Question

Kirby-Bauer Test time-lapse with E. coli and S. aureus Elapsed Time: 24 hours coll Il 0 :18/1:11

Answer 1

Answer 3:

A zone of clearing is observed surrounding an antibiotic if bacterial cells are sensitive to it and are unable to grow under its effect.

The given results for E. coli is :

Ampicillin Gentamicin Neomycin Vancomycin Tetracycline Bacitracin Trimethoprim/ Sulfamethoxazole © Erythromycin Optochin Penicillin Streptomycin Amoxicillin/ Clavulanic Acid E. coli

Note that there is no zone of clearing around penicillin antibiotic for E.coli.

The results given for S.aureus is :

Ampicillin Neomycin Gentamicino Bacitracin ine Vancom Trimethoprim/ Sulfamethoxazole © Optochin Penicilli mycin Streptomycin Amoxicillin/ Clavulanic Acid S aureus

Note that there is zone of clearing surrounding penicillin in the S.aureus plate.

From the above two observations, we can infer that E. coli is less sensitive to penicillin whereas S.aureus is highly sensitive to penicillin and hence E.coli can grow in the presence of penicillin but S. aureus cannot grow.

Thus, S. aureus appears to be more sensitive against penicillin.

Answer 4:

We can observe from the results above that E. coli is less sensitive to penicillin, optochin, vanomycin, etc. and for other antibiotics it has a narrower zone of clearing.

However, in the S. aureus plate, we can observe broad zones of clearing surrounding each antibiotic.

Hence, E. coli appears difficult to treat with these antibiotics.