We first isolate lactic acid bacterias from milk samples on MRS Agar Medium. Then we use M17 agar for lactococus species-specific medium. Can we say these strains lactococcus spp or not without biochemical tests?
No, you cannot. A high proportion of your isolates may belong to other genera. In our samples from traditional cheeses, many of the M17 isolates were, in fact, enterococci and streptococci. I would regard this agar more as an elective than as a selective medium.
Hello greetings
The MRS agar is used primarily to isolate and quantify lactic acid bacteria, with some modifications (mainly the pH with acetic acid), can do selective for Lactobacillus and can also do even more selective for Lactobacillus probiotic potential (changing pH and adding bile salts ). M17 Agar is a selective medium for Streptococcus lactic origin, though some authors mention that can be used for Lactococcus. You command an article, I think it could be very useful.
No, you are only isolating LAB. Even the biochemical tests can not be enough to classify the LAB.
I agree with Eva M. Santos. In most cases, to identify LAB - even at the genus level - you may need to resort to molecular biology techniques. Using the "classical" tests (see, for instance, the 1st chapter of the book edited by Salminen and von Wright - Lactic Acid Bacteria. Microbiology and Functional Aspects), or miniaturized kits (such as API 50CHL) won't get you very far.
And resorting to Elliker and other "selective" culture media will not help much. You still won't be sure you got predominantly lactococci among your cultures.
If you want to detect/quantify lactococci in a sample, why don't you use culture independent methodologies (as we used in the article I'm annexing)? Presently, they aren't even so expensive as they used to be.
Good luck!
Article Characterization of the bacterial biodiversity in Pico chees...
Amongst the many media which have been described for the isolation of lactococci
from foods, Elliker agar (Elliker et a1.,1956) and M 17 (Terzaghi and Sandine, 1975)
are most commonly used for the detection of lactococci. They are, however, not completely
selective. WACCA-agar (Galesloot et a1.,1961) can be used for the collective
enumeration of lactococci and leuconostocs in starter and dairy products.
Page 133, (Eds.) Progress in Industrial Microbiology 34
Culture Media for Food Microbiology [1 ed.]
So, we must supoort the results with biochemical or molecular tests. Right?
you can not be sure in M17 streptococcus Enterococcus some yeast can also grow
MRS is perfect for Lactobacillus, so you must do the bio chemical tests
The M17 medium is not so species-specific.You'd better to do molelular biological classification and biochemical tests.
You can use Neutral Red Chalk Lactose Agar (NRCLA) (Harrigan and McCance 1966). NRLCA is better than M17 and MRS for isolation of lactococci. This medium is semi selective for isolation of Lactococcus genius. However, you should make culturel and biochemical tests for identification.
Unfortunately, there is not selective media for isolation of lactococci.
İbrahim NRLCA besiyeri MRS ve M17 ye göre Laktokokların izolasyonu için daha selektif bir besiyeridir. M17 ve MRS de diğer laktik asit bakterilerinden laktokokları koloni morfolojisine göre ayırt edemezsin. Ancak, NRLCA besiyerinde tipik laktokok kolonileri koyu kırmızı renkte ve çevrelerinde berrak zon oluşumu kriterine göre seçilir. Bu besiyeri ancak tam selektivite göstermez. Yakın akraba cinsler özellikle Enterokoklarda izole edilebilir. Bu nedenle seçtiğin kolonilere kültürel testler uygulaman gerekir. (10 C, 45C, pH 9.6, %6.5 NaCl vb.).
Bu arada kültürel ve biyokimyasal testler yapmadan Laktokokların tanımlanacağı bir besiyeri malesef yok.
Çalışmalarında başarılar dilerim.
Simple colony-PCR using 16S rRNA primers will do! it will take only two hours...
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