Search tips
Search criteria

Results 1-25 (39)

Clipboard (0)
Year of Publication
Document Types
1.  Analysis of 16S rRNA gene sequences and circulating cell-free DNA from plasma of chronic fatigue syndrome and non-fatigued subjects 
BMC Microbiology  2002;2:39.
The association of an infectious agent with chronic fatigue syndrome (CFS) has been difficult and is further complicated by the lack of a known lesion or diseased tissue. Cell-free plasma DNA could serve as a sentinel of infection and disease occurring throughout the body. This type of systemic sample coupled with broad-range amplification of bacterial sequences was used to determine whether a bacterial pathogen was associated with CFS. Plasma DNA from 34 CFS and 55 non-fatigued subjects was assessed to determine plasma DNA concentration and the presence of bacterial 16S ribosomal DNA (rDNA) sequences.
DNA was isolated from 81 (91%) of 89 plasma samples. The 55 non-fatigued subjects had higher plasma DNA concentrations than those with CFS (average 151 versus 91 ng) and more CFS subjects (6/34, 18%) had no detectable plasma DNA than non-fatigued subjects (2/55, 4%), but these differences were not significant. Bacterial sequences were detected in 23 (26%) of 89. Only 4 (14%) CFS subjects had 16S rDNA sequences amplified from plasma compared with 17 (32%) of the non-fatigued (P = 0.03). All but 1 of the 23 16S rDNA amplicon-positive subjects had five or more unique sequences present.
CFS subjects had slightly lower concentrations or no detectable plasma DNA than non-fatigued subjects. There was a diverse array of 16S rDNA sequences in plasma DNA from both CFS and non-fatigued subjects. There were no unique, previously uncharacterized or predominant 16S rDNA sequences in either CFS or non-fatigued subjects.
PMCID: PMC140017  PMID: 12498618
chronic fatigue syndrome; CFS; novel infectious agents; 16S rDNA
2.  Intrastrain and interstrain genetic variation within a paralogous gene family in Chlamydia pneumoniae 
BMC Microbiology  2002;2:38.
Chlamydia pneumoniae causes human respiratory diseases and has recently been associated with atherosclerosis. Analysis of the three recently published C. pneumoniae genomes has led to the identification of a new gene family (the Cpn 1054 family) that consists of 11 predicted genes and gene fragments. Each member encodes a polypeptide with a hydrophobic domain characteristic of proteins localized to the inclusion membrane.
Comparative analysis of this gene family within the published genome sequences provided evidence that multiple levels of genetic variation are evident within this single collection of paralogous genes. Frameshift mutations are found that result in both truncated gene products and pseudogenes that vary among isolates. Several genes in this family contain polycytosine (polyC) tracts either upstream or within the terminal 5' end of the predicted coding sequence. The length of the polyC stretch varies between paralogous genes and within single genes in the three genomes. Sequence analysis of genomic DNA from a collection of 12 C. pneumoniae clinical isolates was used to determine the extent of the variation in the Cpn 1054 gene family.
These studies demonstrate that sequence variability is present both among strains and within strains at several of the loci. In particular, changes in the length of the polyC tract associated with the different Cpn 1054 gene family members are common within each tested C. pneumoniae isolate. The variability identified within this newly described gene family may modulate either phase or antigenic variation and subsequent physiologic diversity within a C. pneumoniae population.
PMCID: PMC140016  PMID: 12460455
3.  High resolution, on-line identification of strains from the Mycobacterium tuberculosis complex based on tandem repeat typing 
BMC Microbiology  2002;2:37.
Currently available reference methods for the molecular epidemiology of the Mycobacterium tuberculosis complex either lack sensitivity or are still too tedious and slow for routine application. Recently, tandem repeat typing has emerged as a potential alternative. This report contributes to the development of tandem repeat typing for M. tuberculosis by summarising the existing data, developing additional markers, and setting up a freely accessible, fast, and easy to use, internet-based service for strain identification.
A collection of 21 VNTRs incorporating 13 previously described loci and 8 newly evaluated markers was used to genotype 90 strains from the M. tuberculosis complex (M. tuberculosis (64 strains), M. bovis (9 strains including 4 BCG representatives), M. africanum (17 strains)). Eighty-four different genotypes are defined. Clustering analysis shows that the M. africanum strains fall into three main groups, one of which is closer to the M. tuberculosis strains, and an other one is closer to the M. bovis strains. The resulting data has been made freely accessible over the internet to allow direct strain identification queries.
Tandem-repeat typing is a PCR-based assay which may prove to be a powerful complement to the existing epidemiological tools for the M. tuberculosis complex. The number of markers to type depends on the identification precision which is required, so that identification can be achieved quickly at low cost in terms of consumables, technical expertise and equipment.
PMCID: PMC140014  PMID: 12456266
4.  The expression, processing and localization of polymorphic membrane proteins in Chlamydia pneumoniae strain CWL029 
BMC Microbiology  2002;2:36.
Chlamydiae are obligate intracellular bacteria, which are important human pathogens. Genome sequences of C. trachomatis and C. pneumoniae have revealed the presence of a Chlamydia specific gene family encoding polymorphic outer membrane proteins, Pmps. In C. pneumoniae the family comprises twenty-one members, which are all transcribed. In the present study, the expression, processing and localisation of the sixteen full-length Pmps in C. pneumoniae strain CWL029 have been further investigated by two-dimensional gel electrophoresis and immunofluorescence microscopy.
Ten Pmps were identified in elementary bodies (EBs). Eight of these were investigated with respect to time dependent expression and all were found to be up-regulated between 36 and 48 hours post infection. Antibodies against Pmp6, 8, 10, 11 and 21 reacted with chlamydiae when infected cells were formalin fixed. Pmp6, Pmp20 and Pmp21 were found in cleaved forms, and the cleavage sites of Pmp6 and Pmp21 were identified.
The Pmps are heavily up-regulated at the time of conversion of RB to EB, and at least ten Pmps are present in EBs. Due to their reaction in formalin fixation it is likely that Pmp6, 8, 10, 11 and 21 are surface exposed. The identified cleavage sites of Pmp6 and Pmp21 are in agreement with the theory that the Pmps are autotransporters.
PMCID: PMC140015  PMID: 12453305
5.  Dynamics of success and failure in phage and antibiotic therapy in experimental infections 
BMC Microbiology  2002;2:35.
In 1982 Smith and Huggins showed that bacteriophages could be at least as effective as antibiotics in preventing mortality from experimental infections with a capsulated E. coli (K1) in mice. Phages that required the K1 capsule for infection were more effective than phages that did not require this capsule, but the efficacies of phages and antibiotics in preventing mortality both declined with time between infection and treatment, becoming virtually ineffective within 16 hours.
We develop quantitative microbiological procedures that (1) explore the in vivo processes responsible for the efficacy of phage and antibiotic treatment protocols in experimental infections (the Resistance Competition Assay, or RCA), and (2) survey the therapeutic potential of phages in vitro (the Phage Replication Assay or PRA). We illustrate the application and utility of these methods in a repetition of Smith and Huggins' experiments, using the E. coli K1 mouse thigh infection model, and applying treatments of phages or streptomycin.
1) The Smith and Huggins phage and antibiotic therapy results are quantitatively and qualitatively robust. (2) Our RCA values reflect the microbiological efficacies of the different phages and of streptomycin in preventing mortality, and reflect the decline in their efficacy with a delay in treatment. These results show specifically that bacteria become refractory to treatment over the term of infection. (3) The K1-specific and non-specific phages had similar replication rates on bacteria grown in broth (based on the PRA), but the K1-specific phage had markedly greater replication rates in mouse serum.
PMCID: PMC138797  PMID: 12453306
6.  Sulphonamide resistant commensal Neisseria with alterations in the dihydropteroate synthase can be isolated from carriers not exposed to sulphonamides 
BMC Microbiology  2002;2:34.
Development of sulphonamide resistance in Neisseria meningitidis has been suggested to involve horizontal DNA-transfer from a commensal Neisseria species. In this study, we isolated commensal Neisseria from throat specimens and examined the isolates with respect to sulphonamide resistance.
Three resistant clones were identified and the resistance phenotype could be explained by amino acid variations in their dihydropteroate synthase, the target molecule for sulphonamides. Some of these variations occurred in positions corresponding to previously detected variations in resistant N. meningitidis.
Sulphonamide resistant commensal Neisseria were isolated from an environment not exposed to sulphonamides, suggesting that resistant Neisseria has become a natural part of the commensal throat flora.
PMCID: PMC138796  PMID: 12435277
7.  Colony shape as a genetic trait in the pattern-forming Bacillus mycoides 
BMC Microbiology  2002;2:33.
Bacillus mycoides Flügge, a Gram-positive, non-motile soil bacterium assigned to Bacillus cereus group, grows on agar as chains of cells linked end to end, forming radial filaments curving clock- or counter-clockwise (SIN or DX morphotypes). The molecular mechanism causing asymmetric curving is not known: our working hypothesis considers regulation of filamentous growth as the prerequisite for these morphotypes.
SIN and DX strains isolated from the environment were classified as B. mycoides by biochemical and molecular biology tests. Growth on agar of different hardness and nutrient concentration did not abolish colony patterns, nor was conversion between SIN and DX morphotypes ever noticed. A number of morphotype mutants, all originating from one SIN strain, were obtained. Some lost turn direction becoming fluffy, others became round and compact. All mutants lost wild type tight aggregation in liquid culture. Growth on agar was followed by microscopy, exploring the process of colony formation and details of cell divisions. A region of the dcw (division cell wall) cluster, including ftsQ, ftsA, ftsZ and murC, was sequenced in DX and SIN strains as a basis for studying cell division. This confirmed the relatedness of DX and SIN strains to the B. cereus group.
DX and SIN asymmetric morphotypes stem from a close but not identical genomic context. Asymmetry is established early during growth on agar. Wild type bacilli construct mostly uninterrupted filaments with cells dividing at the free ends: they "walk" longer distances compared to mutants, where enhanced frequency of cell separation produces new growing edges resulting in round compact colonies.
PMCID: PMC138795  PMID: 12429070
8.  Recognition of secretory proteins in Escherichia coli requires signals in addition to the signal sequence and slow folding 
BMC Microbiology  2002;2:32.
The Sec-dependent protein export apparatus of Escherichia coli is very efficient at correctly identifying proteins to be exported from the cytoplasm. Even bacterial strains that carry prl mutations, which allow export of signal sequence-defective precursors, accurately differentiate between cytoplasmic and mutant secretory proteins. It was proposed previously that the basis for this precise discrimination is the slow folding rate of secretory proteins, resulting in binding by the secretory chaperone, SecB, and subsequent targeting to translocase. Based on this proposal, we hypothesized that a cytoplasmic protein containing a mutation that slows its rate of folding would be recognized by SecB and therefore targeted to the Sec pathway. In a Prl suppressor strain the mutant protein would be exported to the periplasm due to loss of ability to reject non-secretory proteins from the pathway.
In the current work, we tested this hypothesis using a mutant form of λ repressor that folds slowly. No export of the mutant protein was observed, even in a prl strain. We then examined binding of the mutant λ repressor to SecB. We did not observe interaction by either of two assays, indicating that slow folding is not sufficient for SecB binding and targeting to translocase.
These results strongly suggest that to be targeted to the export pathway, secretory proteins contain signals in addition to the canonical signal sequence and the rate of folding.
PMCID: PMC137694  PMID: 12427258
9.  Detection and characterization of the S. typhimurium HilA protein 
BMC Microbiology  2002;2:31.
Virulence genes on Salmonella pathogenicity island 1 (SPI1) are coordinately regulated by HilA, a member of the OmpR/ToxR family of transcription factors. Although a great deal is known about the complex regulation of hilA gene expression, very little is known about the HilA protein.
In order to detect and localize the HilA protein in S. typhimurium, we raised polyclonal antiserum against purified His-tagged HilA. This allowed us to study the effect of environmental conditions on the production of HilA. We also used the antiserum to examine the fractionation properties and SDS-PAGE mobility of native HilA. Our results indicate that S. typhimurium initiates translation of HilA from the first AUG codon in the hilA open-reading frame (ORF), producing a soluble 553 amino acid (63 kDa) protein product.
Materials and methods are now available to study the environmental regulation of the HilA protein in S. typhimurium. Our results also indicate that future in vitro studies of the interaction between HilA and DNA should utilize soluble preparations of HilA. Previous analyses used preparations of HilA in which the protein fractionated with the membrane, greatly limiting the types of experiments that could be conducted.
PMCID: PMC134461  PMID: 12396235
10.  Mycosin-1, a subtilisin-like serine protease of Mycobacterium tuberculosis, is cell wall-associated and expressed during infection of macrophages 
BMC Microbiology  2002;2:30.
Exported proteases are commonly associated with virulence in bacterial pathogens, yet there is a paucity of information regarding their role in Mycobacterium tuberculosis. There are five genes (mycP1-5) present within the genome of Mycobacterium tuberculosis H37Rv that encode a family of secreted, subtilisin-like serine proteases (the mycosins). The gene mycP1 (encoding mycosin-1) was found to be situated 3700 bp (four ORF's) from the RD1 deletion region in the genome of the attenuated vaccine strain M. bovis BCG (bacille de Calmette et Guérin) and was selected for further analyses due to the absence of expression in this organism.
Full-length, 50 kDa mycosin-1 was observed in M. tuberculosis cellular lysates, whereas lower-molecular-weight species were detected in culture filtrates. A similar lower-molecular-weight species was also observed during growth in macrophages. Mycosin-1 was localized to the membrane and cell wall fractions in M. tuberculosis by Western blotting, and to the cell envelope by electron microscopy. Furthermore, M. tuberculosis culture filtrates were shown to contain a proteolytic activity inhibited by mixed serine/cysteine protease inhibitors and activated by Ca2+, features typical of the subtilisins.
Mycosin-1 is an extracellular protein that is membrane- and cell wall-associated, and is shed into the culture supernatant. The protein is expressed after infection of macrophages and is subjected to proteolytic processing. Although proteolytically active mycosin-1 could not be generated recombinantly, serine protease activity containing features typical of the subtilisins was detected in M. tuberculosis culture filtrates.
PMCID: PMC131053  PMID: 12366866
Mycosin; Subtilisin-like serine protease; Mycobacterium tuberculosis; Macrophage infection; RD1 deletion region
11.  Physiological function of the maltose operon regulator, MalR, in Lactococcus lactis 
BMC Microbiology  2002;2:28.
Maltose metabolism is initiated by an ATP-dependent permease system in Lactococcus lactis. The subsequent degradation of intracellular maltose is performed by the concerted action of Pi-dependent maltose phosphorylase and β-phosphoglucomutase. In some Gram-positive bacteria, maltose metabolism is regulated by a maltose operon regulator (MalR), belonging to the LacI-GalR family of transcriptional regulators. A gene presumed to encode MalR has been found directly downstream the maltose phosphorylase-encoding gene, malP in L. lactis. The purpose of this study was to investigate the physiological role of the MalR protein in maltose metabolism in L. lactis.
A L. lactis ssp. lactis mutant, TMB5004, deficient in the putative MalR protein, was physiologically characterised. The mutant was not able to ferment maltose, while its capability to grow on glucose as well as trehalose was not affected. The activity of maltose phosphorylase and β-phosphoglucomutase was not affected in the mutant. However, the specific maltose uptake rate in the wild type was, at its lowest, five times higher than in the mutant. This difference in maltose uptake increased as the maltose concentration in the assay was increased.
According to amino acid sequence similarities, the presumed MalR is a member of the LacI-GalR family of transcriptional regulators. Due to the suggested activating effect on maltose transport and absence of effect on the activities of maltose phosphorylase and β-phosphoglucomutase, MalR of L. lactis is considered rather as an activator than a repressor.
PMCID: PMC130022  PMID: 12296976
12.  Hepatitis C virus whole genome position weight matrix and robust primer design 
BMC Microbiology  2002;2:29.
The high degree of sequence heterogeneity found in Hepatitis C virus (HCV) isolates, makes robust nucleic acid-based assays difficult to generate. Polymerase chain reaction based techniques, require efficient and specific sequence recognition. Generation of robust primers capable of recognizing a wide range of isolates is a difficult task.
A position weight matrix (PWM) and a consensus sequence were built for each region of HCV and subsequently assembled into a whole genome consensus sequence and PWM. For each of the 10 regions, the number of occurrences of each base at a given position was compiled. These counts were converted to frequencies that were used to calculate log odds scores. Using over 100 complete and 14,000 partial HCV genomes from GenBank, a consensus HCV genome sequence was generated along with a PWM reflecting heterogeneity at each position. The PWM was used to identify the most conserved regions for primer design.
This approach allows rapid identification of conserved regions for robust primer design and is broadly applicable to sets of genomes with all levels of genetic heterogeneity.
PMCID: PMC130017  PMID: 12323075
13.  Bacterial discrimination by means of a universal array approach mediated by LDR (ligase detection reaction) 
BMC Microbiology  2002;2:27.
PCR amplification of bacterial 16S rRNA genes provides the most comprehensive and flexible means of sampling bacterial communities. Sequence analysis of these cloned fragments can provide a qualitative and quantitative insight of the microbial population under scrutiny although this approach is not suited to large-scale screenings. Other methods, such as denaturing gradient gel electrophoresis, heteroduplex or terminal restriction fragment analysis are rapid and therefore amenable to field-scale experiments. A very recent addition to these analytical tools is represented by microarray technology.
Here we present our results using a Universal DNA Microarray approach as an analytical tool for bacterial discrimination. The proposed procedure is based on the properties of the DNA ligation reaction and requires the design of two probes specific for each target sequence. One oligo carries a fluorescent label and the other a unique sequence (cZipCode or complementary ZipCode) which identifies a ligation product. Ligated fragments, obtained in presence of a proper template (a PCR amplified fragment of the 16s rRNA gene) contain either the fluorescent label or the unique sequence and therefore are addressed to the location on the microarray where the ZipCode sequence has been spotted. Such an array is therefore "Universal" being unrelated to a specific molecular analysis. Here we present the design of probes specific for some groups of bacteria and their application to bacterial diagnostics.
The combined use of selective probes, ligation reaction and the Universal Array approach yielded an analytical procedure with a good power of discrimination among bacteria.
PMCID: PMC128835  PMID: 12243651
14.  HIV-1 expression induces cyclin D1 expression and pRb phosphorylation in infected podocytes: cell-cycle mechanisms contributing to the proliferative phenotype in HIV-associated nephropathy 
BMC Microbiology  2002;2:26.
The aberrant cell-cycle progression of HIV-1-infected kidney cells plays a major role in the pathogenesis of HIV-associated nephropathy, however the mechanisms whereby HIV-1 induces infected glomerular podocytes or infected tubular epithelium to exit quiescence are largely unknown. Here, we ask whether the expression of HIV-1 genes in infected podocytes induces cyclin D1 and phospho-pRb (Ser780) expression, hallmarks of cyclin D1-mediated G1 → S phase progression.
We assessed cyclin D1 and phospho-pRb (Ser780) expression in two well-characterized models of HIV-associated nephropathy pathogenesis: HIV-1 infection of cultured podocytes and HIV-1 transgenic mice (Tg26). Compared to controls, cultured podocytes expressing HIV-1 genes, and podocytes and tubular epithelium from hyperplastic nephrons in Tg26 kidneys, had increased levels of phospho-pRb (Ser780), a target of active cyclin D1/cyclin-dependent kinase-4/6 known to promote G1 → S phase progression. HIV-1-infected podocytes showed markedly elevated cyclin D1 mRNA and cyclin D1 protein, the latter of which did not down-regulate during cell-cell contact or differentiation, suggesting post-transcriptional stabilization of cyclin D1 protein levels by HIV-1. The selective suppression of HIV-1 transcription by the cyclin-dependent kinase inhibitor, flavopiridol, abrogated cyclin D1 expression, underlying the requirement for HIV-1 encoded products to induce cyclin D1. Indeed, HIV-1 virus deleted of nef failed to induce cyclin D1 mRNA to the level of other single gene mutant viruses.
HIV-1 expression induces cyclin D1 and phospho-pRb (Ser780) expression in infected podocytes, suggesting that HIV-1 activates cyclin D1-dependent cell-cycle mechanisms to promote proliferation of infected renal epithelium.
PMCID: PMC128834  PMID: 12241561
16.  Growth of Helicobacter pylori in a long spiral form does not alter expression of immunodominant proteins 
BMC Microbiology  2002;2:24.
We have previously reported that altered culture conditions (a broth media with shaking) could induce a strain of Helicobacter pylori to assume a long spiral morphology resembling that described for Helicobacter heilmannii. The present study was initiated to determine if other strains of H. pylori could be induced to assume that morphology and if doing so would alter the expression of immunodominant proteins.
The six strains used in this study were American Type Culture Collection 43504, 43579, 49503, 51652, and 51653, and Sydney Strain I. Each strain was grown on solid media and in broth culture using conditions previously shown to induce the long spiral morphology in strain 43504. DNA from each was subjected to urease gene fingerprint analysis. Results of the molecular analysis showed identical fingerprint patterns for each strain independent of culture source, indicating that only a single strain was present in each culture. Expression of immunodominant proteins was assessed by SDS polyacrylamide gel electrophoresis and Western blotting with hyperimmune rabbit anti H. pylori sera or serum from an H. pylori infected patient. Analysis of protein profiles revealed some variation between strains but no significant differences associated with morphologic alterations.
These results indicate that growth of H. pylori in a long spiral form does not affect expression of immunodominant proteins, thus in vivo growth in the long spiral form (not documented to date) would not be distinguishable by serology.
PMCID: PMC126220  PMID: 12213186
17.  Diversity and abundance of bacteria in an underground oil-storage cavity 
BMC Microbiology  2002;2:23.
Microorganisms inhabiting subterranean oil fields have recently attracted much attention. Since intact groundwater can easily be obtained from the bottom of underground oil-storage cavities without contamination by surface water, studies on such oil-storage cavities are expected to provide valuable information to understand microbial ecology of subterranean oil fields.
DNA was extracted from the groundwater obtained from an oil-storage cavity situated at Kuji in Iwate, Japan, and 16S rRNA gene (16S rDNA) fragments were amplified by PCR using combinations of universal and Bacteria-specific primers. The sequence analysis of 154 clones produced 31 different bacterial sequence types (a unique clone or group of clones with sequence similarity of > 98). Major sequence types were related to Desulfotomaculum, Acetobacterium, Desulfovibrio, Desulfobacula, Zoogloea and Thiomicrospira denitrificans. The abundance in the groundwater of bacterial populations represented by these major sequence types was assessed by quantitative competitive PCR using specific primers, showing that five rDNA types except for that related to Desulfobacula shared significant proportions (more than 1%) of the total bacterial rDNA.
Bacteria inhabiting the oil-storage cavity were unexpectedly diverse. A phylogenetic affiliation of cloned 16S rDNA sequences suggests that bacteria exhibiting different types of energy metabolism coexist in the cavity.
PMCID: PMC126219  PMID: 12197947
18.  Measurement of microbial activity in soil by colorimetric observation of in situ dye reduction: an approach to detection of extraterrestrial life 
BMC Microbiology  2002;2:22.
Detecting microbial life in extraterrestrial locations is a goal of space exploration because of ecological and health concerns about possible contamination of other planets with earthly organisms, and vice versa. Previously we suggested a method for life detection based on the fact that living entities require a continual input of energy accessed through coupled oxidations and reductions (an electron transport chain). We demonstrated using earthly soils that the identification of extracted components of electron transport chains is useful for remote detection of a chemical signature of life. The instrument package developed used supercritical carbon dioxide for soil extraction, followed by chromatography or electrophoresis to separate extracted compounds, with final detection by voltammetry and tandem mass-spectrometry.
Here we used Earth-derived soils to develop a related life detection system based on direct observation of a biological redox signature. We measured the ability of soil microbial communities to reduce artificial electron acceptors. Living organisms in pure culture and those naturally found in soil were shown to reduce 2,3-dichlorophenol indophenol (DCIP) and the tetrazolium dye 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide inner salt (XTT). Uninoculated or sterilized controls did not reduce the dyes. A soil from Antarctica that was determined by chemical signature and DNA analysis to be sterile also did not reduce the dyes.
Observation of dye reduction, supplemented with extraction and identification of only a few specific signature redox-active biochemicals such as porphyrins or quinones, provides a simplified means to detect a signature of life in the soils of other planets or their moons.
PMCID: PMC119848  PMID: 12150716
19.  Identification of cultured isolates of clinically important yeast species using fluorescent fragment length analysis of the amplified internally transcribed rRNA spacer 2 region 
BMC Microbiology  2002;2:21.
The number of patients with yeast infection has increased during the last years. Also the variety of species of clinical importance has increased. Correct species identification is often important for efficient therapy, but is currently mostly based on phenotypic features and is sometimes time-consuming and depends largely on the expertise of technicians. Therefore, we evaluated the feasibility of PCR-based amplification of the internally transcribed spacer region 2 (ITS2), followed by fragment size analysis on the ABI Prism 310 for the identification of clinically important yeasts.
A rapid DNA-extraction method, based on simple boiling-freezing was introduced. Of the 26 species tested, 22 could be identified unambiguously by scoring the length of the ITS2-region. No distinction could be made between the species Trichosporon asteroides and T. inkin or between T. mucoides and T. ovoides. The two varieties of Cryptococcus neoformans (var. neoformans and var. gattii) could be differentiated from each other due to a one bp length difference of the ITS2 fragment. The three Cryptococcus laurentii isolates were split into two groups according to their ITS2-fragment lengths, in correspondence with the phylogenetic groups described previously. Since the obtained fragment lengths compare well to those described previously and could be exchanged between two laboratories, an internationally usable library of ITS2 fragment lengths can be constructed.
The existing ITS2 size based library enables identification of most of the clinically important yeast species within 6 hours starting from a single colony and can be easily updated when new species are described. Data can be exchanged between laboratories.
PMCID: PMC117793  PMID: 12139769
20.  Epstein-Barr virus reactivation after superinfection of the BJAB-B1 and P3HR-1 cell lines with cytomegalovirus 
BMC Microbiology  2002;2:20.
Studies examining herpesvirus-herpesvirus (cytomegalovirus (CMV)-Epstein-Barr virus (EBV)) interactions are limited, and many of the studies have been clinical observations suggesting such an interaction exists. This report aims to examine the in vitro susceptibilities of BJAB-B1 and P3HR-1 cells (EBV positive Burkitt's lymphoma B-cell lines) to a CMV superinfection; and show that EBV reactivation occurs after CMV superinfects these cell lines.
The BJAB-B1 and P3HR-1 cells were observed to be susceptible to a CMV superinfection by the detection of the major immediate early (MIE) viral transcript and protein (p52) expression. The BZLF1 transcript was observed in both cell lines superinfected with CMV, indicating EBV reactivation. BZLF1 protein was observed in the BJAB-B1 cells. Antigen detection was not performed in the P3HR-1 cells.
The results from the in vitro superinfections support the in vivo studies suggesting a CMV infection is related to an EBV reactivation and suggests that CMV may be important as a co-factor in EBV pathogenesis in the immunocompromised patient.
PMCID: PMC119847  PMID: 12137568
21.  Avian papillomaviruses: the parrot Psittacus erithacus papillomavirus (PePV) genome has a unique organization of the early protein region and is phylogenetically related to the chaffinch papillomavirus 
BMC Microbiology  2002;2:19.
An avian papillomavirus genome has been cloned from a cutaneous exophytic papilloma from an African grey parrot (Psittacus erithacus). The nucleotide sequence, genome organization, and phylogenetic position of the Psittacus erithacus papillomavirus (PePV) were determined. This PePV sequence represents the first complete avian papillomavirus genome defined.
The PePV genome (7304 basepairs) differs from other papillomaviruses, in that it has a unique organization of the early protein region lacking classical E6 and E7 open reading frames. Phylogenetic comparison of the PePV sequence with partial E1 and L1 sequences of the chaffinch (Fringilla coelebs) papillomavirus (FPV) reveals that these two avian papillomaviruses form a monophyletic cluster with a common branch that originates near the unresolved center of the papillomavirus evolutionary tree.
The PePV genome has a unique layout of the early protein region which represents a novel prototypic genomic organization for avian papillomaviruses. The close relationship between PePV and FPV, and between their Psittaciformes and Passeriformes hosts, supports the hypothesis that papillomaviruses have co-evolved and speciated together with their host species throughout evolution.
PMCID: PMC117442  PMID: 12110158
22.  Determination of PCR efficiency in chelex-100 purified clinical samples and comparison of real-time quantitative PCR and conventional PCR for detection of Chlamydia pneumoniae 
BMC Microbiology  2002;2:17.
Chlamydia pneumoniae infection has been detected by serological methods, but PCR is gaining more interest. A number of different PCR assays have been developed and some are used in combination with serology for diagnosis. Real-time PCR could be an attractive new PCR method; therefore it must be evaluated and compared to conventional PCR methods.
We compared the performance of a newly developed real-time PCR with a conventional PCR method for detection of C. pneumoniae. The PCR methods were tested on reference samples containing C. pneumoniae DNA and on 136 nasopharyngeal samples from patients with a chronic cough. We found the same detection limit for the two methods and that clinical performance was equal for the real-time PCR and for the conventional PCR method, although only three samples tested positive. To investigate whether the low prevalence of C. pneumoniae among patients with a chronic cough was caused by suboptimal PCR efficiency in the samples, PCR efficiency was determined based on the real-time PCR. Seventeen of twenty randomly selected clinical samples had a similar PCR efficiency to samples containing pure genomic C. pneumoniae DNA.
These results indicate that the performance of real-time PCR is comparable to that of conventional PCR, but that needs to be confirmed further. Real-time PCR can be used to investigate the PCR efficiency which gives a rough estimate of how well the real-time PCR assay works in a specific sample type. Suboptimal PCR efficiency of PCR is not a likely explanation for the low positivity rate of C. pneumoniae in patients with a chronic cough.
PMCID: PMC117782  PMID: 12106506
23.  Genomic comparisons among Escherichia coli strains B, K-12, and O157:H7 using IS elements as molecular markers 
BMC Microbiology  2002;2:18.
Insertion Sequence (IS) elements are mobile genetic elements widely distributed among bacteria. Their activities cause mutations, promoting genetic diversity and sometimes adaptation. Previous studies have examined their copy number and distribution in Escherichia coli K-12 and natural isolates. Here, we map most of the IS elements in E. coli B and compare their locations with the published genomes of K-12 and O157:H7.
The genomic locations of IS elements reveal numerous differences between B, K-12, and O157:H7. IS elements occur in hok-sok loci (homologous to plasmid stabilization systems) in both B and K-12, whereas these same loci lack IS elements in O157:H7. IS elements in B and K-12 are often found in locations corresponding to O157:H7-specific sequences, which suggests IS involvement in chromosomal rearrangements including the incorporation of foreign DNA. Some sequences specific to B are identified, as reported previously for O157:H7. The extent of nucleotide sequence divergence between B and K-12 is <2% for most sequences adjacent to IS elements. By contrast, B and K-12 share only a few IS locations besides those in hok-sok loci. Several phenotypic features of B are explained by IS elements, including differential porin expression from K-12.
These data reveal a high level of IS activity since E. coli B, K-12, and O157:H7 diverged from a common ancestor, including IS association with deletions and incorporation of horizontally acquired genes as well as transpositions. These findings indicate the important role of IS elements in genome plasticity and divergence.
PMCID: PMC117601  PMID: 12106505
24.  Interaction of the Yersinia pestis type III regulatory proteins LcrG and LcrV occurs at a hydrophobic interface 
BMC Microbiology  2002;2:16.
Secretion of anti-host proteins by Yersinia pestis via a type III mechanism is not constitutive. The process is tightly regulated and secretion occurs only after an appropriate signal is received. The interaction of LcrG and LcrV has been demonstrated to play a pivotal role in secretion control. Previous work has shown that when LcrG is incapable of interacting with LcrV, secretion of anti-host proteins is prevented. Therefore, an understanding of how LcrG interacts with LcrV is required to evaluate how this interaction regulates the type III secretion system of Y. pestis. Additionally, information about structure-function relationships within LcrG is necessary to fully understand the role of this key regulatory protein.
In this study we demonstrate that the N-terminus of LcrG is required for interaction with LcrV. The interaction likely occurs within a predicted amphipathic coiled-coil domain within LcrG. Our results demonstrate that the hydrophobic face of the putative helix is required for LcrV interaction. Additionally, we demonstrate that the LcrG homolog, PcrG, is incapable of blocking type III secretion in Y. pestis. A genetic selection was utilized to obtain a PcrG variant capable of blocking secretion. This PcrG variant allowed us to locate a region of LcrG involved in secretion blocking.
Our results demonstrate that LcrG interacts with LcrV via hydrophobic interactions located in the N-terminus of LcrG within a predicted coiled-coil motif. We also obtained preliminary evidence that the secretion blocking activity of LcrG is located between amino acids 39 and 53.
PMCID: PMC117220  PMID: 12102728
25.  Detection of Mycobacterium avium subspecies paratuberculosis specific IS900 insertion sequences in bulk-tank milk samples obtained from different regions throughout Switzerland 
BMC Microbiology  2002;2:15.
Since Mycobacterium avium subspecies paratuberculosis (MAP) was isolated from intestinal tissue of a human patient suffering Crohn's disease, a controversial discussion exists whether MAP have a role in the etiology of Crohn's disease or not. Raw milk may be a potential vehicle for the transmission of MAP to human population. In a previous paper, we have demonstrated that MAP are found in raw milk samples obtained from a defined region in Switzerland. The aim of this work is to collect data about the prevalence of MAP specific IS900 insertion sequence in bulk-tank milk samples in different regions of Switzerland. Furthermore, we examined eventual correlation between the presence of MAP and the somatic cell counts, the total colony counts and the presence of Enterobacteriaceae.
273 (19.7%) of the 1384 examined bulk-tank milk samples tested IS900 PCR-positive. The prevalence, however, in the different regions of Switzerland shows significant differences and ranged from 1.7% to 49.2%. Furthermore, there were no statistically significant (p >> 0.05) differences between the somatic cell counts and the total colony counts of PCR-positive and PCR-negative milk samples. Enterobacteriaceae occur as often in IS900 PCR-positive as in PCR-negative milk samples.
This is the first study, which investigates the prevalence of MAP in bulk-tank milk samples all over Switzerland and infers the herd-level prevalence of MAP infection in dairy herds. The prevalence of 19.7% IS900 PCR-positive bulk-milk samples shows a wide distribution of subclinical MAP-infections in dairy stock in Switzerland. MAP can therefore often be transmitted to humans by raw milk consumption.
PMCID: PMC117219  PMID: 12097144

Results 1-25 (39)