SALMONELLA ISOLATION AS EASY AS ABC!!
IDG has introduced a new chromogenic agar, under the LAB M brand, for
selective isolation of Salmonella spp. Demonstrating superior sensitivity
and specificity to desoxycholate citrate agar (DCA), the new ABC medium
(Freeman formulation) can significantly reduce the labour time and costs
associated with Salmonella detection using traditional agars.
Isolation of Salmonella spp. by culture remains the gold standard method of
detection. However most media are highly non-specific, and consequently
place a heavy burden on the laboratory in terms of biochemical and
serological confirmation of suspect colonies.
With improved specificity, the new ABC medium dramatically reduces the need
for Ofalse positive¹ screening, saving labour and reducing consumable costs.
ABC medium incorporates two chromogenic substrates which exploit the fact
that Salmonella spp. can be distinguished from other Enterobacteriaceae by
the presence of
a-galactosidase activity in the absence of b-galactosidase activity.
CHE-Galactoside is utilised by most Enterobacteriaceae, yielding black
colonies. The X-µ-Gal is hydrolysed by Salmonella spp. to produce
characteristic, easy to distinguish, green colonies.
A recent study, using the LAB M formulation, examined 1,022 strains of
Salmonella spp, and 300 other Gram negative strains. 99.7% of Salmonella
spp. produced typical green colonies on ABC medium and only one false
positive reaction was seen.
283 stool samples, selectively enriched in selenite broth were also
sub-cultured onto DCA and ABC medium. Overall, the sensitivity and
selectivity were clearly superior for ABC medium (100 and 90.5%,
respectively) than for DCA (88 and 26.9% respectively) as indicated in the
table below.
283 samples ABC DCA
Sensitivity 100 % 88 %
Selectivity 90.5 % 26.9 %
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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
--
Damian Bond
Tel 0161 236 7816
Mobile 0498 600 833
e-mail damian.bond at virgin.net
