Bacteria culturing is an essential part in the medical field especially in identifying treatments such as antibiotic prescription for a certain disease. In addition to this, bacteria culturing and microbiological tests also aids in diagnosing certain diseases by identifying what bacteria or microorganism is causing it. In that case, Medical technologists should leave no room for mistakes in order to assure accurate and correct results.
Hi Nicole! I have listed here some common errors related to false negative results in bacteriology.
- Improper Agar Plate Preparation and Incubation- Inaccurate amounts of media or improper mixing of media components can lead to false negative results as cells may not receive the correct nutrients required for growth (Nebeker et al, 2018). Additionally, if an agar plate is incubated in wrong temperature or humidity, it may alter the ability of bacteria to grow (Tseng et al, 2002).
- Microbiological Sampling Errors- Sampling errors such as improper sampling technique, a contaminated sample container, improper sample storage and transportation may all lead to false negative results (Weinberger and Ornat, 2017).
- Poor Quality Reagents and Supplies- Contaminated reagents, diluents, buffers, sera and other supplies used for bacteria culturing may lead to false negative results (Nebeker et al, 2018).
- Excessively Low Bacteria Counts- Low colony counts of some organisms may be misinterpreted as a false negative (Weinberger and Ornat, 2017).
References:
Nebeker, C. G., Perry, S. G., Leonard, T. J.,& Henderson, J. G. (2018). Clinical microbiology made ridiculously simple (5th ed.): Medmaster.
Tseng, S. S., Chen, C. C., Chiu, C. H., Tsai, T. F., Lee, T. N., & Chen, Y. C. (2002). Improvement of false-negative results in bacterial cultures of haemodialysis-associated infected grafts by use of two growth media. Nephrology Dialysis Transplantation, 17(10), 1785-1790.
Weinberger, M., & Ornat, J. (2017). A practical guide to microbiology: Routledge.
Good day! The common reasons why false negative results may occur are low volume of bacteria, fastidious or difficult culture organisms present, and even the timing of specimen collection. The patient should also be free from the administration of antimicrobial agents for 30 minutes to avoid false negativity in results.
Laura Chandler. (2013) Accurate Results in Clinical Laboratory. Retrieved from https://www.sciencedirect.com/topics/nursing-and-health-professions/false-negative-result
The reason of false negative result performed by medical technologist in culturing bacteria is:
1. Wrong choice of suitable medium or specimen.
2. The medium is contaminated because of the medical technologist did not use aseptic technique, for example, using fire to sterilize loop and before opening the culture tube.
3. There is not enough nutrients prepared in the medium, did not set at the right pH and temperature set to enable the growth of bacteria.
4. The sample is very diluted.
5. Improper inoculation technique and handling of specimen.
6. Insufficient incubation time of bacteria.
References:
- Kirk, Ellen. "Bacillus Subtilis ." Missouri Biological Sciences . N.p., n.d. Web. 2 Mar. 2015. .
- Sargen, M. (2020). How Microbes Grow. SITNBoston. Retrieved from https://sitn.hms.harvard.edu/flash/2020/how-microbes-grow/
- Bonnet M, Lagier JC, Raoult D, Khelaifia S. Bacterial culture through selective and non-selective conditions: the evolution of culture media in clinical microbiology. New Microbes New Infect. 2019 Nov 30;34:100622. doi: 10.1016/j.nmni.2019.100622. PMID: 31956419; PMCID: PMC6961714.
- Badges
- Science topic