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The growth patterns of microcolonies of 59 different pure cultures were studied on eight selective solid media. A method of growing microcolonies on the surface of polycarbonate membrane filters, placed on the selective agar media, followed by staining and examination by epifluorescent microscopy was developed. The patterns of growth of the pure cultures as microcolonies were studied on the eight selective media. Only four media proved to be reliable for this purpose and the relationship between the microcolony count and plate count was studied on these media together with nutrient agar. Microcolony counts using three of these media (enriched lauryl sulphate aniline blue, pseudomonas selective agar (C-F-C) and Baird-Parker medium) were capable of giving reliable estimates of coliforms (r = 0.89), pseudomonads (r = 0.93) and staphylococci (r = 0.92) after incubation at 30 degrees C for 3 or 6 h (staphylococci) at contamination levels of above 10(3) bacteria/g in a variety of foods. The results are available within a working day and should allow the more efficient management of food supplies.

With the direct epifluorescent filter technique (DEFT), differentiation of bacteria was achieved by a modified Gram-staining procedure using acridine orange as the counterstain. The method enumerated viable Gram-negative and all Gram-positive bacteria. Counts of clumps of orange fluorescent cells (Gram-negative DEFT count) correlated well with colony counts of Gram-negative bacteria in samples of raw milk (r = 0.94). The use of stainless steel membrane filter supports and the addition of citrate-NaOH buffer (0.1 M, pH 3.0) during filtration enabled 10 ml samples of milk to be filtered, thereby increasing the sensitivity of the DEFT five-fold. The relationship between colony and DEFT counts with 10 ml samples was better (r = 0.90) than that using standard 2 ml samples (r = 0.88). Alternatively, these modifications in procedure allowed the preincubation time for 2 ml milk samples to be reduced from 10 to 2 min. Sonication was successful in dispersing bacterial clumps in both pure cultures and in raw milk samples to yield a bacterial count by DEFT which should give a better indication of the hygienic status and keeping quality of a product, than counts of colony forming units.

Gram‐positive cocci which dominate in the intestinal flora of domestic pigeons were found to constitute a new species of the genus Enterococcus. The strains were most closely related to Enterococcus cecorum, originally described as Streptococcus cecorum, a carboxyphilic species from chicken intestines, and to Enterococcus avium. The pigeon strains resemble E. cecorum and also many E. avium strains in their lack of group D antigen and in being more sensitive to NaCl than other enterococci. The type strain is strain STR 345 (NCIMB 13013).