Un vivo depletion of murine CD8 positive T cells impairs survival during infection with a highly virulent strain ofCryptococcus neoformans

Cell-mediated immunity plays an important but incompletely understood role in host defense againstCryptococcus neoformans. Because of their multiple capacities as cytokine-secreting cells, cytotoxic cells, and antigen-specific suppressor cells, CD8 positive T lymphocytes could potentially either enhance or impair host defense againstC. neoformans. To determine whether CD8 T cells enhance or inhibit host defence during an infection with a highly virulent strain ofC. neoformans, we examined the effect of in vivo CD8 cell depletion on suNival and on the number of organisms in mice infected by either the intratracheal or intravenous routes. Adequacy of depletion was confirmed both phenotypically and functionally. Regardless of the route of infection, we found that survival of mice depleted of CD8 T cells was significantly reduced compared to undepleted mice. Surprisingly, however, CD8 depletion did not alter organism burden measured by quantitative CFU assay in mice infected by either route. These data demonstrate that CD8 positive T cells participate in the immune response to a highly virulent strain ofC. neoformans. By contrast to minimally virulent isolates that do not cause a life threatening infection, the immune response to a highly virulent isolate does not alter the burden of organisms, but does enhance host defense as it is necessary for the optimal survival of infected mice.Abbreviations ³H-TdR ³H-thmidine - CFU colony forming units - FITC Fluorescein isothiocyanate - MLR mixed lymphocyte reaction - PBS phosphate buffered saline     

A comparison of dinitrogen fixation rates in wood litter decayed by white-rot and brown-rot fungi

Nitrogen fixation rates, as estimated by the acetylene reduction technique, were determined in conifer wood litter being decayed by brown- and white-rot fungi. Average ethylene production rates were significantly higher in white-rotted wood (15.1 nmol g^–1 day^–1) than in brown-rotted wood (2.3 nmol g^–1 day^–1). This difference may be related to a higher soluble sugar content in white-versus brown-rotted wood. The nitrogen-fixing bacteriumAzospirillum was not detected in any of the decaying wood samples examined. Greater nitrogen additions from nitrogen-fixing bacteria may be a factor in the more rapid white-rot decay of hardwood litter, as compared to the slower brown-rot decay of conifer wood.     

Distribution of Escherichia coli O157 in Bovine Fecal Pats and Its Impact on Estimates of the Prevalence of Fecal Shedding

The distribution of Escherichia coli O157 in bovine feces was examined by testing multiple samples from fecal pats and determining the density of E. coli O157 in immunomagnetic separation (IMS)-positive fecal samples. The density of E. coli O157 in bovine feces was highly variable, differing by as much as 76,800 CFU g⁻¹ between samples from the same fecal pat. The density in most positive samples was <100 CFU g⁻¹, the limit of reliable detection by IMS. Testing only one 1-g sample of feces per pat with IMS may result in a sensitivity of detection as low as 20 to 50%. It is therefore probable that most surveys have greatly underestimated the prevalence of E. coli O157 shedding in cattle and the proportion of farms with shedding cattle. The sensitivity of the detection of E. coli O157 in bovine feces can be as much as doubled by testing two 1-g samples per pat rather than one 1-g sample.     

Fuel Characteristics of Solid Biofuel Derived from Oil Palm Biomass and Fast Growing Timber Species in Malaysia

The fuel characteristics of solid biofuels derived from biomass that is abundantly available in Malaysia are presented. The objectives of the study were to characterize fuel properties of oil palm biomass (empty fruit bunch (EFB) and oil palm trunk (OPT)) and wood from a range of fast growing timber species (Albizia falcataria, Acacia spp., Endospermum spp. and Macaranga spp.), inclusive and exclusive of bark. Among the fast-growing timber species, the higher heating values ranged from 4288 cal g^-1 to 4383 cal g^-1 for wood inclusive of bark, and 4134 cal g^-1 to 4343 cal g^-1 for wood exclusive of bark. The inclusive of bark portion in the biomass sample generally increased the heating value except for Macaranga spp. Empty fruit bunch and oil palm trunk had heating values of 4315 cal g^-1 and 4104 cal g^-1, respectively. Ash-forming elements and trace elements were much higher in the timber species samples inclusive of bark than samples exclusive of bark. On the other hand, oil palm biomass contained higher ash-forming elements and trace elements than the wood from the fast growing timber species. The European energy crops show higher HHV, Cl and Si content but lower K, Mg, Na and P compared to the local biomass used in this study. The data obtained from this study can serve as a foundation for the selection of suitable biomass to be used as solid fuel, or as a reference on the fabrication of conversion systems for the selection of biomass solid fuel.     

The relationship between colonisation and crown rot symptoms in strawberry plants infected with Phytophthora cactorum

Strawberry tissues infected with Phytophthora cactorum were comminuted and plated in a selective antibiotic agar medium to determine levels of tissue colonisation as indicated by the number of colony forming units (CFU) recovered per gramme of infected tissue. The number of CFU recovered per gramme of tissue increased logarithmically with the amount of necrosis in infected crown, leaf and petiole tissues. Under the conditions of enhanced susceptibility to infection and colonisation caused by cold storage treatments, this relationship between colonisation and necrosis was not significantly altered in the susceptible cv. Tamella. A recovery index was used to determine the effect of infected tissues on the recovery of CFU. This indicated that increasing levels of host colonisation stimulated CFU recovery and may partly explain the large increase in CFU g^-1 with larger amounts of necrosis. The amount of tissue colonisation was greater in inoculated plants of the susceptible cv. Tamella than in less susceptible cv. Cambridge Favourite, although the necrotic tissues of the latter contained more CFU g^-1, indicating a greater level of tolerance to colonisation. In cv. Tamella small amounts of colonisation were capable of causing wilt symptoms, although no wilted plants contained less than 200 CFU g^-1. Conversely, plants containing more than 1000 CFU g^-1 always wilted. In the early stages of infection, low levels of colonisation could be detected in strawberry crowns in the absence of symptoms. Dormant strawberry plants of cv. Tamella were readily infected by P. cactorum zoospore inoculations but, unlike actively growing plants, the majority of infections remained latent. These latent infections exhibited little or no symptoms and CFU recoveries from infected tissues were always below 100 CFU g^-1.     

Study of Adhesion and Survival of Lactobacilli and Bifidobacteria on Table Olives with the Aim of Formulating a New Probiotic Food

With the aim of developing new functional foods, a traditional product, the table olive, was used as a vehicle for incorporating probiotic bacterial species. Survival on table olives of Lactobacillus rhamnosus (three strains), Lactobacillus paracasei (two strains), Bifidobacterium bifidum (one strain), and Bifidobacterium longum (one strain) at room temperature was investigated. The results obtained using a selected olive sample demonstrated that bifidobacteria and one strain of L. rhamnosus (Lactobacillus GG) showed a good survival rate, with a recovery of about 10⁶ CFU g⁻¹ after 30 days. The Lactobacillus GG population remained unvaried until the end of the experiment, while a slight decline (to about 10⁵ CFU g⁻¹) was observed for bifidobacteria. High viability, with more than 10⁷ CFU g⁻¹, was observed throughout the 3-month experiment for L. paracasei IMPC2.1. This strain, selected for its potential probiotic characteristics and for its lengthy survival on olives, was used to validate table olives as a carrier for transporting bacterial cells into the human gastrointestinal tract. L. paracasei IMPC2.1 was recovered from fecal samples in four out of five volunteers fed 10 to 15 olives per day carrying about 10⁹ to 10¹⁰ viable cells for 10 days.     

Evaluation of the Biological Sampling Kit (BiSKit) for Large-Area Surface Sampling

Current surface sampling methods for microbial contaminants are designed to sample small areas and utilize culture analysis. The total number of microbes recovered is low because a small area is sampled, making detection of a potential pathogen more difficult. Furthermore, sampling of small areas requires a greater number of samples to be collected, which delays the reporting of results, taxes laboratory resources and staffing, and increases analysis costs. A new biological surface sampling method, the Biological Sampling Kit (BiSKit), designed to sample large areas and to be compatible with testing with a variety of technologies, including PCR and immunoassay, was evaluated and compared to other surface sampling strategies. In experimental room trials, wood laminate and metal surfaces were contaminated by aerosolization of Bacillus atrophaeus spores, a simulant for Bacillus anthracis, into the room, followed by settling of the spores onto the test surfaces. The surfaces were sampled with the BiSKit, a cotton-based swab, and a foam-based swab. Samples were analyzed by culturing, quantitative PCR, and immunological assays. The results showed that the large surface area (1 m²) sampled with the BiSKit resulted in concentrations of B. atrophaeus in samples that were up to 10-fold higher than the concentrations obtained with the other methods tested. A comparison of wet and dry sampling with the BiSKit indicated that dry sampling was more efficient (efficiency, 18.4%) than wet sampling (efficiency, 11.3%). The sensitivities of detection of B. atrophaeus on metal surfaces were 42 ± 5.8 CFU/m² for wet sampling and 100.5 ± 10.2 CFU/m² for dry sampling. These results demonstrate that the use of a sampling device capable of sampling larger areas results in higher sensitivity than that obtained with currently available methods and has the advantage of sampling larger areas, thus requiring collection of fewer samples per site.     

Biological control of postharvest blue mold of oranges by <Emphasis Type="Italic">Cryptococcus laurentii </Emphasis>(Kufferath) Skinner

Cryptococcus laurentii (Kufferath) Skinner was evaluated for its activity in reducing postharvest blue mold decay of oranges caused by Penicillium italicum in vitro and in vivo. The results showed that washed cell suspensions of yeast provided control of blue mold decay better than yeast in culture broth. Autoclaved cell culture and cell-free culture filtrate failed to provide protection against the pathogen. The concentrations of antagonist had significant effects on biocontrol effectiveness. When the washed yeast cell suspension reached the concentration of 1 × 10⁹ CFU/ml, challenged with pathogen spore suspension at 1 × 10⁴ spores/ml, the blue mold decay was completely inhibited during 5 days of incubation at 20 °C. No complete control was obtained when oranges were stored at 4 °C for 30 days, but the decay was distinctly prevented. Efficacy of C. laurentii was maintained when applied simultaneously or prior to inoculation with P. italicum. Efficacy was reduced when C. laurentii was applied after inoculation. In drop-inoculated wounds of oranges, the populations of C. laurentii increased by approximately 50-fold during the first 24 h at 20 °C. The maximum yeast populations, approximately 250-fold over the initial populations, were reached 15 days after inoculation at 4 °C.     

Sodium citrate induces apoptosis in biocontrol yeast Cryptococcus laurentii

Aim: To provide the observation that sodium citrate induced apoptosis in biocontrol yeast Cryptococcus laurentii. Methods and Results: The viability of the yeast cells was evaluated using the percentage of colony‐forming units (CFU) of treated cells. The induction of cell death was dependent on the concentration of sodium citrate and exhibited typical apoptotic markers such as phosphatidylserine (PS) translocation as shown by annexin V coupled with fluorescein isothiocyanate (FITC) labelling and DNA fragmentation as detected by TdT‐mediated dUTP‐biotin nick end labelling (TUNEL) assay. The annexin V‐positive cells reached the maximum (14·8%) on the third day, whereas TUNEL‐positive cells increased gradually from 5·92 to 27·9% within 5 days of incubation in sodium citrate. In addition, confocal laser microscopy and flow cytometric analysis revealed that the induction of apoptosis was associated with the production of reactive oxygen species (ROS) that reached the highest intracellular level in the first day, before the peak of the early event (PS exposure) in apoptosis. The apoptosis was delayed by the addition of antioxidant glutathione (GSH), suggesting that ROS generated in this process plays a key role in the regulation of the apoptosis in C. laurentii cells. Conclusions: This study indicated that the apoptotic signals in C. laurentii are dependent on citrate ions and/or sodium ions, the concentration and initial acidity of sodium citrate. Induction of ROS in response to sodium citrate plays a significant role in apoptosis. Significance and Impact of the Study: Yeast Cryptococcus laurentii has been selected as an effective biocontrol indicator for the postharvest diseases because of its competition for nutrients and space with the pathogen in the wound of fruits. This study presents a convenient method for commercial production of yeast as biocontrol agent.     

Use of zero-valent iron biosand filters to reduce Escherichia coli O157:H12 in irrigation water applied to spinach plants in a field setting

Aims:  Zero‐valent iron (ZVI) filters may provide an efficient method to mitigate the contamination of produce crops through irrigation water. Methods:  A field‐scale system was utilized to evaluate the effectiveness of a biosand filter (S), a biosand filter with ZVI incorporated (ZVI) and a control (C, no treatment) in decontaminating irrigation water. An inoculum of c. 8·5 log CFU 100 ml^?1 of Escherichia coli O157:H12 was introduced to all three column treatments in 20‐l doses. Filtered waters were subsequently overhead irrigated to ‘Tyee’ spinach plants. Water, spinach plant and soil samples were obtained on days 0, 1, 4, 6, 8, 10, 13 and 15 and analysed for E. coli O157:H12 populations. Results:  ZVI filters inactivated c. 6 log CFU 100 ml^?1E. coli O157:H12 during filtration on day 0, significantly (P < 0·05) more than S filter (0·49 CFU 100 ml^?1) when compared to control on day 0 (8·3 log CFU 100 ml^?1). On day 0, spinach plants irrigated with ZVI‐filtered water had significantly lower E. coli O157 counts (0·13 log CFU g^?1) than spinach irrigated with either S‐filtered (4·37 log CFU g^?1) or control (5·23 log CFU g^?1) water. Soils irrigated with ZVI‐filtered water contained E. coli O157:H12 populations below the detection limit (2 log CFU g^?1), while those irrigated with S‐filtered water (3·56 log CFU g^?1) were significantly lower than those irrigated with control (4·64 log CFU g^?1). Conclusions:  ZVI biosand filters were more effective in reducing E. coli O157:H12 populations in irrigation water than sand filters. Significance and Impact of the Study:  Zero‐valent ion treatment may be a cost‐effective mitigation step to help small farmers reduce risk of foodborne E. coli infections associated with contamination of leafy greens.     

Bacterial species in raw and cured compost from a large-scale urban composter

Summary Raw and cured compost samples from a large-scale urban composter were studied over a period of eight months to gain information on bacterial species present. Total viable, aerobic heterotrophic bacteria, lactose-positive bacteria, antibiotic and metal-resistant bacteria and thermophilic bacteria were enumerated. Both raw and cured compost samples contained metal and antibiotic-tolerant bacteria (–1 compost) as well as high numbers (as high as Log 7.4 CFU g^–1 dry weight compost) of thermophilic bacteria isolated by growth at 55 °C. Selected colonies were also identified using the Biolog 95 substrate identification system.Escherichia coli andSalmonella spp. were not detected in compost samples.     

Detection of Mycobacterium avium ssp. paratuberculosis in cheese, milk powder and milk using IS900 and f57-based qPCR assays

Aims: To develop a quantitative PCR assay for sensitive and specific detection of Mycobacterium avium ssp. paratuberculosis (Map) in a range of dairy products. Methods and Results: TaqMan^® assays were designed to target the IS900 and f57 genetic elements of Map. Both real‐time PCR assays were integrated with the Adiapure^® Map DNA extraction kit and assessed separately for the detection/quantification of Map in spiked milk, Cheddar cheese and milk powder. Assays were validated against Cheddar cheese samples containing known concentrations of Map. The IS900 qPCR assay was significantly more sensitive than the assay based on the f57 primer/probe. At a threshold cycle value of 38, limits of detection (LOD) for the IS900 qPCR assay were 0·6 CFU ml^?1, 2·8 CFU g^?1 and 30 CFU g^?1 for artificially contaminated pasteurized milk, whole milk powder and Cheddar cheese, respectively. The respective LOD’s for the f57 assay were 6·2 CFU ml^?1, 26·7 CFU g^?1 and 316 CFU g^?1. Conclusion: The integrated Adiapure^® extraction – IS900 real time assay described is a sensitive, quantitative method for the detection of Map in dairy products. This is the first study to consider qPCR as a quantitative estimation of Map‐DNA in cheese and whole milk powder. Significance and Impact of the Study: The assay developed allows sensitive detection and quantification of Map DNA in a range of dairy products which is valuable for the screening and surveillance of this potential zoonotic organism.     

ASSESSMENT OF Cryptococcus albidus FOR BIOPULPING OF EUCALYPTUS

Cryptococcus albidus shows delignification activity in nature. It was used for the biopulping of eucalyptus wood (Eucalyptus grandis) to access its potential for industrial application in the pulp and paper industry. Enzyme analysis on days 15, 30, and 60 showed the presence of laccase and xylanase as key enzymes. The production of endo-glucanase (CMCase) and exo-glucanase (FPase) was very low. Scanning electron microscopy (SEM) showed the surface colonization of wood and loosening of wood fibers in C. albidus-treated samples. Fourier-transformation infrared spectroscopy (FT-IR) indicated the chemical modification of eucalyptus wood. Denaturing gradient gel electrophoresis (DGGE) analysis on days 15, 30, and 60 confirmed the presence of C. albidus throughout the experiments. Cryptococcu albidus was able to suppress the growth of a native population. Further, after 60 days both the control and treated eucalyptus wood chips were given kraft pulping treatment. The kappa number of pulp of control wood was 21 and for treated wood was 17. Kappa number is considered a measure of lignin content in wood; hence the treatment of eucalyptus by C. albidus (biopulping) was effective in reducing its lignin content and can be used for biopulping in the pulp and paper industry.     

Isolation of Cryptococcus laurentii from Canada Goose guano in rural upstate New York

Cryptococcus neoformans and Cryptococcus gattii are etiologic agents of cryptococcal pneumonia and meningitis, potentially lethal syndromes associated with AIDS. A related species, Cryptococcus laurentii, has recently been implicated in several cases of human disease. Guano from Canada Goose (Branta canadensis), an organism that lives closely beside man and inhabits recreational space in rural and suburban areas, might be a significant environmental reservoir of Cryptococcus organisms in non-urban areas. Cryptococcal organisms were isolated from Canada Goose guano from a site in rural northern New York, with identification based upon colony and microscopic morphology, ability to metabolize l-Dopa to melanin, and positive reaction with a commercial anti-cryptococcal capsular polysaccharide latex bead agglutination test. DNA sequences from five positive isolates were identical to each other, and identical to the ITS1-5.8S-ITS2 sequences of C. laurentii strain CBS7140 (Accession AY315665) across a 511 bp sequence. All five isolates of C. laurentii possess three of the known virulence factors common to cryptococcal organisms that cause human disease: capsule, ability to grow at 37 °C, and laccase activity.     

Fate of Escherichia coli O157:H7 in ground beef following high‐pressure processing and freezing

Aims: The purposes of this study were to evaluate the efficacy of high pressure to inactivate Escherichia coli O157:H7 in ground beef at ambient and subzero treatment temperatures and to study the fate of surviving bacteria postprocess and during frozen storage. Methods and Results: Fresh ground beef was inoculated with a five‐strain cocktail of E. coli O157:H7 vacuum‐packaged, pressure‐treated at 400 MPa for 10 min at ?5 or 20°C and stored at ?20 or 4°C for 5–30 days. A 3‐log CFU g^?1 reduction of E. coli O157:H7 in the initial inoculum of 1 × 10⁶ CFU g^?1 was observed immediately after pressure treatment at 20°C. During frozen storage, levels of E. coli O157:H7 declined to <1 × 10² CFU g^?1 after 5 days. The physiological status of the surviving E. coli was affected by high pressure, sensitizing the cells to pH levels 3 and 4, bile salts at 5% and 10% and mild cooking temperatures of 55–65°C. Conclusions: High‐pressure processing (HPP) reduced E. coli O157:H7 in ground beef by 3 log CFU g^?1 and caused substantial sublethal injury resulting in further log reductions of bacteria during frozen storage. Significance and Impact of the Study: HPP treatment of packaged ground beef has potential in the meat industry for postprocess control of pathogens such as E. coli O157:H7 with enhanced safety of the product.     

Gram-negative bacteria associated with timber as a potential respiratory hazard for woodworkers

The concentration and species composition of viableGram-negative bacteria was determined in samples of coniferous wood (Scots pine) and deciduous wood (European beech), and in air samples taken during the processing of these woods in sawmills. The concentration of Gram-negative bacteria in the sapwood of pine logs ranged from 1.0 × 10¹ to 6.2 × 10⁴ CFU/g. Their concentration in the air of the pine processing sawmill was within a range of 1.0 × 10²–6.3 × 10² CFU/m³. Concentration of Gram-negative bacteria in the sapwood of beech logs was similar to that in the sapwood of pine logs, ranging from 1.0 × 10¹ to 4.6 × 10⁴ CFU/g. However, the concentration of these bacteria in the air of a beech processing sawmill was within a range of 7.8 × 10³–1.3 × 10⁴ CFU/m³, being significantly higher than in a pine processing sawmill. Enterobacteriaceae strains, mostly Enterobacter spp. and Rahnella spp., made up 70–75% of Gram-negative bacteria isolated from pine and beech wood and from the air pollutedwith sawdust from these woods. The aerial exposure to Gram-negative bacteria possessing endotoxic andallergenic properties poses potential risk ofoccupational respiratory disorders among sawmillworkers, in particular those processing beech wood.     

Metabolism,thermogenesis and daily rhythm of body temperature in the wood lemming,Myopus schisticolor

Wood lemmings (Myopus schisticolor) were captured during their autumnal migration in September and October. The animals were maintained at 12°C and under 12L:12D photoperiod. Basal metabolic rate and thermogenic capacity of the wood lemming were studied. Basal metabolic rate was 3.54 ml O₂·g^-1·h^-1, which is 215–238% of the expected value. The high basal metabolic rate seems to be typical of rodents living in high latitudes. The body temperature of the wood lemming was high (38.0–38.8°C), and did not fluctuate much during the 24-h recording. The high basal metabolic rate and the high body temperature are discussed with regard to behavioural adaptation to a low-quality winter diet. Thermogenic capacity, thermal insulation and non-shivering thermogenesis of the wood lemming displayed higher values than expected: 53.0 mW·g^-1, 0.53 mW·g^-1·C^-1 and 53.2 mW·g^-1, respectively. Brown adipose tissue showed typical thermogenic properties, although its respiratory property was fairly low, but mitochondrial protein content was high compared to other small mammals. The 24-h recording of body temperature and motor activity did not reveal whether the wood lemming is a nocturnal animal. Possibly, the expression of a circadian rhythm was masked by peculiar feeding behaviour. It is concluded that the wood lemming is well adapted to living in cold-temperature climates.Abbreviations BAT brown adipose tissue; bm, body mass - BMR basal metabolic rate - C conductance - Cox cytochrome-c-oxidase - HP heat production - HP_max maximum heat production - M metabolism - NA noradrenaline - NST non-shivering thermogenesis - NST_max maximum non-shivering thermogenesis - RMR resting metabolic rate - RQ respiratory quotient - T _a anibient temperature - T _b body temperature - T _lc lower critical temperature - UCP uncoupling protein - vO₂ oxygen consumption - vO_{2 max} maximum oxygen consumption     

Microbial survey of shared-use cosmetic test kits available to the public

Summary Some people like to try cosmetics before purchasing them. With repeated use by different customers, however, the tester kits provided by many retail outlets can become potential vectors of microbial pathogens. A survey was conducted to assess the health risk from bacteria found on shared-use cosmetics. A total of 3027 shared-use cosmetic product samples were collected from 171 retail establishments throughout the contiguous United States. Eye, face and lip cosmetics were tested within situ nondestructive swabbing and the use of the Transette 3R Modified Amies Charcoal Culture and Transport System. Bacteria were isolated from about 50% of the items for all three categories. Semiquantitatively-estimated mean densities were 2288, 1685 and 1088 CFU g^–1 for eye, face and lip products, respectively. Ranges for all categories were 0–15⁵ CFU g^–1. About 5% of the items had bacterial counts above 5000 CFU g^–1 (eye products) or 10 000 CFU g^–1 (other products). More than 60% of isolates were typical of microflora from human skin; the remainder were environmental microbes. About 60% of the isolates were Gram-positive cocci:Staphylococcus spp. (especiallyS. epidermidis) andMicrococcus spp. The Gram-negative pathogenPseudomonas aeruginosa constituted 0.07% of the isolates. The survey results suggest that the preservation systems of some of the cosmetics failed under excessive use (abuse), and indicated a potential for microbiological safety problems with shared-use consmetics.     

The mycoflora and toxicity of feedstuffs from a production plant in córdoba, Argentina

Feedstuffs used for poultry nutrition in Argentina were analyzed for fungal flora and natural incidence of mycotoxins. Survey of 120 samples of poultry feeds, taken from May 1998 to April 1999, showed the presence of 15 genera of filamentous fungi. The predominant genera wereFusarium spp. andPenicillium ssp., isolated in 67.5 % of the samples, followed byAspergillus spp. (57.5 %). Yeast, were significantly isolated from most of the samples. Species identification was carried down for the toxigenic genera. Fungal total counts of poultry feeds ranged from 2.0 × 10³ to 3.0 × 10⁵ CFU g^-1 The fungal total counts during two months of sampling, were slightly over the limit value of 1 × 105 CFU g^-1, which ensure the hygienic quality of the feed. Potentially toxicogenic species presented moderate mean colony counts. Many of the fungi isolated from poultry feeds are mycotoxin producers. Fumonisins had the highest incidence, and were found in 97 % of the analyzed samples followed by aflatoxin B₁ (46 %), zearalenone (18 %) and deoxynivalenol (6 %). On the co-occurrence of both carcinogenic mycotoxins, all of the FBs contaminated feed samples were co-contaminated with AFB₁. The results show the relevance of the samples screening for viable fungi propagules and the surveillance of their associated mycotoxins in poultry feeds.     

新生隐球菌对角质形成细胞活力的作用研究

目的研究新生隐球菌体外对角质形成细胞活力的影响。方法将新生隐球菌父代标准株与子代荚膜缺陷株于体外分别与角质形成细胞分别共培养,同时设立热灭活的菌体、空白对照,再分别设立菌体与细胞直接接触与不接触共培养相互对照,分别作用0.5 h、1 h和2 h后,采用流式细胞仪检测隐球菌角质形成细胞的调亡率。结果随着时间延长,与空白对照组及热灭活组比较,实验组角质形成细胞的凋亡率逐渐增加。无荚膜株与父代有荚膜株比较,无荚膜株对细胞活力的影响在作用后1 h、2 h明显低于有荚膜株。2种菌株不直接接触培养使细胞的凋亡率明显下降;不直接接触的有荚膜株与热灭活的菌体之间比较差异不显著。结论虽然有荚膜株与无荚膜株隐球菌均可以使角质形成细胞活性明显降低,但荚膜可以显著增强菌体对细胞活力的影响;角质形成细胞活力的降低主要是通过与菌体接触培养后产生的,诱导细胞调亡需要菌体与细胞的直接接触。