died in Europe, Asia, Australia and New Zealand during the past 17 years following infection by Rabbit haemorrhagic disease virus (RHDV). This highly contagious and deadly disease was first identified in China in 1984. Epidemics of RHDV then radiated across Europe until the virus apparently appeared in Britain in 1992. However, this concept of radiation of a new and virulent virus from China is not entirely consistent with serological and molecular evidence. This study shows, using RT-PCR and nucleotide sequencing of RNA obtained from the serum of healthy rabbits stored at 4 degrees C for nearly 50 years, that, contrary to previous opinions, RHDV circulated as an apparently avirulent virus throughout Britain more than 50 years ago and more than 30 years before the disease itself was identified. Based on molecular phylogenetic analysis of British and European RHDV sequences, it is concluded that RHDV has almost certainly circulated harmlessly in Britain and Europe for centuries rather than decades. Moreover, analysis of partial capsid sequences did not reveal significant differences between RHDV isolates that came from either healthy rabbits or animals that had died with typical haemorrhagic disease. The high stability of RHDV RNA is also demonstrated by showing that it can be amplified and sequenced from rabbit bone marrow samples collected at least 7 weeks after the animal has died.

Evaluation of the spiral plating system for the routine assessment of indicator microorganisms in raw ewe's milk.

The numbers of members of different microbial groups in bulk raw ewe's milk used for cheesemaking (46 samples, taken on receipt at the dairy over 1 year) were assayed by the spiral plating system to determine the effectiveness of this method compared with that of widely accepted conventional methods in providing counts. The results indicated that for ewe's milk, the suitability of the spiral plating system depends to a great extent on the microbial group studied. Although "spiral" counts of mesophiles, psychrotrophs, coliforms, and Enterobacteriaceae could be considered equivalent to those obtained by conventional techniques (r > or = 0.90; variance between replicate platings approximately 0.005), the automated method was found not to be suitable for the assessment of other groups of indicator bacteria (thermodurics and enterococci). Counts of lactic acid bacteria and yeasts and molds were affected significantly (P < 0.05) by the plating method, although other statistical parameters were more favorable (r = 0.88 and r = 0.82, respectively; 95% confidence limits within 0.5 log units). Finally, counts of staphylococci, particularly on Baird-Parker medium, showed less variation and higher reproducibility with the spiral method. Nevertheless, for the routine microbiological analysis of ewe's milk, the spiral plating system, with its time-, effort-, and material-saving advantages, is preferred over the conventional method.

Temperature characterization of psychrotrophic and mesophilic Bacillus species from milk.

A total of 50 isolates of Bacillus spp. and one reference strain were investigated for their growth at 6.5 degrees C for 10 d, 30 degrees C for 3 d and 40 degrees C for 2 d. The results obtained differentiated three physiological groups: one clearly psychrotrophic (able to grow at 6.5 degrees C in 10 d, but not at 40 degrees C in 2 d), one intermediate in psychrotrophy (it grew at both 40 and 6.5 degrees C) and one mesophilic (capable of growth at 30 and 40 degrees C, but not at 6.5 degrees C). The proportion of strains in the second group was higher among isolates of B. cereus than for other Bacillus spp. However, the proportion of real mesophilic strains was lower for B. cereus isolates. Psychrotrophic B. cereus grew better at both 6.5 and 30 degrees C than other psychrotrophic Bacillus spp. Using eight strains, a correlation between differential growth at mesophilic temperatures (count at 30 degrees C minus count at 40 degrees C) and a standard psychrotrophic count at 6.5 degrees C for 10 d (r = 0.95) was obtained in mixed cultures when the psychrotrophic flora count was < or = 1 log (cfu/ml) lower than the mesophilic count.

Evaluation of different systems for the identification of Bacillus strains isolated from Spanish fermented sausages.

Sixty-nine isolates obtained during the manufacture and ripening of Spanish fermented sausages were identified to species level using the Vitek Bacillus biochemical card, the dichotomous key and table proposed by Berkeley et al. ((1984). In Methods in Microbiology, Vol. 16. Academic Press, London, p. 291), morphological and physiological tests and the API 20E miniaturized system. None of the tested systems was entirely satisfactory and the final identification was mainly done on the basis of cellular morphology and the table of test results. Our isolates belonged to the species: B. subtilis (37), B. megaterium (22), B. pumilus (5), B. circulans (3) and unidentified (2). Forty-five cultures (65.2%) were accurately identified with the dichotomous key. A similar figure for the Vitek Bacillus biochemical card was 36%. The results of the API 20E system were very reproducible, especially those of the Voges-Proskauer test. Most of the strains of B. megaterium were misidentified as B. subtilis with the dichotomous key. On the other hand, a high percentage of the cultures belonging to B. subtilis were misidentified as B. megaterium with the Vitek system.

Numerical characterization study of Micrococcaceae associated with lamb spoilage.

A computer-assisted characterization of 296 Micrococcaceae isolates obtained from aerobically chill-stored lamb carcasses was carried out using a probability matrix and Bayesian identification theorems, complemented with cluster analysis. Preliminary identification was done with an original probability matrix comprising 37 previously described taxa and 32 tests. Although its statistical quality was adequate, the percentage of identification of field strains to species level was only 70% (96.6% identified with genera). To achieve an improved characterization, cluster analysis was subsequently performed on this group and an additional 26% could be associated with defined species, with five more taxa defined. The combined use of both approaches was judged positive as new identifications and better discrimination could be achieved. The majority of our isolates belonged to the Staphylococcus species group. Many species and groups of staphylococci increased as the spoilage progressed.

[Predisposition of Down syndrome to chronic infection with the hepatitis B virus]. / Predisposición del síndrome de Down a la infección crónica por el virus B de la hepatitis.

In order to know in Down's Syndrome (DS) the age of infection by hepatitis B virus (HBV), the incidence of evolution to a chronic carrier status and the optimal age for vaccination against this virus, a study of the prevalence of HBV-markers was carried out in 302 mentally retarded children: Group I, 51 pre-schoolchildren with DS (mean age 2.9 +/- 1.6 years); Group II, 72 schoolchildren with DS (mean age 13.8 +/- 3 years) and Group III, 179 schoolchildren with other types of mental retarded (OMR). Children from group II and III attended the same school as external day-pupils. Fifty eight percent of schoolchildren with SD presented at least one HBV-marker while this percentage was of 25% in schoolchildren with OMR (p > 0.05) or pre-schoolchildren with DS (p > 0.005); DS schoolchildren become also HBV chronic carrier with higher frequency than ORM schoolchildren (40 vs 17) (p > 0.05) and they maintained HBV replication in a higher proportion of cases (36 vs 4) (p > 0.05). In conclusion children with DS acquire easily HBV infection and this occurs when they attend the school independently that the school is a closed or an open institution. They also become more frequently HBV chronic carriers and they maintain HBV replication; so, they must be vaccinated before they begin to attend school and they must be treated with antiviral agents as soon as possible.

Factors affecting spoilage microflora succession on lamb carcasses at refrigeration temperatures.

Three bacterial groups were detected during the shelf-life of lamb carcasses stored at refrigeration temperatures: coryneforms (mostly Brochothrix thermosphacta), Gram-positive cocci (staphylococci) and Gram-negative bacilli (Pseudomonas spp. and Moraxella spp.). Influence of categorical variables such as sampling day, sampling area and sampling method on their recovery was analysed by a chi-square test of independence and loglinear analysis. Hierarchical loglinear modelling proved to be very useful as several three-way interactions of factors were observed.

Modern microbiological methods for foods: colony count and direct count methods. A review.

Over the last years methods for enumeration of microorganisms in foods are changing rapidly. Techniques based on totally new concepts as well as instruments and miniaturized systems that allow the automation and simplification of existing microbiological procedures have been developed. These rapid methodologies should satisfy the increasing requirements for effective quality assurance of foods. In the present paper we review some of the more interesting methods based on colony count or direct bacterial count.

Species of Pseudomonas obtained at 7 degrees C and 30 degrees C during aerobic storage of lamb carcasses.

A total of 268 strains of Pseudomonas isolated during storage life of lamb carcasses was identified to species level. One-hundred and thirteen strains obtained at 30 degrees C were Ps. fragi (51), Ps. lundensis (17), Ps. fluorescens biovars I (10), III (9) and VI (1), Ps. putida biovar A (8 strains) and unidentified (17 strains). Species and biovars isolated at 7 degrees C (155) were Ps. fragi (101), Ps. lundensis (32), Ps. fluorescens biovar I (6), Ps. putida biovar A (8) and unidentified (8). Numerical analysis (82% SSM, UPGMA) of 'psychrotrophic' and 'mesophilic' strains resulted in the formation of nine and eight clusters respectively. The dendrograms obtained exhibited similar structures. Most of the strains of Ps. lundensis and Ps. fragi clustered together. Strains of this latter species also joined the type strain of Ps. testosteroni and appeared included with phenons containing the Ps. putida strains. There were clusters made up exclusively of strains assigned to one biovar or group (Ps. fluorescens biovars I and II and unidentified). A high level of similarity was observed between clusters of Ps. fluorescens biovar I and those containing the Ps. fragi-Ps. lundensis complex (> 74% SSM) and Ps. lundensis (> 80%). The recovery of pseudomonads seemed to be affected by the sampling day.

Numerical taxonomy of gram-negative, nonmotile, nonfermentative bacteria isolated during chilled storage of lamb carcasses.

A numerical taxonomic study using 75 characters was performed with 132 strains of gram-negative, nonmotile, nonfermentative bacteria selected on the basis of lack of motility and Gram reaction among 1,200 cultures isolated during aerobic storage of lamb carcasses. At the 80% similarity level (SSM), eight clusters were formed. Strains in clusters 1 to 6 could be identified as members of the family Moraxellaceae and, more specifically, as members of the Psychrobacter-[Moraxella] phenylpyruvica subgroup. Of these strains, clusters 1 and 2 (88 strains) were identified as [Moraxella] phenylpyruvica and cluster 3 (15 strains) was identified as Psychrobacter immobilis. Clusters 4, 5, and 6 were not identifiable with any species. Clusters 7 and 8 consisted of 14 strains considered nonmotile variants of Pseudomonas fragi. The highest separation indices corresponded to acid production from certain carbohydrates (melibiose, L-arabinose, and cellobiose). Although strains of Psychrobacter-Moraxella clusters were relatively frequently identified at the completion of slaughter, very few cultures were detected on spoiled carcasses. It appears, therefore, that this group of organisms has only low spoilage potential.