Estreptococos del grupo Streptococcus anginosus Parte I. Taxonomía, características microbiológicas e identificación / Streptococcus anginosus groupb Part I. Taxonomy, microbiological characteristics and identification / Estreptococos do grupo Streptococcus anginosus Parte I. Taxonomia, características microbiológicas e identificação

Resumen Los estreptococos del grupo Streptococcus anginosus (EGA), también llamados "Streptococcus milleri" fueron reconocidos como parte de los estreptococos del grupo viridans (EGV) desde principios del siglo XX. Sin embargo, su rol como patógenos humanos comenzó a destacarse recién en la década de 1970. Esta actualización consta de tres partes: en esta primera parte se tratarán los aspectos taxonómicos y microbiológicos así como los métodos de identificación de los EGA. El crecimiento de estas bacterias es relativamente lento, las colonias son pequeñas, incluso a las 48-72 horas de incubación y la mayoría de las cepas despide un olor a caramelo característico cuando crecen en agar sangre. Su crecimiento es estimulado en una atmósfera con 5% de CO2. Últimamente, con el reconocimiento de la asociación de los EGA con episodios indeseables en pacientes con fibrosis quística se han desarrollado medios selectivos para poner de manifiesto su presencia en las vías aéreas. Los métodos fenotípicos e incluso algunos genotípicos carecen de precisión para identificar las tres especies del grupo (Streptococcus anginosus, Streptococcus constellatus y Streptococcus intermedius) e incluso pueden fallar en su clasificación a nivel de grupo. Dentro de los métodos moleculares, matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) no puede ser tomado como referencia para llegar a subespecie, pero sí es muy eficiente en la identificación a nivel de especie. Para algunos autores la secuenciación del gen sodA podría ser una buena opción, pero el gold standard es el multilocus sequence analysis (MLSA).

Abstract Streptococci from the Streptococcus anginosus group (SAG), also called "Streptococcus milleri", have been recognized as belonging to the viridans group (VGS) since the beginning of the 20th century. Their role as human pathogens, however, only began to emerge in the 1970s. This review consists of three parts: the first part will deal with the taxonomic and microbiological aspects and the identification methods of SAGs. The growth of these bacteria is relatively slow; the colonies are small even after 48-72 hours of incubation and most of the strains give off a characteristic caramel odor when they grow on blood agar. Their growth is stimulated in an atmosphere with 5% CO2. Lately, with the recognition of the association of SAGs with undesirable episodes in patients with cystic fibrosis, selective media have been developed to reveal their presence in the airways. Phenotypic and even some genotypic methods lack precision in identifying the three species in the group (Streptococcus anginosus, Streptococcus constellatus, and Streptococcus intermedius) and may even fail to classify at the group level. Among the molecular methods, MALDI-TOF MS cannot be taken as a reference to arrive at subspecies, but it is very efficient to identify at the species level. For some authors, sequencing the sodA gene may be a good option, but the gold standard is multilocus sequence analysis (MLSA).

Resumo Os estreptococos do grupo Streptococcus anginosus (EGA), também chamados de "Streptococcus milleri", foram reconhecidos como pertencentes ao grupo viridans (EGV) desde o início do século XX. Seu papel como patógenos humanos, no entanto, só começou a surgir na década de 1970. Esta atualização consiste em três partes: nesta primeira parte, trataremos dos aspectos taxonômicos e microbiológicos e dos métodos de identificação dos EGAs. O crescimento dessas bactérias é relativamente lento, as colônias são pequenas mesmo após 48-72 horas de incubação e a maioria das cepas emitem um cheiro de caramelo característico quando crescem em ágar sangue. Seu crescimento é estimulado em uma atmosfera com 5% de CO2. Ultimamente, com o reconhecimento da associação dos EGAs com episódios indesejáveis em pacientes com fibrose cística, foram desenvolvidos meios seletivos para revelar sua presença nas vias aéreas. Os métodos fenotípicos e mesmo alguns genotípicos carecem de precisão na identificação das três espécies do grupo (Streptococcus anginosus, Streptococcus constellatus e Streptococcus intermedius) e podem até falhar em sua classificação em nível de grupo. Entre os métodos moleculares, matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) não pode ser tomado como referência para chegar a subespécie, mas é muito eficiente na identificação em nível de spécie. Para alguns autores, o sequenciamento do gene sodA poderia ser uma boa opção, mas o padrão-ouro é a análise de sequência multilocus (MLSA).

Phenotypic and genotypic heterogeneity among Streptococcus iniae isolates recovered from cultured and wild fish in North America, Central America and the Caribbean islands.

Streptococcus iniae, the etiological agent of streptococcosis in fish, is an important pathogen of cultured and wild fish worldwide. During the last decade outbreaks of streptococcosis have occurred in a wide range of cultured and wild fish in the Americas and Caribbean islands. To gain a better understanding of the epizootiology of S. iniae in the western hemisphere, over 30 S. iniae isolates recovered from different fish species and geographic locations were characterized phenotypically and genetically. Species identities were determined biochemically and confirmed by amplification and sequencing of the 16S rRNA gene. Repetitive-element palindromic PCR fingerprinting as well as biochemical and antimicrobial susceptibility profiles suggest that a single strain of S. iniae was responsible for two different disease outbreaks among reef fishes in the Caribbean, one in 1999 and another in 2008. Interestingly, a majority of the isolates recovered from cultured fish in the Americas were genetically distinct from the Caribbean isolates and exhibited a trend toward higher minimal inhibitory concentration with respect to several antibiotics as well as greater genetic variability. The biological significance of this genetic variability is unclear, but it could have implications for future vaccine development and treatment.

Identification of the 'Streptococcus anginosus group' by matrix-assisted laser desorption ionization--time-of-flight mass spectrometry.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) provides rapid, accurate and cost-effective identification of a range of bacteria and is rapidly changing the face of routine diagnostic microbiology. However, certain groups of bacteria, for example streptococci (in particular viridans or non-haemolytic streptococci), are less reliably identified by this method. We studied the performance of MALDI-TOF MS for identification of the 'Streptococcus anginosus group' (SAG) to species level. In total, 116 stored bacteraemia isolates identified by conventional methods as belonging to the SAG were analysed by MALDI-TOF MS. Partial 16S rRNA gene sequencing, supplemented with sialidase activity testing, was performed on all isolates to provide 'gold standard' identification against which to compare MALDI-TOF MS performance. Overall, 100 % of isolates were correctly identified to the genus level and 93.1 % to the species level by MALDI-TOF MS. However, only 77.6 % were correctly identified to the genus level and 59.5 % to the species level by a MALDI-TOF MS direct transfer method alone. Use of a rapid in situ extraction method significantly improved identification rates when compared with the direct transfer method (P<0.001). We recommend routine use of this method to reduce the number of time-consuming full extractions required for identification of this group of bacteria by MALDI-TOF MS in the routine diagnostic laboratory. Only 22 % (1/9) of Streptococcus intermedius isolates were reliably identified by MALDI-TOF MS to the species level, even after full extraction. MALDI-TOF MS reliably identifies S. anginosus and Streptococcus constellatus to the species level but does not reliably identify S. intermedius.

Invasive Streptococcus anginosus group infection-does the species predict the outcome?

OBJECTIVE: To determine whether there is an association between the species of Streptococcus anginosus group (SAG) bacteria and the clinical outcome. METHODS: Isolates from invasive infections caused by SAG bacteria at our institution between January 2004 and February 2009 were identified phenotypically to the taxonomic level of species. Clinical data from the medical records of the patients from whom these isolates were recovered were obtained retrospectively and analyzed. RESULTS: Patients with invasive Streptococcus intermedius infections had a significantly longer hospital stay than patients infected with S. anginosus (p = 0.024) and a significantly higher 30-day all-cause mortality than patients infected with Streptococcus constellatus (p = 0.049). CONCLUSION: Identification of SAG bacteria to the taxonomic level of species may be of prognostic importance.

Milleri group streptococcus--a stepchild in the viridans family.

The purpose of this investigation was to provide a comprehensive review of the pathogenic role and spectrum of disease of milleri group streptococci, with special attention to bloodstream invasion and to possible differential roles among the three species. All consecutive isolates of milleri group streptococci from any anatomic source, during a 37-month period, in a tertiary care teaching hospital in Tel-Aviv, Israel, were thoroughly investigated. Identification to the species level was performed by an automated system.Streptococcus anginosus constituted 82% of the 245 patient-unique isolates from hospitalized patients. All nonurinary isolates were involved in pyogenic infections mostly originating from the gastrointestinal tract, with bacteremia in 28 cases. The 71 urinary isolates represented either urinary tract infection or nonsignificant bacteriuria. No specific association could be detected between species and the infection site, except for a higher relative representation of Streptococcus constellatus in bacteremia. Milleri group streptococci are common in clinical practice and play a different pathogenic role to other viridans streptococci. Due to their invariable association with pyogenic processes, their presence in blood warrants immediate focus identification. In addition, they have a previously unappreciated clinical niche concerning urinary tract infection. The identification of viridans streptococci to the species level is of paramount clinical significance.

Amplification of minute amounts of oral bacterial DNA for real-time quantitative PCR analysis.

BACKGROUND: High-throughput technologies for typing caries or health-associated bacterial populations including PCR, DNA microarrays and next-generation sequencing techniques require significant amounts of bacterial DNA. In clinical settings, the amount of sampled DNA is often limited and amplification is therefore essential. Protocols should be able to reproducibly amplify sequences in order to maintain initial sequence ratios and should not bias the representation of particular DNA sequence types. METHODS: A linear amplification protocol using DNA polymerase I was modified to permit the amplification and subsequent analysis of small amounts of bacterial DNA. The protocol was tested on human oral bacterial biofilms from different sources, including carious dentine and plaque, and compared to amplification by degenerate PCR of 16S rDNA sequences. Real-time quantitative PCR of 24 bacterial species was used as a readout system to test amplified DNA against unamplified DNA. RESULTS: The amplification protocol reliably yielded 5-10 µg DNA from as little as 12.5 ng of template DNA. Correlation coefficients between real-time quantitative PCR results from amplified and unamplified DNA were between 0.78 and 0.98. CONCLUSION: The optimized protocol consistently produced amplification products from minute amounts of bacterial DNA from caries and plaque; the amplification products are suitable for downstream genetic analyses.

Evaluation of genotypic and phenotypic methods for differentiation of the members of the Anginosus group streptococci.

The terminology and classification of the Anginosus group streptococci has been inconsistent. We tested the utility of 16S rRNA gene and tuf gene sequencing and conventional biochemical tests for the reliable differentiation of the Anginosus group streptococci. Biochemical testing included Rapid ID 32 Strep, API Strep, Fluo-Card Milleri, Wee-tabs, and Lancefield antigen typing. Altogether, 61 Anginosus group isolates from skin and soft tissue infections and four reference strains were included. Our results showed a good agreement between 16S rRNA gene and tuf gene sequencing. Using the full sequence was less discriminatory than using the first part of the 16S rRNA gene. The three species could not be separated with the API 20 Strep test. Streptococcus intermedius could be differentiated from the other two species by beta-galactosidase (ONPG) and beta-N-acetyl-glucosaminidase reactions. Rapid ID 32 Strep beta-glucosidase reaction was useful in separating S. anginosus strains from S. constellatus. In conclusion, both 16S rRNA gene and tuf gene sequencing can be used for the reliable identification of the Anginosus group streptococci. S. intermedius can be readily differentiated from the other two species by phenotypic tests; however, 16S rRNA gene or tuf gene sequencing may be needed for separating some strains of S. constellatus from S. anginosus.

Identification of the anginosus group within the genus Streptococcus using polymerase chain reaction.

The aim of this study was to establish an identification method for the anginosus group within the genus Streptococcus by polymerase chain reaction (PCR). Using a primer pair based on the group-specific sequences of penicillin-binding protein 2B (pbp2b) gene, a 275-bp fragment was amplified from each species in the group but no size-matched products were obtained in other streptococci. Further identification in the species or subspecies level was possible by a multiplex PCR with primers for the 16S ribosomal RNA gene of Streptococcus anginosus, the hyaluronate lyase genes both of Streptococcus intermedius and Streptococcus constellatus subsp. constellatus, and the intermedilysin (ily) gene of S. intermedius. In the case ofStreptococcus constellatus subsp. pharyngis, the amplified fragment from the S. intermedius-type hyaluronate lyase gene was obtained, while that from the ily gene was not. These results also indicate that two different hyaluronate lyase genes are distributed among the anginosus group.