The combined antibacterial and anticancer properties of nano Ce-containing Mg-phosphate ceramic

AIM

This paper was mainly aimed at synthesis of Ce-containing nano-Mg-phosphate ceramic as a multifunctional material.

MATERIALS AND METHODS

Two ceramics based on Mg₃(PO₄)₂ and Ce_0.2Mg_2.8(PO₄)₂ formulas (MP and MP-C, respectively) were synthesized. The synthesized powders were characterized by XRD, TEM, Zeta potential, and FTIR. Also, their dissolution behavior was tested in Tris-HCl buffer solution. Moreover, the antimicrobial efficacy was evaluated against gram-positive bacteria (Bacillus sphaericus MTCC 511 &Staphylococcus aureus MTCC 87) and gram-negative bacteria (Enterobacter aerogenes MTCC 111 &Pseudomonas aeruginosa MTCC 1034) using dick diffusion assay and microdilution method. Furthermore, the cell viability test was performed for the ceramics on Vero cells (African green monkey kidney cells), and their antitumor activity was determined by PC3 cell line (prostatic cancer). Also, the cellular uptake was determined by the flow cytometry.

KEY FINDINGS

The results showed that the substitution of Mg by Ce decreased the particle size from 40 to 90 nm for MP sample to 2-10 nm for MP-C sample and increased the degradation rate. Both samples showed excellent antimicrobial activities. Moreover, MP demonstrated more cell viability than MP-C on Vero cells at high concentrations, whereas, MP-C showed more antitumor activity on PC3 cells than MP sample. Moreover, MP-C showed a higher cell uptake than MP due to its smaller size and more negative charge.

SIGNIFICANCE

Mg-phosphate ceramic can be used in this study successfully as a delivery system for cerium ions and showed a high antitumor activity, which makes it highly recommended as safe and effective cancer treatment materials.

Antibiotic resistance and heavy metal tolerance in cultured bacteria from hot springs as indicators of environmental intrinsic resistance and tolerance levels

Antibiotic resistance (AR) in the environment is a growing and global concern for public health, and intrinsic AR from pristine sites untouched by pharmaceutical antibiotics is not commonly studied. Forty aerobic bacteria were isolated from water and sediment samples of hot springs in South Africa. Resistance against ten antibiotics (carbenicillin, gentamicin, kanamycin, streptomycin, tetracycline, chloramphenicol, ceftriaxone, co-trimoxazole, nalidixic acid and norfloxacin) was tested using a standard disk diffusion assay. Resistance to one or two antibiotics were equally found in 37.5%, while the remaining 22% showed complete sensitivity. Intermediate resistance was found for ceftriaxone (52.5%), nalidixic acid (37.5%) and carbenicillin (22.5%), while low levels of resistance were observed for streptomycin (5%) and kanamycin (2.5%), and total sensitivity towards the other antibiotics. Twenty-nine isolates were also tested against eight different heavy-metal salts (Al, Cr, Cu, Fe, Hg, Mn, Ni and Pb) at 10 and 40 mM. All isolates were tolerant and able to grow on ≥2 heavy-metal salts at both concentrations. No association was observed between AR and heavy metal tolerance (HMT). Based on the relatively low AR levels, hot spring sites are pristine environments reflecting baseline levels for comparison to other potentially contaminated groundwater sites.

Two selenium tolerant Lysinibacillus sp. strains are capable of reducing selenite to elemental Se efficiently under aerobic conditions

Microbes play important roles in the transport and transformation of selenium (Se) in the environment, thereby influencing plant resistance to Se and Se accumulation in plant. The objectives are to characterize the bacteria with high Se tolerance and reduction capacity and explore the significance of microbial origins on their Se tolerance, reduction rate and efficiency. Two bacterial strains were isolated from a naturally occurred Se-rich soil at tea orchard in southern Anhui Province, China. The reduction kinetics of selenite was investigated and the reducing product was characterized using scanning electron microscopy and transmission electron microscopy-energy dispersive spectroscopy. The bacteria were identified as Lysinibacillus xylanilyticus and Lysinibacillus macrolides, respectively, using morphological, physiological and molecular methods. The results showed that the minimal inhibitory concentrations (MICs) of selenite for L. xylanilyticus and L. macrolides were 120 and 220 mmol/L, respectively, while MICs of selenate for L. xylanilyticus and L. macrolides were 800 and 700 mmol/L, respectively. Both strains aerobically reduced selenite with an initial concentration of 1.0 mmol/L to elemental Se nanoparticles (SeNPs) completely within 36 hr. Biogenic SeNPs were observed both inside and outside the cells suggesting either an intra- or extracellular reduction process. Our study implied that the microbes from Se-rich environments were more tolerant to Se and generally quicker and more efficient than those from Se-free habitats in the reduction of Se oxyanions. The bacterial strains with high Se reduction capacity and the biological synthesized SeNPs would have potential applications in agriculture, food, environment and medicine.

A genome-scale metabolic reconstruction of Lysinibacillus sphaericus unveils unexploited biotechnological potentials

The toxic lineage (TL) of Lysinibacillus sphaericus has been extensively studied because of its potential biotechnological applications in biocontrol of mosquitoes and bioremediation of toxic metals. We previously proposed that L. sphaericus TL should be considered as a novel species based on a comparative genomic analysis. In the current work, we constructed the first manually curated metabolic reconstruction for this species on the basis of the available genomes. We elucidated the central metabolism of the proposed species and, beyond confirming the reported experimental evidence with genomic a support, we found insights to propose novel applications and traits to be considered in further studies. The strains belonging to this lineage exhibit a broad repertory of genes encoding insecticidal factors, some of them remain uncharacterized. These strains exhibit other unexploited biotechnological important traits, such as lactonases (quorum quenching), toxic metal resistance, and potential for aromatic compound degradation. In summary, this study provides a guideline for further research aimed to implement this organism in biocontrol and bioremediation. Similarly, we highlighted the unanswered questions to be responded in order to gain a deeper understanding of the L. sphaericus TL biology.

Biofilm characteristics and evaluation of the sanitation procedures of thermophilic Aeribacillus pallidus E334 biofilms

The ability of Aeribacillus pallidus E334 to produce pellicle and form a biofilm was studied. Optimal biofilm formation occurred at 60 °C, pH 7.5 and 1.5% NaCl. Extra polymeric substances (EPS) were composed of proteins and eDNA (21.4 kb). E334 formed biofilm on many surfaces, but mostly preferred polypropylene and glass. Using CLSM analysis, the network-like structure of the EPS was observed. The A. pallidus biofilm had a novel eDNA content. DNaseI susceptibility (86.8% removal) of eDNA revealed its importance in mature biofilms, but the purified eDNA was resistant to DNaseI, probably due to its extended folding outside the matrix. Among 15 cleaning agents, biofilms could be removed with alkaline protease and sodium dodecyl sulphate (SDS). The removal of cells from polypropylene and biomass on glass was achieved with combined SDS/alkaline protease treatment. Strong A. pallidus biofilms could cause risks for industrial processes and abiotic surfaces must be taken into consideration in terms of sanitation procedures.

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.

Toxic metals and associated sporulated bacteria on Andean hummingbird feathers

Human activities in the Sabana de Bogotá, Colombia, release toxic metals such as lead (Pb) and chromium (Cr) into the environment polluting the air, water, and soil. Because birds are in contact with these pollutants and their sources, they may serve as bioindicator organisms. We evaluated the use of hummingbird feathers obtained from individuals captured in three sites of the Sabana de Bogotá as bioindicators of toxic metal pollution using spectrophotometric and spectroscopic methods based on single-feather samples. We also characterized the bacterial microbiota associated with hummingbird feathers by molecular identification using the 16S rRNA with a special focus on sporulated bacteria. Finally, we described the interactions which naturally occur among the feathers, their associated bacteria, and pollutants. We found differences in Pb and Cr concentrations between sampling sites, which ranged from 2.11 to 4.69 ppm and 0.38 to 3.00 ppm, respectively. This may reflect the impact of the activities held in those sites which release pollutants to the environment. Bacterial assemblages mainly consisted of sporulated bacilli in the Bacillaceae family (65.7 % of the identified morphotypes). We conclude that the feathers of wild tropical birds, including hummingbirds, can be used as lead and chromium bioindicators and that bacteria growing on feathers may in fact interact with these two toxic metals.

Oxidative stress response in dye degrading bacterium Lysinibacillus sp. RGS exposed to Reactive Orange 16, degradation of RO16 and evaluation of toxicity

Lysinibacillus sp. RGS degrades sulfonated azo dye Reactive Orange 16 (RO16) efficiently. Superoxide dismutase and catalase activity were tested to study the response of Lysinibacillus sp. RGS to the oxidative stress generated by RO16. The results demonstrated that oxidative stress enzymes not only protect the cell from oxidative stress but also has a probable role in decolorization along with an involvement of oxidoreductive enzymes. Formation of three different metabolites after degradation of RO16 has been confirmed by GC-MS analysis. FTIR analysis verified the degradation of functional groups of RO16, and HPTLC confirmed the removal of auxochrome group from the RO16 after degradation. Toxicity studies confirmed the genotoxic, cytotoxic, and phytotoxic nature of RO16 and the formation of less toxic products after the treatment of Lysinibacillus sp. RGS. Therefore, Lysinibacillus sp. RGS has a better perspective of bioremediation for textile wastewater treatment.

[The high ethanol tolerance in a thermophilic bacterium Anoxybacillus sp. WP06]

Anoxybacillus sp. WP06 is a thermophilic (optimum temperature for growth, 60 degrees C), facultative anaerobe. Strain WP06 is able to utilize a wide range of carbon sources such as glucose, xylose, arabinose, starch, maltose and sorbitol. Anaerobically, glucose and xylose were fermented to ethanol as minor products. Unlike most thermophilic bacteria isolated to date, strain WP06 is tolerant (maintained viability) to high ethanol concentrations up to 15% at 60 degrees C. The growth rate was slightly inhibited at 8% ethanol. The observation that strain WP06 exhibits higher tolerance of 15% ethanol at 60 degrees C exploits the level of ethanol tolerance in thermophilic bacteria. Strain WP06 may be candidate for mechanisms of ethanol tolerance in thermophilic bacteria.

Phenotypic and genotypic characterization of Paenibacillus larvae isolates

Paenibacillus larvae is the causative agent of American Foulbrood (AFB), a severe disease of honeybees (Apis melifera). The aim of this work was to develop a strategy for the subtyping and the epidemiological analysis of P. larvae. Phenotypic characterisation, susceptibility to several antibiotics, electrophoresis of whole bacterial proteins, rep-PCR, ribotyping and DGGE were assessed using a collection of P. larvae isolates from different Uruguayan and Argentinean locations. Results indicated that there are two P. larvae genotypes circulating in Uruguay ERIC I-BOX A (worldwide distributed) and ERIC I-BOX C (exclusively detected in Argentina until this study). These results suggest that P. larvae isolates had moved between Argentina and Uruguay, probably through the Uruguay River. Patterns of whole bacterial proteins, DGGE and ribotyping did not improve the P. larvae intraspecific discrimination. Antibiotic susceptibility assays showed that 100% isolates were OTC-sensitive and 22% (belonging to ERIC I-BOX A group) were sulfisoxazole-resistant. This work may contribute to the elucidation of basic aspects related to the epidemiology of AFB in Uruguay and in the region.

Sporicidal Activity of the KMT reagent in its vapor phase against Geobacillus stearothermophilus Spores

In an investigation of the sporicidal activity of the KMT reagent, a vapor phase study was performed using five kinds of carriers contaminated with Geobacillus stearothermophilus spores. When 25 ml of the KMT reagent was vaporized in a chamber (capacity; approximately 95 liters), the 2-step heating method (vaporization by a combination of low temperature and high temperature) showed the most effective sporicidal activity in comparison with the 1-step heating method (rapid vaporization). The 2-step heating method appeared to be related to the sporicidal activity of vaporized KMT reagent, i.e., ethanol and iodine, which vaporized mainly when heated at a low temperature such as 55 C, and acidic water, which vaporized mainly when heated at a high temperature such as 300 C. We proposed that the KMT reagent can be used as a new disinfectant not only in the liquid phase but also in the vapor phase in the same way as peracetic acid and hydrogen peroxide.

Salinity-dependent switching of osmolyte strategies in a moderately halophilic bacterium: glutamate induces proline biosynthesis in Halobacillus halophilus

The moderately halophilic bacterium Halobacillus halophilus copes with the salinity in its environment by the production of compatible solutes. At intermediate salinities of around 1 M NaCl, cells produce glutamate and glutamine in a chloride-dependent manner (S. H. Saum, J. F. Sydow, P. Palm, F. Pfeiffer, D. Oesterhelt, and V. Müller, J. Bacteriol. 188:6808-6815, 2006). Here, we report that H. halophilus switches its osmolyte strategy and produces proline as the dominant solute at higher salinities (2 to 3 M NaCl). The proline biosynthesis genes proH, proJ, and proA were identified. They form a transcriptional unit and encode the pyrroline-5-carboxylate reductase, the glutamate-5-kinase, and the glutamate-5-semialdehyde dehydrogenase, respectively, catalyzing proline biosynthesis from glutamate. Expression of the genes was clearly salinity dependent and reached a maximum at 2.5 M NaCl, indicating that the pro operon is involved in salinity-induced proline biosynthesis. To address the role of anions in the process of pro gene activation and proline biosynthesis, we used a cell suspension system. Chloride salts lead to the highest accumulation of proline. Interestingly, chloride could be substituted to a large extent by glutamate salts. This unexpected finding was further analyzed on the transcriptional level. The cellular mRNA levels of all three pro genes were increased up to 90-fold in the presence of glutamate. A titration revealed that a minimal concentration of 0.2 M glutamate already stimulated pro gene expression. These data demonstrate that the solute glutamate is involved in the switch of osmolyte strategy from glutamate to proline as the dominant compatible solute during the transition from moderate to high salinity.

Basic Characteristics of Sporolactobacillus inulinus BCRC 14647 for Potential Probiotic Properties

The basic characteristics of the spore-forming lactic acid bacterium, Sporolactobacillus inulinus BCRC 14647, was evaluated in vitro for its potential probiotic properties. Assessments including acid and bile salt tolerance, adhesiveness, and antagonistic effects on pathogenic Salmonella enteritidis BCRC 10744, as well as inhibition factors of spent culture supernatant (SCS) and an invasion assay, were conducted using Lactobacillus acidophilus BCRC 10695 and two bifidobacteria (Bifidobacterium bifidum BCRC 14615 and B. longum BCRC 11847) as a reference. In the results, S. inulinus spores presented significantly higher survival rates than the vegetative cell form in acidic conditions as well as the reference bifidobacteria. However, L. acidophilus showed the highest viability among all tested strains. Similar results were found in the bile tolerance test. Compared with the reference strains, the vegetative cell form of S. inulinus possessed a proper adhesive characteristic (71.7 bacteria/field for S. inulinus and 91.3 and 45.7 bacteria/field for B. bifidum and B. longum, respectively). In the adhesion assay, both the spore form of S. inulinus (17.1 bacteria/field) and the negative control, L. bulgaricus BCRC 14009 (5.9 bacteria/field), displayed nonadhesive traits. The vegetative cells of S. inulinus and its SCS both dramatically decrease the adhesion of S. enteritidis to Caco-2 cells; meanwhile, the SCS of S. inulinus vegetative cells inhibited the growth of S. enteritidis in the inhibition zone test. The existing inhibition factor could be assumed to be lactic acid in the SCS. From the results of the invasion assay, S. inulinus showed high safety properties. In conclusion, based on these in vitro evaluations, results suggest that S. inulinus presents probiotic features of great potential in the vegetative cell form.

Geobacillus toebii subsp. decanicus subsp. nov., a hydrocarbon-degrading, heavy metal resistant bacterium from hot compost

A thermophilic, spore-forming bacterial strain L1(T) was isolated from hot compost "Pomigliano Environment" s.p.a., Pomigliano, Naples, Italy. The strain was identified by using a polyphasic taxonomic approach. L1(T) resulted in an aerobic, gram-positive, rod-shaped, thermophilic with an optimum growth temperature of 68 degrees C chemorganotrophic bacterium which grew on hydrocarbons as unique carbon and energy sources and was resistant to heavy metals. The G+C DNA content was 43.5 mol%. Phylogenetic analysis of 16S rRNA gene sequence and Random Amplified Polymorphic DNA-PCR (RAPD-PCR) analysis of L1(T) and related strains showed that it forms within Geobacillus toebii, a separate cluster in the Geobacillus genus. The composition of cellular fatty acids analyses by Gas-Mass Spectroscopy differed from that typical for the genus Geobacillus in that it is lacking in iso-C15 fatty acid, while iso-C16 and iso-C17 were predominant. Isolates grew on a rich complex medium at temperatures between 55-75 degrees C and presented a doubling time (t(d)) of 2 h and 6 h using complex media and hydrocarbon media, respectively. Among hydrocarbons tested, n-decane (2%) was the more effective to support the growth (1 g/L of wet cells). The microorganism showed resistance to heavy metal tested during the growth. Furthermore, intracellular alpha-galactosidase and alpha-glucosidase enzymatic activities were detectable in the L1(T) strain. Based on phenotypic, phylogenetic, fatty acid analysis and results from DNA-DNA hybridization, we propose assigning a novel subspecies of Geobacillus toebii, to be named Geobacillus toebii subsp. decanicus subsp. nov., with the type strain L1(T) (=DSM 17041=ATCC BAA 1004).

Cadmium ion biosorption by the thermophilic bacteria Geobacillus stearothermophilus and G. thermocatenulatus

This study reports surface complexation models (SCMs) for quantifying metal ion adsorption by thermophilic microorganisms. In initial cadmium ion toxicity tests, members of the genus Geobacillus displayed the highest tolerance to CdCl2 (as high as 400 to 3,200 microM). The thermophilic, gram-positive bacteria Geobacillus stearothermophilus and G. thermocatenulatus were selected for further electrophoretic mobility, potentiometric titration, and Cd2+ adsorption experiments to characterize Cd2+ complexation by functional groups within and on the cell wall. Distinct one-site SCMs described the extent of cadmium ion adsorption by both studied Geobacillus sp. strains over a range of pH values and metal/bacteria concentration ratios. The results indicate that a functional group with a deprotonation constant pK value of approximately 3.8 accounts for 66% and 80% of all titratable sites for G. thermocatenulatus and G. stearothermophilus, respectively, and is dominant in Cd2+ adsorption reactions. The results suggest a different type of functional group may be involved in cadmium biosorption for both thermophilic strains investigated here, compared to previous reports for mesophilic bacteria.

Protein expression analysis of Halobacillus dabanensis D-8T subjected to salt shock

To investigate the mechanism of salt tolerance of gram-positive moderately halophilic bacteria, two-dimensional gel electrophoresis (2-D PAGE) was employed to achieve high resolution maps of proteins of Halobacillus dabanensis D-8T. Approximately 700 spots of proteins were identified from these 2-D PAGE maps. The majority of these proteins had molecular weights between 17.5 and 66 kDa, and most of them were distributed between the isoelectric points (pI) 4.0 and 5.9. Some protein spots were distributed in the more acidic region of the 2-D gel (pI <4.0). This pattern indicated that a number of proteins in the strain D-8T are acidic. To understand the adaptation mechanisms of moderately halophilic bacteria in response to sudden environmental changes, differential protein profiles of this strain were investigated by 2-D PAGE and Imagemaster 2D Platinum software after the cells were subjected to salt shock of 1 to 25% salinity for 5 and 50 min. Analysis showed 59 proteins with an altered level of expression as the result of the exposure to salt shock. Eighteen proteins had increased expression, 8 proteins were induced, and the expression of 33 proteins was down-regulated. Eight of the up-regulated proteins were identified using MALDI-TOF/MS and MASCOT, and were similar to proteins involved in signal transduction, proteins participating in energy metabolism pathways and proteins involved in stress.

Microbial Contamination of Endodontic Files Received from the Manufacturer

This study was conducted to test the sterility of new unused endodontic files received from manufacturers. Fifteen types of hand and rotary files from five manufacturers were tested. Positive microbial cultures were obtained from 13% of the 150 files tested. Autoclaved files were intentionally contaminated with bacterial species recovered from the positive cultures to evaluate a chairside sterilization method. Immersion of contaminated files in 5.25% sodium hypochlorite for five minutes sterilized the files. The results of this study indicate that endodontic files should be sterilized before clinical use. It is also suggested that manufacturers list the sterility state of their endodontic files on their packaging.

Decontamination assessment of Bacillus anthracis, Bacillus subtilis, and Geobacillus stearothermophilus spores on indoor surfaces using a hydrogen peroxide gas generator

AIMS

To evaluate the decontamination of Bacillus anthracis, Bacillus subtilis, and Geobacillus stearothermophilus spores on indoor surface materials using hydrogen peroxide gas.

METHODS AND RESULTS

Bacillus anthracis, B. subtilis, and G. stearothermophilus spores were dried on seven types of indoor surfaces and exposed to > or =1000 ppm hydrogen peroxide gas for 20 min. Hydrogen peroxide exposure significantly decreased viable B. anthracis, B. subtilis, and G. stearothermophilus spores on all test materials except G. stearothermophilus on industrial carpet. Significant differences were observed when comparing the reduction in viable spores of B. anthracis with both surrogates. The effectiveness of gaseous hydrogen peroxide on the growth of biological indicators and spore strips was evaluated in parallel as a qualitative assessment of decontamination. At 1 and 7 days postexposure, decontaminated biological indicators and spore strips exhibited no growth, while the nondecontaminated samples displayed growth.

CONCLUSIONS

Significant differences in decontamination efficacy of hydrogen peroxide gas on porous and nonporous surfaces were observed when comparing the mean log reduction in B. anthracis spores with B. subtilis and G. stearothermophilus spores.

SIGNIFICANCE AND IMPACT OF THE STUDY

These results provide comparative information for the decontamination of B. anthracis spores with surrogates on indoor surfaces using hydrogen peroxide gas.

Validation of low-temperature steam with formaldehyde sterilization for endoscopes, using validation device

BACKGROUND

Validation of sterilization is an important step before clinical use of medical equipment. Adequate validation of sterilization of the endoscope has not been reported. One reason for this is the lack of suitable devices for validation.

METHODS

The VDES (validation device for endoscope sterilization; Olympus prototype model, Olympus, Tokyo, Japan) was designed in two types (type A and type B) and resembles gastroscopes and duodenoscopes, respectively. Each type consists of inner and outer tubing and a central capsule containing a biological indicator. The device was designed to examine the effectiveness of low-temperature sterilizers, such as ethylene oxide gas, hydrogen peroxide gas plasma, and low-temperature steam with formaldehyde (LTSF) sterilizer. The aim of this study was to validate the sterilization of GI endoscopes by the LTSF sterilizer. Sterilization was assessed using both types of VDES after a 60-min application of LTSF.

RESULTS

Culture of the biological indicator confirmed the complete eradication of the bacteria in a total of 10 experiments with each type of VDES after LTSF sterilization.

CONCLUSIONS

Our results confirm that the LTSF sterilizer may sterilize endoscopes currently distributed by Olympus. Commercialization of VDES will make it possible to evaluate the reliability of sterilization when it is set in the sterilization device with endoscopes.

[Randomised placebo controlled double blind study on the effect of prebiotic oligosaccharides on intestinal flora in healthy infants]

AIM

Effects of supplementing prebiotic oligosaccharides to formula for healthy infants were studied in this placebo controlled, randomised, double blind study.

METHODS

Ninety-seven infants were included into the study; among them 42 breast-fed infants, 14 infants fed formula supplemented with 0.4 g/100ml oligosaccharides (9 to 1 mixture of galacto- and fructooligosaccharides) and 13 infants fed control formula were followed-up throughout the 12-week-long study period. The groups receiving formula were compared with statistical methods, whereas data of breast-fed infants served as reference values.

RESULTS

Infants fed the two formulae did not differ in nutrient intakes, growth, occurrence rate of feeding difficulties and atopic manifestations, or in calcium excretion. The intestinal flora did not differ between the two formula fed groups at the beginning of the study. In contrast, numbers of Bifidobacteriae were significantly higher in infants receiving the formula supplemented with prebiotic oligosaccharides both at the 14th day (9 x 1011 versus 5 x 1010, colony forming units/g faeces, median, p < 0.05) and 28th day (9 x 1012 versus 5 x 1010, p < 0.05) of the study.

CONCLUSION

In this study, supplementation of infant formula with prebiotic oligosaccharides resulted in ameliorating the difference in intestinal flora between formula fed and breast-fed healthy infants.

Rapid differentiation and enumeration of the total, viable vegetative cell and spore content of thermophilic bacilli in milk powders with reference to Anoxybacillus flavithermus

AIMS

The development of a rapid method for the selective detection and enumeration of the total and viable vegetative cell and spore content of thermophilic bacilli in milk powder by PCR.

METHODS AND RESULTS

Quantitative PCR and microscopy indicate the presence of up to 2.9 log units more cells in milk powder than accounted for by plate counting due to the majority of cells being killed during milk processing. Two approaches for viable and dead cell differentiation of thermophilic bacilli by quantitative PCR were evaluated, these being the nucleic binding dye ethidium monoazide (EMA) and DNase I digestion. The former agent exposed to a viable culture of Anoxybacillus flavithermus caused considerable cell inactivation. In contrast, DNase I treatment had no effect on cell viability and was utilized to develop DNA extraction methods for the differential enumeration of total, viable vegetative cells and spores in milk powder. Moreover, the methods were further applied and evaluated to 41 factory powder samples taken throughout eight process runs to assess changes in numbers of vegetative cells and spores with time. DNase I treatment reduced vegetative cell numbers enumerated with PCR by up to 2.6 log units. The quantification of spores in the factory milk powders investigated indicates on average the presence of 1.2 log units more spores than determined by plate counting.

CONCLUSIONS

The method presented in this study provides the ability to selectively enumerate the total and viable cell and spore content of reconstituted milk.

SIGNIFICANCE AND IMPACT OF THE STUDY

The current study provides a tool to monitor the extent of thermophilic contamination during milk powder manufacturing 60-90 min after sampling.

Inactivation of Geobacillus stearothermophilus spores by high-pressure carbon dioxide treatment

High-pressure CO2 treatment has been studied as a promising method for inactivating bacterial spores. In the present study, we compared this method with other sterilization techniques, including heat and pressure treatment. Spores of Bacillus coagulans, Bacillus subtilis, Bacillus cereus, Bacillus licheniformis, and Geobacillus stearothermophilus were subjected to CO2 treatment at 30 MPa and 35 degrees C, to high-hydrostatic-pressure treatment at 200 MPa and 65 degrees C, or to heat treatment at 0.1 MPa and 85 degrees C. All of the bacterial spores except the G. stearothermophilus spores were easily inactivated by the heat treatment. The highly heat- and pressure-resistant spores of G. stearothermophilus were not the most resistant to CO2 treatment. We also investigated the influence of temperature on CO2 inactivation of G. stearothermophilus. Treatment with CO2 and 30 MPa of pressure at 95 degrees C for 120 min resulted in 5-log-order spore inactivation, whereas heat treatment at 95 degrees C for 120 min and high-hydrostatic-pressure treatment at 30 MPa and 95 degrees C for 120 min had little effect. The activation energy required for CO2 treatment of G. stearothermophilus spores was lower than the activation energy for heat or pressure treatment. Although heat was not necessary for inactivationby CO2 treatment of G. stearothermophilus spores, CO2 treatment at 95 degrees C was more effective than treatment at 95 degrees C alone.

Enhanced secretion and low temperature stabilization of a hyperthermostable and Ca2+-independent alpha-amylase of Geobacillus thermoleovorans by surfactants

AIMS

Selection of suitable surfactants for enhancing and stabilizing alpha-amylase of Geobacillus thermoleovorans.

METHODS AND RESULTS

Geobacillus thermoleovorans was cultivated in shake flasks containing 50 ml of starch-yeast extract-tryptone (SYT) medium with/without surfactants. Titres of the enzyme in media were monitored. The enzyme was also preserved at 4 degrees C with/without surfactants and enzyme activities were determined. Among polyethylene glycol (PEGs) of different molecular weights, PEG 8000 (0.5%, w/v) caused a slight increase in the enzyme titre, while Tween-20, Tween-40 and Tween-60 (0.03%, w/v) exerted a significant stimulatory effect on enzyme secretion. In the presence of SDS, Tween-80 and cholic acid (0.03%, w/v), the enzyme production was nearly twofold higher than that in the control. The anionic (SDS, cholic acid) and non-ionic (Tweens) detergents increased the cell membrane permeability, and thus, enhanced alpha-amylase secretion. Furthermore, anionic surfactants exhibited stabilizing effect on the enzyme during preservation at 4 degrees C.

CONCLUSIONS

PEG 8000 and the ionic detergents (SDS, cholic acid and Tween-80) were more effective in the solubilization of cell membrane components, and enhancing enzyme yields than the cationic detergents such as CTAB (N,Cetyl-N,N,N-trimethyl ammonium bromide). Further, these surfactants were found to stabilize the enzyme at 4 degrees C.

SIGNIFICANCE AND IMPACT OF THE STUDY

The secretion of Ca2+-independent hyperthermostable alpha-amylase was enhanced in the presence of certain anionic and non-ionic detergents in the medium. Furthermore, the surfactants stabilized the enzyme during preservation at 4 degrees C. The use of this enzyme in starch hydrolysis eliminates the addition of Ca2+ in starch liquefaction and its subsequent removal by ion exchange from sugar syrups.

Novel pyrazine metabolites found in polymyxin biosynthesis by Paenibacillus polymyxa

A complex mixture of methyl-branched alkyl-substituted pyrazines was found in the growth medium of the polymyxin-producing bacterium Paenibacillus polymyxa, and of these, seven are new natural compounds. A total of 19 pyrazine metabolites were identified. The dominant metabolite was 2,5-diisopropylpyrazine as identified using a combination of high-resolution mass spectrometry, (1)H- and (13)C-nuclear magnetic resonance, gas chromatography-mass spectrometry as well as co-elution with an authentic standard. Its biosynthesis was correlated with growth and production was strongly stimulated by valine supplementation. The other pyrazine metabolites, all related pyrazines with either one, two or three alkyl substituents, were identified by means of their mass spectral data and/or co-elution with authentic standards.

Effect of nutrient limitation on product formation during continuous fermentation of xylose with Thermoanaerobacter ethanolicus JW200 Fe(7)

Thermoanaerobacter ethanolicus JW200 Fe(7) was grown in continuous culture, using xylose as the primary carbon source, with progressively lower concentrations of supplementary yeast extract. This enabled the comparison of metabolic flux to fermentation end-products under carbon-limited and carbon-sufficient (yeast extract-limited) conditions and the determination of process data under fully mass-balanced conditions. Under carbon-limitation, the specific ethanol-formation rate was described by q (p)=40.34 micro +3.74, the specific rate of substrate utilisation for maintenance was 0.31+/-0.02 g x g(-1) x h(-1) and the maximum cell yield on xylose, corrected for maintenance requirements, was 0.15+/-0.04 g x g(-1). Based on the product profiles, these corresponded to a maintenance coefficient of m(ATP)=4.1+/-0.5 mmol x g(-1) x h(-1) and a maximum cell yield of = 14.7+/-0.8 x g x mol(-1). Limitation by a component in yeast extract resulted in incomplete xylose utilisation, increased catabolic flux rates (primarily resulting in increased lactate production, due to limitations in the flux through the phosphoroclastic reaction), a reduction in cell yield = 10.0+/-1.0 g x mol(-1) and an increase in maintenance energy requirements of m(ATP)=7.95+/-0.7 mmol x g(-1). The latter was also reflected in a shift from ethanol to acetate production at lower growth rates. An analysis of ethanol and acetate tolerance indicated that any high-intensity process employing this strain would require a bioreactor design which incorporated continuous ethanol stripping.

[Changes in Acholeplasma laidlawii plasma membrane functions during development of resistance to ciprofloxacin and tetracycline]

The role of transport activity of Acholeplasma laidlawii plasmatic membrane in the development of resistance to ciprofloxacin and tetracycline was investigated. It was shown that one of the important steps of resistance development in acholeplasms is a complex of adaptation metabolic reactions providing limited antibiotic accumulation by the cells. In the case of ciprofloxacin resistance metabolism changes concerning transport systems took place before mutations in target genes. Development of tetracycline resistance of mollecutes after incubation in the medium with enhancing antibiotic concentrations and not connected with the presence of tet(M) determinant was demonstrated for the first time.

Effect of linoleic acid concentration on conjugated linoleic acid production by Butyrivibrio fibrisolvens A38

Butyrivibrio fibrisolvens A38 inocula were inhibited by as little as 15 microM linoleic acid (LA), but growing cultures tolerated 10-fold more LA before growth was inhibited. Growing cultures did not produce significant amounts of cis-9, trans-11 conjugated linoleic acid (CLA) until the LA concentration was high enough to inhibit biohydrogenation, growth was inhibited, and lysis was enhanced. Washed-cell suspensions that were incubated anaerobically with 350 microM LA converted most of the LA to hydrogenated products, and little CLA was detected. When the washed-cell suspensions were incubated aerobically, biohydrogenation was inhibited, CLA production was at least twofold greater, and CLA persisted. The LA isomerase reaction was very rapid, but the LA isomerase did not recycle like a normal enzyme to catalyze more substrate. Cells that were preincubated with CLA lost their ability to produce more CLA from LA, and the CLA accumulation was directly proportional (r(2) = 0.98) to the initial cell density. Growing cells were as sensitive to CLA as LA, the LA isomerase and reductases of biohydrogenation were linked, and free CLA was not released. Because growing cultures of B. fibrisolvens A38 did not produce significant amounts of CLA until the LA concentration was high, biohydrogenation was arrested, and the cell density had declined, the flow of CLA from the rumen may be due to LA-dependent bacterial inactivation, death, or lysis.

Efficacy of disinfectants in killing spores of Alicyclobacillus acidoterrestris and performance of media for supporting colony development by survivors

Alicyclobacillus has recently emerged as a spoilage microorganism of concern in a wide range of pasteurized fruit products. The focus of this study was to determine the efficacy of chemical disinfectants in killing Alicyclobacillus acidoterrestris spores. Direct plating media were evaluated for their suitability to support germination and outgrowth of spores surviving exposure to these disinfectants. Significant (P < or = 0.05) reductions of about 2.2, 0.4, and 0.1 logs in the number of viable A. acidoterrestris spores in a five-strain mixture were achieved when spores were suspended in 200 ppm chlorine, 500 ppm acidified sodium chlorite, or 0.2% H2O2 solutions, respectively, for 10 min at 23 degrees C. When treated with either 1,000 ppm chlorine or 4% H2O2, the number of spores was reduced by more than 5 logs. Treatment with 8% trisodium phosphate or 80 ppm Tsunami did not significantly reduce numbers of viable spores. Spores of individual strains of A. acidoterrestris varied little in resistance to the same chemical treatment. K agar (pH 3.7) was judged best for recovering chemically treated spores, compared to orange serum agar (pH 5.0) and potato dextrose agar (pH 3.5). Experiments were done to determine the effectiveness of chemical treatments in killing a mixed-strain inoculum of A. acidoterrestris spores on the surface of apples. Treatment with 500 ppm chlorine or 1,200 ppm acidified sodium chlorite for 1 min significantly (P < or = 0.05) reduced the number of viable spores, but reductions were less than 1 log. Hydrogen peroxide (2%) was ineffective in killing spores remaining on the apple skin after treatment.

Modeling the inhibitory effects of organic acids on bacteria

The inhibitory effect of acids on microbial growth has long been used to preserve foods from spoilage. While much of the effect can be accounted for by pH, it is well known that different organic acids vary considerably in their inhibitory effects. Because organic acids are not members of a homologous series, but vary in the numbers of carboxy groups, hydroxy groups and carbon-carbon double bonds in the molecule, it has typically not been possible to predict the magnitude, or in some cases even the direction, of the change in inhibitory effect upon substituting one acid for another or to predict the net result in food systems containing more than one acid. The objective of this investigation was to attempt to construct a mathematical model that would enable such prediction as a function of the physical and chemical properties of organic acids. Principal Components Analysis (PCA) was applied to 11 properties for each of 17 acids commonly found in food systems; this resulted in four significant principal components (PCs), presumably representing fundamental properties of the acids and indicating each acid's location along each of these four scales. These properties correspond to polar groups, the number of double bonds, molecular size, and solubility in non-polar solvents. Minimum inhibitory concentrations (MICs) for each of eight acids for six test microorganisms were determined at pH 5.25. The MICs for each organism were modeled as a function of the four PCs using partial least squares (PLS) regression. This produced models with high correlations for five of the bacteria (R2 = 0.856, 0.941, 0.968, 0.968 and 0.970) and one with a slightly lower value (R2 = 0.785). Acid susceptible organisms (Bacillus cereus, Bacillus subtilis, and Alicyclobacillus) exhibited a similar response pattern. There appeared to be two separate response patterns for acid resistant organisms; one was exhibited by the two lactobacilli studied and the other by E. coli. Predicting the inhibitory effects of the organic acids as a function of their chemical and physical properties is clearly possible.

Detoxification of aflatoxin-polluted peanut cakes with monomethylamine/Ca(OH)2: pilot industrial application, nutrition experiments, toxicity evaluation

The process described has been studied up to an industrial pilot scale. In this article this article we summarize the basic knowledge on the process and the technological conditions of pilot application for detoxifying peanut cakes polluted by up to 3,500 ppb Aflatoxine (2,300 ppb B1). The nutritional experiments carried out on rats and other mammals are described, and the toxicological and biochemical evaluation of the cakes on Bacillacea are reported and discussed. The data collected show that the MMA/Ca(OH)2 process offers promising possibilities for industrial application on the basis of technological and economic criteria, as well as from the point of view of efficiency and safety.

Anaerobic bacteria: evaluation of disc susceptibility to four cephalosporins

The disc diffusion technique was evaluated with 178 strains of anaerobes and four cephalosporins (cephalothin, cefamandole, cefazolin and cefoxitin). Good correlation in results was found in comparison with the agar dilution technique (p less than 0.001) with the exception of cefamandole and cefazolin against anaerobic cocci (p greater than 0.05). Choosing a breakpoint of 8 microgram/ml for distinguishing susceptible and resistant strains, we determined corresponding incubation, the rate of error is less than 1% for false susceptible and less than 5% for false resistant. However, some strains of anaerobic cocci required a 48 hour incubation period for allowing visible growth. Moreover, a great deal (60.5%) of overlapping zone diameters made interpretation of disc diffusion test difficult among Bacteroides fragilis strains classed as susceptible, intermediate and resistant occuring with cefoxitin. The results have shown that the cephalothin disk will not accurately predict susceptibility of B. fragilis to cefoxitin.

A randomized prospective evaluation of orally administered antibiotics in operations on the colon

In this randomized, prospective study of 91 patients undergoing operations on the colon, we found that neomycin, neomycin-phthalylsulfathiazole and neomycin-erythromycin base all provided adequate intestinal antisepsis. Wound infection rates for all groups were also similar and close to the national average for operations on the colon. A detailed analysis of the wound infections in our series revealed that 60 per cent of these infections were from organisms different from those found on the colonic mucosa. This evidence indicates the possible advantage of parenteral antibiotic therapy to achieve adequate tissue levels of antibiotics not presently possible with orally administered agents.