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PubMed2001

Review of methods to collect settled dust and isolate culturable microorganisms.

Examination of settled dust is often included in investigations of indoor environments to identify the types and concentrations of particles to which building occupants may be exposed. Fungi and bacteria are among the many components in dust that have been studied. Isolation by culture is an established method that is used widely to quantify and identify microorganisms in environmental samples. However, no standard procedures for culturing fungi or bacteria from dust have been adopted widely to ensure the validity of comparing findings from different studies. This paper reviews methods various researchers have used to study surface particles and to isolate culturable microorganisms from dust. Factors that were found to differ included the method of sample collection, the ways dust was prepared for inoculation onto growth media, and the culture media chosen for specific categories of agents. The need for reference methods in environmental microbiology for use in the assessment of indoor environmental quality is discussed.

Air Pollution, Indoor↗
PubMed2001

Extensive surface diversity of a commensal microorganism by multiple DNA inversions.

The dynamic interactions between a host and its intestinal microflora that lead to commensalism are unclear. Bacteria that colonize the intestinal tract do so despite the development of a specific immune response by the host. The mechanisms used by commensal organisms to circumvent this immune response have yet to be established. Here we demonstrate that the human colonic microorganism, Bacteroides fragilis, is able to modulate its surface antigenicity by producing at least eight distinct capsular polysaccharides-a number greater than any previously reported for a bacterium-and is able to regulate their expression in an on-off manner by the reversible inversion of DNA segments containing the promoters for their expression. This means of generating surface diversity allows the organism to exhibit a wide array of distinct surface polysaccharide combinations, and may have broad implications for how the predominant human colonic microorganisms, the Bacteroides species, maintain an ecological niche in the intestinal tract.

Antigenic Variation↗
PubMed1994

Drug synthesis by genetically engineered microorganisms.

The interplay between chemical and biological approaches to drug discovery and development is increasing with the advent of combinatorial methods that accelerate the output of screening programs and the development of genetically modified microorganisms able to make new metabolites and larger amounts of known ones. Actinomycetes, the most prolific microbial source of known drugs, can produce new aromatic compounds by manipulation of the Type II polyketide synthase genes as well as analogs of existing macrolide antibiotics, unavailable by chemical synthesis, through targeted mutation of specific biosynthetic genes. Genetic alteration of pathways to aminoglycoside and oligopeptide antibiotics should offer equally promising approaches to manufacturing novel metabolites. When coupled with DNA-based prescreening of microbial isolates for genes associated with known pharmacologically active agents, these new genetic-based approaches are creating an expanded role for microorganisms in drug research.

Anti-Bacterial Agents↗
PubMed2003

Evolution experiments with microorganisms: the dynamics and genetic bases of adaptation.

Microorganisms have been mutating and evolving on Earth for billions of years. Now, a field of research has developed around the idea of using microorganisms to study evolution in action. Controlled and replicated experiments are using viruses, bacteria and yeast to investigate how their genomes and phenotypic properties evolve over hundreds and even thousands of generations. Here, we examine the dynamics of evolutionary adaptation, the genetic bases of adaptation, tradeoffs and the environmental specificity of adaptation, the origin and evolutionary consequences of mutators, and the process of drift decay in very small populations.

Adaptation, Biological↗
PubMed2005

Identifying microorganisms responsible for ecologically significant biogeochemical processes.

Throughout evolutionary time, and each day in every habitat throughout the globe, microorganisms have been responsible for maintaining the biosphere. Despite the crucial part that they play in the cycling of nutrients in habitats such as soils, sediments and waters, only rarely have the microorganisms actually responsible for key processes been identified. Obstacles that have traditionally impeded fundamental microbial ecology inquiries are now yielding to technical advancements that have important parallels in medical microbiology. The pace of new discoveries that document ecological processes and their causative agents will no doubt accelerate in the near future, and might assist in ecosystem management.

Anaerobiosis↗
PubMed2006

Bug juice: harvesting electricity with microorganisms.

It is well established that some reduced fermentation products or microbially reduced artificial mediators can abiotically react with electrodes to yield a small electrical current. This type of metabolism does not typically result in an efficient conversion of organic compounds to electricity because only some metabolic end products will react with electrodes, and the microorganisms only incompletely oxidize their organic fuels. A new form of microbial respiration has recently been discovered in which microorganisms conserve energy to support growth by oxidizing organic compounds to carbon dioxide with direct quantitative electron transfer to electrodes. These organisms, termed electricigens, offer the possibility of efficiently converting organic compounds into electricity in self-sustaining systems with long-term stability.

Bacteria↗
PubMed1992

The essential features of microorganisms and the rationale for antimicrobial therapy.

Antimicrobial agents have had a major impact on the control of most bacterial diseases; however, viral, fungal, protozoal and helminthic diseases have generally been less amenable to drug therapy. The reason for this lies in the different structural and physiological features that each group of microorganisms have. This article will outline the basic features of the various types of microorganisms, and relate these to the mode of action of commonly used antimicrobial agents.

Animals↗
PubMed2001

Intake of sweet foods and counts of cariogenic microorganisms in obese and normal-weight women.

OBJECTIVE: To study the intake of sweet foods in obese and normal-weight women, while also taking menstrual cycle effects on eating behaviour into consideration. An objective test of the intake of sugar-containing foods was introduced by measuring salivary counts of mutans streptococci and lactobacilli. DESIGN: A cross-sectional comparison of the intake of sweet foods in obese and normal-weight women. The obese women were also studied longitudinally after 10 weeks in a weight reduction programme. SUBJECTS: Obese (n=72, body mass index (BMI) 42.0+/-5.2 kg/m2) and normal-weight women (n=67, BMI 22.2+/-1.6 kg/m2) participated. RESULTS: Mutans streptococci in saliva were higher in obese than in normal-weight women (P<0.0001), although the reported habitual daily intake of sweet foods did not differ. Of the menstruating women, 80% of the obese subjects and 62% of the normal-weight ones (P<0.05) reported periods during the menstrual cycle with an 'extra large' intake of sweet foods; these intakes were higher in obese than in normal-weight women (P<0.01). The obese women reduced their intake of sweet foods after 10 weeks of weight reduction, although these changes were not pronounced enough to significantly affect the counts of cariogenic microorganisms. CONCLUSIONS: In contrast to most previous cross-sectional studies, this study shows that obese women have a higher intake of sweet foods, especially pre-menstrually. This was indicated by higher salivary counts of cariogenic microorganisms. SPONSORSHIP: Karolinska Institute Research Funds.

Adult↗
PubMed2005

In vitro evaluation of probiotics microorganisms adhesion to an artificial caries model.

OBJECTIVE: This in vitro study compared the adhesion of two probiotics microorganisms (Lactobacillus casei Shirota and Lactobacillus acidophilus) to an artificial caries model. METHOD: In total, 30 bovine teeth were longitudinally sectioned, excluding the lingual half surface. The specimens were covered with nail varnish, except for an area of 3 by 5 mm in dentin, suspended in an artificial caries solution promoted by Streptococcus mutans, and incubated at 37 degrees C. After 14 days, the specimens were separated equally into two groups and transferred to a brain heart infusion culture media containing L. acidophilus (group A) and L. casei Shirota (group S), at 37 degrees C. After 48 h, the exposed area of dentin was washed with 1 ml of distilled water and the caries dentin was removed and dispersed in 1 ml of saline solution. The samples of distilled water and caries dentin were diluted and inoculated in Rogosa selective Lactobacillus agar. The results in CFU/ml were analysed by the Mann-Whitney test. RESULTS: There was no significant difference between Groups A and S for the lactobacilli count in samples of distilled water (P = 0.237). CONCLUSIONS: The amount of L. acidophilus in the artificially caries dentin was significantly superior compared to L. casei Shirota (P = 0.047), suggesting an inferior adhesion potential for this microorganism.

Animals↗
PubMed2002

Photoreception and photomovements of microorganisms.

Many freely motile microorganisms can perceive and transduce external photic stimuli to the motor apparatus, eventually moving, by means of various behavioural strategies, into environments in which the illumination conditions are the most favourable for their life. In different microorganisms, a wide range of chromophores operate as light detectors, each of them set in a special molecular pocket that, in its turn, can be linked to another component of the transduction chain. The diverse photosensors are organized in special (and in many cases dedicated) photoreceptor units or subcellular organelles. The main molecular mechanisms connecting the early event of photon absorption to the formation of the signalling state down to the dark steps of the transduction chain are discussed in a selected number of case examples. The possible importance of an intensive multidisciplinary approach to these problems in an evolutionary perspective is finally briefly outlined.

Microbiology↗
PubMed2003

Differences between intrafollicular microorganism profiles in perioral and seborrhoeic dermatitis.

Although often associated with overuse of topical corticosteroids, perioral dermatitis seems to develop seldom in patients with typical seborrhoeic dermatitis in spite of long-term application of corticosteroids. In order to compare the profiles of intrafollicular microorganisms in the lesions of perioral and seborrhoeic dermatitis, tape-stripped samples were obtained from eight lesions of perioral dermatitis, 10 lesions of seborrhoeic dermatitis, and the perioral skin of 31 normal subjects. After staining with Toluidine blue, resident microorganisms on plucked hair roots were evaluated microscopically. In all patients with perioral dermatitis and two normal subjects, 20-70% of sample hairs were positive for fusiform bacteria regarded as fusobacteria. Malassezia-positive hairs were rarely seen in these cases. Seborrhoeic dermatitis showed the opposite results. Perioral dermatitis may tend to develop under fusiform-bacteria-rich conditions, rather than Malassezia-rich conditions as in the case of seborrhoeic dermatitis.

Adult↗
PubMed1999

Antimicrobial effects of various endodontic irrigants on selected microorganisms.

AIM: This study was undertaken to determine the antimicrobial effect of various endodontic irrigants against six selected microorganisms. METHODOLOGY: Staphylococcus aureus, Enterococcus faecalis, Streptococcus salivarius, Str. pyogenes, Escherichia coli and Candida albicans were included in the study. Pre-sterilized Whatman paper discs, 6 mm in diameter and soaked with the test solution, were prepared and placed onto the previously seeded agar Petri plates. Each plate was incubated aerobically. A zone of inhibition was recorded for each plate and the results were analysed statistically. RESULTS: 5.25% NaOCl was effective against all test microorganisms with a substantial zone of inhibition. Saline was always ineffective. Decreased concentration of NaOCl significantly reduced its antimicrobial effect. Cresophene showed a significantly larger (P < 0.05) average zone of inhibition compared to the other experimental irrigants. Alcohol had smaller but not significantly different zones of inhibition than chlorhexidine. CONCLUSIONS: 5.25% NaOCl was superior in its antimicrobial abilities compared with other irrigants used. A reduced concentration of NaOCl (0.5%) resulted in significantly decreased antimicrobial effects. When compared with 21% alcohol, 0.5% NaOCl and 2% chlorhexidine, paramonochlorophenol (cresophene) showed a greater antimicrobial effect.

Analysis of Variance↗
PubMed2002

The characterization of oil-degrading microorganisms from lubricating oil contaminated (scale) soil.

AIMS: To isolate and characterize oil-degrading microorganisms from contaminated (scale) soil. METHODS AND RESULTS: Oil-degrading microorganisms were isolated from enrichment cultures of scale soil. Each isolate was identified using 16S rDNA gene and oil degradability was determined on both unused and used lubricating oil. The weight of the extracted remaining oil revealed that most isolates degraded unused lubricating oil more than used lubricating oil. Chemical composition of oil analysed by TLC-FID and GC-MS demonstrated that Nocardia simplex W9 degraded used oil the best, and resulted in a decrease in saturates, aromatics and resins to 52.46, 38.13 and 18.81%, respectively. CONCLUSIONS: Nocardia simplex W9 is the best degrader, among all the isolates, on both used and unused lubricating oil. SIGNIFICANCE AND IMPACT OF THE STUDY: The presence of Nocardia simplex W9 in scale soil enables iron to be recycled by biodegradation.

Biodegradation, Environmental↗
PubMedDate not supplied

Infection with antimicrobial-resistant microorganisms in dialysis patients.

The prevalence of antimicrobial-resistant microorganisms in various health care settings, including outpatient dialysis facilities, has increased dramatically in the last decade. Antimicrobial use and patient-to-patient transmission of resistant strains are the two main factors that have contributed to this rapid increase. Methicillin-resistant Staphylococcus aureus (MRSA) and coagulase-negative staphylococci are commonly isolated as a cause of hemodialysis (HD) catheter-related bacteremia and peritoneal dialysis (PD)-related catheter infection and peritonitis. The widespread use of vancomycin in dialysis patients is of concern because of an increase in the prevalence of vancomycin-resistant enterococci (VRE) in dialysis patients. Staphylococci with reduced sensitivity to vancomycin have also appeared in dialysis patients. A more recent problem is the appearance of S. aureus isolates with a high degree of resistance to the topical antimicrobial agent mupirocin. This has been seen in PD patients who have received prophylactic application of mupirocin at the peritoneal catheter exit site. Appropriate antimicrobial use will help protect the efficacy of currently used antibiotics, such as vancomycin. Published guidelines for use of vancomycin should be followed. New antimicrobials such as linezolid and quinupristin/dalfopristin have activity against VRE and MRSA, but resistance to these agents has already occurred. Preventing transmission of antimicrobial-resistant microorganisms in health care settings, including outpatient dialysis facilities, is important in limiting the spread of these resistant organisms.

Anti-Bacterial Agents↗
PubMed2000

Adsorption of microorganism components by lixelle beads.

We reported previously that Lixelle, which was used for beta-2 microglobulin (BMG) adsorption columns, could adsorb not only BMG but also inflammatory cytokines. We then were interested in the application of Lixelle to patients with systemic inflammatory response syndrome (SIRS) and tried to find out its ability to adsorb microorganism components in vitro using lipopolysaccharide (LPS) (E. coli: B8), endotoxin (ET) containing water, and peptidoglycan (PG: Micrococcus luteus). The initial concentrations of each solution were LPS (ET: 29,135 EU/L), contaminated water (ET: 3,523 EU/L), and PG (67.1 ng/ml) and 2.5 ml of each of the stock solutions and adjusted diluted solutions contained 0.5 ml of Lixelle beads. After shaking at 37 degrees C for 2 h, ET in the solutions was determined by the ET specific-limulus amebocyte lysate (ES-LAL) method and PG by the silkworm larbae plasma (SLP) method. The results revealed that even when ET concentrations in LPS and contaminated water were high, the samples containing Lixelle beads showed significant decreases. There was some adsorption of PG but no significant differences. Thus, Lixelle beads can adsorb not only BMG but also microorganism components such as ET and PG. These findings, together with the ability to adsorb inflammatory cytokines by Lixelle, show the possibility of application for the treatment of infectious SIRS.

Adsorption↗
PubMed2003

Isolation and identification of biofilm microorganisms from silicone gastrostomy devices.

BACKGROUND/PURPOSE: Silicone gastrostomy devices (tubes and "buttons") are used extensively for long-term feeding and administration of special diets and medications. However, their potential for harboring microorganisms and possibly compromising the host largely is unknown. This study was conducted to isolate and identify the microbial species in viable biofilms attached to these devices in a pediatric cohort. METHODS: A total of 78 domains on 18 silicone gastrostomy devices (12 "buttons" and 6 tubes converted to skin level devices), previously used for feeding (3 to 47 months) in children ranging in age from 6 months to 17 years were analyzed for microbial content. Biofilms were removed from the silicone tube surfaces and inoculated into enriched nutrient media using standard procedures. Intact biofilms also were observed using scanning electron microscopy (SEM) and confocal scanning laser microscopy. RESULTS: All devices analyzed in this investigation were found to exhibit biofilm growth. Of the 24 identified bacterial species, the predominant genera included Bacillus, Enterococcus, and Staphylococcus. Control studies of the tubes under SEM showed a multitude of crevices serving as niches for microbial colonization. Observation of the attached biofilm by SEM showed various biomasses with numerous morphologies. CONCLUSIONS: Biofilm composition and attachment to silicone enteral access devices has not received appropriate attention previously. This study shows that devices are colonized with various bacteria and fungi posing a potential threat to patients, particularly those who are immunocompromised. These microorganisms also may play a significant role in the formation of granulation tissue and contribute to device failure.

Adolescent↗
PubMed1998

Antimicrobial activity of magnolol and honokiol against periodontopathic microorganisms.

Magnolol (1) and honokiol (2), main compounds from the stem bark of Magnolia obovata Thunb., were evaluated for an antimicrobial activity against periodontopathic microorganisms, Porphyromonas gingivalis, Prevotella gingivalis, Actinobacillus actinomycetemcomitans, Capnocytophaga gingivalis, and Veillonella disper, and a cytotoxicity against human gingival fibroblasts and epithelial cells. Our results indicate that magnolol and honokiol, although less potent than chlorhexidine, show a significant antimicrobial activity against these microorganisms, and a relatively low cytotoxic effect on human gingival cells. Thus, it is suggested that magnolol and honokiol may have a potential therapeutic use as a safe oral antiseptic for the prevention and the treatment of periodontal disease.

Aggregatibacter actinomycetemcomitans↗