Cellular Fatty Acid Analysis in the Differentiation of Clostridium Species in the Clinical Microbiology Laboratory

Abstract

The identification of Clostridium species can be problematic for the diagnostic microbiology laboratory. The introduction of the MIDI Microbial Identification System (MIS) has enabled personnel in diagnostic laboratories to perform cellular fatty acid analyses on a variety of microorganisms. We used the Virginia Polytechnic Institute (Blacksburg, VA) Anaerobe Library (Moore Version 3.8) to perform analyses on 216 strains representing 18 species of Clostridium. The organisms were characterized with use of traditional biochemical methods that employ prereduced anaerobically sterilized media and other reference diagnostic methods. The MIS identified 86% of the strains correctly to the species level without the need for supplemental tests, and identified an additional 6% of the strains to species levels with the aid of a few supplemental tests. Only 3% of strains were identified by genus incorrectly. The cellular fatty acid patterns of selected, medically important clostridia were so distinctive that 100% of these species were identified correctly. The MIS has many practical benefits, including speed of identification, and few disadvantages (such as equipment cost) for the clinical microbiology laboratory.

Clostridium aldenense sp. nov. and Clostridium citroniae sp. nov. Isolated from Human Clinical Infections

“…Although the rapid methods that measure preformed enzymes are convenient, their accuracy has not been adequate for identifying clostridia (1,5,9,20,27). Therefore, basic characteristics, such as Gram stain and colony morphology, continue to play an important role in their identification (1,2,20). However, this approach also has limitations because some Clostridium strains stain gram negative and others do not consistently exhibit spores.…”

“…Susceptibility testing is generally not done in clinical laboratories, although resistance to antibiotics by C. clostridioforme has been noted, and some strains produce ␤-lactamase (2,6,13,24,25). In addition, C. clostridioforme strains produce a higher metabolic enzyme activity among the intestinal microflora, which leads to the generation of toxic or carcinogenic metabolites (22,28).…”

Molecular Characterization of Lactobacillus plantarum Genes for β-Ketoacyl-Acyl Carrier Protein Synthase III ( fabH ) and Acetyl Coenzyme A Carboxylase ( accBCDA ), Which Are Essential for Fatty Acid Biosynthesis

“…In bacteria, fatty acids are primarily the precursors of phospholipids rather than storage fuel, and thus ACC activity is coordinated with cell growth and division (1,25,26). The requirement for biotin and lipids in most lactobacilli suggests that expression of the acc operon might play an important role in growth of the bacteria.…”

Multiplex PCR for rapid differentiation of three species in the “Clostridium clostridioformegroup”

“…Identification of C. clostridioforme can pose a problem for the routine clinical laboratory because it typically stains gram‐negative, and the spores are often difficult to observe [2,3]. The traditional methods for identifying Clostridium isolates include morphological examination, various biochemical tests including carbohydrate fermentation reactions, analysis of volatile and nonvolatile fatty acid production [4,5], and gas–liquid chromatography of bacterial cellular fatty acids [6]. These methods are labor‐intensive, time‐consuming, and sometimes result in inconclusive identification [2].…”