Fatty acid characterization of rapidly growing pathogenic aerobic actinomycetes as a means of identification

Abstract

The fatty acid compositions of 39 type strains and 529 clinical or reference strains of pathogenic aerobic actinomycetes were analyzed after standardized culture by using the Microbial Identification System (MIS). Library entries for each type strain were created by using the MIS Library Generation Software, and the fatty acid profiles of clinical and reference strains were compared to these library entries. The bacteria separated into two large groups based upon major amounts of branched-chain or of saturated or monounsaturated straight-chain fatty acids. Identification of isolates was possible by using only the type strains for comparison, but fatty acid heterogeneity occurred within most species. The genera Gordona, Mycobacterium, Nocardia, Rhodococcus, Rothia, and Streptomyces, as well as strains of Amycolatopsis orientalis, Dermatophilus congolensis, Nocardiopsis dassonvillei, Pseudonocardia autotrophica, Saccharothrix aerocolonigenes, and Tsukamurella paurometabola, are aerobic actinomycetes that have been implicated in human infections (3, 29, 40). Prior attempts to improve the identification of these aerobic actinomycetes by cellular fatty acid analysis have used various culture media, growth conditions, incubation times, extraction methods, and chromatography techniques, all factors which affect the fatty acids expressed (9, 20, 22, 23, 26). The Microbial Identification System (MIS; Microbial Identification Inc., Newark, Del.) standardizes the chromatography variables associated with quantitative fatty acid analysis and facilitates fatty acid analysis as a means of identifying bacteria (53). We analyzed the type strains of 39 pathogenic aerobic actinomycete species after standardized growth and incubation and created library entries for each species. The fatty acid profiles of 529 clinical and reference strains were then compared to these library entries. Fatty acid analysis is a limited, but practical method for the rapid identification of aerobic actinomycetes, and our results are consistent with some prior claims for the existence of subgroups within defined taxa (8, 33, 39, 42, 48). MATERIALS AND METHODS Bacteria. The sources of the type strains, reference strains, and other strains that were used to establish additional taxa defined by fatty acid profiles are listed in Table 1. Other isolates were obtained from commercial culture collections, the collections of other researchers, and clinical specimens. Actinomadura madurae and Actinomadura pelletieri were excluded from this study due to their fastidious growth requirements and need for prolonged incubation. Culture conditions. All strains, with the exception of Nocardia brevicatena, were grown at 28°C for 96 h in ambient air on four TSBA plates composed of Trypticase soy broth (no. 11768; BBL) and 1.5% agar (no. 11849; BBL). Isolates of N. brevicatena were cultured on plates of TSBA with 1% Tween 80 (T164-500; Fisher Scientific), because we found a slight growth enhancement in the presence of Tween 80. Identification by biochemical tests. Clinical ...

The use of fatty acid methyl esters as biomarkers to determine aerobic, facultatively aerobic and anaerobic communities in wastewater treatment systems

“…Gram-positive or negative anaerobic and Gram-negative facultatively aerobic bacteria constituted Group IV. Finally, Group V presented Gram-positive or negative aerobic and Lechevalier (1981), Vestal & White (1989), Welch (1991), Rajendran et al (1992), McNabb et al (1997), Sundh et al (1997), Bossio & Scow (1998) Gram-negative facultatively aerobic bacteria. A clear distinction between aerobic and anaerobic bacteria was thus obtained by the PCA method.…”

“…The analysis of fatty acid methyl esters (FAME) profiles provides insight into important changes in microbial communities in wastewater treatment plants, in such a way as to avoid the microbial culture bias. FAME analysis may be used to identify isolated and pure microbial cultures (Sasser, 1997), in taxonomic studies (Yamamoto et al, 1998) or for the identification of bacteria of medical importance (McNabb et al, 1997).…”

The genus Rhodococcus

“…This makes it difficult to assess the reliability of the system for identifying Rhodococcus strains. McNabb et al (1997) investigated use of the MIS for identifying various actinomycetes. While the system was able to differentiate those Rhodococcus species tested, heterogeneity within species was observed, e.g.…”

Identification and environmental detection of Rhodococcus species by 16S rDNA-targeted PCR

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