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PubMed2004

Influence of substrate composition and flow rate on growth of Azospirillum brasilense Cd in a co-culture with 3 sorghum rhizobacteria.

The ability of Azospirillum brasilense Cd to colonize the niche occupied by 3 bacterial strains previously isolated from sorghum rhizosphere was studied by means of the Biolog system. The isolates were identified by different methods as strains belonging to Pseudomonas putida, Stenotrophomonas maltophilia, and Klebsiella terrigena species. Several C sources, also chosen among the constituents of sorghum root exudates, were used to evaluate the metabolic profiles of Azospirillum and the sorghum rhizobacteria. Azospirillum brasilense Cd exploited the same class of C compounds as the sorghum rhizobacteria and overlapped in their niche requirements. Since structure and functioning of a microbial community are largely affected by the flow rate of nutrient supply, the competitive behavior of A. brasilense Cd was studied in a chemostat mixed culture under C-limited conditions using disodium succinate as C source. Only at high growth rates, i.e., when the C source was highly supplied, A. brasilense Cd appeared to be a good competitor and it became the dominant species, whereas at low growth rates, it was outnumbered by the other species. However, the coexistence of all the strains was always maintained, thus suggesting that interactions other than competition or a potential cross-feeding might occur within the mixed culture.

Amino Acids↗
PubMedDate not supplied

Distribution of three cariogenic bacteria in secondary carious lesions around amalgam restorations.

Secondary dental caries remains an unresolved problem in dentistry and little is known of its microbial etiology. The purpose of this study was to compare the distribution of the three most suspected cariogenic groups of bacteria, mutans streptococci. Actinomyces naeslundii genospecies 2 and lactobacilli, in natural secondary caries around amalgam restorations. Extracted teeth with secondary caries were sectioned to obtain three samples that were randomly distributed to three different groups. Each group was immunolabeled with antibodies to either Streptococcus mutans, A. naeslundii genospecies 2 or Lactobacillus casei and subsequently labeled with secondary fluorescent antibodies. All samples were analyzed three-dimensionally using confocal microscopy. The results indicated that the three different bacteria were widely present and could have an important role in the development of secondary caries around amalgam restorations.

Actinomyces↗
PubMed2001

Comparison of the effectiveness of several denture sanitizing systems: a clinical study.

The purpose of this clinical study was to test the effectiveness of three methods of decontamination on complete dentures. Dentures worn by patients for varying lengths of time were handled aseptically and treated with three different treatment modalities. The dentures were touched and sectioned and then retouched to a variety of microbiological media. The quantity of microbial growth was recorded and predominating microorganisms were identified using standard microbiological techniques. System A was found to consistently decontaminate and sanitize dentures worn by patients. System B and System C showed variable reduction of microorganisms. An unexpected spectrum of both pathogenic and opportunistic microorganisms was found in the dentures examined, including a wide range of gram-negative bacteria, gram-positive bacteria, and yeasts. A wide range of microorganisms must be considered when treating either oral or systemic diseases in denture wearers. Denture hygiene and decontamination are critical to the prevention of oral and systemic disease transmission. The dentures of ill patients must be considered as possible sources of pathogenic microorganisms.

Analysis of Variance↗
PubMed1992

Bacteriology of periodontal disease.

The microbial flora associated with the periodontal tissues in health and disease is extremely complex, and much research is being directed toward identifying those species that may be etiologic agents or that can be used as prognostic indicators. Recent work has resulted in changes in the taxonomic position of several periodontal species and the recognition that several others, particularly species of Eubacterium and Peptostreptococcus, as well as a novel oral spirochete, may be important in disease. New rapid techniques for identifying and enumerating the periodontal flora are being applied to cross-sectional and longitudinal studies to assess the significance of the various species; the DNA probe and immunologic detection methods demonstrate both advantages and limitations when compared with methods based on determining the predominant cultivable flora.

Antigens, Bacterial↗
PubMed1990

Lactic acid and pH as indicators of spoilage for vacuum-packed cooked ring sausages.

Lactic acid production and pH changes of 206 vacuum-packed cooked ring sausages stored at 2, 4 and 12 degrees C from 21 different production runs were monitored as a function of time and of microbial growth. The total lactic acid concentrations and pH values were first at a constant level, starting to increase sharply after the lactobacilli count reached about 5 x 10(7) or 6 x 10(7) cfu/g, respectively. The lactic acid and pH changes as a function of the lactobacilli count were similar at 4 and 12 degrees C. The sharp increase at high lactobacilli counts was observed in both L-lactic acid and D-lactic acid. The variation was lesser and the increase greater in D-lactic acid formation than in L-lactic acid. Above a level of 3-4 mg lactic acid/g most of the samples were deemed unfit. The pH started to decrease from a level of approx. 6.3; below 5.8-5.9 the samples were deemed unfit. The lowest pH value observed was 4.58. Both a high lactic acid content and a low pH indicated that the sausage was spoiled. These changes, however, took place at later stages of storage, and do not give information about the early phase of spoilage.

Animals↗
PubMed1993

Gingivitis in young and old dogs.

The aim of the investigation was to study the development of gingivitis in young and old dogs. 10 beagle dogs were used. 5 of the dogs were 1 year old and 5 dogs were between 8 and 9 years of age. On day 0, all the teeth of all 10 dogs were scaled and polished. A 6-week period of plaque control was initiated. On day 42, a clinical examination was performed, microbial samples from the gingival sulcus were harvested and biopsies obtained from tooth regions 3P and 4P. The tooth-cleaning measures were abandoned following biopsy and the animals were during the subsequent 3 weeks allowed to form plaque. On day 63, i.e., day 21 of plaque formation, the clinical examination, sampling of the subgingival plaque and harvesting of biopsies were repeated in the contralateral premolar regions (P3 and P4). The histological analysis revealed that the cellular infiltrate (the lesion) of inflamed gingiva was larger and extended more apically in the old than in the young dogs. The lesion in the old dogs contained significantly more plasma cells but less macrophages, lymphocytes and PMN cells than the infiltrate in the young dogs.

Aggregatibacter actinomycetemcomitans↗
PubMed2006

Anidulafungin pharmacokinetics and microbial response in neutropenic mice with disseminated candidiasis.

Candidemia is often fatal, especially in patients with persistent neutropenia. New therapies are needed. We performed 24-h pharmacodynamic studies to compare the efficacies of anidulafungin, fluconazole, and amphotericin B in neutropenic mice with disseminated candidiasis caused by one of three strains of Candida glabrata. Anidulafungin produced a maximal fungal kill (E(max)) of 1.4 to 1.9 log(10) CFU/g in kidneys and was not influenced by resistance to either fluconazole or amphotericin B. Fluconazole produced an E(max) of 1.3 log(10) CFU/g in mice infected with fluconazole-susceptible C. glabrata, but the E(max) was 0 for mice infected with a C. glabrata strain that had a fluconazole MIC of >/=32 mg/liter. Amphotericin B achieved an E(max) of 4.2 log(10) CFU/g in mice infected with amphotericin B-susceptible C. glabrata, but the E(max) was 0 for mice infected with a C. glabrata strain with an amphotericin B MIC of 2 mg/liter. In all instances, anidulafungin's maximal microbial kill was superior to that of fluconazole. Next, we performed a 96-h anidulafungin pharmacokinetic-pharmacodynamic study. Anidulafungin exhibited delayed peak concentrations in kidneys compared to those in serum, after which the concentrations declined, with a serum terminal half-life of 21.6 (+/-4.6) h. This was accompanied by a persistent 96-h decrease in the kidney fungal burden after treatment with a single anidulafungin dose of >/=8 mg/kg of body weight. This pharmacokinetic-pharmacodynamic picture of anidulafungin persistence in tissues and the resultant persistent fungal decline should be exploited to improve the efficacy of anidulafungin therapy for candidemia.

Algorithms↗
PubMed1994

Amphiphilic property of chlorhexidine and its toxicity against Streptococcus mutans GS-5.

The toxicity of chlorhexidine digluconate against Streptococcus mutans GS-5 was comparatively determined by measuring its bactericidal activity, and its inhibitory effect on microbial dehydrogenases was studied by the resazurin reduction method. Both methods indicated that chlorhexidine within the range 0.75-5.00 mg/l was highly toxic to Streptococcus mutans, probably due to inhibition of dehydrogenase activity, and the extent of toxicity was closely associated with concentration. In an attempt to better understand the relationship between the amphiphilic nature of chlorhexidine and its toxicity against Streptococcus mutans, the effect of solvent polarity on dehydrogenase inhibition was investigated. A decrease in solvent polarity, induced by inclusion of 5% acetone in the reaction mixture, did not enhance the toxicity of chlorhexidine. This implies that the antimicrobial action of chlorhexidine is mainly attributable to its hydrophilicity, and that the nature of the lipophilic groups is only of secondary importance.

Acetone↗
PubMed2001

Alfalfa seed germination and yield ratio and alfalfa sprout microbial keeping quality following irradiation of seeds and sprouts.

Foods can be treated with gamma radiation, a nonthermal food process, to inactivate foodborne pathogens and fungi, to kill insects on or in fruits and vegetables, and to increase shelf life. Gamma irradiation is especially well suited for these treatments because of its ability to penetrate commercial pallets of foods. Irradiated fruits, vegetables, poultry, and hamburger have been received favorably by the public and are now available in supermarkets. The use of irradiation on fresh alfalfa sprouts was studied to determine its effect on keeping quality as related to aerobic microbial load. After an irradiation dose of 2 kGy, the total aerobic count decreased from 10(5-8) to 10(3-5) CFU/g, and the total coliform counts decreased from 10(5-8) to 10(3-0) CFU/g. The results showed that the sprouts maintained their structure after irradiation, and the keeping quality was extended to 21 days, which is an increase of 10 days from the usual shelf life. The effect of various doses of irradiation on alfalfa seeds as measured by percent germination and yield ratio (wt/wt) of sprouts was determined. There was little effect on the percent germination, but as the dose increased, the yield ratio of alfalfa sprouts decreased. As the length of growing time increased, so did the yield ratio of the lower dose irradiated seeds (1 to 2 kGy). The irradiation process can be used to increase the shelf life of alfalfa sprouts, and irradiating alfalfa seeds at doses up to 2 kGy does not unacceptably decrease the yield ratio for production of alfalfa sprouts.

Bacteria↗
PubMed2002

Enumeration and identification of yeasts associated with commercial poultry processing and spoilage of refrigerated broiler carcasses.

Yeasts associated with broiler carcasses taken from various stages of commercial poultry processing operations and broiler carcasses stored at refrigerated temperatures were enumerated and identified. Whole carcass rinses were performed to recover yeasts from carcasses taken from a processing facility and processed carcasses stored at 4 degrees C for up to 14 days. Yeasts in the carcass rinsates were enumerated on acidified potato dextrose agar and identified with the MIDI Sherlock Microbial Identification System. Dendrograms of fatty acid profiles of yeast were prepared to determine the degree of relatedness of the yeast isolates. Findings indicated that as the carcasses are moved through the processing line, significant decreases in the number of yeasts associated with broiler carcasses usually occur, and the composition of the yeast flora of the carcasses is altered. Significant (P < 0.05) increases in the yeast population of the carcasses generally occur during storage at 4 degrees C, however. Furthermore, it was determined that the same strain of yeast may be recovered from different carcasses at different points in the processing line and that the same strain of yeast may be isolated from carcasses processed on different days in the same processing facility.

Animals↗
PubMed1999

[Microbial exposure in collection of residential garbage--results of field studies].

Since 1995 the communal accident insurance carrier of the county Wetfalen-Lippe conducts investigations into the exposure to biological agents related to refuse collection. Total fungal exposure during refuse collection turned out to range from 10,000 up to 750,000 colony forming units per cubic meter. Most of the measurement values exceeded the limit of 50,000. During hot periods in the summertime, the concentration of Aspergillus fumigatus increased up to 90,000 cfu/m3. The mean values of the bacterial concentrations ranged from 15,000 up to 50,000 cfu/m3, the endotoxin concentration from 12 up to 59 EU/m3. In the driver's cabin fungal exposure sometimes exceeded 10,000 cfu/m3 especially in autumn and winter. Maximum values were 5,000 cfu/m3 for bacteria and 15 EU/m3 for endotoxins. High values were measured irrespective of the kind of refuse.

Air Microbiology↗
PubMed2005

Long-term performance and microbial dynamics of an up-flow fixed bed reactor established for the biodegradation of fluorobenzene.

An up-flow fixed bed reactor (UFBR) was established to investigate the biodegradation of fluorobenzene (FB) under a number of operating conditions, which included variation in the concentration of FB in the feed stream (up to 180 mg l(-1)) and temporary suspension of feeding. Degradation of FB was followed for a period of 8 months under a continuous flow regime. During the operation of the UFBR, FB was never detected in the reactor effluent, being biodegraded by the microbial biofilm or adsorbed to the granular activated carbon (GAC). Biodegradation of FB was observed from the beginning of the reactor operation, and overall, it accounted for 50% of the total amount fed to the bioreactor. High organic loads of FB (210-260 mg d(-1) dm(-3)) were found to affect the biological removal efficiency, possibly due to an inhibitory effect caused by the higher FB concentrations fed to the bioreactor (149-179 mg l(-1)). When FB feeding was suspended for 1 month, biodegradation continued, indicating that the adsorbed FB became bioavailable. Biofilm bacterial dynamics were followed throughout the UFBR operation by denaturing gradient gel electrophoresis and plate-counting techniques, showing that a quite stable community was found in the bioreactor, and this was mainly attributed to the high selective pressure exerted by the presence of FB.

Biofilms↗
PubMed2006

Metabolite production of yeasts on a strawberry-agar during storage at 7 degrees C in air and low oxygen atmosphere.

Changes of different quality factors of strawberries have been described until now from a physiological point of view. Possible effects on quality caused by yeast proliferation have not been described. To elucidate the metabolic activity of yeasts (i.e. Debaryomyces melissophilus, Rhodotorula glutinis, Cryptococcus laurentii), isolated from strawberries, they were inoculated on a simulation medium of strawberries (strawberry-agar). Their activity was measured by analysing and correlating microbiological counts, metabolite concentration in the headspace as well as in the medium, and sugar consumption. The isolated yeasts from strawberries could grow on the strawberry-agar, both under air conditions and modified atmosphere (MA) conditions. The maximum count for the yeasts reached 7.5-8.5 log cfu cm(-2) (air conditions) and 5.6-6.4 log cfu cm(-2) (MA conditions). Production or consumption of a number of compounds could be detected when microbial counts reached levels between 4.7 log cfu cm(-2) and 8.5 log cfu cm(-2) depending on species and atmospheric conditions. A range of volatile organic compounds, produced by the yeasts, was detected: acetone, ethyl acetate, ethanol, isopropyl acetate, ethyl butyrate, 1-propanol, 2-methyl-1-propanol, 1-butanol, 2-methyl-1-butanol, 3-methyl-1-butanol, 1-hexanol and hexyl acetate. These compounds are able to influence the sensory properties of strawberries. A simultaneous decrease in sugar concentrations (sucrose, glucose, fructose) was observed. When ethanol reached high concentrations, ethyl acetate and ethyl butyrate were produced. This production can be attributed to a detoxification of ethanol by yeasts. The fermentative metabolism of yeasts during aerobic conditions could be explained by the Crabtree effect. As the detected volatile organic compounds produced by yeasts are also found in fresh strawberries, it can be concluded that these compounds are produced both by microbiological and physiological processes.

Colony Count, Microbial↗
PubMedDate not supplied

A generalized plate method for estimating total aerobic microbial count.

The plate method outlined in Chapter 61: Microbial Limit Tests of the U.S. Pharmacopeia (USP 61) provides very specific guidance for assessing total aerobic bioburden in pharmaceutical articles. This methodology, while comprehensive, lacks the flexibility to be useful in all situations. By studying the plate method as a special case within a more general family of assays, the effects of each parameter in the guidance can be understood. Using a mathematical model to describe the plate counting procedure, a statistical framework for making more definitive statements about total aerobic bioburden is developed. Such a framework allows the laboratory scientist to adjust the USP 61 methods to satisfy specific practical constraints. In particular, it is shown that the plate method can be conducted, albeit with stricter acceptance criteria, using a test specimen quantity that is smaller than the 10 g or 10 mL prescribed in the guidance. Finally, the interpretation of results proffered by the guidance is re-examined within this statistical framework and shown to be overly aggressive.

Air Microbiology↗
PubMed1995

Postoperative selective bowel decontamination prevents gram-negative bacterial translocation in small-bowel graft recipients.

Gram-negative septic episodes are a potential risk of small-bowel transplantation; bacterial translocation through the graft is considered the mechanism. As a measure to prevent this complication, we evaluated postoperative selective bowel decontamination (SBD) in the rat model of orthotopic small-bowel transplantation [Lewis (LEW) and Brown-Norway (BN) rats as donors and recipients]. For 4 days after transplantation we gave FK 506, 2 mg/kg, which prevents rejection and results in indefinite recipient survival. For SBD, 24 mg/kg/day polymyxin E and 20 mg/kg/day tobramycin were administered via orogastric gavage to allograft recipients, both with and without FK 506 therapy. On Day 9, all rats were sacrificed, the peritoneal cavity was swabbed, and mesenteric lymph nodes (MLN), spleen, liver, and ileum were harvested for microbial qualitative and quantitative analysis. Animals with positive peritoneal swab cultures were excluded. SBD resulted in a significant reduction of the quantitative gram-negative bacterial flora in the ileum and cecum and of bacterial translocation to the MLN [0% versus 50% (no FK 506 therapy) and 8% versus 50% (FK 506 treated)]. In the allograft groups not treated with FK 506, SBD failed to significantly prolong survival, suggesting that acute rejection is not hastened by infection (bacterial translocation). We conclude that SBD in small-bowel-graft recipients prevents bacterial translocation by reducing intestinal gram-negative bacterial flora; this may reduce local and systemic infections by gut-derived organisms.

Animals↗
PubMedDate not supplied

Chemical, microbial and sensory changes during the anaerobic cold storage of beef inoculated with a homofermentative Lactobacillus sp. or a Leuconostoc sp.

Slices of beef were inoculated with about 3.5 log cfu/cm2 of Lactobacillus sp. 93 SMRICC 235 (homofermentative) or Leuconostoc sp. 89 SMRICC 189 and stored in 5% CO2 + 95% N2 at 4 degrees C. The microbial, chemical (glucose, L-lactate, D-lactate, acetate, formate, ethanol, H2S) and sensory changes of the beef slices were studied. For beef inoculated with Lactobacillus sp. 93 the flavour score started to decrease when the maximum bacterial count was reached. Leuconostoc sp. 89 caused a rapid decrease in the flavour score before reaching the maximum bacterial count. Concentrations of acetate and D-lactate increased while glucose and L-lactate decreased in beef slices inoculated with Lactobacillus sp. 93. In the presence of Leuconostoc sp. 89 ethanol and D-lactate increased while glucose decreased. Lactobacillus sp. 93 formed the highest level of H2S, and a sulphurous off-odour was noted only in the presence of this strain. D-Lactate and acetate indicated high numbers of Lactobacillus sp. 93 on the meat surface, while D-lactate and ethanol indicated high numbers of Leuconostoc sp. 89. More studies are needed in order to correlate levels of D-lactate, acetate and ethanol with sensory changes.

Acetates↗
PubMed2003

Mars-like soils in the Atacama Desert, Chile, and the dry limit of microbial life.

The Viking missions showed the martian soil to be lifeless and depleted in organic material and indicated the presence of one or more reactive oxidants. Here we report the presence of Mars-like soils in the extreme arid region of the Atacama Desert. Samples from this region had organic species only at trace levels and extremely low levels of culturable bacteria. Two samples from the extreme arid region were tested for DNA and none was recovered. Incubation experiments, patterned after the Viking labeled-release experiment but with separate biological and nonbiological isomers, show active decomposition of organic species in these soils by nonbiological processes.

Air Microbiology↗
PubMed1989

Adherence of microorganisms to breast prostheses: an in vitro study.

The quantitative and morphological characteristics of microbial adherence of four organisms--Staphylococcus epidermidis, S. aureus, Escherichia coli and Candida albicans--to the surfaces of different breast prostheses were observed. Semiquantitative adherence studies based on a modification of Maki's roll culture technique even after short contact times showed (1) increased microbial adherence at higher concentrations of the organisms and (2) differences in adherence properties between gram-positive bacteria and other organisms tested, noted also at lower organism concentrations. Scanning electron microscopy (SEM) to identify microorganisms on foam-covered prostheses, however, revealed organisms in the interstitial spaces that were not recovered by the plating technique. Other features on SEM were extracellular "slime" produced by S. epidermidis, which appears to act as a cement by which bacteria are held against prosthetic surfaces. These in-vitro findings suggest that brief exposure of the prostheses to a few organisms, particularly gram-positive bacteria, at the time of implantation would be sufficient inoculum for bacterial adherence to prosthetic surfaces.

Bacterial Adhesion↗