An A1 broth is a liquid culture medium used in

microbiology Microbiology () is the scientific study of microorganisms, those being unicellular (single cell), multicellular (cell colony), or acellular (lacking cells). Microbiology encompasses numerous sub-disciplines including virology, bacteriology, prot ...

for the detection of

fecal coliforms A fecal coliform (British: faecal coliform) is a facultatively anaerobic, rod-shaped, gram-negative, non-sporulating bacterium. Coliform bacteria generally originate in the intestines of warm-blooded animals. Fecal coliforms are capable of growth ...

in foods, treated wastewater and seawater bays using the

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 (incidence) data. There are many discrete entities that are eas ...

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

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 so they are freely movable. The culture media to be tested is then added to the la ...

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

Typical formula (g/L)

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 An autoclave is a machine used to carry out industrial and scientific processes requiring elevated temperature and pressure in relation to ambient pressure and/or temperature. Autoclaves are used before surgical procedures to perform sterilizat ...

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.

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

References

Microbiological media {{Microbiology-stub