Giolitti-Cantoni Broth for Staphylococcus aureus

Aim

Giolitti Cantoni Broth Base with the addition of potassium tellurite is utilized to enrich selectively Staphylococcus aureus, a food-borne pathogen, from suspected items, according to ISO.

Principle

Oxoid Giolitti-Cantoni Broth, a tellurite-mannitol-glycine enrichment broth, based on the formulation of Giolitti and Canton is used for the selection and enrichment of Staphylococcus aureus from foodstuffs. Mannitol and sodium pyruvate act as staphylococcal growth stimulants and help in the detection of the organism if it is present in small quantities.

The development of Gram-negative lactose-fermenting bacteria is blocked by lithium chloride. Gram-positive bacteria are inhibited by potassium tellurite when combined with Glycine. The creating of anaerobic conditions via applying 2 cm of sterile paraffin reduces the development of micrococci. Giolitti-Cantoni Broth is suggested for identification of Staphylococcus aureus in baby milk as well as other weaning food items in which the organism must be absent from 1 gram the material to test.

This medium can be used for study of meat and the meat-based products.’ To do this, the concentration of the potassium tellurite should be decreased to 0.35 percent and it is suggested for the test sample to weigh less than 0.01 grams. sample should be decreased by 0.1-0.01 grams.

Giolitti-Cantoni Broth Composition

pH 6.9 ± 0.2

Giolitti-Cantoni Broth Preparation

1. Submerge 54.2 grams into 1 liter of distilled water, then heat it gently until dissolve.
2. Use 19 ml portions to fill 200 test tubes that measure 200 mm x 200 mm and sterilize them by autoclaving at 121°C for 15 minutes.
3. Cool quickly and then apply to every tube 0.3 milliliters of a sterile solution of potassium tellurite 3.5 percent (SR30).
4. The solution calls for the addition of the addition of a 3.5 percent solution of potassium tellurite if it is directly added of one gram of the sample to 19mls of broth. The amount of tellurite potassium is essential to reduce the number of organisms that are contaminating the broth. This could be anticipated.
5. Utilizing a diluted solutions of potassium tellurite is appropriate for 1 in 10 diluting of the food sample is taken.’ In these instances, the SR30 must be first diluted 1/10 with the sterile distillation water.
6. It is recommended to add 0.1 percent Tween 80 could be suggested to speed up recovery for damaged Staph. aureus cells e.g. made from milk powder.
7. 1 gram of Tween80 is to be added into 1 Liter of CM523 prior to autoclaving.

Technique

1. The medium should be vaccinated when it has been cool after autoclaving. If there is time delay before putting it in use, it should be removed from the dissolved air by immersion in freely moving steam for 20 minutes.
2. Innoculate one Gram of sample material as well as 1 ml of aliquots from a set of appropriate decimal dilutions into tubes that contain 19 ml of Giolitti Contoni Broth.
3. Two tubes are used to collect the sample as well as for the dilutes. This improves the probability of finding Staphylococcus aureus when it’s only present in very small quantities.
4. The medium is covered with two centimeters of paraffin wax sterile (melting temperature between 42 and 44 degC) and then incubated for an average of 48 hours with a temperature at around 35 degrees Celsius. Then, it is inspected every day.

Results

• Negative Result: This result is deemed negative for Staphylococcus aureus if there is no evidence of blackening of the media is detected. If blackening is observed on the bottom of tubes or if there’s a general blackening of the medium it is streaked on staphylococcal isolation media, such as Baird Parker Medium6 CM275 and then incubated at 35degC for 24 to 48 hours.
• Positive Result: The outcome is considered to be positive when colonies of black with an elongated white margin enclosed by a zone of clearing, appear.

The Shelf’s Life and Storage Conditions

• The dehydrated medium should be stored at a temperature below 25°C, and use it before the expiry date printed on the label.
• Keep the medium in storage at temperatures between 2 and 8 degrees Celsius.

Quality Control

• Positive control: Staphylococcus aureus ATCC”‘ 25923
• Negative controls: Staphylococcus epidermidis ATCC”‘ 1228

Certain varieties of Staph. epidermidis might grow and produce blackening based on the level of inoculum. The growth, should it occur, is usually smaller than Staph. aureus.