Mixed Bacterial Suspension Research Articles

PHENOL BIODEGRADATION BY RALSTONIA PICKETTII EXTRACTED FROM PETROLEUM REFINERY OIL SLUDGE

Phenol-degrading bacterial strains have been extracted from oil-sludge samples collected from a local refinery. A selective medium was used to isolate the active strain capable of utilizing phenol as a sole carbon source, which was identified as Ralstonia pickettii. The growth kinetics of mixed and isolated R. pickettii suspensions were investigated using different initial concentrations of phenol in the range of 25 to 200 g m−3 at 35°C and pH of 8.5. The results were compared to those of a commercially available mixed bacterial suspension, which was either acclimatized to 100 g m−3 phenol concentration, extracted from PVA particles that were subjected to real petroleum refinery wastewater containing phenol, or an isolated active strain grown on a selective medium that was identified as Pseudomonas putida. The effect of substrate inhibition was observed using all bacterial suspensions, and the growth results were used to determine the parameters of a suitable kinetic model. It was found that the phenol biodegradation ability of the indigenous bacteria, R. pickettii, isolated from refinery sludge was comparable to that of the commercially available bacteria.

Exploring the potential synergistic effects of chemical disinfectants and UV on the inactivation of free-living bacteria and treatment of biofilms in a pilot-scale system

The main objective of this study is to explore possible synergistic or additive effects of combinations of chemical disinfectants (sodium hypochlorite, peracetic acid, hydrogen peroxide, chlorine dioxide) and UV in their efficacy in inactivating free-living bacteria and removing biofilms. In contrast to most studies, this study examines disinfection of municipal water in a pilot-scale system using a mixed bacterial suspension, which enables a better simulation of the conditions encountered in actual industrial environments. It was shown that the combination of either hypochlorite, hydrogen peroxide, peracetic acid, or chlorine dioxide with UV yielded additive effects on the inactivation of free-living bacteria. Actual synergy was observed for the combination of UV and 5 ppm hydrogen peroxide. Regarding biofilm treatment, additive effects were observed using the combination of hydrogen peroxide and UV. The promising results obtained in this study indicate that the combination of UV and chemical disinfectants can considerably reduce the amount of chemicals required for the effective disinfection and treatment of biofilms.

A model of experimental acute hematogenous pyelonephritis in the rat

The OBJECTIVE of the study was to create a model of acute hematogenous pyelonephritis in the rat without causing urinary retention by ligation of the ureter. Mixed bacterial suspension containing 1.5 x 10(6) colony-forming units (CFU) of S. aureus and 3.0 x 10(6) CFU of E. coli was inoculated in the caudal vein at a dose of 0.5 ml/kg. Control animals received the same amount of saline solution. Pyelonephritis was confirmed by lab urine tests and histopathological study of the kidneys. Infected animals initially developed sepsis with a significant increase of leukocytes and C-reactive protein in the blood. Originally only bacteriuria was found in the urine of experimental animals, but later, in the course of the development of pyelonephritis (12-18 days), leucocyturia and active leukocytes (glitter cells) were also available in urine. The levels of beta-2 microglobulin in the urine of infected animals (4.02 +/- 0.04 mmol/l on day 16 and 4.18 + 0.07 mmol/l on day 18) were significantly highly increased (p <0.0001) in comparison with the value of the control group (0.088 +/- 0.005 mmol/l). In the early days the histopathological examination of the kidneys established erythrocyte stasis. Later leukocyte infiltrates were observed in the interstitial tissue around the kidney tubules, glomeruli and vascular walls, and inflammatory cell infiltration and degenerative changes were present in the epithelium of the canaliculi. Combined hematogenous infection with S. aureus and E. coli led to the development of pyelonephritis in rats. The pathology in the kidney tubules was confirmed by histopathological study and by the elevated levels of beta-2 microglobulin and the presence of active leukocytes in urine.

Cloning and organisation analysis of a hepcidin-like gene and cDNA from Japan sea bass, Lateolabrax japonicus

A hepcidin gene was amplified from the liver of Lateolabrax japonicus challenged with a mixed bacterial suspension. Using RT-PCR and RACE, a full length cDNA sequence of the hepcidin like antimicrobial peptide was determined (GenBank accession number AY604195). The complete hepcidin cDNA Hepc2 is 581 bases and contains an ORF of 258 bases with a coding capacity of 86 amino acids. The deduced amino acid sequence, which shares eight cysteines at the identical conserved positions, and gene organisation are conserved between Japan sea bass and other fish species. The predicted molecular weight of the peptide is 9.4 kDa. The 3′-untranslated region is composed of 225 bp with a polyadenylation signal AATAAA sequence appearing at 189 nt and the poly(A) tail at 212 nt downstream of stop codon TGA. The predicted signal peptide cleavage site of its deduced peptide is between codons 24 and 25. Japan sea bass hepcidin-like genomic DNA hepc2 sequence including upstream and downstream regions (GenBank accession number AY864813) was composed of two introns and three exons. The cloned 173-bp upstream sequence of Japan sea bass hepcidin-like gene contains putative regulatory elements and several binding motifs for transcription factors. High homologies with hepcidin cDNAs and peptides of white bass ( Morone chrysops), human and other fish were shown. Hepc2 of Lateolabrax japonicus is a new member of the hepcidin gene family.

In vitro evaluation of the antibacterial activity of Arctium lappa as a phytotherapeutic agent used in intracanal dressings

The discovery of natural biocomponents from plants with antibacterial activity on endodontic microbiota may lead to new therapies. This study evaluated the antibacterial activity of a phytotherapeutic agent prepared from an ethyl acetate fraction (AcOEt) extracted from Arctium lappa. This agent was compared with calcium hydroxide as an intracanal dressing. Twenty-seven maxillary canines were instrumented, sterilized and inoculated with a mixed bacterial suspension of Pseudomonas aeruginosa, Escherichia coli, Lactobacillus acidophilus, Streptococcus mutans and Candida albicans. The teeth were divided into three groups and their canals filled with: group 1, calcium hydroxide and propylene glycol; group 2, a paste containing AcOEt fraction of A. lappa and propylene glycol; group 3, propylene glycol (control). At 7, 14 and 30 days, three teeth from each group were opened and a paper point was placed in the root canal for 5 min. The paper points were transferred to Petri dishes with Brain Heart Infusion (BHI). The bacterial growth was classified. Mild bacterial growth was found in group 1 at all time intervals; in group 2 there was severe growth at 7 days, but no growth at 14 and 30 days. The phytotherapeutic agent extracted from an AcOEt fraction of A. lappa inhibited the growth of all the microorganisms in this study.

Effect of Root Canal Filling/Sealer Systems on Apical Endotoxin Penetration: A Coronal Leakage Evaluation

Endotoxin, elaborated by gram-negative organisms, is an important factor in apical periodontitis. The objective of this study was to evaluate the magnitude of endotoxin penetration through root canal treated teeth using a dual chamber model system. Forty-four maxillary anterior teeth were prepared endodontically and canals filled either by lateral condensation or a warm thermoplasticized technique in combination with either Roth's 801 or AH 26 sealer. Teeth were suspended in the model system with a mixed anaerobic bacterial suspension in the upper chamber and HBSS in the lower chamber. The QCL-1000 LAL assay was used to measure endotoxin at 0, 1, 7, 14, and 21 days. Response feature analysis using trapezoidal area under the curve was performed; the four treatment groups were compared using nonparametric methods. Groups differed (p = 0.028), with thermoplasticized root canal filling/Roth's 801 sealer permitting the least apical endotoxin penetration. Results suggest that Roth's 801 sealer may have a role in inhibiting endotoxin penetration.

A selective medium and a specific probe for detection of Vibrio vulnificus.

A selective medium (VVM) and a specific 16S rRNA gene (rDNA) probe (V3VV) for the detection of Vibrio vulnificus were developed. The medium contains D-(+)-cellobiose as the main carbon source and electrolytes (MgCl(2)-6H(2)O and KCl), which stimulate bacterial growth. Polymyxin B, colistin, and moderate alkalinity and salinity provide selectivity properties. V. vulnificus grows on VVM as flat, bright yellow colonies. Other Vibrio species tested either did not grow or showed green-bluish colonies, with the exception of V. campbelli, V. carchariae, and V. navarrensis. There is a higher colony count on VVM agar than on cellobiose-colistin agar or on modified cellobiose-polymyxin B-colistin agar. The specific probe was evaluated by colony hybridization and dot blot hybridization with PCR-amplified 16S rDNA using collection strains and environmental isolates. No strain studied other than V. vulnificus showed positive hybridization with this oligonucleotide. The combined use of VVM agar and the V3VV probe provided the recovery of V. vulnificus from mixed bacterial suspensions and spiked mussels.

Powdered Milk Micellar Casein Prevents Oral Colonization by Streptococcus sobrinus and Dental Caries in Rats: A Basis for the Caries–Protective Effect of Dairy Products

Three animal studies were performed to investigate the influence of the macromolecular structure of milk casein on caries incidence and the possible ecological changes of the oral microbiota by such casein fractions. Towards this end, rats were infected with mixed bacterial suspensions of Streptococcus sobrinus OMZ 176 and Actinomyces viscosus Ny1. Various milk protein fractions were incorporated into carefully balanced powdered cariogenic diets to constitute the sole major protein component. Diets containing micellar casein had a pronounced and highly significant effect on almost all clinical and microbiological parameters examined. Both the formation of advanced dentinal fissure (B) and smooth surface (E) caries lesions was inhibited by diets containing micellar casein; this caries–inhibiting effect appeared to be due mainly to modifications within the plaque microbiota. The proportion of S. sobrinus in the oral cavity of rats was reduced (73–80%) by micellar casein–containing preparations, whereas the A. viscosus population was increased. Both these microbiological parameters were always negatively correlated. This appears to be the first example of a food component other than dietary sugars, selectively modifying the composition of the dental plaque microbiota of rats in such a way as to reduce its pathogenic potential. It also demonstrates the importance of establishing a molecular basis for the role of food components, which prove to be beneficial to oral health.

Separation and Deletion of Porphyromonas gingivalis by Immunomagnetic Beads.

The present study describes the immunomagnetic separation of Polphyromonas gingivalis (P. gingivalis). Immunomagnetic beads (IMB) coated with anti-P. gingivalis serum were incubated with cells of P. gingivalis. After separation by magnetic bar, the IMB with the bacterial cells were inoculated on blood agar plates for the count of bacterial number. The IMB were able to capture cells of P. gingivalis ranging from 7×10102 to 107. In addition, specific IMB could selectively capture. P. gingivalis cells from a mixed bacterial suspension. Propionibacterium acnes (P. acnes) and Eubacterium saburreum (E. saburreum) were also separated by the IMB coated with the respective antibodies. When the IMB-bound bacterial cells were exposed to microwave irradiation after the immunomagnetic separation, specific IMB were found to accelerate the bacterial killing. This study demonstrates that the IMB system is a simple and rapid technique for selective separation and deletion of bacteria. This approach may be useful to delete certain target bacteria from disease sites in human oral cavities, such as periodontal pockets.

The deposition of oral bacteria at the solid/liquid and solid/liquid/air interfaces

A technique for quantifying the deposition of microorganisms at the solid/liquid and solid/liquid/air interfaces enabled the deposition characteristics of representative strains of five oral species on glass from saline and saliva to be compared using single and mixed bacterial suspensions. The deposited bacteria were quantified microscopically and by viable counts. All the strains attached to the glass surfaces. Streptococcus sanguis NCTC 7868, Actinomyces viscosus WVU 371, and Streptococcus mutans NCTC 10449 generally attached or deposited more readily from saliva than Streptococcus salivarius NCTC 7366 or Lactobacillus casei L 8822 due perhaps to polymers on their cell surfaces forming bridges to the saliva-covered glass surfaces. The findings show that the quantity of deposited material cannot be correlated directly with its content of viable bacteria.

Regional defense mechanisms of the guinea pig lung.

Many pulmonary diseases, such as tuberculosis, cancer, and pneumonia, are localized to lobes or segments of the lung suggesting regional differences in host defense mechanisms in the lungs. To determine the intrinsic regional differences in transport or phagocytic defense mechanisms, particle deposition, bactericidal activity, and particle transport were measured in each of the 5 individual lobes of guinea pig lungs. Animals were exposed by aerosol to a mixed bacterial suspension containing Proteus mirabilis labeled with sulfur-35 and Staphylococcus aureus labeled with phosphorus-32 or Proteus mirabilis labeled with phosphorus-32 and unlabeled staphylococci. Deposition of particles 3.5 μ or less in diameter was directly proportional to the weight of the lobes; however, on an equal weight basis, no preferential deposition was observed in any of the individual regions. No delay or enhancement in bactericidal activity or transport was observed among the lobes regardless of size or geographic position. These ...

Electrophoresis of glucose-6-phosphate dehydrogenase of Streptococcus mitis and Streptococcus salivarius

A technique for quantifying the deposition of microorganisms at the solid/liquid and solid/liquid/air interfaces enabled the deposition characteristics of representative strains of five oral species on glass from saline and saliva to be compared using single and mixed bacterial suspensions. The deposited bacteria were quantified microscopically and by viable counts. All the strains attached to the glass surfaces. Streptococcus sanguis NCTC 7868, Actinomyces viscosus WVU 371, and Streptococcus mutans NCTC 10449 generally attached or deposited more readily from saliva than Streptococcus salivarius NCTC 7366 or Lactobacillus casei L 8822 due perhaps to polymers on their cell surfaces forming bridges to the saliva-covered glass surfaces. The findings show that the quantity of deposited material cannot be correlated directly with its content of viable bacteria.

Bacterial degradation of nicotinic acid.

A BACTERIUM utilizing nicotinic acid was isolated from culture media made up of a solution of nicotinic acid and dilute sodium sulphide and inoculated with a small amount of Potomac mud. After allowing the bacteria to grow anaerobically, several successive transfers were made into a medium containing nicotinic acid, peptone, yeast extract, metals, phosphate and sodium sulphide. The mixed bacterial suspension was then serially diluted in agar media of the same composition under anaerobic conditions. This serial dilution was repeated until the bacterium utilizing nicotinic acid was isolated in pure culture. By this enrichment culture technique, an anaerobic spore-forming rod was isolated which ferments nicotinic acid and which utilizes high concentrations of this compound for its growth. Maximum growth is achieved in the presence of 0.6 per cent yeast extract, 0.2 per cent peptone and 0.4 per cent nicotinic acid. No growth occurs with yeast extract and peptone alone. Neither will the bacterium grow on nicotinic acid as a sole source of carbon.