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The Importance of Checking the Sterility of the Nutrient Media for the Identification of Microorganisms before Use in the Microbiological Laboratory

Adis Hrvačić orcid id ; Zavod za javno zdravstvo SBK/KSB-a, Travnik, Bosna i Hercegovina

Puni tekst: hrvatski pdf 447 Kb

str. 305-311

preuzimanja: 580



Microbial contamination of the nutrient media used for the cultivation of microorganisms is quite common in microbiology laboratories. During the preparation of nutrient media for the cultivation and isolation of pure bacterial cultures, the likelihood of contamination is high either due to inadequate sterilization, improper handling or inadequate control of storage conditions and to check shelf life. Prepared plates should not be used immediately or stored at low temperature until they are tested for sterility. Sterility testing is a very important segment prior to the use of microbial plates and procedures and one of the major factors affecting the validity of test results in a microbiology laboratory.

The aim of the paper is to establish criteria for rejection of contaminated plates. Three sets of plates of nutrient medium were prepared and incubated at room temperature for 18-24 h to check for sterility. Contamination assessment: colony growth on or below the surface. Plate incubation was extended by another day for the development of contamination on plates on which no colonies had grown on day one.

The results revealed that two types of contamination were found in the two groups. The first set of plates had colonies on the surface and contamination was not found the next day on uncontaminated plates indicating that contamination could occur during improper handling of the plates. The second group has colonies below the surface and pollution developed on the second day in non-contaminated plates due to improper sterilization of glassware or improper sterilization of nutrient media.

Understanding the importance of sterility testing before using nutrient media for the cultivation of microorganisms of interest, it is recommended that sterility confirmed plates be used for further microbiological procedures, while all other sets of contaminated plates establish rejection criteria regardless of how they are produced and what type of contamination is found.

Ključne riječi

microbiological contamination, sterility, microorganisms, laboratory

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Podaci na drugim jezicima: hrvatski

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