Abstract: The invention concerns the use of bioluminescence dependent on the reaction (1): luciferin+ATP+O2+Mg2++luciferase?oxyluciferin+photons for detecting and counting living cells of a given species potentially present in a liquid sample, said use being characterized in that it consists in measuring the total free intracellular adenyl nucleotides (AN) content, expressed in ATP form, of living cells of a given non-viral species, taking into account the fact that the sum of free intracellular ATP, ADP and AMP of said family is constant according to the relationship (2): [AN]=[ATP]+[ADP]+[AMP]=Cte after transforming the free intracellular ATP, ADP and AMP by using myokinase and pyruvate kinase, said measurement being performed (i) without adding ATP and (ii) after adding a known amount of ATP. The invention also concerns a method for detecting and counting cells by ATP-metry.

Abstract: The invention concerns the use of ATP-metry for detecting and counting viruses, via free adenyl nucleotides of their target host cells or via adenyl nucleotides bound to the viral DNA or RNA The invention also concerns the method for determining viruses by ATP-metry.