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Application of molecular typing methods to dermatophyte species that cause skin and nail infections.

Typing methods utilising DNA technology were applied to a collection of Trichophyton mentagrophytes and T. rubrum isolates from skin and nail infections. The methods included restriction enzyme analysis (REA), hybridisation with the DNA probe poly (dG-dT), randomly amplified polymorphic DNA (RAPD) by PCR and restriction analysis of a segment of PCR-amplified rDNA. All these tests successfully differentiated the species, but few intra-species differences were detected. REA demonstrated some isolate variation, but this was limited and difficult to interpret, making it unsuitable as a typing tool. RAPD demonstrated few variations amongst T. mentagrophytes and none in T. rubrum.

DNA Probes↗

Soil Type and Maize Cultivar Affect the Genetic Diversity of Maize Root-Associated Burkholderia cepacia Populations.

Abstract Burkholderia cepacia populations associated with the Zea mays root system were investigated to assess the influence of soil type, maize cultivar, and root localization on the degree of their genetic diversity. A total of 180 B. cepacia isolates were identified by restriction analysis of the amplified 16S rDNA (ARDRA technique). The genetic diversity among B. cepacia isolates was analyzed by the random amplified polymorphic DNA (RAPD) technique, using the 10-mer primer AP5. The analysis of molecular variance (AMOVA) method was applied to estimate the variance components for the RAPD patterns. The results indicated that, among the factors studied, the soil was clearly the dominant one in affecting the genetic diversity of maize root-associated B. cepacia populations. In fact, the percentage of variation among populations was significantly higher between B. cepacia populations recovered from maize planted in different soils than between B. cepacia populations isolated from different maize cultivars and from distinct root compartments such as rhizoplane and rhizosphere. The analysis of the genetic relationships among B. cepacia isolates resulted in dendrograms showing bacterial populations with frequent recombinations and a nonclonal genetic structure. The dendrograms were also in agreement with the AMOVA results. We were able to group strains obtained from distinct soils on the basis of their origin, confirming that soil type had the major effect on the degree of genetic diversity of the maize root-associated B. cepacia populations analyzed. On the other hand, strains isolated from distinct root compartments exhibited a random distribution which confirmed that the rhizosphere and rhizoplane populations analyzed did not significantly differ in their genetic structure.http://link.springer-ny.com/link/service/journals/00248/bibs/38n3p273.html</hea

Journal Article↗

In situ hybridization of phytoplankton using fluorescently labeled rRNA probes.

Phytoplankton are one of the major components of ecosystem processes and play an important role in many biogeochemical cycles in the marine and freshwater environment. Despite their importance, many microalgae are poorly described and little is known of broad spatial and temporal scale trends in their abundance and distribution. Reasons for this are that microalgae are often small, lack distinct morphological features, and are unculturable, which make analyses difficult. It is now possible by using molecular biological techniques to advance our knowledge of aquatic biodiversity and to understand how biodiversity supports ecosystem structure, dynamics, and resilience. We present in this chapter a brief review of the progress that has been made in analyzing microalgae from populations to the species level. The described methods range from DNA fingerprinting techniques, such as random amplified polymorphic DNA (RAPD), amplified fragment length polymorphisms (AFLPs), and simple sequence repeats (SSRs), to microsatellites, which are used in population studies, to sequence analysis, which help to reconstruct the evolutionary history of organisms and to examine relationships at various taxonomic levels. Special emphasis is given to the application of molecular probes for the identification and characterization of microalgal taxa. The fast and secure identification of phytoplankton, especially of toxic species, is important from an ecological and economical point of view and whole-cell hybridization with specific fluorochrome-labeled probes followed by fluorescence microscopy or flow cytometry offers a fast method for this purpose. In this context, we present a detailed protocol for fluorescence in situ hybridization (FISH) of ribosomal RNA (rRNA) probes that can be applied to many algal cell types and discuss practical considerations of its use.

DNA Fingerprinting↗

Genotyping of clinical Serratia marcescens isolates: a comparison of PCR-based methods.

The polymerase chain reaction (PCR)-based procedures of randomly amplified polymorphic DNA (RAPD) and repetitive element (RE)-based PCR were used to amplify total DNA prepared from each of 62 clinical Serratia marcescens isolates. Three different random primers, designated 1060, 1254 and 1283, were used individually in RAPD-PCR. Primers representing enterobacterial repetitive intergenic consensus (ERIC) sequences, extragenic palindromic (REP) elements, and polymorphic GC-rich repetitive sequences (PGRS) constituted the repetitive element-PCR. We were able to generate 40, 40 and 58 genotypic groupings using the 1060, 1254 and 1283 RAPD primers, respectively. Using the ERIC, REP and PGRS primers, 19, 54 and 60 unique genotypic profiles were yielded, respectively. The PGRS primers, which were developed to amplify GC-rich repetitive sequences in the genome of Mycobacteria, were the most discriminatory. These data indicate that both of these PCR-based approaches are a valid means of discriminating strain differences among isolates of S. marcescens and the amount of differentiation depends on the primer used. These techniques should prove useful for routine surveillance or in examining outbreaks of S. marcescens in clinical settings.

Bacterial Typing Techniques↗

[Molecular methods and techniques used in diagnosis and epidemiology of infections caused by pathogenic fungi].

In this paper we reviewed the latest literature on molecular techniques used in diagnosis and epidemiology of infections caused by pathogenic fungi. Traditional methods used for the identification and typing of medically relevant fungi include morphological and biochemical analysis. These methods are time-consuming and base on phenotypic features what makes them unreliable. We described the usefulness in mycological studies of fast and very sensitive molecular methods which rely on PCR and hybridization techniques.

DNA Fingerprinting↗

Conventional and molecular typing of Salmonella typhi strains from Brazil.

Phenotypic and genotypic characteristics of Salmonella Typhi were studied in 30 strains, isolated in different years, from some areas in Brazil. Conventional typing methods were performed by biochemical tests, Vi phage-typing scheme, and antimicrobial susceptibility test. Molecular typing methods were performed by analysis of plasmid DNA and by random amplified polymorphic DNA (RAPD-PCR). For the latter, an optimization step was performed to ensure the reproducibility of the process in genetic characterization of S. Typhi. The predominance of 76.7% of biotype I (xylose +, arabinose -) was noticed in all studied areas. Three phage types were recognized, with prominence for the phage types A (73.3%) and I+IV (23.3%). All the strains were susceptible to the drugs used. However, 36.7% of the strains contained plasmids, with predominance of the 105 Kb plasmid. RAPD was capable of grouping the strains in 8 genotypic patterns using primer 784, in 6, using primer 787 and in 7, using primer 797. Conventional phenotypic typing methods, as well as the DNA plasmid analysis, presented nonsignificant discriminatory power; however, RAPD-PCR analysis showed discriminatory power, reproducibility, easy interpretation and performance, being considered as a promising alternative typing method for S. Typhi.

Bacterial Typing Techniques↗

Molecular mapping of Stb1, a potentially durable gene for resistance to septoria tritici blotch in wheat.

Septoria tritici blotch (STB), caused by the ascomycete Mycosphaerella graminicola (anamorph Septoria tritici), was the most destructive disease of wheat in Indiana and adjacent states before deployment of the resistance gene Stb1 during the early 1970s. Since then, Stb1 has provided durable protection against STB in widely grown wheat cultivars. However, its chromosomal location and allelic relationships to most other STB genes are not known, so the molecular mapping of Stb1 is of great interest. Genetic analyses and molecular mapping were performed for two mapping populations. A total of 148 F1 plants (mapping population I) were derived from a three-way cross between the resistant line P881072-75-1 and the susceptible lines P881072-75-2 and Monon, and 106 F6 recombinant-inbred lines (mapping population II) were developed from a cross between the resistant line 72626E2-12-9-1 and the susceptible cultivar Arthur. Bulked-segregant analysis with random amplified polymorphic DNA (RAPD), amplified fragment length polymorphism (AFLP), and microsatellite or simple-sequence repeat (SSR) markers was conducted to identify those that were putatively linked to the Stb1 gene. Segregation analyses confirmed that a single dominant gene controls the resistance to M. graminicola in each mapping population. Two RAPD markers, G7(1200) and H19(520), were tightly linked to Stb1 in wheat line P881072-75-1 at distances of less than 0.68 cM and 1.4 cM, respectively. In mapping population II, the most closely linked marker was SSR Xbarc74, which was 2.8 cM proximal to Stb1 on chromosome 5BL. Microsatellite loci Xgwm335 and Xgwm213 also were proximal to Stb1 at distances of 7.4 cM and 8.3 cM, respectively. The flanking AFLP marker, EcoRI-AGC/ MseI-CTA-1, was 8.4 cM distal to Stb1. The two RAPD markers, G7(1200) and H19(520), and AFLP EcoRI-AGC/ MseI-CTA-1, were cloned and sequenced for conversion into sequence-characterized amplified region (SCAR) markers. Only RAPD allele H19(520) could be converted successfully, and none of the SCAR markers was diagnostic for the Stb1 locus. Analysis of SSR and the original RAPD primers on several 5BL deletion stocks positioned the Stb1 locus in the region delineated by chromosome breakpoints at fraction lengths 0.59 and 0.75. The molecular markers tightly linked to Stb1 could be useful for marker-assisted selection and for pyramiding of Stb1 with other genes for resistance to M. graminicola in wheat.

Ascomycota↗

Salmonella enteritidis outbreak in Thailand: study by random amplified polymorphic DNA (RAPD) analysis.

An outbreak of Salmonella enteritidis in Thailand was reported in 1990. The majority of isolates were found in chicken and human throughout the country. The continuation of a high rate of spreading which is presently continuing prompted us to investigate possible clonal involvement in the outbreak. One hundred and twenty five isolates of S. enteritidis which were isolated between 1990-1993 were clonally identified by the technique of Random Amplified Polymorphic DNA (RAPD) analysis. Eight profiles were found indicating the presence of 8 clones, designated no. 1-8. The predominant clone was profile no. 4 which was encountered in 93.6% of tested isolates while the rest of the profile comprised only 0.8-1.6%. The predominant clone was distributed mainly in isolates from chickens and humans which is suggestive that the profile no. 4 is the major clone involved in this outbreak and that chickens were the source of S. enteritidis infection. The information from the Microbiology Laboratory at Ramathibodi Hospital revealed that nearly 40% of S. enteritidis were isolated from blood specimens. This may reflect the invasiveness of S. enteritidis in Thailand. We concluded that the outbreak involved the single clone, RAPD profile no. 4 which may disperse dominantly during the epidemic.

Animals↗

Vr2: a new apple scab resistance gene.

Reports from several European countries of the breakdown of the Vf resistance, the most frequently used source of resistance in breeding programs against apple scab, emphasize the urgency of diversifying the basis of apple scab resistance and pyramiding different apple scab resistances with the use of their associated molecular markers. GMAL 2473 is an apple scab resistant selection thought to carry the resistance gene Vr. We report the identification by BSA of three AFLP markers and one RAPD marker associated with the GMAL 2473 resistance gene. SSRs associated with the resistance gene were found by (1) identifying the linkage group carrying the apple scab resistance and (2) testing the SSRs previously mapped in the same region. One such SSR, CH02c02a, mapped on linkage group 2, co-segregates with the resistance gene. GAML 2473 was tested with molecular markers associated with other apple scab resistance genes, and accessions carrying known apple scab resistance genes were tested with the SSR linked to the resistance gene found in GMAL 2473. The results indicate that GMAL 2473 does not carry Vr, and that a new apple scab resistance gene, named Vr2, has been identified.

Ascomycota↗

Fungal colonization in neutropenic patients: a randomized study comparing itraconazole solution and amphotericin B solution.

We assessed the impact of prophylaxis with the oral itraconazole solution and amphotericin B solution on fungal colonization and infection in a randomized study among patients with hematological malignancies and neutropenia. Infecting and colonizing Candida strains of patients suffering from candidiasis were genotyped by random amplification of polymorphic DNA (RAPD) analysis. A total of 106 patients were evaluated in this study: 52 patients in the itraconazole and 54 in the amphotericin B arm. During neutropenia fungal colonization in the oropharynx occurred in 11 (19.6%) and 24 (40.6%) and in the rectum in 11 (19.6%) and 23 (38.9%) courses in the itraconazole and amphotericin B groups ( P<0.05), respectively. Candida albicans was the most prevalent species in both study groups. Mixed fungal colonization with Candida krusei and Candida glabrata was increased in the amphotericin B group, yet without clinical importance since infections were due to C. albicans. The occurrence of invasive candidiasis was significantly increased in multicolonized compared to monocolonized patients. In the amphotericin B group 20 and in the itraconazole group 2 neutropenic patients showed multicolonization with Candida spp. ( P<0.05). Overall fungal infections were 3.8% in the itraconazole and 14.8% in the amphotericin B group ( P<0.05). RAPD typing showed oropharynx strains involved in superficial infections in four of five patients. In all four patients with deep fungal infections, it appears that the colonizing rectum strains were identical to infecting strains of Candida spp. Itraconazole solution significantly reduced Candida colonization and infection compared to amphotericin B solution. Most patients remained infected with the colonized strains for the entire study period, irrespective of antifungal prophylaxis.

Amphotericin B↗

Evaluation of the resolving power of three different DNA fingerprinting methods to discriminate among isolates of a natural Rhizobium meliloti population.

In a comparative study, the PCR-based RAPD and ERIC fingerprint methods were evaluated for their resolving power to discriminate among 21 isolates of a natural Rhizobium meliloti population. PCR fingerprint patterns were analysed by using an automated laser fluorescent (ALF) DNA sequencer, thus allowing the automated on-line storage of data. Results obtained were compared to a classification system using insertion sequence (IS) fingerprinting. Both PCR fingerprint methods were comparable in their ability to resolve differences amongst Rh. meliloti isolates. Grouping of strains on the basis of their RAPD as well as their ERIC fingerprints correlated with grouping of strains according to their IS fingerprints. Moreover, strains displaying identical PCR patterns could be further differentiated according to their IS fingerprints, thus allowing a detailed insight into phylogenetic relationship among strains. The automated evaluation of strain-specific fingerprint patterns has the potential to become a valuable tool for studies of bacterial population genetics. Moreover, the rapid identification of single strains, e.g. pathogens in epidemiological studies seems feasible.

Bacterial Typing Techniques↗

Identification of F. o. cucumerinum and F. o. luffae by RAPD-generated DNA probes.

AIMS: To create a fast, sensitive and specific method for identifying Fusarium oxysporum f. sp. cucumerinum and F. o. luffae. METHODS AND RESULTS: Specific DNA bands were selected as probes from RAPD profiles of 13 formae speciales of F. oxysporum. The forma specialis-specific probe OPC18300c and OPC18520f could be used to identify F. o. cucumerinum and F. o. luffae by RAPD-PCR followed dot blot hybridization, respectively. CONCLUSIONS: A specific method for identifying F. o. cucumerinum and F. o. luffae was achieved. SIGNIFICANCE AND IMPACT OF THE STUDY: F. oxysporum formae speciales identification with a DNA probe can be relatively rapid and provides a method to identify the pathogen without host inoculation tests.

Bacterial Typing Techniques↗

Clonal infection with Actinobacillus actinomycetemcomitans following periodontal therapy.

Mechanical debridement results in a shift of the bacterial composition in the periodontal pocket on the species level. It is unknown, however, whether a clonal change within a species could lead to the emergence of strains with different levels of virulence. Therefore, in the present study, the genetic variability of Actinobacillus actinomycetemcomitans was assessed and strains identified which were associated with periodontal disease progression following periodontal therapy, i.e., refractory periodontitis. Twenty adult patients with untreated periodontitis and subgingival colonization of A. actinomycetemcomitans were randomly assigned to receive full-mouth scaling alone or scaling with an adjunctive antimicrobial therapy. Both groups received supportive periodontal therapy at 3, 6, 9, 12, 18, and 24 months. Subgingival plaque samples were taken at every visit; venous blood was obtained at 24 months only. A. actinomycetemcomitans isolates were typed by the RAPD method, and antibody reactivity against outer membrane proteins was assessed by immunoblot analysis. Eleven distinct RAPD patterns were found in 18 patients completing the study. All patients harbored only one A. actinomycetemcomitans genotype, and within each patient this genotype persisted throughout the 24-month observation period. No differences in the expression of antibody reactivity against outer membrane proteins were found between strains isolated at baseline and at 24 months. Three genotypes were associated with reduced survival rates of teeth without probing attachment loss of 2 mm or more. The results indicated that (i) most patients harbored only one A. actinomycetemcomitans genotype; (ii) the genotype persisted following therapy; and (iii) only some genotypes were associated with refractory periodontitis.

Adult↗

Comparison of PCR-based methods for typing Escherichia coli.

OBJECTIVE: To establish a library typing system appropriate for studying cross-transmission of Escherichia coli. METHODS: Eighteen epidemiologically unrelated isolates were genotyped by means of pulsed-field gel electrophoresis (PFGE), random amplified polymorphic DNA (RAPD), repetitive (rep) PCR, and fluorescent amplified fragment length polymorphism (AFLP). Fingerprints were analyzed either by Pearson correlation or, in the case of AFLP, by Dice coefficients employing the novel 'uncertain band' software tool from GelCompar II. During a nine-month period, 112 isolates taken from 93 patients hospitalized in five intensive care units were analyzed by use of the two most discriminative PCR typing methods. RESULTS: Genotyping by RAPD and rep-PCR revealed insufficient discrimination. Among 18 epidemiologically unrelated strains with 17 different PFGE patterns, IS3 rep-PCR and AFLP distinguished 10 and 18 types, respectively. Comparison of the different methods for analysis of AFLP fingerprints showed that the Dice coefficients, which ignore 'uncertain bands', offered the best concordance with visual interpretation. Consecutive isolates originating from the same patient differed in less than three fragments. CONCLUSIONS: AFLP analysis showed the highest discriminative capacity for PCR typing of E. coli isolates. Analysis of fingerprints employing the Dice coefficients proved the most efficient method for an automated software-based retrieval of visually indistinguishable genotypes in an AFLP fingerprint database.

Bacterial Typing Techniques↗

High annealing temperature-random amplified polymorphic DNA (HAT-RAPD) analysis of three paramphistome flukes from Thailand.

The rumen flukes of 37 cows (Bos indicus) from Chiang Mai and Lamphun provinces were investigated, and the overall prevalence of infection was 78.38% (29/37). Three species were found: Paramphistomum epiclitum, Orthocoelium streptocoelium, and Fischoederius elongatus with prevalences of infection of 75.68%, 48.65%, and 40.54%, respectively. Genomic DNA was amplified by polymerase chain reaction based on the high annealing temperature-random amplification of polymorphic DNA (HAT-RAPD) technique. Five random 10-mer oligonucleotide primers (OPA2, OPA4, OPB18, OPC9, and OPH11) produced distinct banding patterns in three species. No genetic variations in these three species were identified using 10 arbitary primers.

Animals↗

Development of RAPD protocol for typing of strains of lactic acid bacteria and enterococci.

A protocol for typing strains of lactic acid bacteria and enterococci based on randomly amplified polymorphic DNA (RAPD) fragments has been developed. Using a single 10-mer primer, fingerprints were achieved without the need to isolate genomic DNA. Different conditions of DNA release and amplification were investigated in order to obtain reproducible results and high discrimination among strains. This RAPD protocol was successfully applied for the typing of strains belonging to the species Lactobacillus acidophilus, Lact. helveticus, Lact. casei, Lact. reuteri, Lact. plantarum, Enterococcus faecalis, Ent. faecium and Streptococcus thermophilus.

Bacterial Typing Techniques↗

Helicobacter pylori detection in Chinese subjects: a comparison of two common DNA fingerprinting methods.

This study aims to demonstrate DNA diversity in Helicobacter pylori strains obtained from patients with peptic ulcer disease and compare the results from two DNA fingerprinting techniques. H. pylori strains (n = 42), collected from June 1996 to August 1999, were cultured from storage at -80 degrees C. DNA diversity was determined by the polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) analysis, and random amplified polymorphic DNA (RAPD)-PCR. Isolates showed a significant DNA sequence diversity by both methods. RAPD-PCR demonstrated 33 distinct strain-specific band patterns, whereas PCR-RFLP demonstrated six distinct restriction patterns. PCR-RFLP identified four of the 42 strains as mixed growth, compared with RAPD-PCR which did not reveal any co-colonisation. Diversity among H. pylori clinical isolates was demonstrated distinctly by both methods; however, RAPD-PCR showed greater discriminatory power in distinguishing between isolates.

Bacterial Typing Techniques↗

Application of random amplified polymorphic DNA analysis to differentiate strains of Salmonella typhi and other Salmonella species.

A Random Amplified Polymorphic DNA (RAPD) fingerprinting method was developed to differentiate isolates of Salmonella serotype typhi (S. typhi) and other Salmonella isolates. A panel of five primers was used to examine 63 isolates of Salm. typhi, including 56 strains isolated in Taiwan and seven strains obtained abroad. Twenty-one RAPD types were revealed using the RAPD fingerprinting method. An RAPD with primer 6032 yielded a polymorphism in a 350 bp fragment that differentiated the attenuated vaccine strain Salm. typhi Ty21a from the rest of the Salm. typhi strains. Strains of Salm. typhi were divided into five types with primer D14307. Primer D14307 also proved capable of discrimination among 65 other Salmonella isolates representing 42 different serotypes. The bacterial DNA used in this RAPD protocol was obtained using a commercially available DNA extraction kit (GeneReleaser). The DNA of various strains of Salmonella from this simple extraction procedure could be discriminated within a few hours using the RAPD technique.

Bacterial Typing Techniques↗