Biomedical subjects

C Hagedorn

Publications and source records attributed to C Hagedorn.

At least 19 recordsLinked to original sources

PubMed2003

Carbon source utilization profiles as a method to identify sources of faecal pollution in water.

AIMS: Carbon source utilization profiles as a phenotypic fingerprinting methodology for determining sources of faecal pollution in water were evaluated. METHODS AND RESULTS: Three hundred and sixty-five Enterococcus isolates were collected from known faecal sources in four different geographical regions and were identified to species with the commercial Biolog system. Discriminant analysis (DA) was used to identify the substrate-containing wells that best classified the 365 isolates by source. By using 30 of the 95 wells for the analysis, the average rate of correct classification (ARCC) by source was 92.7% for a human vs non-human two-way classification when isolates from all regions were combined into one library. Corresponding ARCCs for other classification schemes were 81.9% for a four-way classification of human vs livestock vs wildlife vs domestic pets, and 85.7% for a three-way classification without human isolates. When three individual libraries were made based on classification of sources within Enterococcus species, the ARCC was 95.3% for the Ent. faecalis library, 95.8% for the Ent. gallinarum library and 94.7% for the Ent. mundtii library. Thirty Enterococcus isolates (unknown sources) were obtained from each of three stream sites where a specific source of pollution was apparent; 90.0% of the isolates from a human-suspected source were classified as human, 86.6% were classified as livestock from a livestock-suspected site, and 93.3% were classified as wildlife from a wildlife-suspected site. CONCLUSIONS: Phenotypic fingerprinting with carbon source utilization profiles provided levels of correct classification by sources from an Enterococcus library that were in the upper range of those reported in the literature. ARCCs for three Enterococcus species-specific libraries were very high and may be the best approach for further developing this concept and methodology. SIGNIFICANCE ANC IMPACT OF THE STUDY: The results, based on a modest Enterococcus library and a preliminary field validation test, demonstrated the potential for carbon source utilization profiles to be employed as a phenotypic method for determining sources of faecal pollution in water.

Animals↗

PubMed2001

Abdominal spiral CT in children: which radiation exposure is required?

We decided to test to what extent dose reduction is possible in abdominal spiral computed tomography (CT) in young children without loss of anatomic diagnostic information. A retrospective study was performed of 30 abdominal CT examinations of children aged 3 months to 7 years. These were divided into two groups: group A with reduced radiation exposure (tube current 50 mA, CT dose index CTDIFDA < or =0.83 mGy) and group B with standard radiation exposure (tube current > or =100 mA, CTDIFDA > or =1.66 mGy). Image quality was assessed using a four-part scale ('excellent', 'good', 'sufficient', 'poor') on visual image impression and visibility of 32 anatomical details. Five experienced radiologists read the CT scans independently who were blinded to the examination parameters. Differences in ranked data were evaluated with Wilcoxon's rank sum test. No difference between groups A and B was observed in visual image impression. Detail visibility was significantly lower in group A, but the differences were limited to right upper quadrant structures (portal vein, common bile duct, pancreatic head, adrenals) and to arterial branches. Significant differences in visibility rated as 'poor' were only found for the hepatic, splenic and renal arteries; all other structures showed no difference between groups A and B. A protocol with reduced radiation exposure (50 mA, CTDIFDA < or =0.83 mGy) allowed the demonstration of most anatomic structures in abdominal spiral CT in young children. For the precise demonstration of small details (e.g. structures of the right upper quadrant), a protocol with standard radiation exposure (> or =100 mAs) was superior.

Child↗

PubMed1999

Determining sources of fecal pollution in a rural Virginia watershed with antibiotic resistance patterns in fecal streptococci.

Nonpoint sources of pollution that contribute fecal bacteria to surface waters have proven difficult to identify. Knowledge of pollution sources could aid in restoration of the water quality, reduce the amounts of nutrients leaving watersheds, and reduce the danger of infectious disease resulting from exposure to contaminated waters. Patterns of antibiotic resistance in fecal streptococci were analyzed by discriminant and cluster analysis and used to identify sources of fecal pollution in a rural Virginia watershed. A database consisting of patterns from 7,058 fecal streptococcus isolates was first established from known human, livestock, and wildlife sources in Montgomery County, Va. Correct fecal streptococcus source identification averaged 87% for the entire database and ranged from 84% for deer isolates to 93% for human isolates. To field test the method and the database, a watershed improvement project (Page Brook) in Clarke County, Va., was initiated in 1996. Comparison of 892 known-source isolates from that watershed against the database resulted in an average correct classification rate of 88%. Combining all animal isolates increased correct classification rates to > or = 95% for separations between animal and human sources. Stream samples from three collection sites were highly contaminated, and fecal streptococci from these sites were classified as being predominantly from cattle (>78% of isolates), with small proportions from waterfowl, deer, and unidentified sources ( approximately 7% each). Based on these results, cattle access to the stream was restricted by installation of fencing and in-pasture watering stations. Fecal coliforms were reduced at the three sites by an average of 94%, from prefencing average populations of 15,900 per 100 ml to postfencing average populations of 960 per 100 ml. After fencing, <45% of fecal streptococcus isolates were classified as being from cattle. These results demonstrate that antibiotic resistance profiles in fecal streptococci can be used to reliably determine sources of fecal pollution, and water quality improvements can occur when efforts to address the identified sources are made.

Animals↗

PubMed1994

Field evaluation of two colorimetric coliphage detection methods.

Two new methods for coliphage detection, a colorimetric agar-based (CAB) method and a liquid colorimetric presence-absence (LCPA) method, were compared to the coliphage method proposed by the American Public Health Association (APHA; Standard Methods for the Examination of Water and Wastewater, 18th ed., American Public Health Association, Washington, D.C., 1992). Both new methods are based on the induction of beta-galactosidase in Escherichia coli and the release of the enzyme through a lytic cell infection. The released enzyme then cleaves a chromogenic substrate which produces a colored reaction product. Ninety split water samples from four different sources were tested. A total of 52 samples were positive by the CAB method, 52 were positive by the LCPA method, and 53 were positive by the APHA method. Results indicated that (i) the CAB and LCPA methods were as sensitive in coliphage detection as the APHA method, (ii) both the CAB and LCPA methods were easier to read and interpret than the APHA method, and (iii) the CAB method detected more coliphages in a positive sample than the APHA method in two of the four types of water sources. Importantly, the rapid and simple LCPA method was as reliable and sensitive as either of the two agar-based methods in coliphage detection.

Journal Article↗

PubMed1993

A liquid, colorimetric presence-absence coliphage detection method.

A liquid, colorimetric presence-absence coliphage detection method based on the induction of beta-galactosidase by Escherichia coli is described. The release of beta-galactosidase in the medium due to lytic cell infections by coliphages permits the hydrolysis of a yellow chromogenic substrate that develops into a distinct red coliphage positive sample, while a coliphage negative sample remains yellow. This method has proven to be rapid, simpler to perform than an agar medium assay, easy to read and interpret, inexpensive, and highly sensitive.

Chlorophenols↗

PubMed1992

Improved method for coliphage detection based on beta-galactosidase induction.

An improved method for coliphage detection based on the induction of beta-galactosidase in Escherichia coli is described. Upon infection by coliphages, the cells are lysed and a stable indolyl product that is dark blue becomes visible within each plaque. The improved method is compared to the proposed coliphage detection procedure described in Standard Methods for the Examination of Water and Wastewater.

Coliphages↗

PubMed1991

Soil and groundwater transport of microorganisms.

Releases of GEMs into the environment are expected to increase in the next few years, with the most dramatic increases resulting from the application of pest-control agents in agriculture and forestry. Of major significance in assessing the environmental risk impact of GEMs is an understanding of their survival and transport in soil and subsurface environments. While information on the transport and survival of microorganisms through soil is available, it is neither abundant nor extensive in terms of microbial types tested or soils examined. Though the transport of microorganisms from an application site depends primarily upon passive mechanisms, broad generalizations pertaining to the transportability of a specific microorganism within a particular soil environment may not be possible. Indeed, to extrapolate from information about one microbe to another, or from one geographical location to another, may not be appropriate. What is clear, however, is that the broader the data base, the more powerful the argument for making reasoned judgement, and consequently the more satisfactory the results of the predictive process. Several inherent difficulties exist in studying the transport behavior of GEMs in soil and subsurface environments. Detection of low microbial numbers or of stressed microbial populations is exceedingly difficult with traditional technology. In an effort to improve detection sensitivity, many improved methods of monitoring GEMs in the soil and subsurface are currently under development (Chaudhry et al. 1989). Beyond the difficulties of making accurate measurements of microorganisms to determine their spatial and temporal situation in the soil and subsurface environment, lies the need to ascertain the dynamic relationships between indigenous populations of microorganisms and how they may interact with a released GEM. Also, research strategies have not adequately addressed methods to predict the potential interactions between GEMs and natural microorganisms. These issues must be addressed if environmental risk assessment is to be valuable. There is clearly a need for focused research on the survival and transport of GEMs in these environments.

Bacteria↗

PubMed1990

Isolation of Rhizobium leguminosarum (biovar trifolii) Strains from Ethiopian Soils and Symbiotic Effectiveness on African Annual Clover Species.

Strains of Rhizobium leguminosarum (biovar trifolii) isolated from two Ethiopian soils or obtained from a commercial source were evaluated for symbiotic effectiveness on five African annual clover species. Numerous Rhizobium trifolii strains that exhibited varying levels of symbiotic effectiveness were isolated from both soils (a nitosol and a vertisol), and it was possible to identify strains that were highly effective for each clover species. The soil isolates were, as a group, superior to the strains from the commercial source. Several R. trifolii strains were found to be effective on more than one clover species, and there appeared to be at least two and possibly three distinct cross-inoculation effectiveness groups.

Journal Article↗

PubMed1989

Rhizobacteria of cotton and their repression of seedling disease pathogens.

During the 1983 field season, the rhizobacteria (including organisms from rhizosphere soil and the root rhizoplane) of cotton plants at one location in Mississippi were inventoried at different plant growth stages. Isolates (1,000) were identified to the genus level and characterized for repression of Pythium ultimum and Rhizoctonia solani. Cotton seedlings were initially colonized by bacteria of many different genera, and populations quickly reached 10 CFU/g of root tissue. As the season progressed, the bacterial populations declined as root mass increased and the roots became more woodlike in consistency. Fluorescent pseudomonads were the most numerous gram-negative rhizobacterial isolates of those that were randomly collected and identified, and they provided the largest number of isolates with fungal repressive activity. Several other gram-negative bacterial genera were recovered throughout the growing season, and some gram-positive bacteria were also isolated routinely, but at lower numbers. There was no correlation between the proportion of rhizobacterial isolates that possessed fungal repressive activity and the plant growth stage from which the isolates were obtained. Approximately twice as many bacterial isolates demonstrated fungal repression in the agar assay compared with the inplanta assay, and isolates were found more frequently with fungal repressive activity against P. ultimum than against R. solai.

Journal Article↗

PubMed1987

A selective medium for enumeration and recovery of Pseudomonas cepacia biotypes from soil.

TB-T medium provides a high degree of selectivity for and detection of Pseudomonas cepacia biotypes upon initial plating from soil. TB-T medium consists of a basal medium with glucose as the sole carbon source and asparagine as the sole nitrogen source. The selectivity of TB-T medium is based on the combination of trypan blue (TB) and tetracycline (T) (pH 5.5). On TB-T medium, 216 of 300 isolates (72%) from five different soil types were identified as P. cepacia. The remaining 28% were facultative organisms that could be separated readily from P. cepacia by anaerobic glucose fermentation and by their inability to grow at 41 degrees C. Molds were controlled on low soil dilutions by adding crystal violet, nystatin, or both. Elimination of either ingredient or elevation of the pH to 7.5 resulted in a pronounced loss of selectivity. The efficiency of recovery varied considerably among P. cepacia strains but was high enough for some strains (76 to 86%) to permit quantitative studies. TB-T medium combines a defined formulation with high selectivity and allows recovery of P. cepacia biotypes from low soil dilutions (10(1) to 10(3)).

Culture Media↗

PubMed1985

New selective media for enumeration and recovery of fluorescent pseudomonads from various habitats.

New media (S1 and S2) were formulated that provide a high degree of selectivity and detection of fluorescent pseudomonads on initial plating. The selectivity of the S-type media was based on a detergent, sodium lauroyl sarcosine, and an antibiotic, trimethoprim. A total of five soils from different geographical locations and one sewage sludge sample were examined. On S1 medium, isolates from two soils with low fluorescent pseudomonad populations exhibited a high frequency of arginine dihydrolase (78%) and oxidase-positive (95%) phenotypes, but no fermentative isolates were recovered. Medium S2 was more defined and selective than S1, but lower numbers of fluorescent pseudomonads were recovered on S2. In soils in which fluorescent pseudomonads represent a small proportion of the total population, S1 medium consistently recovered high percentages of fluorescent phenotypes (82.5%).

Journal Article↗

PubMed1983

Microtechnique for isolating fecal coliforms from soil.

A most-probable-number microtitration technique for isolating fecal coliforms from soil was developed. A correlation coefficient of 0.86, with a 95% confidence interval of 0.76 less than zeta less than 0.92, was obtained when this technique was compared with the standard elevated-temperature fecal coliform most-probable-number procedure.

Bacteriological Techniques↗

PubMed1982

Competitiveness of Rhizobium trifolii Strains Associated with Red Clover (Trifolium pratense L.) in Mississippi Soils.

Five strains of Rhizobium trifolii were evaluated in competition with indigenous populations in nodulating red clover (Trifolium pratense L.) cv. Kenland in two different soils in Mississippi. Double antibiotic resistance acquisition was used to measure the proportion of nodules occupied by the introduced mutant strains. In vertisol soil, strains RP113-7, 162BB1, LM1, and 162P17 were recovered in at least 94% of the assayed nodules, whereas TA1 was found in 83.8% of the nodules. At an ultisol location, significant differences were detected within the introduced rhizobia. Strain RP113-7 was recovered at very high rates (99.2% of the assayed nodules), whereas strains 162BB1, LM1, 162P17, and TA1 were all found in 84.9 to 96.0% of the nodules sampled. Forage yield and percent crude protein levels were lower with the less effective but competitive strain (TA1) at both locations. Results indicated that more effective strains of R. trifolii can increase red clover production and symbiotic nitrogen fixation under different environmental conditions in Mississippi.

Journal Article↗

PubMed1978

[Hodgkin's disease: effect of spenectomy on the immune status (author's transl)].

In 22 untreated Hodgkin's patients the following parameters were studied before and after splenectomy: the total WBC, lymphocytes, B- and T-cells and mitogenic stimulation of peripheral lymphocytes using autologous and control serum. The results were correlated to patient groups with favourable and unfavourable prognosis according to pathological stage, histology, spleen involvement and constitutional symptoms. 1. All Patients. Significant increase of the absolute number of peripheral lymphocytes and B-cells. Significant increase of the spontanous DNA synthesis in the presence of AB-control serum, but no change after mitogenic stimulation of peripheral lymphocytes. No change in the number of peripheral T-cells. 2. Patients with Favourable Prognosis. Significant increase of the absolute number of peripheral lymphocytes and B-cells. Significant increase of the spontanous DNA synthesis in the presence of AB-control-serum. Significant decrease of the T-cell function (PHA- and Con-A-stimulation in the presence of autologous serum). Significant decrease of the PHA-, Con-A- and PWM stimulation rate using control serum in the lymphocytic predominance and nodular sclerosis group. No change in the number of peripheral T-cells. 3. Patients with Unfavourable Prognosis. No change in the absolute number of B-cells, of the spontanous DNA-synthesis using autologous serum and of the PHA- and Con-A-stimulation. Significant increase of the EBV-induced blastogenesis in the mixed cellularity and lymphocytic depletion group.

Adolescent↗

PubMed1978

Detection of antibiotic-producing Streptomyces inhabiting forest soils.

A modified agar overlay technique was developed for detecting antibiotic production by Streptomyces isolates and compared with two routinely used overlay procedures and the shake flask-disk assay method. Two types of inhibitory patterns could be discerned in the modified overlay method, and one of these was always exhibited by Streptomyces isolates which produced extractable antimicrobial substances. In a preliminary screening of 600 isolates, higher numbers of antibiotic-producing streptomyces were detected with the modified overlay procedure than with the streak or pour overlay method and the shake flask assay. The modified overlay distinguished between antibiotic production and other antagonistic effects. The inhibitory agents extracted after 6 days of culture growth on the modified overlay agar were of a higher concentration and more stable over longer periods of time than those recovered from shake flasks. It was observed that acidoduric streptomyces produced a greater proportion of antibiotics against gram-negative bacteria than did neutrophilic cultures, and this effect was greatest with the isolates from the most acidic soils. The neutrophiles were more active against gram-positive bacteria and, upon antibiotic classification, it appeared that the neutrophilic and acidoduric cultures from various soils produced different antimicrobial compounds.

Anti-Bacterial Agents↗

PubMed1978

Use of fecal streptococci as indicators of pollution in soil.

The survival, recovery, and identification of Streptococcus isolates from soil was investigated by (i) examination of survival in soil under different moisture and temperature conditions, (ii) evaluation of media combinations for recovering fecal streptococci from soil, and (iii) partial identification of isolates from diverse habitats. Cool, moist conditions prolonged the survival of Streptococcus faecalis in soil for at least 12 weeks, whereas freezing was lethal, with the populations being reduced up to 95% when several freeze-thaw treatments occurred. Media evaluations indicated that both the efficiency of recovery and enumeration of the fecal streptococci from soil can be influenced by the combination of media used. Taxonomic data revealed a need to develop procedures to differentiate between isolates of fecal origin and plant-derived streptococci that possess many of the cultural reactions of S. faecalis. It was found that recent fecal isolates exhibited a much greater incidence of multiple antibiotic resistance than soil or vegetation isolates, and this characteristic, coupled with the use of enterococci as indicators of fecal contamination in soil systems, is discussed.

Anti-Bacterial Agents↗

PubMed1976

Influences of soil acidity on Streptomyces populations inhabiting forest soils.

The Streptomyces populations inhabiting five acidic forest soils were examined. It was found that lowering the pH of a medium selective for streptomycetes (starch-casein agar) to the pH of the particular soil horizon being plated influenced both the total numbers and types of streptomycetes that were isolated from the soils examined in this study. On the acidified medium both the numbers of streptomycetes and the percentage of total bacteria on the plates represented by streptomycetes increased (as compared with the same medium with a pH of 7.2). These differences were greatest on the isolations from the most acid soils. The largest concentrations of streptomycetes were found in the surface horizon (0 to 15 cm) and the litter layer immediately over the surface mineral horizon. Acidity tolerance tests demonstrated that random samplings of isolates contained acidophilic, neutrophilic, and acidoduric strains, with the largest numbers of acidophiles being found on the acidified media from the most acid soils. There were no differences between overall utilization of selected carbohydrates among the isolates taken from either the neutral or acidic media, although a larger proportion of the acid media isolates produced acid from the carbohydrates. Evidence is presented which indicates that different types of streptomycetes were isolated on the acid media, and possible reasons for the presence of these acid-tolerant populations are discussed.

Carbohydrate Metabolism↗

PubMed1975

Ecology of soil arthrobacters in clarion-webster toposequences of iowa.

Toposequence variations in soil properties were characterized and related to variations in populations of total isolatable bacteria and arthrobacters. Increases in soil NO(3)-N, available phosphorous, NO(3)-N-producing power, Arthrobacter counts, and the percentage of the total counts represented by arthrobacters were correlated with decreases in soil acidity. The total bacterial counts were not correlated with soil acidity but were associated with percentage of soil organic matter and percentage of clay. The percentage of the total counts represented by arthrobacters was lowest at the summit position and increased downslope to the highest value in the toeslope position. Factor analysis of the data revealed that 67 to 81% of the total variance exhibited by all variables per site-sampling period could be accounted for by soil acidity, soil structure, soil fertility, soil moisture, and bacterial factors. A selective medium was developed for soil arthrobacters and tested on a wide variety of central Iowa soils to determine its potential as a medium for enumeration as well as isolation. The medium developed in this study was found to be superior to the other available direct-isolation media for soil arthrobacters.

Journal Article↗