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PubMed2003

The microflora recovered from the outer-surfaces of the Frialit-2 implanto-prosthetic connector.

The aim of the present investigation was to examine the outer-surface microbiota of the prosthetic connector of Frialit-2 implants, and to compare the microbial findings with the peri-implant parameters 2 years after functional loading. In 16 implant-treated patients (55.8 +/- 9.5 years) the outer-surface micro-organisms of the prosthetic connectors were determined in 32 Frialit-2 implants. The functional loading time of the prosthetic suprastructures was 24.1 +/- 13.8 months on average. After removal of the implant-supported restoration, microbial samples were obtained from the outer-surfaces of the Frialit-2 prosthetic connector. The microbial plaque samples were specified on CDC-blood agar as percentages of the total cultivable flora. Actinobacillus actinomycetemcomitans was semiquantitively determined on TSBV-agar in CFU/ml. The microbial plaque samples were dominated by Actinomyces israelii (68.8%), Eubacterium lentum (56.3%) and Veillonella parvula (43.8%) with proportions ranking between 3.9% (V. parvula) and 11.1% (A. israelii). The most frequently detected gram-negative microorganisms were Fusobacterium nucleatum (87.5%), Porphyromonas gingivalis (81.3%), and Peptostreptococcus micros (68.8%) with enhanced proportions for P. gingivalis (11.4%) and P. micros (11.4%). No statistical significant correlation could be established between the microbiota present on the outer-surfaces of the F2-connector and the peri-implant parameters examined. The outer-surface microflora recovered from the implanto-prosthetic-connector of Frialit-2 implants reveals a colonization with gram-positive bacteria and potentially harmful gram-negative micro-organisms that were frequently detected, but present at low levels. After 2 years of restorative loading, the outer-surface microbial colonization is compatible with peri-implant soft tissue health.

Actinomyces↗

PubMed2003

Shifts in archaeal communities associated with lithological and geochemical variations in subsurface Cretaceous rock.

Subsurface microbial community structure in relation to geochemical gradients and lithology was investigated using a combination of molecular phylogenetic and geochemical analyses. Discreet groundwater and substratum samples were obtained from depths ranging from 182 to 190 m beneath the surface at approximately 10-cm intervals using a multilevel sampler (MLS) that straddled Cretaceous shale and sandstone formations at a site in the southern San Juan Basin in New Mexico. DNA and RNA were extracted directly from quartzite sand substratum loaded into individual cells of the MLS and colonized in situ. Polymerase chain reaction (PCR)-mediated T-RFLP analysis of archaeal rRNA genes (rDNA) in conjunction with partial sequencing analysis of archaeal rDNA libraries and quantitative RNA hybridization with oligonucleotide probes were used to probe community structure and function. Although total microbial populations remained relatively constant over the entire depth interval sampled, significant shifts in archaeal populations, predominantly methanogens, were observed. These shifts coincided with the geochemical transition from relatively high methane (26 mM), low sulphate (< 3 mg l(-1)) conditions in the region adjacent to the organic matter-rich shale to relatively low-methane (< 0.5 mM), high-sulphate (48 mg l(-1)) conditions in the organic-poor sandstone beneath the shale. These results indicated that active, phylogenetically diverse archaeal communities were present in the subsurface Cretaceous rock environment at this site and that major archaeal clades shifted dramatically over scales of tens of centimetres, corresponding to changes in the lithology and geochemical gradients.

Archaea↗

PubMed1976

Tetracycline in the treatment of uncomplicated male gonorrhea.

A clinical trial was performed to test a loading dose regimen of tetracycline (1.5 gm po sTAT and 0.5 mg po quid for 4 days) against a no-loading dose (0.5 gm po quid for 4 1/2 days) in the treatment of 477 cases of uncomplicated male urogenital gonorrhea. The regimens were equivalent, with an overall cure rate of 96%. A crossover pharmacokinetic study in 10 healthy volunteers demonstrated higher blood levels during the first day on the loading regimen, but equivalence thereafter. Tetracycline, in a total dose of 9.5 gm, is highly effective treatment, and a loading dose is not necessary.

Adult↗

PubMed2005

Role of discontinuous chlorination on microbial production by drinking water biofilms.

Microbial quality in water distribution systems is strongly affected by the development of microbial biofilms. Production and release of microbial cells by the biofilm affect microbial levels in the water column and in some cases this fact constitutes a public health concern. In this study, we attempt to analyze in which way the existence of different episodes of chlorine depletion affects both biofilm formation and microbial load of an artificial laboratory system. The work was carried out using two parallel packed bed reactors both supplied with running tap water. One of the reactors was used as a control and was permanently exposed to the action of chlorine. In the other reactor, chlorine was neutralized at selected times during the experiment and for periods of variable length. During the experiment the concentration of total and viable cells from the effluent was monitored at the exit of each of the reactors. The data obtained were used to estimate microbial production from the biofilms. As an average, release of microbial cells to the water phase increased tenfold in the absence of chlorine. The results also indicate that disinfectant efficiency against the biofilm was not recovered when chlorine returned to normal levels after each event of chlorine neutralization. Cell viability in the water phase in the presence of chlorine was low at the beginning of the experiment but increased 4 orders of magnitude after five neutralization periods. Therefore, subsequent episodes of chlorine depletion may accelerate the development of microbial communities with reduced susceptibility to disinfection in real drinking water systems.

Biofilms↗

PubMed1997

[Changes in the microbial picture during the production of poultry salami].

Changes in microbiological parameters during the production of fine poultry salami was monitored in a private poultry-processing plant in Kosice within a period of six months. This product consists of meat paste or mechanically deboned poultry meat (MDPM), which is produced with the help of a Protecon MPB 30 E deboning machine, pork trimmings, water (in the form of crushed ice), salt, spices, and garlic paste. The main raw food material (hand-boned meat and skin from poultry carcasses intended for mechanical deboning), MDPM immediately after production, salted MDPM after its 24-hour-storage and ripening in the chiller, pork trimmings added to MDPM at an amount of 25%, prepared salami emulsion, and the final product (fine poultry salami) were examined for the presence of pathogenic and potentially pathogenic microorganisms. The total plate count, the counts of indicatory microorganisms (Coliforms and Enterococci), Staphylococci, psychrotrophic, proteolytic and lipolytic bacteria were also determined according to the Slovak government regulations. The results of the quantitative microbiological examination are shown in Figs. 1 and 2. It follows from them that the microbial load of poultry skin is considerably higher than that of hand-boned meat. During the deboning process an increase in all microbial parameters (on average by 1-3 radices) was noticed as compared with the raw food material (defrosted poultry carcasses before the mechanical deboning). MDPM contained 10(4)-10(7) CFU/g; the count of coliforms ranged between 10(3) and 10(6)/g; the count of proteolytic and lipolytic bacteria between 10(4) and 10(6)/g; the count of Staphylococci and Enterococci between 10(2) and 10(4)/g. Staphylococcus aureus was discovered in about 50% samples of MDPM in an average concentration of 10(2)/g. In addition to the groups of bacteria listed above, a wide range of potentially pathogenic microorganisms belonging to the family Enterobacteriaceae, especially those of the genus Proteus, Escherichia coli, Citrobacter and Providencia, was also found in MDPM. In four cases Salmonella enteritidis was also detected in the samples of both the skin of chicken carcasses and the MDPM. The nitrate salting mixture added at a concentration of 2% did not significantly reduce the counts of bacteria present in the MDPM. The prepared salami emulsion was very high in all groups of microorganisms, which was also caused by the addition of pork trimmings. This component seems to be a very important source of microbial contamination, showing the following average bacterial counts: total plate count 4.8 x 10(6)/g, the count of psychrotrophic bacteria 1.0 x 10(6)/g, the count of coliforms 7.0 x 10(5)/g, the count of Enterococci 9.2 x 10(3)/g, the count of Staphylococci 3.0 x 10(4)/g, the count of proteolytic microorganisms 2.7 x 10(5)/g, and the count of lipolytic microorganisms 4.2 x 10(5)/g. However, heat treatment of the final product reliably and almost completely devitalized all the bacteria found in the salami emulsion before heat processing. No pathogenic or potentially pathogenic bacteria were detected in any sample of fine poultry salami. Quite a high number of bacteria in the salami emulsion was reduced by heat treatment to a final average value of 10(2)/g.

Animals↗

PubMed2002

Rapid and quantitative detection of the microbial spoilage of meat by fourier transform infrared spectroscopy and machine learning.

Fourier transform infrared (FT-IR) spectroscopy is a rapid, noninvasive technique with considerable potential for application in the food and related industries. We show here that this technique can be used directly on the surface of food to produce biochemically interpretable "fingerprints." Spoilage in meat is the result of decomposition and the formation of metabolites caused by the growth and enzymatic activity of microorganisms. FT-IR was exploited to measure biochemical changes within the meat substrate, enhancing and accelerating the detection of microbial spoilage. Chicken breasts were purchased from a national retailer, comminuted for 10 s, and left to spoil at room temperature for 24 h. Every hour, FT-IR measurements were taken directly from the meat surface using attenuated total reflectance, and the total viable counts were obtained by classical plating methods. Quantitative interpretation of FT-IR spectra was possible using partial least-squares regression and allowed accurate estimates of bacterial loads to be calculated directly from the meat surface in 60 s. Genetic programming was used to derive rules showing that at levels of 10(7) bacteria.g(-1) the main biochemical indicator of spoilage was the onset of proteolysis. Thus, using FT-IR we were able to acquire a metabolic snapshot and quantify, noninvasively, the microbial loads of food samples accurately and rapidly in 60 s, directly from the sample surface. We believe this approach will aid in the Hazard Analysis Critical Control Point process for the assessment of the microbiological safety of food at the production, processing, manufacturing, packaging, and storage levels.

Artificial Intelligence↗

PubMed2006

Is microbial community composition in boreal forest soils determined by pH, C-to-N ratio, the trees, or all three?

In Fennoscandian boreal forests, soil pH and N supply generally increase downhill as a result of water transport of base cations and N, respectively. Simultaneously, forest productivity increases, the understory changes from ericaceous dwarf shrubs to tall herbs; in the soil, fungi decrease whereas bacteria increase. The composition of the soil microbial community is mainly thought to be controlled by the pH and C-to-N ratio of the substrate. However, the latter also determines the N supply to plants, the plant community composition, and should also affect plant allocation of C below ground to roots and a major functional group of microbes, mycorrhizal fungi. We used phospholipid fatty acids (PLFAs) to analyze the potential importance of mycorrhizal fungi by comparing the microbial community composition in a tree-girdling experiment, where tree belowground C allocation was terminated, and in a long-term (34 years) N loading experiment, with the shifts across a natural pH and N supply gradient. Both tree girdling and N loading caused a decline of ca. 45% of the fungal biomarker PLFA 18:2omega6,9, suggesting a common mechanism, i.e., that N loading caused a decrease in the C supply to ectomycorrhizal fungi just as tree girdling did. The total abundance of bacterial PLFAs did not respond to tree girdling or to N loading, in which cases the pH (of the mor layer) did not change appreciably, but bacterial PLFAs increased considerably when pH increased across the natural gradient. Fungal biomass was high only in acid soil (pH < 4.1) with a high C-to-N ratio (>38). According to a principal component analysis, the soil C-to-N ratio was as good as predictor of microbial community structure as pH. Our study thus indicated the soil C-to-N ratio, and the response of trees to this ratio, as important factors that together with soil pH influence soil microbial community composition.

Bacteria↗

PubMed2006

Influence of raw milk quality on fluid milk shelf life.

Pasteurized fluid milk shelf life is influenced by raw milk quality. The microbial count and somatic cell count (SCC) determine the load of heat-resistant enzymes in milk. Generally, high levels of psychrotrophic bacteria in raw milk are required to contribute sufficient quantities of heat-stable proteases and lipases to cause breakdown of protein and fat after pasteurization. Sanitation, refrigeration, and the addition of CO2 to milk are used to control both total and psychrotrophic bacteria count. It is not uncommon for total bacterial counts of raw milk to be < 10,000 cfu/mL. In the past, fluid milk processors have not focused much attention on milk SCC. Increased SCC is correlated with increased amounts of heat-stable protease (plasmin) and lipase (lipoprotein lipase) in milk. When starting with raw milk that has a low bacterial count, and in the absence of microbial growth in pasteurized milk, enzymes associated with high SCC will cause protein and fat degradation during refrigerated storage, and produce off-flavors. As the ability to kill, remove, or control microbial growth in pasteurized refrigerated milk continues to improve, the original milk SCC will be the factor limiting the time of refrigerated storage before development of an off-flavor in milk. Most healthy cows in a dairy herd have a milk SCC < 50,000 cell/mL. Bulk tank SCC > 200,000 cell/mL are usually due to the contribution of high SCC milk from a small number of cows in the herd. Technology to identify these cows and keep their milk out of the bulk tank could substantially increase the value of the remaining milk for use in fluid milk processing. To achieve a 60- to 90-d shelf life of refrigerated fluid milk, fluid processors and dairy farmers need to work together to structure economic incentives that allow farmers to produce milk with the SCC needed for extended refrigerated shelf life.

Animals↗

PubMed2001

Oxidation of gas mixtures containing dimethyl sulfide, hydrogen sulfide, and methanethiol using a two-stage biotrickling filter.

A biofiltration technique was developed for removing a mixture of hydrogen sulfide (H2S), methanethiol (MeSH), and dimethyl sulfide (Me2S) from waste gases. Since H2S, especially at high concentrations, disturbs the removal of Me2S, two biotrickling filters with different microbes and operating pH levels were connected in series to create a two-stage system. Different loads of these gases were studied in order to determine their impact on the removal capacity of the system. The microbial consortia for these filters were enriched from the sludge of a Finnish refinery with bubbling H2S or Me2S. Acclimation for Me2S took 2 weeks, though no acclimation time was needed for the other gases. The first filter, at a pH of 2, removed most of the H2S and some of the MeSH and Me2S. The second filter, at a pH of approximately 6.5, removed the rest of the MeSH and most of the Me2S. The total maximum loads of the whole two-stage biotrickling filter were 1150 g/m3/day for H2S-S (suffix S indicates the results are counted as sulfur amounts), 879 g/m3/day for Me2S-S, and 66 g/m3/day for MeSH-S treated in a gas mixture. The average removal efficiencies for all gases tested were 99% or higher.

Air Pollutants, Occupational↗

PubMed2004

A randomized clinical trial on the short-term clinical and microbiological effects of the adjunctive use of a 0.05% chlorhexidine mouth rinse for patients in supportive periodontal care.

OBJECTIVE: To evaluate the clinical and microbiological activity of a new mouth rinse formulation, used as an adjunct to oral hygiene, for patients in supportive periodontal care. PATIENTS AND METHODS: This was a randomized, placebo-controlled clinical trial with two groups: test group, rinsing twice per day with the test product (with 0.05% chlorhexidine and 0.05% cetylpyridinium chloride); and control group, rinsing with a placebo. Treated chronic periodontitis patients were included, and two visits were rendered, baseline, and after 15 days. Clinical outcome variables included plaque and gingival indices, and probing pocket depth. Subgingival samples were processed by culturing. Patient-based variables and adverse effects were also assessed. Outcome variables were compared by t-test, chi2, and Mann-Whitney test. RESULTS: The results belonged to 33 patients. Plaque and gingival indices, and the log of bacterial total counts were reduced in the test group (p < or = 0.01), but differences between groups were only statistically significant (p < 0.05) for plaque and bacterial counts. A significant reduction in the proportions of flora (p < 0.05) and frequency of detection (p = 0.01) of Porphyromonas gingivalis was observed in the test group. CONCLUSIONS: The newly formulated mouth rinse demonstrated short-term plaque-inhibitory activity. This was associated with a reduction in the total load of anaerobic subgingival microflora.

Adult↗

PubMed2005

Concurrent quantitation of total campylobacter and total ciprofloxacin-resistant campylobacter loads in rinses from retail raw chicken carcasses from 2001 to 2003 by direct plating at 42 degrees C.

This is the first report on the use of a normally lethal dose of ciprofloxacin in a Campylobacter agar medium to kill all ciprofloxacin-sensitive Campylobacter spp. but allow the selective isolation and quantitation of naturally occurring presumptive ciprofloxacin-resistant Campylobacter CFU in rinses from retail raw chicken carcasses (RTCC). Thermophilic-group total Campylobacter CFU and total ciprofloxacin-resistant Campylobacter CFU (irrespective of species) were concurrently quantified in rinses from RTCC by direct plating of centrifuged pellets from 10 or 50 ml out of 400-ml rinse subsamples concurrently on Campylobacter agar and ciprofloxacin-containing Campylobacter agar at 42 degrees C (detection limit = 0.90 log(10) CFU/carcass). For 2001, 2002, and 2003, countable Campylobacter CFU were recovered from 85%, 96%, and 57% of RTCC, while countable ciprofloxacin-resistant Campylobacter CFU were recovered from 60%, 59%, and 17.5% of RTCC, respectively. Total Campylobacter CFU loads in RTCC rinses ranged from 0.90 to 4.52, 0.90 to 4.58, and 0.90 to 4.48 log(10) CFU/carcass in 2001, 2002, and 2003, respectively. Total ciprofloxacin-resistant Campylobacter CFU loads in RTCC rinses ranged from 0.90 to 4.06, 0.90 to 3.95, and 0.90 to 3.04 log(10) CFU/carcass in 2001, 2002, and 2003, respectively. Overall, total Campylobacter loads of 0.90 to 2.0, 2 to 3, 3 to 4, 4 to 5 log(10) CFU/carcass, respectively, were recovered from 16%, 32%, 26%, and 5% of RTCC tested over the 2-year sampling period. For the same period, total ciprofloxacin-resistant Campylobacter loads of 0.90 to 2.0, 2 to 3, 3 to 4, and 4 to 5 log(10) CFU/carcass, respectively, were recovered from 24%, 11%, 7%, and 0.2% of RTCC tested. There was a steady decline in total Campylobacter and total ciprofloxacin-resistant Campylobacter loads in RTCC rinses from 2001/2002 to 2003.

Animals↗

PubMed2006

Molecular monitoring of microbial population dynamics during operational periods of anaerobic hybrid reactor treating cassava starch wastewater.

This study characterized the microbial community and population dynamics in an anaerobic hybrid reactor (AHR) treating cassava starch wastewater. Methanogens and nonmethanogens were followed during the start-up and operation of the reactor, and linked to operational and performance data. Biomass samples taken from the sludge bed and packed bed zones of the AHR at intervals throughout the operational period were examined by 16S rRNA fluorescence in situ hybridization (FISH). The start-up seed and the reactor biomass were sampled during the feeding of the wastewater with a chemical oxygen demand (COD) value of 8 g L(-1) and a hydraulic retention time (HRT) of 8 days. These samples were characterized by the predominance of cells with long-rod morphology similar to Methanosaeta spp. Following a sharp operational change, accomplished by increasing the COD concentration of the organic influent from 8 to 10 g L(-1) and reducing the HRT from 8 to 5 days, there was a doubling of the organic loading rate, a reduction of the COD removal efficiency, as well as decreased methane content in the biogas and an accumulation of total volatile acids in the reactor. Moreover, this operational change resulted in a significant population shift from long-rod Methanosaeta-like cells to tetrad-forming Methanosarcina-like cells. The distributions of microbial populations involved in different zones of the AHR were determined. The results showed that nonmethanogens became the predominant population in both sludge and the packed bed zone. However, the percentage of methanogens in the packed bed zone was higher than that in the sludge bed zone. This higher percentage of methanogens was likely caused by the fact that the packed bed zone provided a suitable environmental condition with an appropriate nutrient availability for methanogen growth.

Bacteria, Anaerobic↗

PubMed2003

Nylon fibers as supporting media in anaerobic hybrid reactors: it's effects on system's performance and microbial distribution.

The performances of three anaerobic hybrid reactors with various nylon fiber densities per packed bed volume (33, 22, and 11 kg/m(3) in R1, R2, and R3, respectively) as supporting media were evaluated through their ability to remove organic compounds in cassava starch wastewater. In addition, the distributions of non-methanogenic and methanogenic population in the reactors were investigated. During a 6-month operation, the organic loading rate was increased in stepwise from 0.5 to 4.0 kg COD/m3/day and the hydraulic retention time (HRT) shortened to 5.4 days. The COD removal efficiency was more favorable in R1 (87%) and R2 (84%) than in R3 (70%). The total biomass in the reactors with greater nylon fiber densities was also higher and increased from 20.4 to 67.3 g VSS and to 57.5 g VSS in R1 and R2, respectively. When the HRT was further shortened to 3 days, however, the efficiency of both reactors demonstrated a declining trend and reached 74% in R1 and 61% in R2. The distribution of microbial populations involved in the reactors was determined using the Most Probable Number technique. The result showed the lowest number of methanogens in R3 which correlated well to its relatively low efficiency. The number of non-methanogens in all reactors was, nonetheless, comparable. By shortening the HRT to 3 days, the methanogenic population in R2 diminished in both attached and suspended biomass whereas a slight reduction was detected only in the attached biomass of R1.

Bacteria, Anaerobic↗

PubMed1997

[Microbial contamination of small animal ambulatory veterinary clinics and waiting rooms].

Air and contact indicator microflora was monitored for a year during 17 outpatients' examinations at indicated sites of the balance loading area, examination tables and manipulation tables in an outpatients' consulting room partitioned into two sections (I, II) and in two waiting rooms (I, II) of an internal clinic of the Faculty of Veterinary Medicine at Brno. The consulting room and both waiting rooms were after reconstruction. Ambience monitoring by a sedimentation method demonstrated the lower microbial contamination of waiting room II and outpatients' consulting room II, which were reserved for vaccination of healthy animals. The ambience in waiting room I and outpatients' consulting room I, where diseased animals were examined, showed the higher values microbial contamination. The indicators of microbial contamination under observation involved total microbial counts on meat-peptone agar (MPA), counts of hemolytic (H+) and nonhemolytic (H+) micrococci on blood agar with 10% NaCl, counts of lactose positive (L+) and lactose negative (L-) microbes on Endo agar and of molds and other microbes on Czapek-Dox agar. Frequent occurrence of representatives of the genus Aspergillus and Penicillium out of 42 genera and species of identified molds was indicated in the ambience of the waiting rooms and outpatients' consulting rooms. Examination of the indicated sites of the balance loading area in waiting room I and of examination and manipulation tables in outpatients' consulting rooms by smear and impress methods demonstrated the lowest contamination on the surface of examination tables. Microbial contamination of the balance loading area was however highest, and the identified values indicate a risk of the permanent contact of animal patients with the increased microbe concentrations during their weighing. The balance location in the waiting room is not convenient under the present schedule of cleaning and cleansing. In the Discussion section, an overall decrease in the ambience microbial contamination in waiting rooms and outpatients' consulting room under observation in building no. 9 after reconstruction is shown in comparison with the results of preceding monitoring of the waiting room and outpatients' consulting room in building no. 6 under provisional conditions.

Animals↗

PubMed2006

Biodegradation of a phenolic mixture in a solid-liquid two-phase partitioning bioreactor.

A solid-liquid two-phase partitioning bioreactor (TPPB) in which the non-aqueous phase consisted of polymer (HYTREL) beads was used to degrade a model mixture of phenols [phenol, o-cresol, and 4-chlorophenol (4CP)] by a microbial consortium. In one set of experiments, high concentrations (850 mg l(-1) of each of the three substrates) were reduced to sub-inhibitory levels within 45 min by the addition of the polymer beads, followed by inoculation and rapid (8 h) consumption of the total phenolics loading. In a second set of experiments, the beneficial effect of using polymer beads to launch a fermentation inhibited by high substrate concentrations was demonstrated by adding 1,300 and 2,000 mg l(-1) total substrates (equal concentrations of each phenolic) to a pre-inoculated bioreactor. At these levels, no cell growth and no degradation were observed; however, after adding polymer beads to the systems, the ensuing reduced substrate concentrations permitted complete destruction of the target molecules, demonstrating the essential role played by the polymer sequestering phase when applied to systems facing inhibitory substrate concentrations. In addition to establishing alternative modes of TPPB operation, the present work has demonstrated the differential partitioning of phenols in a mixture between the aqueous and polymeric phases. The polymeric phase was also observed to absorb a degradation intermediate (arising from the incomplete biodegradation of 4CP), which opens the possibility of using solid-liquid TPPBs during biosynthetic transformation to sequester metabolic byproducts.

Biodegradation, Environmental↗

PubMed2004

Influence of organic loading on an anaerobic sequencing biofilm batch reactor (ASBBR) as a function of cycle period and wastewater concentration.

The effect of organic loading on the performance of a mechanically stirred anaerobic sequencing biofilm batch reactor (ASBBR) has been investigated, by varying influent concentration and cycle period. For microbial immobilization 1-cm polyurethane foam cubes were used. An agitation rate of 500 rpm and temperature of 30+/-2 degrees C were employed. Organic loading rates (OLR) of 1.5-6.0gCODl(-1)d(-1) were applied to the 6.3-l reactor treating 2.0 l synthetic wastewater in 8 and 12-h batches and at concentrations of 500-2000mgCODl(-1), making it possible to analyze the effect of these two operation variables for the same organic loading range. Microbial immobilization on inert support maintained approximately 60 gTVS in the reactor. Filtered sample organic COD removal efficiencies ranged from 73 to 88% for organic loading up to 5.4gCODl(-1)d(-1). For higher organic loading (influent concentration of 2000mgCODl(-1) and 8-h cycle) the system presented total volatile acids accumulation, which reduced organics removal efficiency down to 55%. In this way, ASBBR with immobilized biomass was shown to be efficient for organic removal at organic loading rates of up to 5.4gCODl(-1)d(-1) and to be more stable to organic loading variations for 12-h cycles. This reactor might be an alternative to intermittent systems as it possesses greater operational flexibility. It might also be an alternative to batch systems suspended with microorganisms since it eliminates both the uncertainties regarding granulation and the time necessary for biomass sedimentation, hence reducing the total cycle period.

Bacteria, Anaerobic↗

PubMed1999

Effects of cadmium on the performance and microbiology of laboratory-scale lagoons treating domestic sewage.

Two experiments were performed to assess the impact of cadmium on the sewage lagoon wastewater treatment process. For each one, three laboratory-scale pilot plants with one tank receiving the same raw effluent were used; one plant served as control and the other two were contaminated once only with cadmium. In the first study, the effects of a shock load of two concentrations of cadmium chloride (60 and 300 micrograms/l) on the plant performance, microbial populations (protists and bacteria) and enzyme activities were determined. Initially, most of the performance parameters were affected concentration-dependently. A reduction in the protist population density and some influence on the total bacterial population were observed, and the potential enzymatic activities were also modified. A second experiment with a lower cadmium concentration (30 micrograms/l), supplied as chloride or sulphate, still perturbed most of the parameters studied, and the effects of the two cadmium salts were identical.

Bacteria↗

PubMed2005

The microbiological status of patients with periodontitis in southern Estonia after non-surgical periodontal therapy.

Our objective was to investigate the presence of periodontal pathogens in comparison with the total degree of microorganisms after non-surgical periodontal therapy. The study material consisted of microbiological samples from periodontal pockets originating from 140 consecutive patients with chronic generalized severe periodontitis. The subgingival samples from periodontal pockets were obtained by a sterile curette, placed into 2 ml of the VMGA III medium, homogenized and serially diluted in the Brucella broth. 100 microl aliquots from the dilutions were inoculated onto the Brucella and the TSBV agar. The plates were incubated in an anaerobic chamber and under microaerobic conditions. The isolates were identified according to colonial and cellular morphology, the potency disk pattern, and the biochemical profiles. After instrumentation, no periodontal pathogens were isolated in 46 (33%) patients, while 94 patients (67%) were infected with one to five different periodontal pathogens. However, higher degree of the total microflora was positively correlated with number of isolated pathogens, a putative indicator of their presence. Therefore, due to the occurrence of residual microorganisms after non-surgical mechanical treatment, information about the pattern of these pathogens is needed for application of antimicrobial therapy. The level of microbial load in gingival pockets, including both pathogenic and non-pathogenic species, is one of the determinants of presence of residual pathogens after non-surgical periodontal therapy.

Bacteria, Aerobic↗