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SUMMARY The properties of strains of Microbacterium thermosphactum obtained from various sources were investigated. All exhibited pleomorphism and occurred both as coccobacilli and as long rods. The change from one morphological form to another was followed by means of slide culture techniques. Electron micrographs of thin sections of M. thermosphactum were also examined. The medium and incubation temperature influenced the catalase and benzidine reactions. The practical implications and the possible taxonomic significance of the results are discussed.

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T. TONG C'c~rctcelle Foocts , Missis.sccrcgcr . Or~t. , Cotccrdn P. DODSWORTH J . M. Schrlrirlrr, 1r1c.. Kitc/lerrc,r, Orlt., Cor~trtlrr S . MCLAUGHLIN Foocl crrltl Drug Aclrr~ir~i.sfrrrlior~, Mirzrlrtrpolis, MN, U.S.A . comparative study of the MPN procedure and the Anderson-Baird-Parker direct plating method for the enumerationof E.sc/i~richicr coli biotype I in raw meats. Can. J. Microbial. 25: 1321-1327. The most probable number(MPN) and a direct membrane-plating (DP) method were compared for enumeration of Esc/lc,ric~hicr coli biotype I in raw meats by I 1 laboratories. The D P method yielded higher counts of E. c d i than the MPN method for frozen samples but neither method consistently gave highercounts fornon-frozen samples. The DPmethod was less variable and gave a higher rate of detection of low numbers of E. c d i in frozen samples. Despite the inability of the D P method to enumerate E. coli biotype I1 and intermediate types, which complise only 3-5% of the Esc~llcrichio strains (Ewing 1972). the method is preferable to the MPN method for enumerating E. c.01; in raw meats because of its lower variability, better recovery from frozen samples, rapidity, decreased requirement for media, and decreased costs for analysts' time. comparative study of the MPN procedure and the Anderson-Baird-Parker direct plating method for theenumeration of E.schrric,/litr c,oli biotype I in raw meats. Can. J. Microbiol. 25: 1321-1327. Onze laboratoires ont compare 121 methode du nombre le plus probable (MPN) et lamethode d e I'ensemencement direct sur membrane (DP) pour la numeration d'E.sc~/~cric~kitr c.01;. biotype I, dans les viz~ndes crues. A pzu-tir d'echantillons congeles, la methode D P donne des valeurs d'E. c,oli plus elevees que la methode MPN. mais ni I'une ni I'autre ne donnent des decomptes regulierement plus eleves k pzu-til-d'echantillons non-congeles. La methode DPcst moins variable et serait plus sensible. permettant de detecter i un taux plus eleve les faibles quantites d'E. coli dans les echnntillons congeles. Malgre son incapacite B faire ledecompte d'E. cwli du biotype I1 ou d e types intermedinires. ce qui represente 3 a 5% des souchcs d'E,sc~/7rric~/licr (Ewing 1972). la methode DP est preferable a la methode MPN h cause d e sa plus faible variabilite, son taux superieur d e recuperation 5 parfir d'echantillons congeles, sa rapidite, sa consommation reduite de milieux et i~ cause d'une reduction des cohts d e temps d e manipulation. [Traduit par le journal]

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