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PubMed1989

Microbial growth and accumulation in industrial metal-working fluids.

The dynamics of microbial growth in metal-working fluids (MWF) and the effect of the addition of biocides were studied in large fluid systems, in this case, one central tank which holds 150 m3. In this system, populations of Pseudomonas pseudoalcaligenes (greater than 10(8) CFU/ml) were sustained for a year, although large quantities of biocides were added. Quantitation of 3-OH lauric acid, a marker for many Pseudomonas spp., by gas chromatography indicated that the bacterial biomass exceeded the viable counts by approximately 15 times. Fungi were grown on several occasions, the dominating genera being Fusarium and Candida. Soon after the old MWF was removed and the tank was provided with fresh MWF, which consisted of an emulsion of mineral oil in water, there was a massive growth of P. pseudoalcaligenes that reached levels of greater than 10(8) bacteria per ml. Initially, only low concentrations of other species were found for some weeks. After this period, different enterobacteria and other gram-negative rods often appeared at high concentrations (10(7) and 10(8) bacteria per ml, respectively). Bacteria identified as P. pseudoalcaligenes showed great variation with respect to colony morphology and a certain heterogeneity with respect to biochemical characteristics. Certain bacterial species grew as microcolonies on metal strips immersed in the circulating MWF, but P. pseudoalcaligenes was not recovered from this habitat. The total bacterial count in the air surrounding the machines in the metal-working shop showed an inverse relation to increasing distance from the machine. The concentration of bacteria in the air varied because of the number of machines in use, temperature, and humidity.(ABSTRACT TRUNCATED AT 250 WORDS)

Air Microbiology↗
PubMed1993

Effect of the protein matrix on the digestion of cereal grains by ruminal microorganisms.

Experiments were conducted to investigate the role of the protein matrix in the digestion of barley and corn by ruminal microorganisms. Grains, ground and collected on sieves as two particle fractions .25 to .89 mm (small particles) and 2.00 to 3.00 mm (large particles), as well as isolated barley and corn starch granules, were incubated with ruminal inocula. For both grains, digestion of starch in small particles was greater (P < .001) than that of large particles. At 16 and 24 h starch digestion was greater (P < .01) in barley than in corn, for small and large particles. Digestion of barley starch granules did not differ (P > .05) from that of corn starch granules at any incubation time. A 4-h preincubation of small-particle corn and barley with protease increased (P < .001) microbial digestion of starch in corn at 16 h but did not affect digestion of barley. When four ruminally cannulated steers were fed diets containing 80% barley, corn, or wheat or 100% alfalfa hay in a 4 x 4 Latin square experiment, amylolytic activity of ruminal inoculum was higher for steers fed grains than for those fed alfalfa. However, when standardized for total viable counts of bacteria, ruminal amylolytic activity did not differ (P > .05) among diet treatments, but proteolytic activity of ruminal inoculum for steers fed alfalfa was higher (P < .01) than that for steers fed cereal grains. Activity of serine proteases in ruminal inoculum was higher (P < .05) for steers fed alfalfa than for steers fed grains.(ABSTRACT TRUNCATED AT 250 WORDS)

Amylases↗
PubMed1989

Microbial inoculation of alfalfa haylage: ensiling characteristics and milk production response when fed to early lactation dairy cows.

Third-cutting alfalfa hay harvested at bud stage and wilted to approximately 65% moisture was treated with a live bacterial inoculant at the rate of 300,000 cfu/g fresh alfalfa. Treated alfalfa was packed in polyethylene bags. Samples were taken at time of ensiling and d 1, 2, 3, 4, 7, and 28 postensiling. Mean pH was lower in the treated haylage (5.09 and 5.71 for treatment and control, respectively). Mean temperatures were higher in the treated haylage (30.0 and 28.0 degrees C for treatment and control, respectively). Mold count, water-soluble carbohydrate, alpha amino nitrogen, CP, and ADF were not affected by treatment. Regardless of treatment, pH, mold counts, and water-soluble carbohydrates declined with time. There was no significant difference between treatments for DM intake, milk production, and milk composition.

Analysis of Variance↗
PubMed2002

Planktonic nitrate-reducing bacteria and sulfate-reducing bacteria in some western Canadian oil field waters.

Oil fields that use water flooding to enhance oil recovery may become sour because of the production of H(2)S from the reduction of sulfate by sulfate-reducing bacteria (SRB). The addition of nitrate to produced waters can stimulate the activities of nitrate-reducing bacteria (NRB) and control sulfide production. Many previous studies have focused on chemolithotrophic bacteria that can use thiosulfate or sulfide as energy sources while reducing nitrate. Little attention has been given to heterotrophic NRB in oil field waters. Three different media were used in this study to enumerate various types of planktonic NRB present in waters from five oil fields in western Canada. The numbers of planktonic SRB and bacteria capable of growth under aerobic conditions were also determined. In general, microbial numbers in the produced waters were very low (<10 ml x (-1)) in samples taken near or at wellheads. However, the numbers increased in the aboveground facilities. No thiosulfate-oxidizing NRB were detected in the oil field waters, but other types of NRB were detected in 16 of 18 produced water samples. The numbers of heterotrophic NRB were equal to or greater than the number of sulfide-oxidizing, chemolithotrophic NRB in 12 of 15 samples. These results showed that each of the oil fields contained NRB, which might be stimulated by nitrate amendment to control H(2)S production by SRB.

Animals↗
PubMed2006

Estimation of microbial cover distributions at Mammoth Hot Springs using a multiple clone library resampling method.

We propose the use of cover as a quick, low-resolution proxy for the abundance of microbial species, which reduces polymerase chain reaction bias. We showcase this concept in a computation that uses clone library information from travertine-forming hot springs in Yellowstone National Park to provide estimates of relative covers at different locations within the spring system. Samples were used from two media: the water column and the travertine substrate. The cover distribution is found to approximate a power law for samples within the water column. Significant commonality of species with the highest cover is observed in the water column for all locations, but not for species present in the substrate at different locations or between media at the same location.

Biodiversity↗
PubMed2006

Electron beam and gamma irradiation effectively reduce Listeria monocytogenes populations on chopped romaine lettuce.

Fresh, chopped romaine lettuce contaminated with a seven-strain cocktail of Listeria monocytogenes (in a solution containing approximately 10(8) organisms per ml) that had attained a level of contamination of between 7 and 8 log CFU/g was packaged in 15-g samples. The lettuce was irradiated with a Co60 source at 1.15 or 0.51 kGy and then stored at 4 degrees C. In addition, samples contaminated with isolated strains 16397, 0733, and 1992 were subjected to either electron beam irradiation at doses ranging from 0.3 to 1.2 kGy or gamma irradiation at 0.56 kGy without subsequent refrigerated storage. All postirradiation and control samples were diluted with Butterfield's phosphate buffer and plated in duplicate on modified Oxford media. Samples that received electron beam or gamma irradiation without subsequent refrigerated storage were also plated in duplicate on modified Oxford media plates coated with two 7-ml layers of basal yeast extract agar. Electron beam irradiation yielded D10-values (the dose required to eliminate 90% of the microbial population) of 0.16, 0.17, and 0.19 kGy for strains 16397, 0733, and 1992, respectively. The corresponding log reductions obtained for these same three strains at 0.56 kGy of gamma irradiation were 2.91, 2.62, and 2.66 log, respectively. Gamma irradiation at 1.15 and 0.51 kGy with subsequent refrigerated storage (4 degrees C) reduced populations by > 5 and > 2 log, respectively, compared with controls. Neither the irradiated samples nor the control samples showed increases in population during the storage periods. Our results indicate that low-dose irradiation can effectively reduce or eliminate L. monocytogenes on chopped romaine lettuce, improving the safety of ready-to-eat salads.

Colony Count, Microbial↗
PubMed2002

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

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

Animals↗
PubMed1998

Microbial populations associated with commercially produced South African sorghum beer as determined by conventional and Petrifilm plating.

Microbial populations of 46 commercially produced sorghum beer samples from retail outlets in Johannesburg, South Africa, were enumerated and characterized. Aerobic plate counts, lactic acid bacteria counts and yeast counts were performed by conventional and Petrifilm plating. Conventional methods yielded yeast counts of 7.84 log CFU/ml, lactic acid bacteria counts of 6.44 log CFU/ml and aerobic plate counts of 5.96 log CFU/ml. In comparison, Petrifilm counts were 7.85 log CFU/ml for yeasts, 5.31 log CFU/ml for lactic acid bacteria and 5.34 log CFU/ml for aerobic bacteria. Characterization of 419 predominant bacterial isolates from Standard One Nutrient Agar, MRS Agar and corresponding Petrifilm plates yielded 88.0% lactic acid bacteria, 8.4% Bacillus species, 2.9% Micrococcus species and 0.7% Gram negative bacteria. Composition of predominant lactic acid bacteria populations from Standard One Nutrient Agar and both types of Petrifilm plates showed marginal differences. Increased proportions of heterofermentative lactic acid bacteria were, however, isolated from conventional MRS Agar compared to the modified Petrifilm product which represented the equivalent to MRS Agar.

Bacillus↗
PubMed1989

[The significance of the contamination of dental care articles. The results of a field study].

Permissible conclusions both from recent available literature and our own field-study results concerning the problematic nature of microbial contamination of dental hygiene articles and the resulting possible health hazard for the consumer can be summarized as follows: Manufacturing practices as are given in the basic instructions for production sites of the cosmetic industry, render a possible degree of microbial contamination. This largely rules out the danger of infection of the consumer upon acquisition of the dental hygiene product. Secondary contamination of these products, as inevitably is the case during use of dental hygiene articles, leads to microbial colonization especially of toothbrush bristles. The extent of this colonization depends at least partially upon the utilization age of the toothbrush. Also for this reason a toothbrush should be replaced by a new one after period of three months, six months at the latest and in all cases of inflammatory changes of the mouth and throat region. The contamination of both the glass or plastic container used for rinsing the teeth after brushing or for gargling can be held within certain limits by dry storage. Only in exceptional cases do mouthwashes show a small degree of contamination. Provided they contain antimicrobial substances, no therapeutically serviceable possibilities worth mentioning follow for the reduction of oropharyngeal flora. Microbial colonization of toothpastes as a result of secondary contamination following use is observed only in exceptional cases due to their preservative content. Significant germination of stagnated residual water in waterpicks often occurs, achieving germ counts up to more than 10(7) cfu per ml. Moreover, waterpicks can represent a biotope for Pseudomonas aeruginosa, and should be used neither by patients with open wounds or mucous membrane lesions in the oropharyngeal area, nor by patients with reduced immune resistance. Manufacturers of waterpicks are urged to impede or prevent the stagnation of residual water more effectively by introducing constructive improvements. Denture and retainer cleansing agents presently on the market display a sufficient antimicrobial effect within the frame of their application, however do not meet the standards set for disinfectants. Dental hygiene products are without relevance for the epidemiology of Legionnaires' disease.

Bacteria↗
PubMed2003

Relevance of microbial interactions to predictive microbiology.

Microbial interaction can be ignored in predictive microbiology under most conditions. We show that interactions are only important at high population densities, using published data on inhibition of growth of Listeria monocytogenes in broth. Our analysis using growth models from predictive microbiology indicated that interactions only occur at population densities of approximately 10(8) cfu/ml of the protective cultures. Spoilage is evident at these levels, except for fermented foods. In bacterial colonies, diffusion limitation acts as a constraint to growth. We have shown that these constraints only become important after large outgrowth of colonies (in the order of 5-log growth in Lactobacillus curvatus colonies), which depends on the initial inoculation density. Intra-colony interactions play an important role under these conditions. There is no large outgrowth of colonies when the initial inoculation densities are high and broth culture growth can be used to approximate colony growth.

Colony Count, Microbial↗
PubMed2005

Accounting for inherent variability of growth in microbial risk assessment.

Risk assessments of pathogens need to account for the growth of small number of cells under varying conditions. In order to determine the possible risks that occur when there are small numbers of cells, stochastic models of growth are needed that would capture the distribution of the number of cells over replicate trials of the same scenario or environmental conditions. This paper provides a simple stochastic growth model, accounting only for inherent cell-growth variability, assuming constant growth kinetic parameters, for an initial, small, numbers of cells assumed to be transforming from a stationary to an exponential phase. Two, basic, microbial sets of assumptions are considered: serial, where it is assume that cells transform through a lag phase before entering the exponential phase of growth; and parallel, where it is assumed that lag and exponential phases develop in parallel. The model is based on, first determining the distribution of the time when growth commences, and then modelling the conditional distribution of the number of cells. For the latter distribution, it is found that a Weibull distribution provides a simple approximation to the conditional distribution of the relative growth, so that the model developed in this paper can be easily implemented in risk assessments using commercial software packages.

Bacteria↗
PubMed2006

Multiplex polymerase chain reaction detection of black-pigmented bacteria in infections of endodontic origin.

The purpose of this study was to detect the presence of Porphyromonas endodontalis, P. gingivalis, Prevotella intermedia, P. nigrescens, and P. tannerae from clinical samples using multiplex polymerase chain reactions (PCR). Two different multiplex PCR protocols were used (one for the two Porphyromonas species and the other for the three Prevotella species), each one using a primer pair specific for each target species. The results were compared to those of the conventional culture procedures. Microbial samples were taken aseptically from 40 infected root canals and abscesses from patients. Samples were cultured in an anaerobic condition for conventional identification using a Rapid ID 32 A kit. Multiplex PCR was processed using the DNA extracted from each sample. At least one of the five species of black-pigmented bacteria (BPB) were detected in 65% (26 of 40) of the samples using multiplex PCR, and in 15% (6 of 40) using the conventional culture procedures. Multiplex PCR was more rapid, sensitive, specific, and effective in detecting BPB than the conventional culture procedures.

Bacteroidaceae Infections↗
PubMed1993

Diagnosis and management of the diabetic foot ulcer.

Infected leg ulcers in patients with diabetes mellitus are a common and potentially serious problem. Neuropathy and vascular disease associated with diabetes mellitus allow the possibility of significant microbial invasion. Infections in diabetic patients are usually polymicrobial reflecting the normal flora of the foot skin. Curettage of the base of foot ulcers and deep tissue cultures are the most reliable methods for identifying the true pathogens, which are aerobic Gram-negative bacilli, anaerobes, and Staphylococcus aureus. Empirical antibiotic therapy should be directed against these pathogens. Once culture and sensitivity results are available, therapy should be targeted specifically for the pathogens present to prevent long-term use of broad-spectrum antibiotics. Preventive care of the foot in patients with diabetes mellitus is extremely important and may reduce complications associated with infections of the foot.

Bacteria↗
PubMed2006

Microbial communities in the garbage composting with rice hull as an amendment revealed by culture-dependent and -independent approaches.

The diversity and succession of microbial communities during the garbage composting with rice hull as an amendment were studied by denaturing gradient gel electrophoresis (DGGE) and clone library analysis of PCR-amplified 16S ribosomal DNA (rDNA) with universal primers. Based on temperature changes, the composting process could be divided into thermophilic, cooling-down, and maturing stages. The DGGE profiles and clone library analysis revealed that the microbial community drastically changed during the composting process from the thermophilic to the maturing stages. The dominant bacterial group changed from the phylum Firmicutes in the thermophilic stage to the phylum Bacteroidetes in the maturing stage. This change in microbial communities may be significant for the composting process. The diversity of cultivated bacteria isolated from samples taken at various stages of the composting process was low. A total of 87 isolates were classified as belonging to only four different groups. These groups were also detected in the DGGE profiles and by the clone library analysis. Our study indicated that a combination of culture-dependent and -independent approaches could be very useful for monitoring both bacterial diversity and the succession of communities during the composting process. This study would be beneficial for assessing the ecological consequences of disposal of organic waste.

Bacteria↗
PubMed2002

A review of the science regarding dental unit waterlines.

BACKGROUND: The National Institute of Dental and Craniofacial Research, or NIDCR; the American Dental Association, or ADA; and the Organization for Safety & Asepsis Procedures, or OSAP, sponsored a workshop on the topic of dental unit waterlines, or DUWLs, on Sept. 29, 2000, at the National Institutes of Health in Bethesda, Md. These organizations invited a group of experts from the ADA, NIDCR, OSAP, the U.S. Food and Drug Administration, the Centers for Disease Control and Prevention, the U.S. Department of Defense, academia and private industry to participate. TYPES OF STUDIES REVIEWED: The sponsors asked the participants to critically review the scientific literature on the subject in an attempt to determine the evidence basis for management of DUWL contamination and potential health risks, if any, in dental procedures. The ultimate goal of the workshop was to determine if a research agenda in the area of DUWLs should be pursued and what questions such an agenda should involve. RESULTS: The workshop yielded four questions that need to be addressed in future research: What is the safest and most effective agent(s)/device(s) for achieving microbial levels of no more than 200 colony-forming units per milliliter, or CFU/mL, in the effluent dental water? How should these products be evaluated and by whom? What are the adverse health effects, if any, of chronic exposure to dental bioaerosol or to the agents introduced into the dental unit to treat the waterlines for both dental staff members and patients? How could these health issues be evaluated? CLINICAL IMPLICATIONS: Developing evidence-based parameters for the management of biofilm contamination that are efficacious and cost-effective will allow clinicians to meet in proposed ADA standard of no more than 200 CFU/mL of effluent water.

American Dental Association↗
PubMed1990

Age and sex relationships of superinfecting microorganisms in periodontitis patients.

The occurrence by age and sex of subgingival enteric rods and pseudomonads, yeasts, and staphylococci was studied in 3075 "refractory" periodontitis patients referred for microbiological analysis. Each subject contributed a pooled subgingival sample obtained from 3 deep periodontal pockets with paper points. Selective and nonselective media and commercial identification kit systems were used for microbial isolation and speciation. Females constituted about 60% of the study subjects, and almost one-third of all patients were in their forties. Females (47.3%) showed a higher prevalence of the study organisms than males (43.9%). Older females (15.9%) and males (15.3%) revealed significantly higher prevalences of enteric rods and pseudomonads than younger individuals (10.9%), and older infected females yielded significantly higher viable counts than younger infected females. The sexes demonstrated a similar prevalence of staphylococci (about 28%), but younger infected females and males showed significantly higher viable counts than older infected individuals. No sex or age relationships were found for yeasts (about 14% of individuals infected). The high level of subgingival enteric rods and pseudomonads in some individuals may be important in the pathogenesis of geriatric and other forms of periodontitis and may have therapeutic implications.

Adolescent↗
PubMed1999

Variable selection and multivariate methods for the identification of microorganisms by flow cytometry.

BACKGROUND: When exploited fully, flow cytometry can be used to provide multiparametric data for each cell in the sample of interest. While this makes flow cytometry a powerful technique for discriminating between different cell types, the data can be difficult to interpret. Traditionally, dual-parameter plots are used to visualize flow cytometric data, and for a data set consisting of seven parameters, one should examine 21 of these plots. A more efficient method is to reduce the dimensionality of the data (e.g., using unsupervised methods such as principal components analysis) so that fewer graphs need to be examined, or to use supervised multivariate data analysis methods to give a prediction of the identity of the analyzed particles. MATERIALS AND METHODS: We collected multiparametric data sets for microbiological samples stained with six cocktails of fluorescent stains. Multivariate data analysis methods were explored as a means of microbial detection and identification. RESULTS: We show that while all cocktails and all methods gave good accuracy of predictions (>94%), careful selection of both the stains and the analysis method could improve this figure (to > 99% accuracy), even in a data set that was not used in the formation of the supervised multivariate calibration model. CONCLUSIONS: Flow cytometry provides a rapid method of obtaining multiparametric data for distinguishing between microorganisms. Multivariate data analysis methods have an important role to play in extracting the information from the data obtained. Artificial neural networks proved to be the most suitable method of data analysis.

Bacillus subtilis↗
PubMed2006

Microbial diversity and succession during the manufacture and ripening of traditional, Spanish, blue-veined Cabrales cheese, as determined by PCR-DGGE.

The diversity and dynamics of the dominant microbial communities arising during the manufacture and ripening of four batches of naturally fermented Cabrales cheese were investigated by the PCR-DGGE culture-independent technique. Total microbial DNA was extracted from cheese milk, curd and cheese samples and used as template material in PCR experiments to amplify the V3 region of the bacterial 16S rRNA gene, plus the D1 region of the eukaryotic 26S rRNA gene. These regions were then analysed using DGGE. Eukaryotic and bacterial bands were identified by isolation, reamplification and sequencing. The results were compared to those obtained in a previous microbial characterization of the same four batches using classical culturing methods. Great variability was recorded between batches by the PCR-DGGE technique. This was also shown by culturing, and underlines the uniqueness of artisanal products. Lactocococcus lactis subsp. lactis was dominant from the cheese milk stage until the end of ripening, whereas populations of certain Lactobacillus species appeared during ripening. Populations of species never isolated by culturing were found to be numerous by the PCR-DGGE method, in particular Lactococcus garvieae and Lactococcus raffinolactis. Other, completely unknown lactococci were also detected. The dominant eukaryotic populations from day 15 onwards were those of Penicillium roqueforti and Geotrichum candidum.

Cheese↗