Agar In Petri Dishes Research Articles

Typing and patterns of cellular morphological alterations inCryptococcus neoformansandCryptococcus gattiiisolates exposed to a panel of killer yeasts

Cryptococcus neoformans and Cryptococcus gattii are encapsulated basidiomycetous yeasts that cause meningoencephalitis. The action of killer yeasts on the growth of one hundred genotypically characterized C. neoformans var. neoformans, C. neoformans var. grubii, and C. gattii clinical and environmental isolates was evaluated. Killer studies were performed on yeast malt-methylene blue (YM-MB) agar Petri dishes, and a dendrogram was obtained based on a quantitative data matrix using the diameter of the inhibition halo. The cellular morphological characteristics of dead cells within the halo were observed by means of optical and scanning electron microscopy. There was no formation of pores on the cell surface of the sensitive cells in contact with the toxins, at least for C. neoformans. The sensitivity patterns of clinical and environmental isolates to the killer toxins demonstrated that there is correlation between killer sensitivity of Cryptococcus species or varieties and some of the killer strains. In this case, the isolates were discriminated using the killer sensitivity patterns, and this could be used as a complementary tool to PCR-fingerprinting in epidemiological studies.

Isolation of Sporothrix schenkii from the nails of healthy cats

Many cases of sporotrichosis in cats were diagnosed in the town of Rio Grande, RS, Brazil, caused mainly by inoculation due to scratches. In this work, we evaluated the frequency of Sporothrix schenckii in the nails of healthy cats living together with cats showing clinical sporotrichosis. The isolation of the fungus was carried out pressing unwashed nails of the forelimbs of 24 cats (48 paws) directly onto the surface of Mycobiotic Agar in Petri dishes. S. schenckii was isolated from seven (29.1%) cats. The procedure for isolation of the fungus was simpler than methods that require sedation and cuts of the nails.

In vitro antifungal effect of human milk

A lower incidence of infection occurs among breast-fed babies because of the presence of antibacterial, antiviral, and antiparasitic effects, but little is known about the antifungal effects to fungi other than Candida albicans. This study was undertaken to assess the antifungal effect of human milk to the fungi in the environmental air, which also may be allergenic. Milk samples were obtained from lactating mothers of healthy term infants between the 3rd and 8th days of lactation. Ninety-six Sabouraud agar petri dishes were separated into three groups, closed, and incubated in the same location after 15 minutes uncovered. The first group (group 1, n=48 dishes) was used to detect the fungal flora of the environmental air. The second group (group 2, n=24 dishes) was rubbed with a thin layer of human milk by a sterile pipette. The last group (group 3, n=24 dishes) was rubbed with 0.9% NaCIlsolution. After 7 days of incubation, the colony-forming fungal growths of all dishes were evaluated by a microbiologist who did not know the groups of the dishes. The number offungal colonies grown in human milk-rubbed dishes in group 2 was less than both of the other groups (group 1 and 3; p < 0.001 and p < 0.001, respectively). These results indicated that human milk may have antifungal effects to fungi present in the environmental air as tested by Sabouraud agar petri dishes. To prevent infections and allergic diseases, human milk must be considered the ideal food for newborns.

Endometritis in the mare: A diagnostic study comparing cultures from swab and biopsy

The objective of this study was to compare results from endometrial culture swabs with results from culturing of endometrial biopsies. The culture results were related to cytological findings (polymorphonuclear; PMN-cells) and histological observations (PMN-cells). Biopsy and swab samples were smeared on the surface of a blood agar petri dish, and examined for growth of bacteria. Cytology samples were obtained from endometrial biopsies, stained and examined under microscopy for the presence of PMN-cells. Endometrial biopsies were examined for the presence of PMN-infiltration of the endometrial luminal epithelium and the stratum compactum. Using the presence of PMNs in a tissue specimen as the “best standard” for diagnosing endometritis, the sensitivity of bacterial growth from an endometrial biopsy was 0.82. The sensitivity for cytology was 0.77, and the sensitivity of bacterial growth from an endometrial surface swab was 0.34. The specificity for biopsy cultures, swab cultures, and cytology to diagnose endometritis were 0.92, 1.0, and 1.0 respectively. The positive predictive value for biopsy cultures, swab cultures, and cytology were 0.97, 1.0, and 1.0 respectively. The negative predictive value for biopsy cultures, swab cultures, and cytology were 0.67, 0.44, and 0.62 respectively. In conclusion, bacteriological culture and cytology from an endometrial biopsy provide the practitioner with the most accurate results regarding both sensitivity and positive predictive value.

Effects of Species Diversity on Establishment and Coexistence: A Phylloplane Fungal Community Model System

A model system was devised, evaluating the influence that species diversity (species richness) has on fungal establishment and coexistence. Seven members of the fungal phylloplane community of Vaccinium macrocarpon (American cranberry) were selected to assess how species diversity affected development and coexistence of another community member, Pestalotia vaccinii. Pestalotia was engaged in competitive interactions on 1% Malt Extract Agar (MEA) petri dishes with each of the seven individual saprotrophs (two-way interaction), in random combinations with three of the seven saprotrophs (four-way interaction), and in random combinations with five of the seven saprotrophs (six-way interaction). The saprotrophic fungi used in this study were Aspergillus sp., Alternaria alternata, Cladosporium cladosporoides, Curvularia lunata, Epicoccum purpuracens, Penicillium sp., and Pithomyces chartarum. We hypothesized that species diversity would have a significant impact on the establishment and coexistence of Pestalotia vaccinii in culture. In an effort to minimize density-dependent effects, the number of viable spores employed in the three types of interactions was kept constant. Target spore concentrations of 50 viable spores of P. vaccinii and 50 saprotroph spores were used, regardless of the number of species involved in the interaction. This proved to be a very important factor in the experiment. As our results show, species diversity had little or no effect on the establishment and coexistence of Pestalotia vaccinii; however, spore density played an extremely important role in the establishment and development of fungal propagules in our model.

Lethal effect of Beauveria bassiana, Metarhizium anisopliae, and Paecilomyces fumosoroseus on the eggs of Tetranychus cinnabarinus (Acari: Tetranychidae) with a description of a mite egg bioassay system

Fungal biocontrol agents, including 10 isolates of Beauveria bassiana, Metarhizium anisopliae, and Paecilomyces fumosoroseus were bioassayed for their lethal effects on the eggs of the carmine spider mite, Tetranychus cinnabarinus. The eggs were naturally laid on detached fava bean leaves on agar in petri dishes at 25 °C under a photophase of 12:12 L:D. Suspensions of aerial conidia produced on rice were sprayed onto the leaves, yielding three conidial concentrations (No. conidia/mm2) from low to high for each of the fungal isolates with 3 or 4 replicates (30–65 eggs/leaf or replicate) at each concentration. During a 12-day observation period after spray, the infected eggs shrunk in shape, then turned orange-brown for B. bassiana and P. fumosoroseus or dark-gray for M. anisopliae, and eventually had outgrowths of the sprayed fungus when maintained under moist conditions. Egg mortalities caused by fungal infection varied over time but had no change from day 8 or 9 onward. Differences of the mortalities on day 9 were significant among the fungal species or isolates tested. Based on the LC50 estimates determined by the concentration–mortality relationships of all isolates from probit analysis, B. bassiana Bb2860 with an LC50 of 548 conidia/mm2 was highly infectious to T. cinnabarinus eggs, followed by P. fumosoroseus Pfr116 (848 conidia/mm2) and Pfr153 (913 conidia/mm2). Two M. anisopliae isolates with LC50s of 1717 and 1985 conidia/mm2 were inferior to the three isolates. The other isolates were poor or very poor in ovicidal activity. Our results confirmed the ovicidal activity of the three fungal species and suggested the feasibility to search for more ovicidal isolates from fungal species that may serve as biocontrol agents against spider mites such as T. cinnabarinus. The mite egg bioassay system developed in this study will be useful towards this goal.

First report of Phomopsis subordinaria in a natural population of Plantago lanceolata in south‐west Finland

In August 2002, darkened and downward-turned flowering stalks were observed on plants of Plantago lanceolata in its natural habitat in the Aland Islands, south-west Finland. An estimated 10% of the P. lanceolata plants in a c. 0·2 ha meadow displayed these symptoms. Stalks with sporulating fungal structures were collected for closer microscopic examination. The morphological characteristics of the conidiogenous cells, which were slightly broadened near the base, were similar to those of Phomopsis subordinaria as described by de Nooij & van der Aa (1987). Of the two conidial types described, alpha and beta, collected samples contained only α -conidia. Twelve-week-old P. lanceolata plants were inoculated as described by de Nooij & van der Aa (1987). A suspension of P. subordinaria conidia was obtained by shaking a 2 cm piece of infected stalk in 30 mL sterile water for 30 min at 250 r.p.m. Stalks were wounded just below the ear with a sterile needle, then brushed with the suspension of conidia. Eight P. lanceolata plants were wounded and inoculated, and eight were wounded and brushed with sterile water to serve as controls in the experiment. Plants were kept in the glasshouse at 22/16 ° C and 16/8 h light period, respectively. After 2 weeks, darkening and bending typical of the stalk disease observed on P. lanceolata in the meadow was observed on 90% of the inoculated stalks. No symptoms were observed on the control plants. After 6 weeks the fungus had grown into the rosette of the wounded inoculated plants, causing severe wilting and eventually plant death. The pathogen was reisolated from affected plants by incubating 5 mm pieces of wounded stalks on water agar in Petri dishes at 20 ± 3 ° C. Conidia exuding from sporulating pycnidia were mass-transferred onto potato dextrose agar. After 7 days’ incubation, pycnidia with newly forming conidia were produced, fitting the description of P. subordinaria . There are reports of P . subordinaria infecting P. lanceolata in both Great Britain (Grove, 1935) and in the Netherlands (de Nooij & van der Aa, 1987). However, no previous record has been found on the occurrence of P. subordinaria in natural populations of P. lanceolata in Finland. Diseased specimens of P. lanceolata have been deposited in the Herbarium at the University of Turku, Finland (accession number TUR 158521).

A new method for rearing the sciarid fly, Lycoriella ingenua (Diptera: Sciaridae), in the laboratory: possible implications for the study of fly — fungal interactions

A new method for rearing the sciarid fly Lycoriella ingenua in the laboratory has been developed. The flies were reared on pure culture of the fungi Absidia cylindrospora or A. glauca cultivated on malt extract agar in Petri dishes. Adult flies were introduced to plates with fresh culture of fungi, laid eggs there and the larvae fed on fungi. The newly emerged generation of adults was collected and transported to new dishes. The whole development of one generation lasted 18 days at 25 °C and one female laid on average 53 eggs. By this technique more than 30 fly generations were reared without introducing any new material from nature. Using the flies obtained from this rearing system the oviposition attractiveness of 68 species of soil fungi were tested in multichoice stellar preference experiments. The oviposition attraction of individual species varied substantially, the frequency of egg laying was significantly higher than random choice in 18 species, in 14 species proportional to random choice and in 30 species lower than random choice, 10 species of which were never used for egg laying. Taxonomic affiliation did not appear to correspond with the flies' oviposition behaviour. In the next experiment the oviposition attraction of 25 species was compared with the suitability for larval development. A significant proportion of the highly preferred fungi did not offer suitable conditions for larval development. On the other hand, a substantial majority of fungi with lower preferences (selected for oviposition with frequency proportional to random choice) did offer suitable conditions for larval development. This appears to be caused by ambivalent relationships of fungi and flies - not only are fungi important as a food source for fly larvae, but also eggs and trapped adult flies are used by some fungi as a source of nutrients. In other cases the attraction of adult flies can be important for fungal spore dispersal.

First Report of Fusarium Wilt of Babaco (Carica × heilbornii var. pentagona) in Ecuador.

Babaco, Carica × heilbornii V.M. Badillo var. pentagona (Heilborn) V.M. Badillo, is a fruit native to Ecuador that has great potential as a cultivated crop. Local market demand and strong potential as an export crop have greatly increased interest in babaco production in Ecuador. Although the crop can be produced in open fields, the majority of crop production is in plastic greenhouses. In 1996, a serious wilt disease developed on babaco in several greenhouses, resulting in up to 100% loss of plants. Symptoms first appeared as chlorosis of the lower leaves, followed by defoliation progressing up the stem until the entire plant was defoliated. When cut in cross section, vascular discoloration was observed in the stem. Eventually necrosis and soft rot of the stem occurred and entire plants collapsed. Fungal isolations were conducted from fine feeder roots of diseased plants by soaking root pieces (2 cm long) in a 0.5% solution of sodium hypochlorite for 3 min. Root pieces were cut into smaller sections and placed on potato dextrose (PDA) or corn meal (CMA) agar in petri dishes. Isolations from larger roots, crowns, stems and fruits were made by soaking tissue sections of each plant part in a 2.87% solution of sodium hypochlorite for 3 min. Tissue sections were rinsed three times in sterile distilled water. Smaller tissue sections (≈0.125 cm3) were cut from surface-disinfested pieces and placed on PDA and CMA in petri dishes. Cultures were incubated at 20°C. A fungus resembling Fusarium sp. was isolated consistently from infected tissues from all infected plant parts. Based on the morphology of the fungal colony and conidia from monosporic isolations, the fungus was identified as Fusarium oxysporum Schlechtend:Fr. (1). Pathogenicity tests were conducted by growing babaco plants in pots containing an equal mixture of sterilized soil, compost, and sand in the greenhouse. Eight 7-month-old plants were inoculated by placing 40 ml of a suspension (106 conidia per ml) of F. oxysporum in four plastic straws placed in the soil (5 cm depth) at equal distances (5 cm) from the base of each plant. Straws around noninoculated control plants received sterile water. Plants were watered with 400 ml of sterile water daily. Pathogenicity tests were repeated once as described. All inoculated plants developed typical wilt symptoms within 45 days after inoculation. No symptoms developed on uninoculated control plants. F. oxysporum was successfully reisolated from infected stem tissues of inoculated plants. Incidence of Fusarium vascular wilt of babaco has continued to increase since 1996 and is currently the major constraint to production.

Influence of weather and time of deposition on sheep faeces colonization by nematophagous fungi in the Mata region of Minas Gerais State, Brazil

The influence of climate and time of deposition on the colonization of sheep faeces by nematophagous fungi was examined in the Mata Region of Minas Gerais State, Brazil. Sheep faeces were collected from the rectums of animals and deposited on pastures of Brachiaria decumbens in the months of July and October 1995 and January and April 1996. Samples of the deposited faeces were recovered 3, 7 and 14 days after deposition. Sub-samples of faeces (2g) were placed in the centre of a 2% water–agar petri dish. Free-living nematodes were added as bait, the plates incubated at room temperature and examined for 3 weeks. Isolated fungi were further cultured on corn-meal agar plates for identification. A total of 123 fungi was isolated from the 120 sheep faecal samples deposited on pastures including 22 in July, 39 in October, 41 in January and 21 in April. More than one-third of the fungi were recovered on the third day after deposition. Arthrobotrys oligospora and Monacrosporium eudermatum, were the most common predatory fungi and Harposporium anguillulae the most common endoparasite. Results showed that sheep faeces deposited on pastures of B. decumbens are colonized rapidly by a variety of nematophagous fungi and seasonality affects colonization.

Use of sublimation to prepare solid microbial media with water-insoluble substrates.

A method was developed to deposit a visible layer of water-insoluble compounds via sublimation onto the surface of solid media. The compound is sublimed from a heated aluminum dish containing the compound onto the surface of an inverted, ice-cooled, inoculated agar petri dish. The method results in the deposition of a thin, even layer on the agar surface without the use of solvent. After incubation, clearing zones around colonies indicate the presence of compound-degrading microorganisms.

Evaluation of the Filtration Performance of Biocide Loaded Filter Media

This paper presents the results of a study designed to evaluate the filtration performance of nonwoven filtration media which have been loaded with a variety of biocides for use as potential indoor air filters. A test stand was constructed based on a modification of the ASTM 1215 Standard to provide testing of the bacterial removal efficiency of the filtration media. Biocide-loaded filtration media were first tested on an ASTM 1215 test stand using standard monodispersed latex spheres to determine the particle removal efficiency as a function of particle sizes in the 0.5 to 2.0 micrometer sizes. A multichannel optical particle counter was used to assess the efficiency. Additional samples of the same media were then tested in the modified ASTM 1215 test stand, referred to as the Biocontaminant Indoor Air Quality Test Stand (BIAQTS) by atomizing bacteria (Gram positive and Gram negative) and fungi into the test stand. Initial bacterial testing was conducted using single-stage microbial samplers to determine the efficiency of filters for removing Escherichia coli (E. coli) bacteria and other bacteria. In addition to testing the filtration efficiency, additional tests were conducted on samples of the filter by placing small disk samples of the unexposed biocide-loaded filters and a non-loaded control filter onto microorganism-loaded agar in petri dishes. Microorganisms studied included four bacteria, a fungus, and an opportunistic pathogen. The samples were then incubated and quantitative analyses were conducted to determine the zone of inhibited growth of the microorganisms around the disks due to the biocide treatments which were applied to the filters. The results are presented for two of a series of biocide-loaded nonwoven filters which were prepared using two different techniques for loading the biocides: 1) nonwoven filters which were prepared by mixing the biocide with the polypropylene polymer prior to meltblowing the polymer into a filter - referred to as impregnated biocide, and 2) spray application of the biocides as a finish onto the filter media–referred to as post treatment. The effects of impregnated versus post treatment applications on filtration efficiency and on the inhibition of bacterial growth on the filters are presented.

Protective effect of beta-glucan against mycobacterium bovis, BCG infection in BALB/c mice.

Beta-1,3-glucan is a potent stimulator of macrophage functions and has a protective effect against a range of infections in rodent models. We examined whether the agent could also protect against the intracellular Mycobacterium bovis, bacillus Calmette-Guérin (BCG) infection in mice. BCG-susceptible BALB/c mice were injected intravenously (i.v.) with beta-glucan or vehicle 3 days before, or with beta-glucan 7 days after i.v. challenge with live BCG bacilli. The animals were killed 4 or 8 weeks later, their organs were homogenized and applied to object slides and stained with auramin for counting of bacilli, or seeded onto agar in Petri dishes. Mice treated with beta-glucan both pre- and postchallenge had significantly lower numbers of BCG bacilli and BCG colony-forming units in spleen homogenates compared with controls 4 weeks after challenge. A similar, but not statistically significant, tendency was observed in spleen homogenates from mice killed 8 weeks after challenge. In homogenates of liver and lungs there were similar findings, but less pronounced. There was a dose-dependent effect of beta-glucan injected before BCG challenge on the number of BCG bacilli found in spleen and liver homogenates. In addition, antibody cross-reactivity was demonstrated between M. tuberculosis cell wall and beta-glucan. The results suggest that beta-glucan has a protective effect against M. bovis, BCG infection in susceptible mice.

Competitive Hierarchies of Wood Decomposing Basidiomycetes in Artificial Systems Based on Variable Inoculum Sizes

In the laboratory, 12 species of wood decay basidiomycetes from various stages of fungal succession in logs of Norway spruce were investigated for their relative competitive ability. Pie slices of different sizes were cut from wood discs made from Norway spruce. After inoculation, the pieces were confronted in most species combinations on water agar in Petri dishes, and were left for six months. With this method the inoculum sizes could be varied, while the contact area remained the same. Photos of the discs were taken regularly during this time. At the end of the experiment, samples of the wood were taken from all discs and the remaining fungi were isolated. Combative success was measured as the ability to take over substrate from competing species by the end of the experiment. Both within and among successional stages, mycelial replacement occurred in a non-random fashion. Species usually producing fruit bodies in the later stages of succession in the field were strong competitors in the laboratory tests, while the species which often fruit during the earlier stages of field succession were weaker competitors.

Comparison of commonly used samplers with a novel bioaerosol sampler with automatic plate exchange

A newly designed automatic bioaerosol sampler (ABS) was commissioned for studies of microbial bioaerosols. The original feature of the ABS is the facility for unattended, microprocessor-controlled sampling with automatic replacement of the agar Petri dishes after each sample. The ABS was compared with a six-stage Andersen sampler, an all-glass impinger and a Casella slit sampler. The air in two cattle and two poultry livestock buildings was sampled for the concentration of total bacteria and total fungi including yeast cells. Slightly smaller concentrations of total bacteria and total fungi were measured with the automatic bioaerosol sampler than with the reference samplers. The automatic bioaerosol sampler correlated best with the Andersen sampler and its cutoff diameter was estimated to be about 1.5 μm. Overall, this new sampler was found to be a useful development in the technology of sampling airborne microbes.

Remote interpretation of microbiology specimens based on transmitted still images.

A pilot study was carried out to examine the feasibility of the remote interpretation of microbiology specimens, that is, micro-organisms grown on agar in Petri dishes. The objective of our study was to decide whether still images contained enough information for microbiology specialists to identify the microorganisms accurately. A representative sample of microbiology specimens grown on the most commonly used agar media was used. Still images were captured using a video camera and a PC-based system. The results from a pilot study with the first video camera were discouraging, the interpretations differing in five out of 22 specimens; results with a second video camera were also disappointing. Images were then captured on photographic film, at a considerably higher resolution than images captured by the digitizer board in the PC. Again, however, the results were disappointing. We conclude that interpretation of microbiology specimens based exclusively on visual information is problematical. Remote microbiology interpretation in the future will require images of higher information content (e.g., including three-dimensional information), and will probably require additional information as well, from other senses, such as smell.

Antimicrobial and toxic effects of established and potential root canal irrigants

Three dilutions of the commonly used irrigant sodium hypochlorite (0.5%, 2.5%, and 5.25%) and the potential irrigants Peridex, chlorhexidine gluconate (0.12%), and Therasol were tested. Alcohol and saline served as controls also. The in vitro portion of this study used four different microorganisms (Streptococcus mutans, Peptostreptococcus micros, Prevotella intermedius, and Porphyromonas gingivalis) to determine antimicrobial effect. Presterilized 7-mm diameter Whatman paper disks soaked with the test solution were prepared, and disks were placed onto the previously seeded agar petri dishes. Each dish was incubated aerobically or anaerobically according to the microorganisms used. An in vivo animal model (guinea pig) was used to examine subcutaneous local tissue reactions using the same materials; 0.1 ml of each test solution was injected subcutaneously into predetermined locations on the animal dorsum. Test site histological examination was done 2 h, 2 days, and 2 wk after the injections. The results of this comparative study indicate Peridex (chlorhexidine gluconate) and Therasol may have good potential for endodontic usage.

Cavity spot of carrots: Interactions between the host and pathogen, related to the cell wall

SummaryThis study investigates the structural aspects of cavity spot pathogenesis. Different Pythium spp. isolated from infected carrots, apples and melons were cultured on agar in Petri dishes and used for inoculation of uninfected carrots. Only slow‐growing Pythium spp. (&lt; 15 mm day‐1), such as P. violae and P. sulcatum caused cavity spot lesions. It is suggested that slow‐growing species are able to penetrate, albeit slowly, into the plant tissue for 3 to 4 days before a hypersensitive reaction develops. Fast‐growing species, however, did not cause lesions. Based on ultrastructural observations, we suggest that the following sequence of events occurs between the plant and the pathogen: The fungus infects the walls and grows for several days, during which time small amounts of wall‐degrading enzymes are secreted. Phenylalanine ammonia lyase (PAL) activity and phenols increase linearly immediately upon inoculation. There was a lag phase of about 5 days before lignin began to increase linearly for about a month. Dissolution of wall components decreases the solute potential and water potential in the apoplast. Thus, water moves from the symplast into the apoplast, the turgor pressure gradually dissipates, and the cells shrink and eventually die.

Delivery and activity of antimicrobial drugs released from human fibrin sealant.

Engraftment and healing of native or cultured skin grafts depend on adherence, vascularization, and control of microbial contamination in the wound bed. Fibrin sealant is a biocompatible polymer that may be used to promote skin engraftment by serving as a delivery vehicle for antimicrobial drugs. Human fibrin sealant (25 mg/ml) was polymerized with antibacterial agents (mupirocin [32 micrograms/ml], nitrofurazone [0.02% wt/vol], polymyxin B [400 U/ml], or norfloxacin [20 micrograms/ml]) on nitrocellulose (nc) backing and was prepared as 6 mm diameter discs with skin punches. Discs (n = 6) were applied in the Wet Disc Assay to clinical isolates of Staphylococcus aureus (mupirocin, nitrofurazone) or Pseudomonas aeruginosa (polymyxin B, norfloxacin). Controls included drug applied to 6 mm paper discs (25 microliter) and nitrocellulose discs submerged in each drug, blotted, and applied to bacterial cultures on agar in petri dishes. Data were expressed as zone of clearing (mm diameter +/- SEM) after overnight incubation at 35 degrees C. Significant differences (ANOVA and Turkey's test, p < 0.05) were found for each drug released from the disc of fibrin sealant compared with other vehicles. Release from filter paper discs compared with nitrocellulose was significant for nitrofurazone and norfloxacin. Serial transfer of fibrin discs to fresh bacterial cultures after 24 hours showed no zones of clearing. The data show that fibrin sealant releases topical drugs with no inhibition of antimicrobial activity on burn organisms. Greater zones of clearing from fibrin sealant may result from passive fluid retention or from active binding to fibrin followed by protease digestion by burn organisms.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of the potato cyst nematode Globodera pallida on in vitro root growth of potato genotypes, differing in tolerance

SummaryRoots of eighteen potato genotypes, differing in tolerance of G. pallida, were grown from tuberpieces on agar in Petri dishes. Juveniles of G. pallida were inoculated directly onto root tips. Root length was measured at various times after inoculation. Inoculation reduced root growth within one day. At later stages, genotypes differed strongly in growth of inoculated roots. Between four and seven days after inoculation, growth of inoculated roots was not significantly correlated with growth of untreated roots, and was only poorly correlated with tolerance assessed in the greenhouse or in the field. However, multiple regression analysis revealed that the tolerance of the tested genotypes was associated with both the rate at which they induced hatching and the growth of roots after inoculation. The combination of these two variables accounted for high percentages explained variance.