Differentiation of some enterococci by gas chromatography

Clinical and epidemiological features of Enterococcus casseliflavus/flavescens and Enterococcus gallinarum bacteremia: a report of 20 cases

The clinical significance of intrinsically vancomycin-resistant enterococci is not yet fully established, as these organisms are infrequently recovered from clinical specimens. We report our experience with 20 cases of Enterococcus gallinarum and Enterococcus casseliflavus/flavescens bacteremia in humans from 1992 through 1998. Sixteen cases of bacteremia were caused by E. gallinarum. Underlying conditions were present in 19 (95%) of the patients and included malignancy, receipt of transplant, and Caroli's disease. Polymicrobial bacteremia was present in 9 patients (45%). E. gallinarum and E. casseliflavus/flavescens, although they are infrequently isolated from clinical specimens, may cause serious invasive infections.

Applications of cellular fatty acid analysis

More than ever, new technology is having an impact on the tools of clinical microbiologists. The analysis of cellular fatty acids by gas-liquid chromatography (GLC) has become markedly more practical with the advent of the fused-silica capillary column, computer-controlled chromatography and data analysis, simplified sample preparation, and a commercially available GLC system dedicated to microbiological applications. Experience with applications in diagnostic microbiology ranges from substantial success in work with mycobacteria, legionellae, and nonfermentative gram-negative bacilli to minimal involvement with fungi and other nonbacterial agents. GLC is a good alternative to other means for the identification of mycobacteria or legionellae because it is rapid, specific, and independent of other specialized testing, e.g., DNA hybridization. Nonfermenters show features in their cellular fatty acid content that are useful in identifying species and, in some cases, subspecies. Less frequently encountered nonfermenters, including those belonging to unclassified groups, can ideally be characterized by GLC. Information is just beginning to materialize on the usefulness of cellular fatty acids for the identification of gram-positive bacteria and anaerobes, despite the traditional role of GLC in detecting metabolic products as an aid to identification of anaerobes. When species identification of coagulase-negative staphylococci is called for, GLC may offer an alternative to biochemical testing. Methods for direct analysis of clinical material have been developed, but in practical and economic terms they are not yet ready for use in the clinical laboratory. Direct analysis holds promise for detecting markers of infection due to an uncultivable agent or in clinical specimens that presently require cultures and prolonged incubation to yield an etiologic agent.

Recent taxonomic changes in the genus Enterococcus

Recent taxonomic changes among the catalase-negative gram-positive cocci have led to the recognition of a separate genus for bacteria previously considered to be members of the genus Streptococcus. Presently, a total of 12 species of the genus Enterococcus have been described. The characteristics, taxonomy and nomenclature of these species, along with the possible clinical implications of revised enterococcal taxonomy, are discussed.

High-performance liquid chromatographic analysis of bacterial fatty acid composition for chemotaxonomic characterization of oral streptococci

A high-performance liquid chromatographic method was developed to analyze the fatty acid composition of bacterial lipids. After saponification of lipids extracted from bacteria, the liberated fatty acids were labeled with a fluorescence reagent, 4-bromomethyl-7-acetoxycoumarin, followed by reversed-phase high-performance liquid chromatographic separation and fluorescence detection. All bacterial fatty acids were simultaneously separated within 30 min and sensitively determined. This method was applied to the chemotaxonomic characterization of oral streptococci. The fatty acid composition of phospholipids and total lipids distinguished Streptococcus mutans from any other species examined and showed that Streptococcus sanguis had a close taxonomic relationship with Streptococcus salivarius.

Fatty acid composition of Streptococcus milleri

The cellular fatty acids of 31 strains belonging to the Streptococcus milleri group were analysed by capillary gas-liquid chromatography. Results were compared with findings from biochemical differentiation of the strains into Streptococcus constellatus (two strains), Streptococcus anginosus (16 strains) and Streptococcus intermedius (13 strains). Eight strains of various other streptococci were included as internal references, including three strains of streptococcus morbillorum, three strains of beta-hemolytic streptococci, and two strains of enterococci. The Streptococcus milleri strains formed a very homogeneous group according to fatty acid composition and were easily differentiated from other groups. However, within the group, it was not possible to differentiate Streptococcus constellatus, Streptococcus anginosus and Streptococcus intermedius by fatty acid composition alone.

Identification of Streptococcus bovis and Streptococcus salivarius in clinical laboratories

Streptococci identified as Streptococcus bovis, S. bovis variant, and Streptococcus salivarius were examined with respect to physiological and serological characteristics and cellular fatty acid content. Similarities in physiological reactions and problems encountered in serological analysis were noted, suggesting that an expanded battery of physiological tests is needed to definitively identify these streptococci. Cellular fatty acid analysis provided an accurate method for distinguishing S. salivarius from S. bovis and S. bovis variant.

Effect of cultural conditions on trimethylsilyl-sugar profiles of Streptococcus mutans

The cellular carbohydrates of Streptococcus mutans NCTC 10832 were converted to methyl glycoside trimethylsilyl ethers and analyzed by gas-liquid chromatography. The resulting profiles revealed the presence of glycerol, xylose, rhamnose, galactose, glucose, N-acetylglucosamine, and N-acetylmuramic acid. The proportions of monosaccharides in the profile were found to be stable with respect to changing growth temperature or duration of growth. However, the type of medium used, and its carbohydrate content, did significantly alter the profile, whereas gaseous atmosphere exerted a lesser effect on carbohydrate composition. By controlling growth parameters, we obtained reproducible profiles. Whole cells are probably a satisfactory alternative to highly purified cell walls.

Detection of 3-hydroxy fatty acids at picogram levels in biologic specimens. A chemical method for the detection of Neisseria gonorrhoeae?

A method for the detection of 3-hydroxy dodecanoic acid at low picogram levels is described. The procedure involves preparation of a heptafluorobutryl derivative of the butyl ester of the fatty acid and its detection by gas-liquid chromatography using an electron capture detector. The method was adapted for use with biological specimens. Potential of the method for screening for gonococcal infection is discussed. Limitations of the method are that about 105 Neisseria gonorrhoeae cells are required for detection and that interfering substances are a major problem working at maximum sensitivity of the electron capture detector necessitating complex purification procedures. The method eliminates the need to maintain the viability of cells in specimens, thus facilitating collection and transport of specimens.

Differentiation of Peptococcus and Peptostreptococcus by gas-liquid chromatography of cellular fatty acids and metabolic products

Gas-liquid chromatographic (GLC) profiles of cellular fatty acids and metabolic products were useful in identifying strains of Peptococcus saccharolyticus, Peptococcus asaccharolyticus, Peptostreptococcus anaerobius, Peptostreptococcus micros, and Streptococcus intermedius. The GLC results supported the recent taxonomic decision to transfer aerotolerant Peptostreptococcus species to the genus Streptococcus. Because inconsistencies in the results prevented our differentiating Peptococcus prevotii. Peptococcus magnus, and Peptococcus variabilis by GLC, additional strains will have to been examined. These GLC techniques are amenable to routine use; however, for interlaboratory results to be meaningful, the classification and nomenclature of the anaerobic gram-positive cocci should be standardized.

Fatty acid fingerprints of Streptococcus mutans NCTC 10832 grown at various temperatures

Fatty acid fingerprints were determined gas chromatographically for Strepcococcus mutans NCTC 1082 which had been grown in batch brain heart infusion at a series of nine temperatures ranging from 29.0 to 40.0 degrees C. The major acids at all temperatures were n-palmitic and octadecenoic acids. Other acids detected at all temperatures included n-myristic, palmitoleic, n-stearic, and eicosenoic acids. An increase in temperature resulted in a decrease in the proportion of unsaturated to saturated fatty acids, indicating the importance of accurate temperature control in such gas-liquid chromatographic, chemotaxonomic studies.

Long-chain fatty acids of peptococci and peptostreptococci

The long-chain fatty acids extracted from the whole cells of 12 clinically significant species of peptococci and peptostreptococci were characterized by gas-liquid chromatography. The resulting methylated fatty acid profiles (and some unidentified compounds) of 82 strains allowed the 12 species to be separated into four groups. Fifteen strains of Peptostreptococcus anaerobius were placed in group I because they had a unique, prominent compound that occurred in the area where a C8 to C10 fatty acid would be expected. Group II, consisting of Peptostreptococcus intermedius, Peptostreptococcus micros, Peptostreptococcus parvulus, Peptococcus morbillorum, and Peptococcus constellatus, produced C14, C16:1, C18:1, and C18 fatty acids. Peptococcus prevotii, Peptococcus variabilus, Peptococcus magnus, Peptococcus asaccharolyticus, and Peptostreptococcus productus were placed in group III because they contained three to six additional, unidentified compounds that strikingly differentiated them from group II. Peptococcus saccharolyticus was the single species assigned to group IV because it yielded C14, C16, C18:1, C18, and C20 fatty acids and a prominent unidentified peak that occurred between C14 and C16 fatty acids. This study indicated that cellular long-chain fatty acids may be an important tool in clarifying the taxonomy of the peptococci and peptostreptococci.

Rapid diagnosis of anaerobic infections by direct gas-liquid chromatography of clinical speciments

Current methods to isolate and identify anaerobic bacteria are laborious and time consuming. It was postulated that the short-chain fatty acids (SCFA) produced by these organisms might serve as microbial markers in clinical material. 98 specimens of pus or serous fluid were analyzed by gas-liquid chromatography, and findings were compared with culture results. Good correlations were found for the recovery of anaerobic Gram-negative bacilli and the presence of isobutyric, butyric, and succinic acids. 19 of 20 specimens with significant amounts of these acids (greater than 0.01 mumol/ml) yielded bacteroides or fusobacteria. Culture of the single "false-positive" specimen failed to grow anaerobic Gram-negative bacilli, although clinical data and Gram-stain suggested their presence. 77 of 78 specimens which has insignificant concentrations of the marker acids failed to yield anaerobic, Gram-negative bacilli in culture. The single "false-negative" specimen yielded Bacteroides pneumosintes, an organism which does not ferment carbohydrates. It is concluded that direct gas-liquid chromatographic analysis of clinical specimens provides a rapid presumptive test for the presence of anaerobic, Gram-negative bacilli.

Cellular fatty acid composition of Streptococcus mutans and related streptococci

The cellular fatty acid composition of 18 strains of Streptococcus mutans and 17 isolates of related streptococci were examined by gas-liquid chromatography. The cultures could be divided into two distinct groups on the basis of their fatty acids. The first group, which included S mutans and S salivarius, contained palmitic (16:0), octadecenoic (18:1), stearic (18:0), eicosenoic (20:1), and eicosanoic (20:0) acids. The presence of the two 20-carbon fatty acids distinguished S mutans and S salivarius from all of the other species. Two of the S mutans cultures were further distinguished by the presence of 19-carbon and 21-carbon cyclopropane acids. The second group included S sanguis, S mitis, S uberis, and a culture of Lancefield group C streptococci. The percentages of the major acids (16:0, 18:1, and 18:0) found in these species were essentially identical. A culture of Lancefield group E streptococci contained large amounts of 16:1 and 18:1 and small amounts of two unidentified acids which were not present in any of the other cultures.