Association for Biology Laboratory Education

The Close-Call in Microbiology Labs – Understanding Microbes
    



Advances in Biology Laboratory Education, 2020, Volume 41

Seema G. Thomas, Maryah A. Glover, Anutthaman Parthasarathy, & André O’Hudson

https://doi.org/10.37590/able.v41.art85

Abstract

For a sophomore student, new to microbiology lab, most of the microbial colonies look alike – kind of a toddler’s view on a dog or a cat; both have 4 legs and a tail, and now what?! The students level of confidence increases within a few weeks as they learn to identify the morphology – the form, the elevation, the margin and the list goes on, followed by the same protocol of testing antimicrobial susceptibility using antibiotic discs and measuring the zone of inhibition with a ruler. My question: Why not include a more relevant approach to learn techniques which demonstrates that the same microbe responds differently based on the form in which they exist; planktonic or biofilm – either relating to clinical biomaterials like stents in human body and its antibiotic treatments or biofilms in Lake Ontario water supply channels and chlorine/ disinfectant treatment as related to the environment.This will enhance their learning on current real world applications, as in medical, scientific or pharmaceutical settings. This paper discusses a study based on determining the Minimum Inhibitory Concentration, Minimum Biofilm Eradication Concentration using the antibiotics neomycin sulfate and co-trimoxazole on the opportunistic pathogens Citrobacter freundii and Aeromonas hydrophila as model organisms, using cost effective 96 wells plates. The results showed a trend indicating higher antibiotic concentrations and increased biofilm elimination, concluding the need of a higher concentration for biofilm eradication rather than the bare minimum concentration of 1mg mL-1 antibiotics used in the study.

Keywords:  biofilm, planktonic antibiotic susceptibility, Minimum Inhibitory Concentration (MIC), Minimum Biofilm Eradication Concentration (MBEC)

University of Ottawa (2019)