For Raman studies, a loopful of biomass from 24-h cultures was transferred onto CaF2 substrate. Comparison between phenotypic identification and FT-IR analysis. Classification scheme based on the Raman spectra of six different Enterococcus species. Clin Infect Dis, 14(6): 1173–1178, Murray P R, Rosenthal K S, Pfaller M A (2009). We present a comparative study using phenotypic, genotypic, and vibrational spectroscopic techniques for typing a collection of 18Enterococcus strains comprising six different species. 2. Emerg Infect Dis, 7(2): 302–305, Blair E B, Emerson J S, Tull A H (1967). (10) as follows: W3, the window between 1,500 and 1,200 cm−1(the mixed region), a spectral region containing information from proteins, fatty acids, and phosphate-carrying compounds; W4, the window between 1,200 and 900 cm−1 (the polysaccharide region), a spectral region dominated by the fingerprint-like absorption bands of the carbohydrates present within the cell wall; W5, the window between 900 and 700 cm−1 (the true fingerprint region), showing some remarkably specific spectral patterns, which are as yet unassigned to cellular components or to functional groups. (i) Phenotypic method: API and MICROSCAN.Phenotypic identification of all strains was performed using the automated API (bioMérieux, Marcy I'Etoile, France) and the MicroScan (Dade International, MicroScan Inc., West Sacramento, Calif.) systems. https://doi.org/10.1007/s11515-012-1183-5, DOI: https://doi.org/10.1007/s11515-012-1183-5, Over 10 million scientific documents at your fingertips, Not logged in Enterococci are opportunistic human pathogens. (ii) Genotypic methods. Enterococcus faecium is a Gram-positive, alpha-hemolytic or non-hemolytic bacterium in the genus Enterococcus. Phenotypic and genotypic methods. A representative data set consisting of three repetitive measurements including all strains was subjected to multivariate statistical analysis to explore the discriminative potential of the spectral information for this taxonomic task. Clin Microbiol Rev, 8(4): 585–615, Yamahara K M, Layton B A, Santoro A E, Boehm A B (2007). (7) for all Enterococcus strains investigated in this study. Clin Microbiol Rev, 6(4): 428–442, Farmer P (2005). The dendrogram suggests a close relatedness between strains 2 and 6 and also between strains 3 and 8, which is in contradiction to the phenotype-based identification results. h�bbd``b`z$��X��G�`V,f � �H�H�.��D| ĭ\Q B u�@�!H�ne`bdZ�20҅����k� [�S
Though enterococci are differentiated from other bacterial genera via classical culture and biochemical methods, nucleic acid sequencing is required to differentiate species within the genus—a costly, time consuming, and technically challenging procedure for laboratory technicians that, in itself, does not necessarily lead to speedy identification of bactericidal antibiotics. This observation underscores important differences in the survival strategies and likelihood of therapeutic success, critical factors usually obscured by lumping the organisms together as Enterococcus species or enterococci. At random locations in each smear, 10 spectra, each with a 30-s signal integration time, were collected. https://doi.org/10.1007/s11515-012-1183-5. Google Scholar, Pang T, Peeling R W (2007). The spectrometer was continuously purged by dry air to reduce contributions from water vapor and CO2. endstream
endobj
startxref
In addition, both spectroscopic techniques proved to be capable of discriminating accurately at the strain level, which opens the door for using these physicochemical techniques as tools for epidemiological studies. Interestingly, this Raman dendrogram suggested, in contrast to the FT-IR dendrogram, that the E. casseliflavus strain shows only little similarity to the other strains. For the IR attenuated total reflectance (ATR) measurements, cells from 18-h-old cultures were carefully harvested from the solid agar plate and homogeneously spread over the whole ATR crystal surface. Briefly, bacterial smears were placed under a microscope objective and excited with 100 mW of laser power (830 nm). Upon closer spectral inspection, the different clustering of E. hirae strain 6 by the Raman approach could be ascribed to the fact that this strain expresses low levels of carotenoid as well. Google Scholar, Elzinga G, Raviglione M C, Maher D (2004). Typical first-derivative IR spectra of the six different species plotted for the spectral ranges used to calculate spectral distances are displayed in Fig.1. While there are 17 or more species of Enterococcus, only two are commonly found in humans: E. faecalis and E. faecium. The Raman spectrum of the pigmented E. casseliflavus exhibits preresonance-enhanced bands of carotenoids. The two vibrational spectroscopic techniques provide complementary information. J Infect Dis, 201(s1 Suppl 1): S73–S77, Valenzuela M S, Ikpeazu E V, Siddiqui K A (1996). The situation is further complicated by the fact that enterococci have developed a number of mechanisms for the transfer of resistance genes (1). Enterococcus faecalis and Enterococcus faecium are both human intestinal colonizers frequently used in medical bacteriology teaching laboratories in order to train students in bacterial identification. Evaluation of IR spectral data (calculation of derivatives, normalization, etc.) In addition, hospitals within the United States and around the world commonly isolate these bacteria because they are a cause of bacteremia, urinary tract infections, endocarditis, wound infections, and nosocomial infections. J Bacteriol, 169(10): 4646–4650, Caldwell B A, Ye C, Griffiths R P, Moyer C L, Morita R Y (1989). An overview of nosocomial infections, including the role of the microbiology laboratory. hirae strain 6. Am J Clin Pathol, 47(1): 30–39, PubMed It is particularly encouraging that of the results of all methods used in this study only the FT-IR result was in accordance with the identification by the gold standard (Table 1). (iii) FT-IR attenuated total reflectance (ATR) spectroscopy. Correspondence to Evaluation of Raman spectra was accomplished as already described for the IR data. Characterization of glycopeptide-resistant enterococci from U.S. hospitals. 1752 N St. NW They are gram positive, Capsule Negative, Catalase Negative, Citrate Negative, Non-Flagellated, Non-Sporing, etc. Similarly for the clustering of the Raman data, again the E. faecium strains cluster into two groups; however, in this case, it is strain 19 that clusters apart. h��Zmo��+���uw��+p����E��{9�������%Cڠ��. Various studies have shown that vibrational spectroscopy provides sufficient resolution power to distinguish microbial cells at different taxonomic levels, even at the strain level (10). Further diagnostic evaluation using genotypic methods—i.e., PCR of the species-specific ligase and glycopeptide resistance genes, which is limited to the identification of only four Enterococcusspecies and 16S RNA sequencing, the “gold standard” for identification of enterococci—confirmed the results obtained by the FT-IR classification. Because of this vibrational spectroscopy is not only advantageous as a tool for taxonomic studies but also proves to be very rapid and reliable as a potential routine classification method. Microbiol Rev, 53(4): 491–516, PubMed What can infrared spectroscopy tell us about the structure and composition of intact bacterial cell? American Society for Microbiology Diagnostic tests for infectious diseases in the developing world: two sides of the coin. Ad`��0p4p$��``0vK��af9D�o���-Ϊ��*R�,����r0
W6�i� -��`��|�)��2=弣�a�;\k4?�<9ıb���K�'��X#����H3�7�L�-�4еR;�.�b`�6��� � x�1l
Overall, this has resulted in an increased need for rapid and accurate identification of enterococci at the species and subspecies level as a means of effectively assisting infection control and epidemiological studies. faecium, which are considered part of the normal intestinal flora, are among the leading causes of nosocomial infections and may cause severe infections, including endocarditis and septicemia (16).
