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Objective: To compare the effect of glassware cleaning solution residues and the different rinsing procedures on microbial testing in microbiology laboratory.
Materials and Methods: The 2.0% glassware-washing solution for laboratory purpose (reagent type A) composing of polyethylene glycol dodecyl and ethylene oxide, 2.0% dish-washing reagent (reagent type B) composing of linear alkylbenzene sulfonate, potassium salt and sodium lauryl ether sulfate, and 0.5% detergent (reagent type C) composing of anionic surfactant, zeolite, sodium carbonate, sodium carboxymethyl and cellulose were used to evaluate the detergent residues after performing 5 different rinsing procedures (No rinsing, rinsing for 1, 3, 6 and 12 times) on petri dishes. Sterile glass petri dishes were included as negative control. The pH of cleaning residue was determined using 0.04% Bromthymol blue. The 50-100 CFU/mL of Staphylococcus aureus (ATCC 6538) was used to explore the efficiency of bacterial growth on glass petri dishes with pour plate method and reported as mean CFU/mL with standard error of the mean (SEM). Statistical analysis was performed with either IBMÒ SPSSÒ version 23 or GraphPad PrismÒ version 6.01. The p-value < 0.05 indicated statistical significant at 95% confident interval.
Results: The reagent type A was alkaline and became neutral after rinsing for 3 times. Additionally, the reagent type B was acidic and turned into neutral after rinsing for 3 times. Moreover, the reagent type C was alkaline and became neutral after rinsing for 6 times. All 3 detergents affect microbial growth at statistically significant level (p < 0.05) in the conditions of no rinsing, rinsing for 1, 3 and 6 times. Using reagent type A or B following by rinsing for 3 times did not show statistically significant in bacterial growth (p > 0.05). However, the bacterial growth was not significant different in the use of reagent type C comparing with reagent type A or B. When considering the rinsing procedures less significantly affecting bacterial growth (p > 0.05), the suggested protocols for using reagent type A or was 3-12 times whereas the protocol for reagent type B was 6-12 times and the protocol for reagent type C was 12 times.
Conclusion: Each cleaning solution has different pH properties in detergent residues, which is solved by rinsing protocols. Moreover, different types of detergent and rinsing procedures significantly affect the bacterial growth. The suitable protocols for each washing solution are rinsing at least 3 time for 2.0% glassware-washing solution, rinsing at least 6 times for 2.0% dish-washing reagent and rinsing at least 12 times for 0.5% detergent, respectively.
2. Polonini HC, Grossi LN, Ferreira AO, Brandão MAF. Development of a standardized procedure for cleaning glass apparatus in analytical laboratories. Journal of Basic and Applied Pharmaceutical Sciences. 2011; 32(1) :133-136.
3. World Health Organization. Glassware and plasticware. [Internet]. [Accessed: Aug 7, 2018]. Available from: https://www.who.int/water sanitation_health/resourcesquality/
4. San Diego County Public Health Laboratory. Water Microbiology Quality Assurance Manual. [Internet]. [Accessed: Aug 10, 2018]. Available from: https://www.waterboards.ca.gov/water_issues/programs/tmdl/records/region_9/2006/ref2714.pdf.
5. Sandle T, Satyada R. Determination of the cleaning efficiency for glassware in the pharmaceutical microbiology laboratory. European Journal of Parenteral & Pharmaceutical Sciences. 2016; 21(1): 16-22.
6. The United States Pharmacopeia. USP 42: NF36 The United Srates Pharmacopeia. Rockville, MD, USA: The United States Phramacopeial convention; 2019.
7. British Pharmacopeia. British Pharmacopeia Volume V. London, UK: The Stationery Office; 2019.
8. Department of Medical Sciences: Ministry of Public Health. Thai Pharmacopoeia II, Volume 1, Part 1. Bangkok, Thailand: Office of National Buddishm Press; 2018.
9. Kahl BC, Becker K, Löffler B. Clinical significance and pathogenesis of staphylococcal small colony variants in persistent infections. Clinical microbiology reviews. 2016; 29(2): 401-27.
10. มาตรฐานผลิตภัณฑ์อุตสาหกรรม มอก.78-2549. ผงซักฟอก. สำนักงานมาตรฐานผลิตภัณฑ์
อุตสาหกรรม. กรุงเทพฯ: กระทรวงอุตสาหกรรม; 2550.
11. อารัมภ์รัตน์ รัชดานุรักษ์. มาตรฐานผงซักฟอกกับการพัฒนาผงซักฟอก. สมอ สาร. 2548; 31: 6-7.