Identification of clinical isolates of gram-negative nonfermentative bacteria by an automated cellular fatty acid identification system

Abstract

An automated cellular fatty acid (CFA) bacterial identification system, Microbial Identification System (MIS; Microbial ID, Newark, Del.), was compared with a conventional system for the identification of 573 strains of gram-negative nonfermentative bacteria. MIS identifications were based exclusively on the CFA composition following 22 to 26 h of growth at 28°C on Trypticase soy agar. MIS identifications were listed with a confidence measurement (similarity index [SI]) on a scale of 0 to 1.0. A value of .0.5 was considered a good match. The MIS correctly listed as the first choice 478 of 532 (90%) strains contained in the data base. However, only 314 (59%) had SI values of 20.5. Of the 54 strains in which there was not agreement, 37 belonged to the genera Acinetobacter, Moraxella, or Alcaligenes or were Pseudomonas pickettii. Reproducibility studies suggest that SI variation is most likely a function of a difference in culture age at the time of analysis, which is due to the relatively low temperature and time of incubation. Other discrepancies were attributable to insufficiently characterized library entries or an inability to differentiate chemotaxonomically closely related species. The MIS, as the first automated CFA identification system, is an accurate, efficient, and relatively rapid method for the identification of gram-negative nonfermentative bacteria. The development of a CFA library with the media and incubation conditions routinely used for the isolation of clinical pathogens could further decrease the identification time and provide an increase in accuracy.

Visceral granulomas in farmed large yellow croaker, Larimichthys crocea (Richardson), caused by a bacterial pathogen, Pseudomonas plecoglossicida

“…Fatty acid methyl ester (FAME) analysis was performed as previously described (Abraham et al 2002). Briefly, the bacterial isolate was inoculated onto TSA, incubated at 28°C for 24 h, after which the cells were saponified, methylated to FAMEs and extracted as described in detail by Osterhout, Shull & Dick (1991). Then, the FAMEs were separated and analysed on an Agilent 6850 gas chromatograph (Agilent Technologies).…”

Adaptive responses of Salmonella enterica serovar Typhimurium DT104 and other S. Typhimurium strains and Escherichia coli O157 to low pH environments

“…Fatty acids were identified on basis of equivalent chain length data (Sasser 1990;Osterhout et al 1991). Clustering methods used were unweighted pair-group method arithmetic averages (UPGMA) as described by Romsburg (1990) on the relative (percentage of the total) peak area of the named peaks.…”

The Indoor Environment of a Modern Museum Building, The Sainsbury Centre for Visual Arts, Norwich, UK

“…The sampling strips were incubated at room temperature, unless indicated otherwise. Fatty acids were extracted and their methyl esters quantified using gas chromatography (Osterhout et al, 1991). The data were processed using Euclidean distance calculations and clustered according to Ward's algorithm.…”