Antibiogram realisation on a bacterial strain

Materials avalaible Materials avalaible

Swab

Agar with bacteria

Antibiotics disks

Mueller Hinton culture medium

Deposit plan

Sterile physiological water tube

1. Preparation of inoculum

1.1. With a sterile inoculation loop, take a bacterial colony on agar Petri dish.

WARNING! The sample is realized in asepsis around the Bunsen burner.

1.2. Make a suspension with this bacterial colony in a steril tube of physiological water (5mL). In the water, rub inoculation loop on the tube side to disperse all the bacteria.

WARNING! The sample is realized in asepsis around the Bunsen burner.

1.3. Repeat 4 times, in order to introduce 5 bacterial colonies in the tube

1.4 Homogenize your tube by manual rotations and write « I » on this tube.II

2. Inoculate Mueller Hinton medium for antibiogram

2.1. In the inoculum tube “I”, insert a sterile swab.

WARNING! The sample is realized in asepsis around the Bunsen burner.

Wet the swab and then wring the excess of liquid on the wall of the tube.

2.2. Inoculate Mueller Hinton agar by rubbing the swab on its surface. Achieve tight streaks.

2.3. Reproducing the operation twice by turning 60° the box each time in order to ensure an good distribution of the inoculum on the surface of the medium :

60° 60°

=

Streaks in 3 passes

2. Filing the antibiotics disks

3.1. Position the Mueller Hinton agar previously sown on the deposit plan provided

3.2. With a sterile forceps, place the antibiotics disks on the surface of the agar

When filing disks, apply slight pressure ton ensure the maintenance of the disk, but not too much to avoid the risk of perforating the agar

4. Medium incubation

Incubate the box, in the inverted position, 16 h at 37°C minimum

5. Analyse your results

5.1. After incubation, measure the diameter of the growth inhibition zones around the antibiotics disks

5.2. Use the reading table, to conclude on the sensitivity or on the resistance of the strain to different antibiotics tested

Antibiotic tested Resistance if the diameter of

inhibition is less than :

Sensitive if the diameter of inhibition is

greater than :Ampicillin 14 mm 19 mm

SXT 10 mm 16 mm

Erythromycin 17 mm 22 mm

Gentamicin 14 mm 16 mm

6. Conclusion

Suggest an antibiotic suitable for the treatment of nosocomial infection caused by

your bacteria