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PubMedDate not supplied

Microbial biomass estimation.

The development of a fully automated on-line monitoring and control system is very important in bioprocesses. One of the most important parameters in these processes is biomass. This review discusses different methods for biomass quantification. A general definition of biomass and biovolume are presented. Interesting concepts about active but not culturable cells considerations are included as well as concepts that must be taken into account when selecting biomass quantification technology. Chemical methods have had few applications in biomass measurement to date; however, bioluminescence can selectively enumerate viable cells. Photometric methods including fluorescence and scattered light measurements are presented. Reference methods including dry and wet weight, viable counts and direct counts are discussed, as well as the physical methods of flow cytometry, impedancimetric and dielectric techniques.

Biomass↗
PubMed2005

Effects of delayed microbial analysis of dental unit water line specimens.

PURPOSE: Monitoring microbial concentrations in water emitted from dental unit water lines (DUWL) is an important safety procedure. Improper handling of test water specimens could give incorrect results. Thus, the objective of this study was to measure the effects delayed culturing might have on DUWL specimens. METHODS: First, 100 mL water specimens were obtained from 10 different handpiece service lines within the School. All units had independent water systems, used DI (deionized water) water and were routinely cleaned using an alkaline peroxide based product. Two specimens of 10 mL were removed from the bottles and placed into individual sterile conical tubes. One set of tubes was processed immediately. 0.05 mL of sterile 1.0% (w/v) sodium thiosulfate solution was added to undiluted and diluted (1:10 and 1:100 with sterile DI water) specimens. After mixing, specimens were spiral plated onto duplicate R2A plates and incubated at 21degrees C for 7 days. Colonies were then counted and the cfu/mL of each original specimen determined. Another set of tubes was placed into a shipping envelope and mailed out to the School. Upon receipt, the tubes were processed as described above. The remaining 80 mL of water in the collection bottles were divided equally into new sterile tubes. One tube was left at 21 degrees C, while the other was placed into a 37 degrees C incubator. Aliquots were processed immediately and then after 1, 3 and 7 days. Next, 30 mL water specimens were obtained from 15 handpiece service lines in three outside clinics. All units had independent water systems, used DI water and were routinely cleaned with an alkaline peroxide-based product. Specimens were then divided equally into three sterile conical tubes. One of the tubes was transported (at 4 degrees C) to the laboratory and immediately processed as described. At the collection site, the second tube was placed into a padded envelope and mailed back to the School. The third tube was returned by overnight delivery using a Cool Pack type container. Upon receipt, all the tubes were processed as described previously. RESULTS: The 10 handpiece waterline specimens processed immediately ranged from 0 to 1000 cfu/mL. Holding specimens at 21 degrees C produced radically higher bacterial counts (1540-866,000 cfu/mL) in water from 90% of the handpieces. Holding at 37 degrees C produced unacceptably high bacterial counts in only 50% of the handpiece specimens. Mailed specimens were cultured 5 days after collection and water of unacceptable quality water was noted in 70% of the specimens. In another experimental set, mailed specimens arrived after 72 hours and were an average of 20 degrees C. Express sent specimens came the next morning at an average temperature of 4.5 degrees C. Only one waterline specimen processed immediately contained more than 500 cfu/mL. In contrast, 80% of specimens returned by post at ambient temperature had unacceptably high bacterial counts (780-376,000 cfu/mL). Express sent specimens produced the same results as those processed immediately.

Bacteria, Aerobic↗
PubMed2006

A novel system for large-scale gene expression analysis: bacterial colonies array.

In the present work, we report the use of bacterial colonies to optimize macroarray technique. The devised system is significantly cheaper than other methods available to detect large-scale differential gene expression. Recombinant Escherichia coli clones containing plasmid-encoded copies of 4,608 individual expressed sequence tag (ESTs) were robotically spotted onto nylon membranes that were incubated for 6 and 12 h to allow the bacteria to grow and, consequently, amplify the cloned ESTs. The membranes were then hybridized with a beta-lactamase gene specific probe from the recombinant plasmid and, subsequently, phosphorimaged to quantify the microbial cells. Variance analysis demonstrated that the spot hybridization signal intensity was similar for 3,954 ESTs (85.8%) after 6 h of bacterial growth. Membranes spotted with bacteria colonies grown for 12 h had 4,017 ESTs (87.2%) with comparable signal intensity but the signal to noise ratio was fivefold higher. Taken together, the results of this study indicate that it is possible to investigate large-scale gene expression using macroarrays based on bacterial colonies grown for 6 h onto membranes.

Algorithms↗
PubMed1996

Biofilms associated with poultry processing equipment.

Aerobic and Gram-negative bacteria were enumerated on non-metallic surfaces and stainless steel test pieces attached to equipment surfaces by swabbing and a mechanical dislodging procedure, respectively, in a South African grade B poultry processing plant. Changes in bacterial numbers were also monitored over time on metal test pieces. The highest bacterial counts were obtained from non-metallic surfaces such as rubber fingered pluckers and plastic defeathering curtains which exceeded the highest counts found on the metal surfaces by at least 1 log CFU cm-2. Gram-negative bacterial counts on all non-metallic surface types were at least 2 log CFU cm-2 lower than corresponding aerobic plate counts. On metal surfaces, the highest microbial numbers were obtained after 14 days exposure, with aerobic plate counts ranging from 3.57 log CFU cm-2 to 5.13 log CFU cm-2, and Gram-negative counts from 0.70 log CFU cm-2 to 3.31 log CFU cm-2. Scanning electron microscopy confirmed the presence of bacterial cells on non-metallic and metallic surfaces associated with poultry processing. Rubber 'fingers', plastic curtains, conveyor belt material and stainless steel test surfaces placed on the scald tank overflow and several chutes revealed extensive and often confluent bacterial biofilms. Extracellular polymeric substances, but few bacterial cells were visible on test pieces placed on evisceration equipment, spinchiller blades and the spinchiller outlet.

Animals↗
PubMed2005

Sustainable reduction in the flux of microbial compliance parameters from urban and arable land use to coastal bathing waters by a wetland ecosystem produced by a marine flood defence structure.

'Natural' treatment systems such as wetlands and reed beds have been proposed as sustainable means of reducing fluxes of faecal indicator organisms (FIOs) to recreational and shellfish harvesting waters. This is because FIO fluxes to coastal waters from both point (effluent) and diffuse (catchment) sources can cause non-compliance with microbiological standards for bathing and shellfish harvesting waters. The Water Framework Directive requires competent authorities in the member states to manage both point and diffuse sources of FIOs in an integrated manner to achieve compliance with 'good' water quality as defined in a series of daughter Directives. This study was undertaken to investigate the relative sources of FIOs to the popular bathing waters around Clacton, UK. In this predominantly arable (mainly cereal cropping) farming area, the principal land use predictor, explaining 76% of the variance in geometric mean presumptive Escherichia coli concentration at sub-catchment outlets during the bathing season, was the proportion of built-up (i.e. urbanised) land in each sub-catchment. This new finding contrasts with earlier studies in livestock farming regions where the proportion of improved grassland has proven to be the strongest predictor of microbial concentration. Also novel in this investigation, a flood defence wall has been built creating a wetland area which discharges every tidal cycle. The wetland produces over 97% reduction in the flux and concentrations of FIOs to the marine recreational waters. Also, FIO concentrations in water draining through the wetland to the sea were similar to concentrations measured in six UK sewage treatment plant effluents subject to secondary (biological) treatment followed by UV disinfection.

Agriculture↗
PubMed1999

A prospective, randomized, controlled trial comparing transparent polyurethane and hydrocolloid dressings for central venous catheters.

BACKGROUND: This study was undertaken to determine the frequency of skin colonization, hub colonization, and central venous catheter colonization in transparent hydrocolloid versus standard polyurethane dressings. METHODS: Adult patients requiring the insertion of a multilumen central venous catheter in an intensive care unit were randomized to receive either a standard polyurethane dressing or a transparent hydrocolloid dressing. Cultures were obtained from 125 skin insertion sites, 141 catheter hubs, 128 catheter tips, and blood samples from 132 patients. Extensive data on patient and catheter characteristics were collected. RESULTS: Skin and hub cultures revealed no significant difference in degree of colonization. However, the hydrocolloid group had a significantly higher level of catheter colonization than the polyurethane group (P =.048). Conversely, there was a significantly higher frequency of positive blood cultures in the polyurethane group (P =.03), although the majority were considered to be potential contaminants. There were only 6 cases in which the same species was simultaneously isolated from a positive blood culture and a colonized catheter, 5 from the hydrocolloid group and 1 from the polyurethane group. CONCLUSIONS: The results of this study suggest that an increased risk of catheter colonization is associated with the use of hydrocolloid dressings, despite previous research suggesting that they significantly reduce microbial growth compared with standard polyurethane. The clinical significance of increased numbers of positive blood cultures in the polyurethane group requires further examination, although distinguishing between contamination and true infection in intensive care settings continues to be methodologically challenging. Further studies are required to determine whether these findings are generalizable across different study settings and whether similar outcomes are obtained when different brands of hydrocolloid dressing are used.

Adolescent↗
PubMed2005

Real-time microbe detection based on director distortions around growing immune complexes in lyotropic chromonic liquid crystals.

We describe director distortions in the nematic liquid crystal (LC) caused by a spherical particle with tangential surface orientation of the director and show that light transmittance through the distorted region is a steep function of the particle's size. The effect allows us to propose a real-time microbial sensor based on a nontoxic lyotropic chromonic LC (LCLC) that detects and amplifies the presence of immune complexes. A cassette is filled with LCLC, antibody, and antigen-bearing particles. Small and isolated particles cause no macroscopic distortions of the LCLC. Upon antibody-antigen binding, the growing immune complexes distort the director and cause detectable optical transmittance between crossed polarizers.

Antigen-Antibody Complex↗
PubMed2003

Large-scale spatial distribution of virioplankton in the Adriatic Sea: testing the trophic state control hypothesis.

Little is known concerning environmental factors that may control the distribution of virioplankton on large spatial scales. In previous studies workers reported high viral levels in eutrophic systems and suggested that the trophic state is a possible driving force controlling the spatial distribution of viruses. In order to test this hypothesis, we determined the distribution of viral abundance and bacterial abundance and the virus-to-bacterium ratio in a wide area covering the entire Adriatic basin (Mediterranean Sea). To gather additional information on factors controlling viral distribution on a large scale, functional microbial parameters (exoenzymatic activities, bacterial production and turnover) were related to trophic gradients. At large spatial scales, viral distribution was independent of autotrophic biomass and all other environmental parameters. We concluded that in contrast to what was previously hypothesized, changing trophic conditions do not directly affect virioplankton distribution. Since virus distribution was coupled with bacterial turnover times, our results suggest that viral abundance depends on bacterial activity and on host cell abundance.

Bacteria↗
PubMed2004

Occurrence of Listeria monocytogenes in green table olives.

Microbiological safety of green table olives from different cultivars, prepared by both the Spanish-style and biological methods and fermented with starter cultures of lactic acid bacteria (Lactobacillus plantarum, Lactobacillus casei, and Lactobacillus pentosus), was investigated. The fermentation process was monitored by measuring pH values, titratable acidities, and growth of lactic acid bacteria over time. During fermentation, lactic acid bacteria and yeasts were major microbial populations. Microbiological safety was evaluated by analysis for Listeria monocytogenes with the use of an enrichment method during storage (from 55 days to 18 months). Results demonstrated that L. monocytogenes can survive and grow in green table olives. L. monocytogenes was found in one of the commercial (thermally treated) samples analyzed and in all samples older than 2 months, irrespective of olive cultivar, lactic acid bacteria starter used, pH and titratable acidity of brine samples, or treatment applied.

Colony Count, Microbial↗
PubMed2003

A retail and consumer phase model for exposure assessment of Bacillus cereus.

An exposure assessment is conducted for psychrotrophic and mesophilic Bacillus cereus in a cooked chilled vegetable product. A model is constructed that covers the retail and consumer phase of the food pathway, using the output of a similar model on the industrial process as input. Microbial growth is the predominant process in the model. Variability in time and temperature during transport and storage is included in the model and different domestic refrigerator temperature distributions are compared. As an end point, probable levels of B. cereus colony forming units (cfu) in packages of vegetable purée are predicted at the moment the consumer takes the product from its refrigerator, that is prior to a cooking process. The psychrotrophic strain is predicted to end up above a threshold level of 10(5) cfu/g in 0.9% to 6.3% of the vegetable purée packages, depending on domestic refrigerator temperature. Accounting for spoilage this reduces to 0.3% to 2.4%. Even if the purée is stored at 4 degrees C in the domestic refrigerator and use-by-date (UBD) is respected, the threshold level may be passed. For the mesophilic strain the threshold level is rarely passed, but in contrast to the total viable count, the spore load at the end point is predicted to be higher than in the psychrotrophic strain. Our study illustrates how an exposure assessment model, which may be used in quantitative risk assessment, can integrate expertise in modelling, food processing and microbiology over the food pathway, and thus evaluate food safety, identify gaps in knowledge and compare risk management measures. As important gaps in knowledge, the lack of sporulation and germination models and data, validated non-isothermal growth models and a spoilage model useful for risk assessment are identified. Knowledge of the dose-response relationship is limited and does not allow a full risk assessment. It is shown that exposure can be lowered by lowering domestic refrigerator temperatures, and less so much by monitoring and withdrawing contaminated products at the end of industrial processing.

Bacillus cereus↗
PubMed2001

Seasonal variations in the microbial population density present in biological sludge.

Sludge produced during the treatment of wastewater is being used as fertilizer in several Gulf countries. The Water and Sewage Authority of Saudi Arabia has targeted the reuse of the total amount of sludge in the future. However, these sludges should be properly treated before reuse as they contain a large number of pathogens and parasites. Little information is available on the microbial characteristics of sludge produced in wastewater treatment plants operating in this region. Variations in the population densities measured by Standard Plate Count, total coliform, fecal coliform, coliphage, and Clostridium perfringens present in the sludge, were monitored during a one year study at Al-Khobar wastewater treatment plant so that the effect of seasonal variations on the fate of these five indicator microorganisms could be investigated. This paper covers an evaluation of the fate of indicator microorganisms in the drying sludge. Insight gained in this study will be helpful in establishing guidelines for the use of sludge as fertilizer for agriculture purposes.

Clostridium perfringens↗
PubMed1999

Combined effects of carbon dioxide addition and barrier films on microbial and sensory changes in pasteurized milk.

The growth of psychrotrophic microorganisms is an important factor in the deterioration of refrigerated pasteurized milk. Dissolved CO2 inhibits certain spoilage microorganisms in foods provided that the packaging offers a sufficient barrier to CO2 evolution. The objectives of this work were, first, to estimate the sensory threshold for dissolved CO2 in 2% milk and, second, to determine the relationship between microbial growth and package barrier properties for pasteurized milk to which CO2 had been added at concentrations near the flavor threshold. The sensory threshold, as determined by a trained panel, for CO2 in 2% pasteurized milk was > 2.8 mM and < 9.1 mM. Pasteurized milk was inoculated with a cocktail of spoilage microorganisms, packaged in different barrier film pouches, and stored at 6.1 degrees C for up to 28 d. The addition of CO2 at concentrations of 8.7 and 21.5 mM increased the time needed to reach 10(6) cfu/ml from 6.4 d (no CO2) to 8.0 and 10.9 d, respectively, in low barrier pouches. In high barrier pouches, the time needed to reach 10(6) cfu/ml was increased to 9.7 and 13.4 d, respectively, at CO2 concentrations of 8.7 and 21.5 mM. This increase represents an increase in shelf-life of approximately 25 to 200%. Microbial counts had longer lag times and lower growth rates and took longer to reach stationary growth as the concentration of CO2 increased in all films than did the control milk. The control milk curdled in less than 17 d, but the test milk in the high barrier packaging had not curdled at 28 d. These data suggest that the shelf-life of pasteurized refrigerated milk could be extended by at least 25 to 200% at CO2 concentrations near the sensory threshold. The major variables in shelf-life are the amount of added CO2 and the barrier properties of the package.

Animals↗
PubMed2003

Morphological quantification of pellets in Streptomyces hygroscopicus var. geldanus fermentation broths using a flatbed scanner.

An image analysis technique has been developed to allow high throughput morphological characterisation of microbial fermentation broths containing spherical pellets greater than 100 microm in diameter. Images of stained Streptomyces hygroscopicus var. geldanus culture samples at three different inoculum levels were captured using a flatbed scanner, at a resolution of 21 microm per pixel (1200 dots per inch) and subsequently analysed leading to the generation of a morphological profile of each sample. The time taken for image capture and analysis of a prepared sample, containing approx. 2000 particles, was 3 min 6 s.

Cell Division↗
PubMed2000

Effect of a water extract of Moringa oleifera seeds on the hydrolytic microbial species diversity of a UASB reactor treating domestic wastewater.

The effect of a continuous supply of a water extract of Moringa oleifera seeds (WEMOS) on the hydrolytic microbial population of biomass grown in mesophilic upflow anaerobic sludge blanket reactors treating domestic wastewater was investigated. The WEMOS-treated sludge had seemingly a wider diversity, with enterobacter and klebsiella as dominant hydrolytic bacteria, compared with the control sludge. Additional tests indicated that various hydrolytic bacteria could degrade WEMOS. It appeared that a continuous supply of WEMOS to an anaerobic digester, treating domestic wastewater, increased the diversity of hydrolytic bacteria and therefore enhanced the biological start-up of the reactor.

Bacteria↗
PubMed2005

[Biological effects of space flight on several opportunistic pathogenic bacteria and biodestructive fungi].

OBJECTIVE: To investigate biological effects of space flight on several conditional pathogenic bacteria and biodestructive fungi. METHOD: Several potentially pathogenic or biodegrading microorganisms, including bacteria, actinomyces and fungi, were carried on-board spacecraft for 7 d. Some of the biological characteristics were studied by using general microbial test technology after recovery. RESULT: In space condition, survival and growth rate were promoted, and soluble pigments were produced, while morphological properties were changed differently. The antibiotic-sensitivity of certain strains decreased, while most of them showed no changes. CONCLUSION: The reproduction ability and growth rate of these microorganisms are promoted after being carried into space, and morphological differentiation increase. The resistance to antibiotics is stable.

Actinomyces↗
PubMed1997

Microbial quality of lamb carcasses during processing and the acridine orange direct count technique (a modified DEFT) for rapid enumeration of total viable counts.

This study was designed to set up a hazard analysis and critical control points (HACCP) system for sheep slaughtering operations at four different plants in Ireland and to determine the differences between plants in terms of microbial contamination. A single carcass area, the abdomen, was examined by swabbing and a microbiological profile was determined at different stages along the slaughter line. The level of contamination was assessed from the total bacteria counts, Enterobacteriaceae and Listeria spp. For the total counts, a modified direct epifluorescent filter technique (acridine orange direct count technique (AODC)) was developed and tested. No significant differences were found among plants in the levels of bacterial contamination. This was observed for all groups of organisms. The rapid direct technique (AODC) was found to be very successful. A correlation coefficient of 0.87 was obtained for this method and the standard plate count. Each test could be carried out in about 10-15 min and could be used to predict the standard plate count.

Abattoirs↗
PubMed2000

Effect of psychrotrophic bacteria and of an isolated protease from Pseudomonas fluorescens M3/6 on the plasmin system of fresh milk.

In the present study, we investigated the effect of Pseudomonas spp. growth on the plasmin enzymatic system in casein and whey fractions of fresh milk. Two bacterial strains, Pseudomonas spp. SRM28A and Pseudomonas fluorescens M3/6, were inoculated at a level of approximately 10(3) cfu/ml into fresh milk and incubated at 7 degrees C for 3 d. Bacterial counts were approximately 10(8) cfu/ml by d 3. Samples collected every 24 h were treated to separate the casein from the whey fraction. Casein and whey fractions were subjected to electrophoresis to visualize protein breakdown and plasmin activity and to colorimetric assays to quantify plasmin-related activities. With psychrotrophic bacterial growth, plasmin levels in casein fractions decreased significantly and in whey fractions increased then decreased significantly. Fresh milk results were similar for the two strains and were similar to earlier results with reconstituted nonfat dry milk. A transmission electron microscopy study by immunocytochemistry showed the presence of plasmin in casein micelles and its disappearance upon microbial growth in the milk. We hypothesized that extracellular microbial proteases produced by psychrotrophic microorganisms are responsible for this effect. To confirm this, an extracellular bacterial protease was isolated from Pseudomonas fluorescens M3/6 by ammonium sulfate fractionation and ion-exchange chromatography and incubated with fresh milk. Milk samples analyzed during incubation with the protease had significantly increased plasmin and plasminogen activities in the whey fraction within 5 h of incubation, while differences in activities in the casein fraction occurred at time 7.5 h for plasmin activity and 10 h of incubation for plasminogen activity. These quantitative data were supported by plasmin activity as visualized by casein-SDS-PAGE. These results suggest that growth of the Pseudomonas strains in fresh milk, and particularly their production of extracellular proteases, may be a causative factor in the release of plasmin from the casein micelle. Such plasmin release could affect the quality of cheeses and other food products that utilize dairy ingredients.

Animals↗
PubMed2005

Effects of storage in ozonised slurry ice on the sensory and microbial quality of sardine (Sardina pilchardus).

The use of slurry ice, both alone and in combination with ozone, as compared with traditional flake ice was investigated as a new refrigeration system for the storage of sardine (Sardina pilchardus). Microbiological, chemical and sensory analyses were carried out throughout a storage period of 22 days. According to sensory analyses, sardine specimens stored in ozonised slurry ice had a shelf life of 19 days, while counterpart batches stored in slurry ice or flake ice had shelf lives of 15 and 8 days, respectively. Storage in ozonised slurry ice led to significantly lower counts of aerobic mesophiles, psychrotrophic bacteria, anaerobes, coliforms, and both lipolytic and proteolytic microorganisms in sardine muscle, and of surface counts of mesophiles and psychrotrophic bacteria in sardine skin as compared with the slurry ice and the flake ice batches. In all cases, the slurry ice batch also exhibited significantly lower microbial counts, both in muscle and skin, than the flake ice batch. Chemical parameters revealed that the use of slurry ice slowed down the formation of TVB-N and TMA-N to a significant extent in comparison with storage in flake ice. A combination of slurry ice with ozone also allowed a better control of pH and TMA-N formation as compared with slurry ice alone. This work demonstrates that the combined use of slurry ice and ozone for the storage of sardine can be recommended to improve the quality and extend the shelf life of this fish species.

Animals↗