SEARCH · PubMed Health

Results for “MLST”

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

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

At least 361 records · Page 20Linked to original sources

PubMed2004

Hypermutable Haemophilus influenzae with mutations in mutS are found in cystic fibrosis sputum.

Hypermutable bacterial pathogens exist at surprisingly high prevalence and benefit bacterial populations by promoting adaptation to selective environments, including resistance to antibiotics. Five hundred Haemophilus influenzae isolates were screened for an increased frequency of mutation to resistance to rifampicin, nalidixic acid and spectinomycin: of the 14 hypermutable isolates identified, 12 were isolated from cystic fibrosis (CF) sputum. Analysis by enterobacterial repetitive intergenic consensus (ERIC)-PCR and ribotyping identified eight distinct genetic fingerprints. The hypermutable phenotype of seven of the eight unique isolates was associated with polymorphisms in conserved sites of mutS. Four of the mutant mutS alleles were cloned and failed to complement the mutator phenotype of a mutS : : TSTE mutant of H. influenzae strain Rd KW20. Antibiotic susceptibility testing of the hypermutators identified one beta-lactamase-negative ampicillin-resistant (BLNAR) isolate with two isolates producing beta-lactamase. Six isolates from the same patient with CF, with the same genetic fingerprint, were clonal by multilocus sequence typing (MLST). In this clone, there was an evolution to higher MIC values for the antibiotics administered to the patient during the period in which the strains were isolated. Hypermutable H. influenzae with mutations in mutS are prevalent, particularly in the CF lung environment, and may be selected for and maintained by antibiotic pressure.

Adenosine Triphosphatases↗

PubMed2004

A virulence-associated gene microarray: a tool for investigation of the evolution and pathogenic potential of Staphylococcus aureus.

An oligonucleotide probe microarray for investigation of the evolution of epidemic Staphylococcus aureus strains has been constructed. The array comprises 383 probes based on virulence-associated genes present in four key strains. Twelve strains including seven for which the complete chromosomal nucleotide sequence was available were tested on the array. Twenty-six per cent of the probes were able to differentiate between strains to give a minimum of two gene differences between pairs. A gene difference distance tree based on the array data had approximately the same topology as one prepared using concatenated MLST sequences. Differences in the topologies of these trees were found to indicate that large-scale recombination events had occurred during the evolution of the species. One such occurrence appears to have been a key event in the genesis of the EMRSA-15 clone (ST22) that currently represents the most prevalent methicillin-resistant S. aureus (MRSA) in the UK.

Bacterial Proteins↗

PubMed2005

Emetic toxin formation of Bacillus cereus is restricted to a single evolutionary lineage of closely related strains.

An in-depth polyphasic approach was applied to study the population structure of the human pathogen Bacillus cereus. To assess the intraspecific biodiversity of this species, which is the causative agent of gastrointestinal diseases, a total of 90 isolates from diverse geographical origin were studied by genetic [M13-PCR, random amplification of polymorphic DNA (RAPD), multilocus sequence typing (MLST)] and phenetic [Fourier transform Infrared (FTIR), protein profiling, biochemical assays] methods. The strain set included clinical strains, isolates from food remnants connected to outbreaks, as well as isolates from diverse food environments with a well documented strain history. The phenotypic and genotypic analysis of the compiled panel of strains illustrated a considerable diversity among B. cereus connected to diarrhoeal syndrome and other non-emetic food strains, but a very low diversity among emetic isolates. Using all typing methods, cluster analysis revealed a single, distinct cluster of emetic B. cereus strains. The isolates belonging to this cluster were neither able to degrade starch nor could they ferment salicin; they did not possess the genes encoding haemolysin BL (Hbl) and showed only weak or no haemolysis. In contrast, haemolytic-enterotoxin-producing B. cereus strains showed a high degree of heterogeneity and were scattered over different clusters when different typing methods were applied. These data provide evidence for a clonal population structure of cereulide-producing emetic B. cereus and indicate that emetic strains represent a highly clonal complex within a potentially panmictic or weakly clonal background population structure of the species. It may have originated only recently through acquisition of specific virulence factors such as the cereulide synthetase gene.

Bacillus cereus↗

PubMed2005

Multilocus sequence analysis and comparative evolution of virulence-associated genes and housekeeping genes of Clostridium difficile.

A multilocus sequence analysis of ten virulence-associated genes was performed to study the genetic relationships between 29 Clostridium difficile isolates of various origins, hosts and clinical presentations, and selected from the main lineages previously defined by multilocus sequence typing (MLST) of housekeeping genes. Colonization-factor-encoding genes (cwp66, cwp84, fbp68, fliC, fliD, groEL and slpA), toxin A and B genes (tcdA and tcdB), and the toxin A and B positive regulator gene (tcdD) were investigated. Binary toxin genes (cdtA and cdtB) were also detected, and internal fragments were sequenced for positive isolates. Virulence-associated genes exhibited a moderate polymorphism, comparable to the polymorphism of housekeeping genes, whereas cwp66 and slpA genes appeared highly polymorphic. Isolates recovered from human pseudomembranous colitis cases did not define a specific lineage. The presence of binary toxin genes, detected in five of the 29 isolates (17 %), was also not linked to clinical presentation. Conversely, toxigenic A-B+ isolates defined a very homogeneous lineage, which is distantly related to other isolates. By clustering analysis, animal isolates were intermixed with human isolates. Multilocus sequence analysis of virulence-associated genes is consistent with a clonal population structure for C. difficile and with the lack of host specificity. The data suggest a co-evolution of several of the virulence-associated genes studied (including toxins A and B and the binary toxin genes) with housekeeping genes, reflecting the genetic background of C. difficile, whereas flagellin, cwp66 and slpA genes may undergo recombination events and/or environmental selective pressure.

Alleles↗

PubMed2005

Intragenomic recombination in the highly leukotoxic JP2 clone of Actinobacillus actinomycetemcomitans.

The highly leukotoxic JP2 clone of Actinobacillus actinomycetemcomitans is strongly associated with aggressive periodontitis in adolescents of African descent. DNA fingerprinting using the frequently cutting restriction enzyme MspI and multilocus sequence typing (MLST) showed that five strains of this clone were genetically virtually identical, although ribotyping of the six rrn genes and EcoRI RFLP analysis of the seven IS150-like elements revealed differences. PCR analyses demonstrated that these multi-copy sequences are subject to intragenomic homologous recombination, resulting in translocations or large inversions. The genome rearrangements were reflected in differences among 25 strains representing the JP2 clone in DNA fingerprinting using the rare-cutting restriction enzyme XhoI and resolved by PFGE. XhoI DNA fingerprinting provides a tool for studying local epidemiology, including transmission of this particularly pathogenic clone of A. actinomycetemcomitans.

Actinobacillus Infections↗

PubMed2006

Phylogenetic analysis of Bacillus cereus isolates from severe systemic infections using multilocus sequence typing scheme.

Bacillus cereus strains from cases of severe or lethal systemic infections, including respiratory symptoms cases, were analyzed using multilocus sequence typing scheme of B. cereus MLST database. The isolates were evenly distributed between the two main clades, and 60% of them had allele profiles new to the database. Half of the collection's strains clustered in a lineage neighboring Bacillus anthracis phylogenetic origin. Strains from lethal cases with respiratory symptoms were allocated in both main clades. This is the first report of strains causing respiratory symptoms to be identified as genetically distant from B. anthracis. The phylogenetic location of the presented here strains was compared with all previously submitted to the database isolates from systemic infections, and were found to appear in the same clusters where clinical isolates from other studies had been assigned. It seems that the pathogenic strains are forming clusters on the phylogenetic tree.

Adult↗

PubMed2007

Multilocus sequence typing of Campylobacter jejuni isolates from New South Wales, Australia.

AIMS: Multilocus sequence typing (MLST) was used to examine the diversity and population structure of Campylobacter jejuni isolates associated with sporadic cases of gastroenteritis in Australia, and to compare these isolates with those from elsewhere. METHODS AND RESULTS: A total of 153 Camp. jejuni isolates were genotyped. Forty sequence types (STs) were found, 19 of which were previously undescribed and 21 identified in other countries. The 19 newly described STs accounted for 43% of isolates, 16 of which were assigned to known clonal complexes. Eighty-eight percent of isolates were assigned to a total of 15 clonal complexes. Of these, four clonal complexes accounted for 60% of isolates. Three STs accounted for nearly 40% of all isolates and appeared to be endemic, while 21 STs were represented by more than one isolate. Seven infections were acquired during international travel, and the associated isolates all had different STs, three of which were exclusive to the travel-acquired cases. Comparison of serotypes among isolates from clonal complexes revealed further diversity. Eight serotypes were identified among isolates from more than one clonal complex, while isolates from six clonal complexes displayed serotypes not previously associated with those clonal complexes. CONCLUSIONS: Multilocus sequence typing is a useful tool for the discrimination of subtypes and examination of the population structure of Camp. jejuni associated with sporadic infections. SIGNIFICANCE AND IMPACT OF THE STUDY: This study highlights the genotypic diversity of Camp. jejuni in Australia, demonstrating that STs causing disease have both a global and a local distribution evident from the typing of domestically and internationally acquired Camp. jejuni isolates.

Bacterial Typing Techniques↗

PubMed1993

Treatment of narcolepsy-cataplexy syndrome with the new selective and reversible MAO-A inhibitor brofaromine-a pilot study.

Eighteen narcoleptic patients were treated in a single-blind study with brofaromine, a new selective and reversible MAO-A-inhibitor. After a drug-free period of seven days, brofaromine was administered for two weeks. Patients were treated with 75 mg brofaromine for the first week and with 150 mg brofaromine for the second week of the study. After an adaptation night nocturnal sleep EEGs were recorded under placebo before brofaromine was given, one week later under 75 mg, and another week later under 150 mg brofaromine. Excessive daytime sleepiness (EDS) was evaluated under placebo at the beginning of the study, under 75 mg at the end of the first week, and under 150 mg brofaromine at the end of the second week by means of the Multiple Sleep Latency Test (MSLT) and the Maintenance of Wakefulness Test (MWT). The number of cataplexies was protocolled by the patients. Compared to placebo the administration of 150 mg brofaromine led to a significant increase of sleep latency in the MLST as well as in the MWT. REM sleep was significantly suppressed in the nocturnal sleep EEG, in the MSLT and in the MWT. The number of cataplexies protocolled by the patient was significantly decreased under 150 mg of brofaromine compared to placebo. Improvement of vigilance and cataplexy occurred in dose-dependent manner. No serious side effects were observed. The results of the present single-blind study indicate that brofaromine seems to be a well-tolerated and effective drug for the treatment of excessive daytime sleepiness and cataplexy in narcoleptic patients.

Journal Article↗

PubMed2006

Genetic relatedness between group B streptococci originating from bovine mastitis and a human group B Streptococcus type V cluster displaying an identical pulsed-field gel electrophoresis pattern.

Twenty isolates of group B streptococcus (GBS) were recovered from the milk of cows with bovine mastitis on three farms located in the south and south-east of Brazil between 1987 and 1988. These isolates were characterised by molecular methods and compared with a collection of 103 human GBS isolates from colonised and infected patients in the same region between 1980 and 2003. Some of the bovine isolates shared identical or similar pulsed-field gel electrophoresis (PFGE) patterns with a PFGE clone of human GBS type V. In addition, these bovine and human isolates also possessed the same ribotype. Multilocus sequence typing (MLST) of representative isolates confirmed the genetic relationship between the human and bovine GBS isolates with identical PFGE patterns, which clustered in the same ST-26 clonal complex. These data support the hypothesis that some bovine GBS strains are related closely to human isolates and may infect humans, or vice versa. Further comparative genomic analyses of GBS isolates from bovine and human origins are required to investigate this hypothesis further.

Animals↗

PubMed2006

Conventional and molecular investigation of meningococcal isolates in relation to two outbreaks in the area of Athens, Greece.

Two local outbreaks caused by serogroup B Neisseria meningitidis occurred in the Athens area of Greece during 2003. In total, 30 N. meningitidis isolates from patients and carriers, as well as sporadic cases, were investigated by conventional techniques (serogroup, serotype and serosubtype), multilocus sequence typing (MLST), analysis of variable number tandem repeats (VNTR) and random amplified polymorphic DNA (RAPD) analysis. Compared with the two other molecular techniques, VNTR analysis was a simple, reliable and highly discriminatory method for fine typing of meningococcal isolates, showing a good correlation with the epidemiological data for the two outbreaks analysed.

Adolescent↗

PubMed2006

Standardized nonculture techniques recommended for European reference laboratories.

Culture-confirmed diagnosis of meningococcal invasive infections is often hindered by early antibiotic treatment. Nonculture molecular standardized methods are now essential tools for the immediate management of meningococcal infections. The European Monitoring Group on Meningococci (EMGM) recommends the following measures. (1) The implementation of standardized protocols of extraction methods for DNA isolation from clinical specimens for PCR-based identification and genogrouping of Neisseria meningitidis. (2) The use of molecular approaches (sequencing of target genes) for the determination of meningococcal susceptibility to antibiotics, such as sequencing of penA and rpoB genes for susceptibility to penicillin G and rifampicin, respectively. (3) The use of nonculture strain characterization by multilocus sequence typing (MLST) and sequence typing of porA and fetA. These approaches can be implemented either by individual reference laboratories or through collaboration and referral between centres.

Bacterial Outer Membrane Proteins↗

PubMed2006

Streptococcus pyogenes isolates with high-level macrolide resistance and reduced susceptibility to telithromycin associated with 23S rRNA mutations.

Seven high-level macrolide-resistant Streptococcus pyogenes isolates had reduced activity to telithromycin but were negative for methylation and efflux genes. All were of the constitutive phenotype, were clonally related (emm type 12 and MLST type 36), and had identical dual mutations (A2058G and U2166C) in domain V of 23S rRNA.

Anti-Bacterial Agents↗

PubMed2005

Molecular analysis of human, porcine, and poultry Enterococcus faecium isolates and their erm(B) genes.

Fifty-nine erm(B)-positive Enterococcus faecium strains isolated from pigs, broilers, and humans were typed using multilocus sequence typing (MLST), and the coding sequence of the erm(B) gene was determined. Identical erm(B) gene sequences were detected in genetically unrelated isolates. Furthermore, genetically indistinguishable strains were found to contain different erm(B) alleles. This may suggest that horizontal exchange of the erm(B) gene between animal and human E. faecium strains or the existence of a common reservoir of erm(B) genes might be more important than direct transmission of resistant strains.

Animals↗

PubMed2005

Phylogenetic characterization of virulence and resistance phenotypes of Pseudomonas syringae.

Individual strains of the plant pathogenic bacterium Pseudomonas syringae vary in their ability to produce toxins, nucleate ice, and resist antimicrobial compounds. These phenotypes enhance virulence, but it is not clear whether they play a dominant role in specific pathogen-host interactions. To investigate the evolution of these virulence-associated phenotypes, we used functional assays to survey for the distribution of these phenotypes among a collection of 95 P. syringae strains. All of these strains were phylogenetically characterized via multilocus sequence typing (MLST). We surveyed for the production of coronatine, phaseolotoxin, syringomycin, and tabtoxin; for resistance to ampicillin, chloramphenicol, rifampin, streptomycin, tetracycline, kanamycin, and copper; and for the ability to nucleate ice at high temperatures via the ice-nucleating protein INA. We found that fewer than 50% of the strains produced toxins and significantly fewer strains than expected produced multiple toxins, leading to the speculation that there is a cost associated with the production of multiple toxins. None of these toxins was associated with host of isolation, and their distribution, relative to core genome phylogeny, indicated extensive horizontal genetic exchange. Most strains were resistant to ampicillin and copper and had the ability to nucleate ice, and yet very few strains were resistant to the other antibiotics. The distribution of the rare resistance phenotypes was also inconsistent with the clonal history of the species and did not associate with host of isolation. The present study provides a robust phylogenetic foundation for the study of these important virulence-associated phenotypes in P. syringae host colonization and pathogenesis.

Adaptation, Physiological↗

PubMed2006

Variation in the presence of neuraminidase genes among Streptococcus pneumoniae isolates with identical sequence types.

Streptococcus pneumoniae frequently colonizes the upper respiratory tract of young children and is an important cause of otitis media and invasive disease. Carriage is more common than disease, yet the genetic factors that predispose a given clone for disease are not known. The relationship between capsule type, genetic background, and virulence is complex, and important questions remain regarding how pneumococcal clones differ in their ability to cause disease. Pneumococcal neuraminidase cleaves sialic acid-containing substrates and is thought to be important for pneumococcal virulence. We describe the distribution of multilocus sequence types (ST), capsule type, and neuraminidase genes among 342 carriage, middle ear, blood, and cerebrospinal fluid (CSF) pneumococcal strains from young children. We found 149 STs among our S. pneumoniae isolates. nanA was present in all strains, while nanB and nanC were present in 96% and 51% of isolates, respectively. The distribution of nanC varied among the strain collections from different tissue sources (P = 0.03). The prevalence of nanC was 1.41 (95% confidence interval, 1.11, 1.79) times higher among CSF isolates than among carriage isolates. We identified isolates of the same ST that differed in the presence of nanB and nanC. These studies demonstrate that virulence determinants, other than capsule loci, vary among strains of identical ST. Our studies suggest that the presence of nanC may be important for tissue-specific virulence. Studies that both incorporate MLST and take into account additional virulence determinants will provide a greater understanding of the pneumococcal virulence potential.

Bacterial Typing Techniques↗

PubMed2025

Colorectal cancer-associated Streptococcus gallolyticus: a hidden diversity expose.

Streptococcus gallolyticus subsp. gallolyticus (SGG) is a bacterial pathogen implicated in bacteremia and endocarditis and is often associated with colon tumors in elderly individuals. The development of colorectal cancer (CRC) has been linked to intestinal dysbiosis, characterized by increased proportions of SGG and other intestinal microbes. In this study, we present the complete nucleotide sequence of five novel clinical isolates of SGG associated with colorectal cancer, revealing unexpected genetic diversity. Sequencing an additional 30 SGG clinical isolates provided a more comprehensive description of this genetic diversity. We did not identify a pathogenicity island specific to CRC-associated SGG isolates. Most of these human-derived SGG isolates exhibit resistance to multiple antibiotics. Our findings also offer additional insights into multilocus sequence typing (MLST), capsular loci, and pilus organization. Analysis of the repertoire of surface proteins reveals high potential for binding and foraging complex polysaccharides. Finally, comparative genomics with the phylogenetically closest non-pathogenic subspecies S. gallolyticus subsp. macedonicus confirmed that SGG pathogenicity-associated factors mostly rely on a large repertoire of surface proteins involved in host colonization, presence of C5a peptidase to avoid innate immunity, bile salt hydrolase to persist in the gut, and of specific bacteriocin and type VII-dependent effectors to colonize the host colon. Additionally, the presence of extracellular polysaccharides in SGG probably helps the bacterium survive in harsher conditions.IMPORTANCEStreptococcus gallolyticus subsp. gallolyticus (SGG) was the first intestinal bacterium associated with colorectal cancer. It is now widely accepted that colonic microbiota dysbiosis contributes to oncogenesis, with a higher relative abundance of several potentially pro-carcinogenic bacteria. For example, the oncogenic role of Escherichia coli pks+ and enterotoxinogenic Bacteroides fragilis in colorectal cancer has been well established, identifying the role of genetic loci encoding toxins. Through the sequencing and analysis of 11 clinical SGG isolates from CRC patients and comparisons with non-CRC isolates, we uncovered a significant diversity among CRC-associated strains. Our findings suggest that SGG association with CRC is complex and is not linked to a specific strain or pathogenicity island, thus highlighting the opportunistic and versatile nature of SGG.

Humans↗

PubMed2006

Multispacer typing to study the genotypic distribution of Bartonella henselae populations.

Bartonella henselae, a worldwide fastidious bacterium, has a feline reservoir and is pathogenic for humans. However, the relationship between human and cat isolates of B. henselae, as well as its population dynamics and geographic heterogeneity, is not fully understood, in part because of the absence of appropriate typing methods. Multilocus sequence typing (MLST), the most discriminatory genotyping method for B. henselae, identified seven genotypes and suggested that human isolates arose from a limited number of cat isolates. Herein, we estimated the discriminatory power of multispacer typing (MST) by studying 126 B. henselae cat isolates from various areas of Europe, Asia, and the United States. We identified the nine most variable intergenic spacers conserved by both B. henselae and Bartonella quintana genomes. By comparing the sequences obtained from these nine spacers for each studied isolate, we identified 39 MST genotypes. The distribution of isolates into MST genotypes matched their phylogenetic organization into four clusters. MST showed that European and Asian isolates were different, in contrast with American isolates, but failed to identify pandemic strains. Our study demonstrated that MST is a powerful method for genotyping B. henselae at the strain level and may serve in studying the population dynamics of this bacterium and understanding the relationships between cat and human isolates. Finally, we provide a free-access MST-Rick online software program (http://ifr48.timone.univ-mrs.fr/MST_BHenselae/mst) that investigators may use to compare their own MST sequences to our database.

Animals↗

PubMed2006

Heterogeneity of methicillin-susceptible Staphylococcus aureus strains at a German University Hospital implicates the circulating-strain pool as a potential source of emerging methicillin-resistant S. aureus clones.

Recently, we demonstrated rapid dissemination of different methicillin-resistant Staphylococcus aureus (MRSA) clones at the Institute for Microbiology at the University of Magdeburg (B. Ghebremedhin, W. König, and B. König, Eur. J. Clin. Microbiol. Infect. Dis. 24:388-398, 2005). The majority of them harbored the readily transmissible mec cassette type IV. Thus, theoretically, methicillin-susceptible Staphylococcus aureus (MSSA) might capture the mecA gene from circulating MRSA, or MRSA strains might catch mobile toxin genes from MSSA. Therefore, we characterized MSSA strains circulating at the University Hospital in Magdeburg. Among a total of 84 MSSA strains under study, about 40% possessed the tst (toxic shock syndrome toxin) gene and up to four additional enterotoxin genes. tst-positive MSSA strains belonged to all known agr groups (I to IV) and to 14 different spa types (t008, t012, t015, t019, t024, t056, t065, t127, t133, t162, t271, t287, t399, and t400), and they were classified by multilocus sequence typing (MLST) as ST1, ST8, ST30, ST39, ST45, ST101, ST121, ST395, and ST426. In contrast, simultaneously circulating MRSA strains (n = 24) harbored in general two or three genes of the enterotoxin gene cluster, and the tst-positive MRSA isolates belonged to the well-known epidemic types ST22, ST45, and ST228 and were classified as spa types t001, t028, and t032. From our results, one may conclude that the pool of circulating MSSA strains is an important parameter with regard to the epidemiology of hospital- and community-acquired MRSA clones and their potential virulence.

Anti-Bacterial Agents↗