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Tritech Research Tritech_Research at lamg.com
Tue Aug 26 16:07:11 EST 1997

fodoran at FALCO.GEOBIO.ELTE.HU,Internet writes:

Csaba Bognar(2), Tibor Vellai(1) and Andras Fodor(1),
1. 	Dept. Genetics, Eotvos University, H-1088 Budapest, Muzeum krt. 4/A,
2. 	Bela Johann National Institute of Public Health in Hungary, Department
	of Bacteriology, (OKI), H-1097 Budapest, Gyali ut 2-6, Hungary.

E. coli OP50 is used practically by everybody in the C. elegans Community
as natural food for C.elegans. Our substrain what we use was kindly
provided by Ian Hope in 1995. We have tested its antibiotics sensitivity,
by the paper disc method routinly used the OKI. We used 30 ug/ml of each
antibiotics tested. The filter paper discs are out on the center of the
NGM plate seeded by OP bacteria. An inhibition zone develops, if the
antibiotics is effective against the baccteria under test. Conventionally,
if the diameter oif the inhibition zone is smaller then 2 cm, we conclude
that the bacteria is resistant to the antibiotics tested. We tested 24
antibiotics, as follows:

gentamycin; tobramycin; sumetrolim; chloramphenicol; tetracycline;
ampicyllin; karbenicillin; cefalexine; cefamandol; cefuroxime; amykacin;
netylmycine; azlocilline; mezlocillin; ceftriaxone; cefatoxim;
cefroperazon; ofloxacin; pestloxacin; cyprofloxacim; ceftazidin; cefaclor;
augmentin; and kanamycin. (Some of the names are probably written in very
Hungarian; we promise the correct them in the Newsletter article).

Well, we found that OP50 was completely resistant to all these

I hope these data help Liz and other fellow Colleauges to work with OP50.

Faithfully yours,

Andras and his gang.   
This sounds very strange to me (?)  If true, it would be one of the heartiest
(and most dangerous) strains of bacteria in the world (?)  My experience
with OP50 is that it is killed easily by Amp and Str.  2 cm requires a lot
of diffusion.  Might this be too much to ask from the filter disks?  Is it
possible that doing the test on NGM with a high agar or agarose content is
limiting diffusion?  Could this possibly be a contaminating yeast?

Andy Papp
tritech_research at LAMG.COM

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