A numerical taxonomic study of the "Streptococcus milleri" group based upon conventional phenotypic tests and pyrolysis mass spectrometry

Characterization of Streptococcus milleri group isolates from expectorated sputum of adult patients with cystic fibrosis

With the recent insights into the Streptococcus milleri group (SMG) as pulmonary pathogens in patients with cystic fibrosis (CF), we sought to characterize 128 isolates from the sputum of adults with CF, along with 45 isolates from patients with invasive diseases for comparison. The tests performed included Lancefield grouping; tests for hemolysis; tests for the production of hyaluronidase, chondroitin sulfatase, DNase, proteases, and hydrogen peroxide; and PCR for the detection of the intermedilysin gene (ily). We also generated biochemical profiles with the Rapid ID Strep 32 API system and tested cell-free supernatants for the presence of the signal molecule autoinducer-2 (AI-2) using a Vibrio harveyi bioassay with a subset of CF strains. The S. intermedius isolates from both strain collections were similar, while the S. constellatus and S. anginosus isolates yielded several biotypes that differed in prevalence between the two strain collections. Beta-hemolytic, Lancefield group C S. constellatus comprised 74.4% of the S. constellatus isolates from patients with CF but only 13.3% of the corresponding isolates from patients with invasive infections. This was the only S. constellatus biotype associated with pulmonary exacerbations. Hyaluronidase-positive S. anginosus was detected only among the isolates from patients with CF. Strain-to-strain variability in AI-2 expression was evident, with the mean values being the highest for S. anginosus, followed by S. constellatus and then S. intermedius. Cluster analysis and 16S rRNA sequencing revealed that the species of SMG could be accurately determined with a minimum of three phenotypic tests: tests for the Lancefield group, hyaluronidase production, and chondroitin sulfatase production. Furthermore, isolates from patients with invasive infections clustered with isolates from the sputum of patients with CF, suggesting that the respiratory tract isolates were equally pathogenic.

Intramedullary abscess from group F Streptococcus

BACKGROUND

Intramedullary abscesses are rare and may be misdiagnosed. We report the case of a 54-year-old man with carcinoma of the gastroesophageal junction who presented after thoracotomy with hemiparesis and a ring-enhancing intramedullary lesion at C2-3 on magnetic resonance imaging.

METHODS

Individual case report and literature review.

RESULTS

Although the lesion was initially mistaken for metastasis, at surgery an intramedullary abscess was discovered, from which group F Streptococcus was isolated. Conclusions : Although other streptococcal species have been found in abscesses of the spinal cord, this particular strain has not been identified previously as a cause of such abscesses. Prompt surgical evacuation is recommended, and should be followed by appropriately tailored antibiotic therapy.

Current classification of the oral streptococci

The classification of the oral streptococci has long remained a difficult area of streptococcal taxonomy. This article reviews the current classification of these bacteria into four species groups, and each group is described in detail. The often confusing changes that have taken place in the classification, identification and nomenclature of the member species are reviewed against a historical background of gradually improving techniques and approaches, leading towards a natural classification based primarily on genotypic evidence. Identification schemes currently in use employing biochemical tests are also reviewed, together with alternative molecular approaches.

Curie-point pyrolysis mass spectrometry as a tool in clinical microbiology

Pyrolysis mass spectrometry is a well established analytical tool that has received a considerable boost from the development of low cost, dedicated instruments and sophisticated statistical analyses on personal computers. Further analytical developments, especially in the area of neural networks, are pushing the technology to the forefront of methods for the discrimination and identification of microorganisms and their products. The speed and reproducibility of pyrolysis mass spectrometry and its applicability to a wide range of microorganisms make it an attractive method for epidemiological studies. For inter-strain comparisons, the method is at least as discriminatory as conventional typing systems and usually gives discrimination similar to that of nucleic acid fingerprinting techniques. There has been some success in using neural networks to make identifications across pyrolysis mass spectrometric batches. Further development of methods used to handle data from multiple PyMS analyses can be expected to extend the value of pyrolysis mass spectrometry in clinical microbiology.

Pyrolysis mass spectrometry: data processing in classification studies

A scheme for numerical processing of pyrolysis mass spectrometry (Py-MS) data is detailed, along with methods for combining the results of conventional phenotypic and Py-MS taxonomic surveys. The importance of this combined approach in polyphasic taxonomy is emphasised; it yields data on cell composition and the nutritional and physiological interactions of strains with their environment. Large collections of strains can be surveyed rapidly and economically, yielding presumptive classifications, which may then be confirmed with a few representative strains in more demanding, difficult and expensive approaches. An objective, non-arbitrary method of establishing suitable cut-off points to delineate group structures in dendrograms is also described.

A numerical taxonomic study of Streptococcus sanguis, S. mitis and similar organisms using conventional tests and pyrolysis mass spectrometry

Numerical taxonomic methods were applied to the results of pyrolysis mass spectrometry (Py-MS) and conventional test reaction patterns (CTRPs) obtained with 46 strains of oral streptococci identified as representative of six species. Of these: Streptococcus gordonii strains formed a single homogeneous well-differentiated cluster both in the Py-MS and CTRP analyses; S. oralis strains were more diverse, forming 2 CTRP and 3 Py-MS clusters; S. crista, S. parasanguis and S. sanguis formed clear, but diverse and poorly differentiated clusters on the basis of CTRPs, and were poorly differentiated in the Py-MS analysis; and S. mitis strains were clearly diverse in both analyses. Peritrichously fimbriate ('tufted') S. mitis strains formed a tight cluster, well differentiated from the type strain in both Py-MS and CTRP analyses, and may represent a previously unrecognised centre of variation.

Polyphasic taxonomic study of clinically significant actinomadurae including the description of Actinomadura latina sp.nov

Thirty-one strains received either as Actinomadura madurae or Actinomadura pelletieri were assigned to four phena, clusters 1 to 4, in a numerical phenetic survey of the genus Actinomadura. Clusters 2 and 4 corresponded to the validly described species A. madurae and A. pelletieri whereas clusters 1 and 3 encompassed strains received as A. madurae and A. pelletieri, respectively. The two clusters that contained A. madurae strains formed a single taxon when a dataset lacking the antibiotic sensitivity entries was examined. Results from pyrolysis mass spectrometric and DNA amplification fingerprinting analyses underpinned the taxonomic status of clusters 2, 3 and 4 and suggested that the A. madurae strains accounted for a relatively wide range of variation. It is proposed that the cluster 3 strains be given species status within the genus Actinomadura given the congruence found between the chemical, molecular and numerical phenetic data. The name Actinomadura latina is proposed for the new taxon. The type strain is DSM 43382.

A pyrolysis mass spectrometry study of temperature-dependent compositional shifts in Xanthomonas (Pseudomonas) maltophilia

Xanthomonas (Pseudomonas) maltophilia strains are frequently susceptible to aminoglycoside antibiotic and polymixin B when incubated at 37 degrees C, but resistant at 30 degrees C. Five strains showing temperature dependent resistance, and five that did not were examined by pyrolysis-mass spectrometry, a characterisation method that gives fingerprint data reflecting cell composition. Cultures grown at 30 degrees C and 37 degrees C in the absence of antibiotic were analysed. Strains showing temperature-dependent resistance exhibited a characteristic compositional difference between cells grown at the two temperatures, whereas strains not showing this type of resistance varied widely in the extent and nature of temperature-dependent differences in composition. The precise nature of the chemical differences cannot be elucidated at present, but could be determined by examining purified cell constituents.

Pyrolysis mass spectrometry characterisation and numerical taxonomy of Aeromonas spp

Reference strains (2) and 29 isolates of Aeromonas spp. from clinical material and environmental specimens were characterised in traditional biochemical tests, and in pyrolysis mass spectrometry, which gives data reflecting whole-cell composition. Numerical taxonomic analyses of the data sets were compared with conventional identification at species level, and pathogenic potential, as inferred from the origin of the isolates. Clustering with conventional test reaction patterns showed, for each of the species represented, a clearly defined core group of 'typical' isolates, surrounded by a halo of aberrant strains. One further cluster comprised strains intermediate between A. caviae and A. hydrophila, and one strain was grossly atypical in both analyses. Clustering from pyrolysis data corresponded less well with species identification. Broadly, the biochemical division between core and halo strains was supported in pyrolysis for A. caviae and A. sobria, but the main group of A. hydrophila in pyrolysis comprised strains clustering in the core and halo groups of this species, and three strains intermediate between A. hydrophila and A. caviae in biochemical tests. Two further pyrolysis clusters comprised core and halo strains of A. hydrophila. However, pyrolysis clustering correlated well with inferred pathogenicity, showing four clusters of probable pathogens, six clusters of probable non-pathogens, and one two member cluster of doubtful status. Most strains that clustered in the species haloes, or in species-intermediate groups in biochemical tests, were non-human isolates, or were isolated in the absence of symptomatic infection. The correlation of inferred pathogenicity with biochemical clustering was poorer than that with pyrolysis clustering.

Classification of black-pigmented anaerobes by pyrolysis mass spectrometry (PMS) and conventional tests (CTs)

Clinical (66: dental 53; vaginal 4; wound 9) and reference (5*) strains of pigmented Gram-negative anaerobic bacilli were examined in pyrolysis mass spectrometry (PMS) and conventional tests (CTs). The strains were identified in CTs as: Prevotella intermedia (48*); Pr. melaninogenica (1); Pr. corporis (7); Porphyromonas asaccharolytica (12*); P. endodontalis (1*) and P. gingivalis (2*). Numerical classification based on CTs resolved five clusters comprising strains identified as (I) Pr. corporis, (II) Pr. melaninogenica, (III) Pr. intermedia, (IV) P. gingivalis and (V) P. asaccharolytica and P. endodontalis. Numerical classification based on PMS showed a similar division, with decreasing homogeneity in the order Pr. intermedia, Pr. corporis, P. asaccharolytica, in agreement with the ordering of homogeneity for these species in CTs. PMS clusters corresponding the Porphyromonas spp. were clearly distinct from those of Prevotella spp. PMS and CT classifications disagreed on cluster membership for only six of the strains. PMS identification from blind challenge sets agreed with conventional identification for 64 of 67 strains.