An A1 broth is a liquid culture medium used in microbiology

Microbiology

Microbiology is the study of microorganisms, which are defined as any microscopic organism that comprises either a single cell , cell clusters or no cell at all . This includes eukaryotes, such as fungi and protists, and prokaryotes...

 for the detection of fecal coliforms

Fecal coliforms

A fecal coliform is a facultatively-anaerobic, rod-shaped, gram-negative, non-sporulating bacterium. Fecal coliforms are capable of growth in the presence of bile salts or similar surface agents, are oxidase negative, and produce acid and gas from lactose within 48 hours at 44 ± 0.5°C.Coliform...

 in foods, treated wastewater and seawater bays using the most probable number

Most probable number

The most probable number method, otherwise known as the method of Poisson zeroes, is a method of getting quantitative data on concentrations of discrete items from positive/negative data....

 (MPN) method. It is prepared according to the formulation of Andrews and Presnell given below. It is used with a Durham tube

Durham tube

Durham tubes are used in microbiology to detect production of gas by microorganisms. They are simply smaller test tubes inserted upside down in another test tube. This small tube is initially filled with the solution in which the microorganism is to be grown. If gas is produced after inoculation...

, a positive tube being one that exhibits a trapped bubble of gas.

Typical formula (g/l)

Tryptone Tryptone Tryptone is the assortment of peptides formed by the digestion of casein by the protease trypsin.Tryptone is commonly used in microbiology to produce Lysogeny broth for the growth of E. coli and other microorganisms...	20.0
Lactose Lactose Lactose is a disaccharide sugar that is found most notably in milk and is formed from galactose and glucose. Lactose makes up around 2~8% of milk , although the amount varies among species and individuals. It is extracted from sweet or sour whey. The name comes from or , the Latin word for milk,...	5.0
Sodium chloride Sodium chloride Sodium chloride, also known as salt, common salt, table salt or halite, is an inorganic compound with the formula NaCl. Sodium chloride is the salt most responsible for the salinity of the ocean and of the extracellular fluid of many multicellular organisms...	5.0
Triton X-100	1.0
Salicin	0.5

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

Autoclave

An autoclave is an instrument used to sterilize equipment and supplies by subjecting them to high pressure saturated steam at 121 °C for around 15–20 minutes depending on the size of the load and the contents. It was invented by Charles Chamberland in 1879, although a precursor known as the...

 at 121°C for 15 minutes. If needed, prepare multi-strength broth weighing the appropriate quantity of the dry medium. The final pH

PH

In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...

is 6.9 ± 0.1.

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 and in Singapore, Malaysia and Thailand