Disposable hygiene products are essential items in our daily lives, and their quality is directly related to our physical health, making them a key topic of concern for everyone. In recent years, CCTV News had a report on tissue sampling: the Jiangsu Market Supervision Bureau tested 150 batches of tissue and found that 36 batches were unqualified, and the total number of bacteria in 9 batches exceeded 13 times the national standard.

Let's learn about the detection knowledge of bacterial colony count in disposable sanitary products together.

definition
Disposable sanitary products refer to various daily necessities that are discarded after one use, come into direct or indirect contact with humans, and are used for the purpose of achieving human physiological hygiene or healthcare (antibacterial or bacteriostatic). The product properties can be solid or liquid. For example, disposable gloves or finger cots (excluding medical gloves or finger cots), tissues, wet wipes, sanitary wipes, phone masks, hats, masks, underwear, women's menstrual products (including sanitary pads), diapers and other excretory products (excluding wrinkled toilet paper), contraceptive covers, etc.

Sample processing

Open at least 3 packages for testing using sterile methods under 100 level purification conditions, take a sample from each package, and accurately weigh 10g of the sample.

Cut it into pieces and add it to 200mL of sterilized physiological saline solution, mix thoroughly, and obtain a physiological saline sample.

If the tested sample contains a large amount of water absorbing resin material and cannot extract enough sample solution, the dilution amount can be increased by 50mL each time until enough test sample solution can be extracted.

Liquid products are directly tested using the original solution.

Operation method

After the physiological saline sample settles naturally, take the supernatant and count the bacterial colonies.

Inoculate 5 petri dishes in total, add 1mL of sample solution to each dish, then use 15-20 mL of nutrient agar medium cooled to around 45 ℃ and melted, pour into each medium, and mix evenly.

After the agar solidifies, flip the petri dish and incubate at 35 ℃± 2 ℃ for 48 hours, then calculate the number of colonies on the plate.

Colony counting method

First observe with the naked eye, count the number of bacterial colonies, and then use a magnifying glass of 5 to 10 times to check to prevent omissions.

After recording the bacterial count of each petri dish, calculate the average bacterial count of each petri dish grown at the same dilution.

If there are contiguous colonies or flower like colonies spreading and growing in a petri dish, the dish should not be counted.

If the number of sheet-like colonies is less than half of the total number in the petri dish, and the distribution of colonies in the remaining half is very uniform, the number of colonies in this half of the petri dish can be counted and multiplied by 2 to represent the total number of colonies in the petri dish.

Colony count and reporting method

When the bacterial count is within 100, report it as the actual number. When it is greater than 100, use the two significant digits.

Reference document: Appendix B of the 2002 edition of the Hygiene Standards for Disposable Sanitary Products - Microbial Testing Methods for Products