SEARCH · PubMed Health

Results for “Microbial Viability”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,459 records · Page 81Linked to original sources

PubMed2005

Beta-D-glucuronidase activity assay to assess viable Escherichia coli abundance in freshwaters.

AIMS: The relationships between the beta-D-glucuronidase (GLUase) activity, the abundance of culturable Escherichia coli and the number of viable E. coli were investigated in river and wastewater samples. METHODS AND RESULTS: GLUase activity was measured as the rate of hydrolysis of 4-methylumbelliferyl-beta-D-glucuronide. Culturable E. coli were enumerated by the most probale number (MPN) microplate method. Viable E. coli were estimated by fluorescent in situ hybridization (FISH) coupled with a procedure of viability testing (DVC-FISH procedure). Significant correlations were found between the log of GLUase activity and both, the log culturable E. coli and the log of viable E. coli. CONCLUSIONS: GLUase activity per viable E. coli gave a broadly constant value from low to highly contaminated waters while GLUase activity per culturable E. coli strongly increased at low contaminated waters because of an underestimation of the number of active E. coli by the culture-based method. SIGNIFICANCE AND IMPACT OF THE STUDY: GLUase activity is a reliable parameter for the rapid quantification of viable E. coli in waters.

Bacteriological Techniques↗

PubMed2002

Development of a flow cytometric method to analyze subpopulations of bacteria in probiotic products and dairy starters.

Flow cytometry (FCM) is a rapid and sensitive technique that can determine cell numbers and measure various physiological characteristics of individual cells by using appropriate fluorescent probes. Previously, we developed an FCM assay with the viability probes carboxyfluorescein diacetate (cFDA) and TOTO-1 [1'-(4,4,7,7-tetramethyl-4,7-diazaundecamethylene)-bis-4-[3-methyl-2,3dihydro(benzo-1,3-oxazole)-2-methylidene]-1-(3'-trimethylammoniumpropyl)-pyridinium tetraiodide] for (stressed) lactic acid bacteria (C. J. Bunthof, K. Bloemen, P. Breeuwer, F. M. Rombouts, and T. Abee, Appl. Environ. Microbiol. 67:2326-2335, 2001). cFDA stains intact cells with enzymatic activity, and TOTO-1 stains membrane-permeabilized cells. Here we used this assay to study the viability of bacterial suspensions in milk, dairy fermentation starters, and probiotic products. To facilitate FCM analysis of bacteria in milk, a commercially available milk-clearing solution was used. The procedure was optimized to increase the signal-to-noise ratio. FCM enumerations were accurate down to a concentration of 10(5) cells ml(-1). The level of retrieval of Lactobacillus plantarum WCFS 1 suspended in milk was high, and viability was not affected by the procedure. The plate counts for cleared samples of untreated cell suspensions were nearly as high as the total FCM counts, and the correlation was strong (r > 0.99). In dairy fermentation starters and in probiotic products the FCM total cell counts were substantially higher than the numbers of CFU. Three functional populations could be distinguished: culturable cells, cells that are intact and metabolically active but not culturable, and permeabilized cells. The proportions of the populations differed in the products tested. This FCM method provides tools to assess the functionality of different populations in fermentation starters and probiotic products.

Animals↗

PubMed2005

Study of adhesion and survival of lactobacilli and bifidobacteria on table olives with the aim of formulating a new probiotic food.

With the aim of developing new functional foods, a traditional product, the table olive, was used as a vehicle for incorporating probiotic bacterial species. Survival on table olives of Lactobacillus rhamnosus (three strains), Lactobacillus paracasei (two strains), Bifidobacterium bifidum (one strain), and Bifidobacterium longum (one strain) at room temperature was investigated. The results obtained using a selected olive sample demonstrated that bifidobacteria and one strain of L. rhamnosus (Lactobacillus GG) showed a good survival rate, with a recovery of about 10(6) CFU g(-1) after 30 days. The Lactobacillus GG population remained unvaried until the end of the experiment, while a slight decline (to about 10(5) CFU g(-1)) was observed for bifidobacteria. High viability, with more than 10(7) CFU g(-1), was observed throughout the 3-month experiment for L. paracasei IMPC2.1. This strain, selected for its potential probiotic characteristics and for its lengthy survival on olives, was used to validate table olives as a carrier for transporting bacterial cells into the human gastrointestinal tract. L. paracasei IMPC2.1 was recovered from fecal samples in four out of five volunteers fed 10 to 15 olives per day carrying about 10(9) to 10(10) viable cells for 10 days.

Adult↗

PubMed1998

Effects of garlic compounds diallyl sulfide and diallyl disulfide on arylamine N-acetyltransferase activity in strains of Helicobacter pylori from peptic ulcer patients.

Arylamine N-acctyltransferase (NAT) activities with p-aminobenzoic acid (PABA) and 2-aminofluorene (2-AF) were determined in the bacterium Helicobacter pylori collected from peptic ulcer patients. Two assay systems were performed, one with cellular cytosols, the other with intact cell suspensions. Cytosols or suspensions of H. pylori with or without specific concentrations of diallyl sulfide (DAS) or diallyl disulfide (DADS) co-treatment showed different percentages of 2-AF and PABA acetylation. The data indicated that there was decreased NAT activity associated with increased levels of DAS or DADS in H. pylori cytosols and suspensions. Viability studies on H. pylori demonstrated that DAS or DADS elicited dose-dependent bactericide affects on H. pylori cultures. The data also indicated that DAS and DADS decreased the apparent values of K(m) and Vmax of NAT enzyme from H. pylori in both systems examined. This report is the first demonstration that garlic components can affect H. pylori growth and NAT activity.

Allyl Compounds↗

PubMed1991

Studies of Helicobacter pylori in a gastric mucosa in vitro animal model.

A gastric mucosa in vitro model for studies of experimental Helicobacter pylori infections has been developed. Biopsy specimens were taken from pig gastric mucosa, infected with H. pylori, and cultured for up to 72 h. To determine the degree of H. pylori adhesion, specimens were vigorously rinsed by vortexing five times before measuring viable count and urease activity. The results showed that it is possible to culture pig gastric mucosa in vitro with maintained viability for at least 72 h. According to the viable count, the bacteria survived and multiplied during the whole culture period. The percentage viable H. pylori in the specimens after rinsing and the urease activity increased with time of culture. The results indicate that the bacteria in the gastric specimens were viable after 72 h and that there was a time-dependent increase in bacterial adhesion to the specimens. This in vitro gastric mucosa model promises to be an applicable and reproducible method, with high capacity, for both pathogenic and mechanistic studies of H. pylori infection.

Animals↗

PubMed2001

Effectiveness of three root canal medicaments to eliminate Actinomyces israelii from infected dentinal tubules in vitro.

The persistence of anaerobic bacteria in the root canal system often leads to treatment failure. One possible reason for this may be the retention of micro-organisms in the dentinal tubules of root canal walls. This study was performed to compare the effectiveness of two root canal medicaments and a chlorhexidine solution in disinfecting Actinomyces israelii-infected root canal walls and dentinal tubules in vitro. Dentinal tubules of root canal walls of human teeth were experimentally infected with A. israelii. The root canals were exposed to either iodine potassium iodide, calcium hydroxide or 2% chlorhexidine for periods of 3, 7 and 60 days. At the end of the medication periods samples were removed at different depths and tested for A. israelii viability. Chlorhexidine was the only disinfectant that was able to eliminate A. israelii from all the samples after 3, 7 as well as 60 days while 25% of the specimens treated with iodine potassium iodide and 50% of the specimens treated with calcium hydroxide still had viable A. israelii after treatment. It is clear from this study that 2% chlorhexidine is superior to iodine potassium iodide and calcium hydroxide in its ability to remove A. israelii from infected dentinal tubules. However, in vivo trials need to be undertaken before its clinical use can be recommended.

Actinomyces↗

PubMed2004

Effect of the application of acid treated biosolids on marigold (Tagetes erecta) development.

The use of biosolids for land restoration and crop production is a potential solution to improve food production worldwide. However, the microbial content usually restricts its application in crops that are consumed uncooked. An alternative practice is their use in floriculture. In this study, the effects of acid treated sludge on the development of marigold (Tagetes erecta) plants were evaluated under green house conditions. Biosolids were applied at the agronomic rate (AR) based on nitrogen requirements of the marigold. In addition, higher rates (10 and 20xAR) were applied to study their effect on the plants. Biosolids were mixed with tepetate (hard volcanic indurate layers). Due to its origin, tepetate lacks nutrients and organic matter to adequately support plant development. The best treatment for marigold development was 10xAR, as plants reached an average height of 107 cm, with a growing speed of 1.01 cm/d, which is 20 times more than the control. Plants that received no biosolids produced 0.25 buds and 0.5 flowers per plant. In contrast, AR and 10xAR showed a production that ranged from 2 to 29 buds/plant and 4 to 15 flowers/plant, respectively. These results indicate the viability of reusing acid treated biosolids to improve marigold development.

Conservation of Natural Resources↗

PubMed1973

Extracellular antigens from Listeria monocytogenes. II. Cytotoxicity of hemolytic and lipolytic antigens of Listeria for cultured mouse macrophages.

Purified preparations of hemolytic and lipolytic antigens were shown to be cytotoxic for tissue cultures of mouse peritoneal macrophage monolayers. The percent reduction in viability was proportional to the concentration of antigen used although, for a brief period, the hemolytic antigen stimulated the growth of cultured macrophages. Hemolytic and lipolytic antigens were synthesized by an hemolysin-producing strain (7973), but were deficient or totally lacking in nonhemolysin-producing strains (9037-7, 4219). The inoculation of strain 7973 onto macrophage monolayers at a bacterium to macrophage ratio of 10:1 resulted in a complete loss of viable phagocytic cells. The decrease in viable phagocytic cells was accompanied by an increase in viable listeria. Pronounced cytopathic activity with proliferation of listeria was also observed when 200 U of lipolytic antigen were added to macrophage monolayers that had been infected with the smooth type nonhemolysin-producing strain (4219) on the previous day. On the other hand, a high percentage of macrophages survived when exposed to nonhemolysin-producing strains only. In this case, listeria were not recovered by routine culture methods. The data presented do not establish that phagocytic cell destruction with accompanying microbial proliferation is the direct result of hemolysin elaboration; however, they suggest that there is need for further exploration of the role of the hemolysin in listeriosis.

Antigens, Bacterial↗

PubMed2005

[Physiological comportment and in vivo sensitivity of Sporothrix schenckii isolates maintained for 18 years by two preservation methods].

We compared two methods for the preservation of fungi, Castellani's method and repeated passage in Sabouraud medium-agar, on five isolates of Sporothrix schenckii that were preserved for 18 years at room temperature by both procedures. They were evaluated for viability of the strains, growth rate, morphological and physiological characteristics, and in vitro sensitivity to iodide, itraconazole, terbinafine and posaconazole. 100% viability was observed in all of the isolates, with slower growth rate on strains preserved in water compared to strains periodically re-cultured. The typical morphological feature of these fungi was preserved by both methodologies. With regard to enzymatic activity, both groups gave urease reactions and were beta glucosidase-positive. Nevertheless, complete inhibition of the capacity to hydrolyse starch was observed only on the isolates preserved in water. This group also was more sensitive to potassium iodide at a concentration of 10 microM in the in vitro sensitivity tests.

Agar↗

PubMed2003

Detection and recovery of sublethally-injured enterotoxigenic Staphylococcus aureus.

AIMS: To determine whether sublethally-injured (acid- or heat-shocked) Staphylococcus aureus cells are recoverable using selective agar overlays. METHODS AND RESULTS: Brain Heart Infusion (BHI) Agar overlaid with either Baird-Parker Agar (BPA) or Gram-Positive Agar (GPA) was compared in the ability to resuscitate heat- and acid-shocked enterotoxigenic Staph. aureus. BHI/BPA overlays allowed for greater recovery of both heat- and acid-shocked cells than BHI/GPA, although the former was not selective and allowed growth of bacteria other than Staph. aureus. No significant difference existed in percent recovery of heat- and acid-shocked cells between the two overlay approaches. Significant differences were noted in counts on BHI/GPA plates and straight selective GPA/GPA plates, however. Viability of heat- and acid-shocked Staph. aureus was also examined using fluorescence microscopy, the relative counts of which correlated well to the calculated percent recovery on selective agar overlays. CONCLUSIONS: This work has shown that an improved agar overlay technique increases the sensitivity of the standard plate count while enumerating sublethally-injured enterotoxigenic Staph. aureus compared with direct plating onto selective media. SIGNIFICANCE AND IMPACT OF THE STUDY: These data emphasize the need to develop practical and cost-effective methods that reliably detect and enumerate sublethally-injured pathogens such as Staph. aureus.

Agar↗

PubMed1997

A novel approach to assessing the drug susceptibility and replication of human immunodeficiency virus type 1 isolates.

Human immunodeficiency virus type 1 (HIV-1) drug susceptibility testing is often curtailed because such testing is expensive and time consuming. A colorimetric tetrazolium dye method previously used for high-throughput antiviral drug screening was adapted to assess the susceptibility of 16 HIV-1 isolates to zidovudine, didanosine, lamivudine, and nevirapine in MT-2 cells. Cell viability was assessed colorimetrically, and all measurements and calculations were automated. Each HIV-1 isolate was tested in > or = 5 assays to determine the reproducibility of the assay in HIV-1 isolates with known reverse-transcriptase mutations. The drug susceptibility of several mutant HIV-1 strains whose drug susceptibilities had not previously been well defined was also determined. Data on HIV-1 replication from the susceptibility assays indicated that some mutant HIV-1 isolates may have been less cytopathic in MT-2 cells than wild type HIV-1 isolates.

Anti-HIV Agents↗

PubMed1997

Time-kill study of the activity of trovafloxacin compared with ciprofloxacin, sparfloxacin, metronidazole, cefoxitin, piperacillin and piperacillin/tazobactam against six anaerobes.

A time-kill method was developed to examine the killing kinetics of trovafloxacin, ciprofloxacin, sparfloxacin, metronidazole, cefoxitin, piperacillin and piperacillin/tazobactam against one strain each of Bacteroides fragilis, Bacteroides thetaiotaomicron, Prevotella melaninogenica, Fusobacterium mortiferum, Peptostreptococcus magnus and Clostridium perfringens. Solutions and suspensions were prepared inside an anaerobic glove box, using syringes and prereduced broth. Bottles were then incubated outside the chamber and viability counts determined after incubation for 0, 6, 24 and 48 h in a shaking water bath, avoiding introduction of air. Bacteriostatic/bactericidal concentrations (mg/L) after 48 h for the six strains were: trovafloxacin, 0.03-1/0.03-1; ciprofloxacin, 0.25-16/0.25-32; sparfloxacin, 0.06-2/0.06-8; metronidazole 1-64/1-64; cefoxitin, 0.125-16/0.125-32; piperacillin, 0.125-64/0.125-64; piperacillin/tazobactam, 0.06-2/0.125-8. Bacteriostatic levels were within two dilutions of broth MICs. By this time-kill method, trovafloxacin had the lowest bacteriostatic concentrations of all compounds tested.

Anti-Infective Agents↗

PubMed2003

Survival of Helicobacter pylori in a natural freshwater environment.

The mode by which Helicobacter pylori, the causative agent of most gastric ulcers, is transmitted remains undetermined. Epidemiological evidence suggests these organisms are waterborne; however, H. pylori has rarely been grown from potential water sources. This may be due to the ability of this organism to rapidly enter the viable but nonculturable (VBNC) state. Our investigation examines the entrance of H. pylori into this state in laboratory cultures and a natural freshwater environment as well as the relationship between morphology and culturability. To this end, membrane diffusion chambers were utilized to expose the cells to the natural fluctuations of a freshwater stream. In both the laboratory and environment, samples were assayed for culturability using plate counts and stained using a LIVE/DEAD BacLight assay for viability and morphological determinations. Additionally, water samples were collected, six environmental parameters were measured, and resuscitation conditions were examined. H. pylori was observed to lose culturability in the laboratory and stream, although viability was maintained. While the results of our study agree with those of previous studies which suggested that there is a transition in morphology from rods to cocci as culturability is lost, the morphological distribution of cells did not change as culturability was lost in the environment. The majority of cells in the VBNC state in the laboratory are cocci; however, all morphological forms were present in the environment. The results of these studies suggest that H. pylori persists in laboratory cultures and the environment in the VBNC state and that cells in this state represent a public health hazard.

Bacteriological Techniques↗

PubMed1987

Establishment of an adult rat fibroblast cell line for studies of collagenase regulation.

Several dermal fibroblast lines have been established from explants taken from adult rats. The cells have been cultured for 2 yr and possess stable and well-defined growth characteristics through subculture 18. The cells are readily stored in liquid nitrogen with good viability after thawing. Collagenase activity secreted into the culture medium of the cells at different periods of growth has been examined. There is an 88% drop in total enzyme activity present in the medium between 4 and 14 d of culture, when the cells were plated to reach confluence at Day 8 to 10. A more pronounced fall is noted at earlier times when the cells are plated at a higher density. The correlation between DNA content of the cell monolayer and enzyme activity was -0.895, indicating a possible relationship between the growth of cells and collagenase release.

Animals↗

PubMed2007

Acid adaptation affects the viability of Salmonella typhimurium during the lactic fermentation of skim milk and product storage.

In this study, Salmonella typhimurium was acid adapted at pH 5.5 for 4 h. The viability of the acid-adapted and non-adapted cells of S. typhimurium was investigated both during the lactic fermentation of skim milk with Streptococcus thermophilus or Lactobacillus bulgaricus, and during the storage of lactic fermented milk products at 5 degrees C. It was found that the viable population of S. typhimurium, regardless of acid adaptation, increased in skim milk during the initial 24 h of lactic fermentation and then declined. However, the viable population of acid-adapted S. typhimurium was significantly higher (P<.05) than that of non-adapted cell at the end of 48 h of fermentation. Acid-adapted cells of S. typhimurium were also found to have survived better than non-adapted cells in the S. thermophilus-prepared fermented milk and two commercial lactic fermented milk products. The viability of the acid-adapted and non-adapted S. typhimurium at 5 and 37 degrees C in cell-free fermented milks that had their pHs adjusted to 6.4 and skim milk (pH 6.4) was further investigated. Results revealed that acid adaptation, in addition to enhancing acid tolerance, reduced the susceptibility of S. typhimurium to refrigerated temperature and other detrimental factors which might be present in lactic fermented milk products. These responses all contribute to the enhanced survival of acid-adapted S. typhimurium in the lactic fermented milk products observed in the present study.

Adaptation, Physiological↗

PubMed1999

Influence of organic matter, cations and surfactants on the antimicrobial activity of Melaleuca alternifolia (tea tree) oil in vitro.

The effect of some potentially interfering substances and conditions on the antimicrobial activity of Melaleuca alternifolia (tea tree) oil was investigated. Agar and broth dilution methods were used to determine minimum inhibitory and cidal concentrations of tea tree oil in the presence and absence of each potentially interfering substance. Activity was determined against Gram-positive and -negative bacteria, and Candida albicans. Minimum inhibitory or cidal concentrations differed from controls by two or more dilutions, for one or more organisms, where Tween-20, Tween-80, skim-milk powder and bovine serum albumin were assessed. These differences were not seen when assays were performed in anaerobic conditions, or in the presence of calcium and magnesium ions. The effect of organic matter on the antimicrobial activity of tea tree oil was also investigated by an organic soil neutralization test. Organisms were exposed to lethal concentrations of tea tree oil ranging from 1-10% (v/v), in the presence of 1-30% (w/v) dry bakers' yeast. After 10 min contact time, viability was determined. At > or = 1%, organic matter compromised the activity of each concentration of tea tree oil against Staphylococcus aureus and C. albicans. At 10% or more, organic matter compromised the activity of each tea tree oil concentration against Pseudomonas aeruginosa. Organic matter affected 1 and 2% tea tree oil, but not 4 and 8%, against Escherichia coli. In conclusion, organic matter and surfactants compromise the antimicrobial activity of tea tree oil, although these effects vary between organisms.

Agar↗

PubMed1981

Regrowth of Pseudomonas aeruginosa and other bacteria after the bactericidal action of carbenicillin and other beta-lactam antibiotics.

Exposure of Pseudomonas aeruginosa, Escherichia coli, and Staphylococcus aureus to bactericidal concentrations of beta-lactam antibiotics in broth culture resulted in a decrease in viability over the first 6--8 hr, followed by regrowth which was not due to the selection of resistant variants or loss of antibiotic potency. During incubation, bacteria adhered to the surface of the culture vessel and multiplied despite the presence of bactericidal concentrations of antibiotic in the medium. It is concluded that the phenomenon of "regrowth" results from such adhesion and the subsequent dispersal of some of these cells into the culture medium. The significance of these findings is discussed in relation to the treatment of infection, the determination of minimal bactericidal concentrations, and the phenomena of tolerance and persisters.

Carbenicillin↗

PubMed1997

An ATP bioluminescence assay applicable to rapid fluconazole susceptibility testing of dermatophytes.

An ATP bioluminescence assay as a rapid reference method for fluconazole (FLCZ) susceptibility testing of dermatophytes, as well as yeasts, was developed and evaluated by comparing it with viability, turbidity and fungal protein content-based conventional methods. FLCZ susceptibility results obtained with strains of Candida albicans and dermatophytes by the bioluminescence method in high-resolution medium were well correlated with those obtained by conventional methods currently used in clinical microbiology laboratories or reported previously, including a broth dilution method by the National Committee for Clinical Laboratory Standards (NCCLS). Thus, ATP bioluminescence assay can be used to monitor fungal growth in liquid culture media. The procedure has considerable potential for the rapid testing of FLCZ susceptibility of dermatophytes and other fungi.

Adenosine Triphosphate↗