Usporedba izravnih i neizravnih metoda za određivanje broja živih mikroorganizama

undergraduate thesis

• Title (english): Comparison of direct and indirect methods for determining the number of live microorganisms
• Author: Nikolina Teskera
• Mentor: Ksenija Markov (mentor)
• Granter: University of Zagreb; Faculty of Food Technology and Biotechnology; (Department of Biochemical Engineering); (Laboratory for General Microbiology and Food Microbiology); Zagreb
• Defense date and country: 2022-09-19, Croatia
• Scientific / art field, discipline and subdiscipline: BIOTECHNICAL SCIENCES; Biotechnology

Abstract

Određivanje broja mikroorganizama u uzorcima hrane, sirovina, tla, vode, zraka ili drugih materijala iz okoliša dio je svakodnevne rutine u mikrobiološkim laboratorijima, a koristi se i u kliničkoj praksi kada je potrebno brzo identificirati mikroorganizme u svrhu postavljanja odgovarajuće terapije. Najboljom mjerom koncentracije stanica smatra se broj živih stanica koji se ujedno i određivao u ovom radu. Metode koje su se pritom koristile podijeljene su na izravne (McFarlandov standard, turbidimetrijsko određivanje, Thomaova komorica) i neizravne. Neizravna metoda uključuje pripremu decimalnih razrjeđenja te nacjepljivanje na odgovarajuće hranjive podloge. Rezultati su pokazali kako broj živih stanica mikroorganizama raste s porastom McFarland jedinica. Pri istim McF jedinicama postoji razlika u CFU vrijednostima i optičkoj gustoći u ovisnosti o vrsti mikroorganizama. Odabrane štapićaste gram-negativne bakterije, pri 2 McF pokazuju manje zamućenje suspenzije (optičku gustoću) u odnosu na odabrane gram-pozitivne bakterije i kvasce. Za pripremu istih vrijednosti McF jedinica potrebno je manje stanica kvasaca, jer su kvasci većih dimenzija od bakterija.

Abstract (english)

Determining the number of microorganisms in samples of food, raw materials, soil, water, air or other materials from the environment is part of the daily routine in the microbiological laboratories, and among other things, it is used in clinical practice when it is necessary to quickly identify microorganisms for the purpose of setting up appropriate therapy. The best measure of cell concentration is considered to be the number of living cells, which was also determined in this study. Used methods can be direct (McFarland standard, turbidimetric determination, Neubauer chamber) or indirect. An indirect method involves the preparation of decimal dilutions and inoculation on appropriate media. The results showed that the number of living cells of microorganisms increases with the increase of McFarland units. For the same McF units, there is a difference in CFU values and optical density depending on the type of microorganisms. Selected rod-shaped gram-negative bacteria, at 2 McF, show less turbidity of the suspension (optical density) compared to selected gram-positive bacteria and yeasts. Fewer yeast cells are needed to prepare the same values of McF units, because yeasts are larger than bacteria.

• Keywords: stanice; McFarland; razrjeđenje; mikroorganizmi
• Keywords (english): cells; McFarland; dilution; microorganisms
• Language: croatian
• URN:NBN: urn:nbn:hr:159:410408
• Study programme: Title: Biotechnology; Study programme type: university; Study level: undergraduate; Academic / professional title: sveučilišni/a prvostupnik/prvostupnica (baccalaureus/baccalaurea) inženjer/inženjerka biotehnologije (sveučilišni/a prvostupnik/prvostupnica (baccalaureus/baccalaurea) inženjer/inženjerka biotehnologije)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2024-04-04 11:15:56