I'm currently doing a research project wherein I will be testing the antibiotic resistance of a bacterial sample. Due to a risk of contamination during transport, I'm not allowed to request a uniform bacterial sample form a clinical laboratory. So, I have to produce my own sample. Then, I'm planning to identify the morphology of the bacteria to confirm the species or type.

The ideal scenario is obtaining a sample which is entirely one species of bacteria. However, taking a swab, either from somewhere in the lab or from the body will produce a sample with multiple bacterial species. What source of bacteria can provide the most uniform sample, i.e. a sample with a majority of one species of bacteria? Or, is there another way to obtain a uniform sample? Also, note: I will be conducting the experiment in a school laboratory, so I must be able to safely contain the pathogen.

Edit: I have recently updated my project to be specified towards testing on bacteria present in the throat. So, a bacteria present in this area or similar areas would be preferable.

  • $\begingroup$ Do you have a particular bacteria in mind? For safety, I have a link. Especially culture well below body temperature, and use common media e.g nutrient agar. riskassess.com.au/info/micro_issues $\endgroup$ Commented May 30, 2020 at 7:24
  • $\begingroup$ I have no specific species/strain in mind. However, I have recently updated my project to be specified towards bacteria in the throat. So, a bacteria which is present there or in similar areas would be preferable (I'll also update the question). $\endgroup$
    – Ali
    Commented Jun 27, 2020 at 7:15
  • 2
    $\begingroup$ This is what streak plating is for. $\endgroup$
    – canadianer
    Commented Jun 27, 2020 at 18:20

1 Answer 1


You could inoculate your sample in a selective medium or an enrichment medium to kill off the unwanted species. Of course, you will need to do a literature search to find the optimum medium for the species of your interest.

Another option is to streak plates like so. With successive 'generations' of streaks, the inoculum gets diluted, so that you ultimately get separate colonies. Each colony is founded by a single bacterial cell: by picking up one such colony, you get a pure sample.

For even better results, combine both the methods described above by first growing in a selective medium and then streaking on a solid medium to get individual colonies.


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