K. Carrick et al., The comparison of four bioluminometers and their swab kits for instant hygiene monitoring and detection of microorganisms in the brewery, J I BREWING, 107(1), 2001, pp. 31-37
Four luminometers and their swab units were evaluated for detecting ATP by
surface swabbing. Testing included pipetting known quantities of ATP direct
ly onto the swabs; pipetting known levels of bacteria and yeast directly on
to the swabs and swabbing samples of bacteria and yeast from a surface. Non
e of these instruments and swab detection kits provided consistent, reprodu
cible detection of ATP standards or ATP from microorganisms even at high co
ncentrations. All of the swab kits/instruments showed poor linearity in mea
suring known quantities of ATP and showed high variability in ATP readings
with replicate swabs containing identical concentrations of microorganisms.
Since good linearity and reproducibility could be obtained using a liquid
sample assay of ATP standards without swabs, it is suggested that the swab
method itself may be unreliable. ATP may not be effectively released from m
icroorganisms on swabs; ATP may adsorb to the swab interfering with detecti
on and/or the swab might block light transmission. Swabs of bacterial/yeast
suspensions dried on a sterilized surface, provided the most inconsistent
ATP readings and lacked linearity, A reason for the poor detection of micro
bial ATP by surface swabbing could be the inability to pick up microorganis
ms effectively.