In this study, the performances of two matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) systems, MALDI Biotyper (Bruker Daltonics) and VITEK MS (bioMérieux), were evaluated in the identification of viridans group streptococci. Two collections of isolates were tested with both methods. From a panel of type collection strains (n = 54), MALDI Biotyper gave correct species-level identification for 51/54 (94 %) strains and 37/54 (69 %) strains for the VITEK MS in vitro diagnostic (IVD) method. Additionally, a collection of blood cultures isolates which had been characterized earlier with partial sequencing of 16S rRNA (n = 97) was analyzed. MALDI Biotyper classified 89 % and VITEK MS 93 % of these correctly to the group level. Comparison of species-level identification from the blood culture collection was possible for 36 strains. MALDI Biotyper identified 75 % and VITEK MS 97 % of these strains consistently. Among the clinical isolates, MALDI Biotyper misidentified 36 strains as Streptococcus pneumoniae. Nevertheless, our results suggest that the current MALDI-TOF methods are a good alternative for the identification of viridans streptococci and do perform as well as or better than commercial phenotypical methods.

Reliable distinction of Streptococcus pneumoniae and viridans group streptococci is important because of the different pathogenic properties of these organisms. Differentiation between S. pneumoniae and closely related Sreptococcus mitis species group streptococci has always been challenging, even when using such modern methods as 16S rRNA gene sequencing or matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry. In this study, a novel algorithm combined with an enhanced database was evaluated for differentiation between S. pneumoniae and S. mitis species group streptococci. One hundred one clinical S. mitis species group streptococcal strains and 188 clinical S. pneumoniae strains were identified by both the standard MALDI Biotyper database alone and that combined with a novel algorithm. The database update from 4,613 strains to 5,627 strains drastically improved the differentiation of S. pneumoniae and S. mitis species group streptococci: when the new database version containing 5,627 strains was used, only one of the 101 S. mitis species group isolates was misidentified as S. pneumoniae, whereas 66 of them were misidentified as S. pneumoniae when the earlier 4,613-strain MALDI Biotyper database version was used. The updated MALDI Biotyper database combined with the novel algorithm showed even better performance, producing no misidentifications of the S. mitis species group strains as S. pneumoniae. All S. pneumoniae strains were correctly identified as S. pneumoniae with both the standard MALDI Biotyper database and the standard MALDI Biotyper database combined with the novel algorithm. This new algorithm thus enables reliable differentiation between pneumococci and other S. mitis species group streptococci with the MALDI Biotyper.KEYWORDS MALDI-TOF, Streptococcus pneumoniae, algorithm, mitis group streptococci, phenotypic identification, pneumococcus T raditional classification of streptococci was based on the potential to cause hemolysis on sheep blood agar. The term "viridans" is used to refer to the greenish coloring (alpha-hemolysis) of the medium around the colonies due to partial lysis of red blood cells. Streptococcus pneumoniae, one of the most common causative agents of bacterial meningitis, community-acquired pneumonia, and otitis media, is clinically the most important alpha-hemolytic streptococcus. Because of the different pathogenic potentials of S. pneumoniae and other alpha-hemolytic streptococci, the practical dichotomy in clinical laboratories has been between S. pneumoniae and viridans group

Actinobaculum schaalii is an emerging uropathogen. So far, its identification has been performed with 16S rRNA gene sequencing or PCR. The diagnosis has often been delayed due to fastidious growth and identification problems. Eleven clinical isolates of A. schaalii from bloodstream infections that were initially identified with 16S rRNA sequencing analysis were recovered and later identified with matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF). We present a review of bacteriological data of these patients, an algorithm for fast laboratory work-up and advocate the use of sensitized culture of urine to allow better recovery of A. schaalii in susceptible patients.

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Various microorganisms isolated from polluted environments, such as Pseudomonas sp. and Micrococcus sp. can synthesize exopolysaccharides (EPSs) which are natural, non-toxic and biodegradable polymers. EPSs play a key role in protection of microbial cells under various external influences. For humans, these substances have potential use in many industries. EPSs can be applied as a flavor or a fragrance carrier, an emulsifier, a stabilizer, a prebiotic, an antioxidant or an antitumor agent. In this study, we characterized an environmental microorganism that produces EPS, optimized EPS production by this strain and characterized the EPS produced. Isolate CH-KOV3 was identified as Brachybacterium paraconglomeratum. The sucrose level in the growth medium greatly influenced EPS production, and the highest yield was when the microorganism was incubated in media with 500g/L of sucrose. The optimal temperature and pH were 28°C and 7.0, respectively. The nuclear magnetic resonance (NMR) results and GC-MS analysis confirmed that the residues were d-fructofuranosyl residues with β-configuration, where fructose units are linked by β-2,6-glycosidic bonds, with β-2,1-linked branches. All these data indicate that the investigated EPS is a levan-type polysaccharide. Thus, it was concluded that Brachybacterium sp. CH-KOV3 could constitute a new source for production of the bioactive polysaccharide, levan.