An '''A1 broth''' is a liquid culture medium used in microbiology for the detection of fecal coliforms in foods, treated wastewater and seawater bays using the most probable number (MPN) method. It is prepared according to the formulation of Andrews and Presnell given below.<ref>{{Cite web|url=http://123exp-biology.com/transdifferentiation-of-stem-cells/1174245593/|archiveurl=https://web.archive.org/web/20070914012002/http://www.123exp-biology.com/t/01174245593/|url-status=dead|title=Transdifferentiation of Stem Cells – Page 1174245593 – Experimental Biology|archivedate=September 14, 2007}}</ref> It is used with a Durham tube, a positive tube being one that exhibits a trapped bubble of gas.

==Typical formula (g/L)== {|cellpadding="3" |--- || Tryptone || 20.0 |--- || Lactose || 5.0 |--- || Sodium chloride || 5.0 |--- || Triton X-100 || 1.0 |--- || Salicin || 0.5 |--- |} <ref>{{Cite web|url=http://www.sigmaaldrich.com/catalog/search/ProductDetail/FLUKA/17112|title=17112 A1 Broth BioChemika, for microbiology<!-- Bot generated title -->}}</ref>

==Directions== Suspend the dry ingredients in one liter of cold distilled water. Gently heat until completely dissolved and distribute 9 mL into test tubes with an inverted Durham tube. Sterilize in an autoclave at 121°C for 15 minutes. If needed, prepare multi-strength broth weighing the appropriate quantity of the dry medium. The final pH is 6.9 ± 0.1.<ref>{{Cite web|url=http://www.srlchem.com/products/product_details.php?productId=3649|title=A1 Broth &#124;Sisco Research Laboratories (SRL) (India)|website=www.srlchem.com}}</ref>

==Widespread usage== Variants of this test has been used for potable water across the globe, for example by the Cree community of Split Lake, Manitoba, by the Mapuche people of Maquehue, Chile<ref>{{Cite web|url=http://www.idrc.ca/en/ev-26962-201-1-DO_TOPIC.html|archiveurl=https://web.archive.org/web/20071204002329/http://www.idrc.ca/en/ev-26962-201-1-DO_TOPIC.html|url-status=dead|title=Portable Water-testing Kit: International Development Research Centre<!-- Bot generated title -->|archivedate=December 4, 2007}}</ref> and in Singapore, Malaysia and Thailand <ref>{{Cite journal|url=https://onlinelibrary.wiley.com/doi/abs/10.1002/tox.2540030510|archiveurl=https://archive.today/20121216141051/http://onlinelibrary.wiley.com/doi/10.1002/tox.2540030510/abstract|url-status=dead|title=Southeast Asian experiences with the coliphage test|first1=Sim Tiow|last1=Suan|first2=Ho Yueh|last2=Chuen|first3=Komol|last3=Sivaborvorn|date=September 9, 1988|journal=Toxicity Assessment|volume=3|issue=5|pages=551–564|via=Wiley Online Library|doi=10.1002/tox.2540030510|archive-date=2012-12-16|access-date=2020-09-09|url-access=subscription}}</ref>

==References== {{Reflist}}

Category:Microbiological media

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