ICMSF methods studies. XIII. An international comparative study of the MPN procedure and the Anderson-Baird-Parker direct plating method for the enumeration of Escherichia coli biotype I in raw meats

The most probable number (MPN) and a direct membrane-plating (DP) method were compared for enumeration of Escherichia coli biotype I in raw meats by 11 laboratories. The DP method yielded higher counts of E. coli than the MPN method for frozen samples but neither method consistently gave higher counts for non-frozen samples. The DP method was less variable and gave a higher rate of detection of low numbers of E. coli in frozen samples. Despite the inability of the DP method to enumerate E. coli biotype II and intermediate types, which comprise only 3–5% of the Escherichia strains (Ewing 1972), the method is preferable to the MPN method for enumerating E. coli 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 physiology of renal tubular transport mechanisms

This manuscript discusses current concepts of glomerular filtration and tubular transport of sodium, water, potassium, and urinary acidification by vertebrate kidneys in a comparative context. Work in mammalian and amphibian nephrons receives major emphasis due to our interest in application of new techniques for investigation of cellular mechanisms; when available, data from other vertebrate classes are discussed.