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Liz Middleton liz.middleton at lewis-associates.co.uk
Thu Aug 19 06:27:02 EST 1999

IDG has added a new medium, Aeromonas Agar, to its range of testing products
available under the LAB M brand. The highly selective nature of this agar
means that Aeromonas spp. can easily be distinguished from genera of the
Enterobacteriaceae, many of which are inhibited on Aeromonas Agar.

The clear purple gel can be used to isolate Aeromonas spp. from food,
clinical and environmental samples. In addition, the medium, based on
selective agents brilliant green and irgasan, will not inhibit those strains
of Aeromonas which are sensitive to the antibiotic ampicillin used in other
selective media.

Two recent studies, in Hull and Aberdeen, have shown that Aeromonas Agar
yields a significantly higher number of positive isolates than other
commonly used media. "In our trial, agar containing Irgasan and Brilliant
Green was found to be more selective in comparison with a standard medium.
The Irgasan/Brilliant Green medium produced approximately 50 per cent more
isolations of Aeromonas spp. (unpublished data), with colonies that were
relatively easier to see", according to Alison Eyre, Senior MLSO at Hull
Public Health Laboratory. "We therefore now routinely use the IDG medium
containing the crucial Irgasan and Brilliant Green constituents", she added.

David Ferguson, Senior MLSO in the Enteric Section of the Microbiology
Laboratory at Aberdeen Royal Infirmary has also noticed an increased number
of isolations when using the new IDG Aeromonas Agar. There has been a
fourfold rise in the number of positive samples identified so far this year.

Aeromonas Agar is easy to prepare and only requires boiling to effect
sterilisation. Once prepared, culture plates of Aeromonas Agar may be stored
for seven days at 2-8ƒC in the dark.

After inoculation, the plates only need to be incubated aerobically at 37oC
for 18-24 hours. Typically, Aeromonas spp. produce translucent pink colonies
that can be distinguished biochemically from the similar colonies formed by
Pseudomonas spp., with only Aeromonas spp. demonstrating fermentative

- ends ­

Editor: For more information, please contact: Phil Smith, IDG (UK) Ltd,
Topley House, 52 Wash Lane, Bury, Lancs, BL9 6AU
Phone: +44 (0) 161 797 5729, Fax: +44 (0) 161 762 9322 Email:
pasmith at idgplc.com

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