Cellular I'atty Acid Composition of the Legionnaires' Disease Bacterium 



M-H agar, with some slight increase (5%-7%) in tiie relative amount of a-15:0 acid on the 

 semisynthetic medium. Even though the relative proportions of total branched-chain fatty acids 

 were lower for all strains grown on CYE agar than for those grown on M-H medium, LDB strains 

 grown on any medium contained relatively large amounts of i-16:0, a-15;0, a-17:0, and i-14:0 

 acids. 



In general, branched-chain fatty acids are characteristic of gram-positive bacteria (5, 6, 17), 

 but they are present in major amounts (> 50% of total) in relatively few genera such as Bacillus 

 L\ -/), Listeria {15), Propiouibacterium (1 1), Micrococcus (2), and Staphylococcus (2). Of the 

 gram-negative organisms, only Then)ius aquaticus and Flavobacterium are known to contain 

 major amounts of these acids (9, 13). A striking feature of the cellular fatty acids of LDB is their 

 high content of branched-chain acids (> 77%). Although branched-chain acids have been found in 

 other bacteria, their presence and relative concentrations and the absence of other acids which 

 are generally present in other bacteria produce a unique cellular fatty acid profile for the LDB. 

 Data show that this unique cellular fatty acid composition is a relatively consistent characteristic 

 of the numerous LDB strains tested. The cellular fatty acid profiles are typical for cells from each 

 growth medium developed to date. Limited data on some other factors known to influence 

 cellular fatty acid composition (3. 6) indicate that they do not significantly affect the general 

 fatty acid profile. Thus, detemiination of cellular fatty acid content is valuable for rapid identi- 

 fication and classification of suspected isolates of the LDB. 



Table 2. 



Comparison of the cellular fatty acid composition of strains of 



the Legionnaires' disease bacterium grown on two different media^ 



a M-H; enriched Mueller-Hinton agar 



CYE; charcoal yeast extract agar 

 bThe number to the left of the colon refers to the number of carbon atoms; the number to the right refers to the number of 



double bonds; (i-) indicates a methyl branch at the iso-carbon atom; (a-) indicates a methyl branch at the anteiso-carbon; and 



(A) indicates a cyclopropane ring, 

 c Number refers to percentage (%) of total fatty acids; T = less than 2%. 



53 



