PRODUCTS

Catalog No. M-1500

R & F® non-O157 STEC Enrichment BrothA Selective Enrichment Broth That Promotes The Growth Of The Six Major

non-O157 STEC Serogroups Similar To A Nutritive Nonselective Broth

The non-O157 Shiga toxin-producing Escherichia coli (STEC) strains have been recognized as an important food-borne pathogen worldwide. Depending on the country, up to 50% of the STEC cases have been attributed to non-O157 STEC mainly involving the 6 major serogroups: O26; O45; O103; O111; O121; and O145.

All of the 28 non-O157 STEC strains which includes the 6 major serogroups grown in the R & F® non-O157 STEC Enrichment Broth (STEC-EB) supported a similar final cells density as cells grown in Tryptic Soy Broth (TSB), whereas the USDA listed modified Tryptone Soya Broth containing 8 mg/l of novobiocin and 10 g/l of casamino acids (m-TSB) inhibited the growth of more than 20% of these strains incubated at 41-42°C for 20-22 h. However, the selectivity of m-TSB and STEC-EB against other competing bacteria was similar.

For the evaluation of the repair/growth of freeze-injured non-O157 STEC cells representing the 6 major serogroups, m-TSB rapidly kills all the freeze-injured non-O157 STEC cells and up to 1.5 log10cfu/ml of the noninjured cells, whereas in STEC-EB, a portion of the injured non-O157 cells dies without affecting the survival of the noninjured cells.

STEC-EB, therefore, is more effective than m-TSB in supporting the growth and survival of freeze-injured non-O157 STEC cells incubated at 41-42°C.

ReferencesRestaino, L. 2012. Growth and repair of Escherichia coli non-O157 STEC strains in selective enrichment broths. Poster (P3-167), IAFP 2012 101st Annual Meeting, Providence, RI.

R & F Products, Inc.2725 Curtiss St.Downers Grove, IL 60515

Phone: 630.969.5300Fax: 630.969.5303E-mail: rf@rf-products.netWeb Site: www.rf-products.net

ORDERING INFORMATION:

M-1500 R & F® non-O157 STEC Enrichment Broth

M-1510 R & F® non-O157 STEC Supplement for Enrichment Broth

M-1550 R & F® non-O157 STEC Enrichment Broth Detection System

Advantages of R & F® non-O157 STEC Enrichment Broth

• ComparedtoTSB,STEC-EBdidnotinhibit 28 non-O157 STEC strains, whereas, the growth of more than 20% of these strains were substantially reduced in m-TSB incubated at 41-42°C for 20-22 h.

•TheselectivityofSTEC-EBandm-TSBis similar; however, STEC-EB inhibits the growth of pseudomonads type bacteria and m-TSB does not which can be the dominate organism in fresh meats.

•ForSTEC-EB,onlyaportionofthefreeze-injured non-O157 STEC cells are killed without affecting the survival of the noninjured cell population, whereas, m-TSB killed all the freeze-injured non-O157 STEC cells and a substantial portion of the noninjured cells.

• AsinthenonselectiveTSBbroth,growthof the freeze-injured non-O157 STEC cells in STEC-EB is initiated after 2 h of incubation at 41-42°C.

Growth Response ofSTEC Strains

Organisms

No. of Strains

Growth ResponseNo. of Strains

STEC-EBbroth

STEC-EBbroth

m-TSB

m-TSB

Growth response of 28 Shiga toxin-producing non-O157 Escherichia coli (STEC) strains and other Gram (-) and (+) bacteria in m-TSB and STEC-EB incubated at 41-42°C for 20-22 h

++++a++++++0

280000

224101

Gram (-) bacteriab Gram (+) bacteria

M. rettgeriE. coli

P. aeruginsosaK. pneumoniaeE. hermanniiHafnia alvei

Shigella sonneiS. dysenteriaeC. sakazakii

P. agglomeransE. faecium

15911111111211

++++0+

++++0

++++++

0+++

+++++++++++

++++

++++0+

+++++++

0+

++++++++++

+ to ++++0

c

a Symbols: ++++, cell density equal to or 1 log₁₀ less than TSB; +++, cell density 1-1.5 log₁₀ less than TSB; ++, cell density 1.5-2.5 log₁₀ less than TSB; +, cell den-sity 2.5-5.0 log₁₀ less than TSB; and 0, cell density less than the detection limit of 100 cfu/ml.

b C. freundii, K. ozaenae, K. pneumoniae, Providencia alcalifaciens, P. stuartii, Sal-monella sp. (3), E. coli (3), E. aerogenes, and E. coli O157:H7 (3).

Listeria innocua, L. monocytogenes (4), L. welshimeri, L. ivanovii, B. cereus, and S. aureus. m-TSB = modified tryptone soya broth, TSB = tryptic soy broth, and STEC-EB = R & F® non-O157 STEC enrichment broth.

C