Letournel-Glomaud C., MD ; Houssaye S., MD
Institut Montsouris, 6 Place de Port au Prince, 75013 Paris, FRANCE

GPAC are frequently found in clinical specimens. The cocci or coccobacilli are sensitive to vancomycin and metronidazole and grow only in an anaerobic atmosphere. Most GPAC use proteins and aminoacids as their major energy source, and do not utilise carbohydrates. Their classification is difficult. The genus Peptostreptococcus is phenotypically and phylogenetically heterogenous. It comprises 14 species of human origin (6 of which were recently described): P. anaerobius, P. asaccharolyticus, P. harei, P. hydrogenalis, P. indolicus, P.ivorii, P. lacrimalis, P. lactolyticus, P. magnus, P. micros, P. octavius, P. prevotii, P. tetradius P. vaginalis and 2 species of animal origin: P. heliotrinreducens, P. bamesae. Additional strains will eventually be classified. In research laboratories, complicated and expensive techniques such as gas-liquid chromatography, pyrolysis mass spectrophotometry and 16 sRNA gene sequence analysis deal with problems of taxonomy. However, in a clinical laboratory, once the anaerobic cocci have been isolated, the differenciation of species is based on: 1. Colonial morphology and microscopic appearance. These vary and although some species have specific aspects, they are not usually recognised and the strains are just classified as GPAC. 2. SPS disk. 3. Novobiocin disk. 4. coagulase production. 5. nitrates. 6. indole (not a reliable test for the identification of butyrate group species). 7. urease. 8. alkaline phosphatase 9. ADH. 10. determination of preformed saccharolytic and proteolytic enzyme profiles (PEP) whose reliability has been validated. The enzyme activities can be analysed by inoculating individual tests (Rosco* tablets, Rosco Diagnostica, Taastrup, Denmark) or commercially available kits (Api 32A*, bioMérieux, La Balme Les Grottes, France; Rapid Ana 11*, Innovative Diagnostic Systems, Norcross, GA, USA), reactions being separately interpreted. The databases of the preformed enzyme kits are not upgraded rapidly enough when new strains are classified. When GPAC are isolated from important clinical specimens, they should be identified to the species level so that their pathological role can be understood. A simplified flowchart of all Peptostreptococcus species, Staphylococus saccharolyticus and some Ruminococcus species (R. productus, R. hansenii) based on DA Murdoch's works is described. This chart can be used in clinical laboratories and in teaching workshops. The protocol is easy to carry out, inexpensive and not time-consuming.