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HC05
Testing bacteria for antibiotic sensitivity
Objectives:
● To determine the threshold of antibiotic sensitivity across bacterial strains using the Kirby-Bauer
method.
○ (AKA Standardized Disc Susceptibility Test)
Procedure:
● Basic equipment:
○ Non selective LB agar
○ Bacteria cultures
○ L spreader
○ Antibiotic disc
○ Tweezers
● Procedure/Steps:
○ Streak bacteria A across an LB agar plate for confluent growth using a sterile L-spreader
○ Evenly place the paper antibiotic discs on the plate
○ Invert the plate and incubate it at 37*C overnight
○ Measure zones of incubation using the diameter
○ Compare the results with a sensitivity chart
Notes:
● White aura = bacteria is susceptible to an antibiotic
● Just disk: Not susceptible to an antibiotic
Results:
● Penicillin → 36mm diameter → susceptible
● Vancomycin → 3.0 0mm diameter → susceptible
● Clindamycin → 16 mm diameter → intermediate
● Oxacillin → 17 mm diameter → susceptible
● Tobramycin → 22 mm diameter → susceptible
● Erythromycin → 24 mm diameter → susceptible
● Gentamicin → 10 mm diameter → resistant
● Cefazolin → 19 mm diameter → susceptible
This study source was downloaded by 1827175 from cliffsnotes.com on 01-08-2026 16:15:04 GMT -06:00
^!#&*^&^*#!(FG*T!^&*#*((*!#&()#_)#!*&$!*#)(!*##(*0Portage_Learning_BIO171_Lab_Notebook__5.docx.pdf*&!#%#&&!%%#^#^&^!#&*^&^*#!(FG*T!^&*#*((*!#&()#_)#!
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https://www.cliffsnotes.com//study-notes/16611924 5:42:03 AM*&!#%#&&!%%#^#^&^!#&*^&^*#!(FG*T!^&*#*((*!#&()#_)#!*&$!*#)(!*##(*0Portage_L
#_)#!*&$!*#)(!*Portage_Learning_BIO171_Lab_Notebook__5.docx10/16/2026,
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5:42:03 AM*&!#%#&&!%%#^#^&^!#&*^&^*#!(FG*T!^&*#*((*!#&()#_)#!*&$!*#)(!*##(*0Portage_L
HC05
Testing bacteria for antibiotic sensitivity
Objectives:
● To determine the threshold of antibiotic sensitivity across bacterial strains using the Kirby-Bauer
method.
○ (AKA Standardized Disc Susceptibility Test)
Procedure:
● Basic equipment:
○ Non selective LB agar
○ Bacteria cultures
○ L spreader
○ Antibiotic disc
○ Tweezers
● Procedure/Steps:
○ Streak bacteria A across an LB agar plate for confluent growth using a sterile L-spreader
○ Evenly place the paper antibiotic discs on the plate
○ Invert the plate and incubate it at 37*C overnight
○ Measure zones of incubation using the diameter
○ Compare the results with a sensitivity chart
Notes:
● White aura = bacteria is susceptible to an antibiotic
● Just disk: Not susceptible to an antibiotic
Results:
● Penicillin → 36mm diameter → susceptible
● Vancomycin → 3.0 0mm diameter → susceptible
● Clindamycin → 16 mm diameter → intermediate
● Oxacillin → 17 mm diameter → susceptible
● Tobramycin → 22 mm diameter → susceptible
● Erythromycin → 24 mm diameter → susceptible
● Gentamicin → 10 mm diameter → resistant
● Cefazolin → 19 mm diameter → susceptible
This study source was downloaded by 1827175 from cliffsnotes.com on 01-08-2026 16:15:04 GMT -06:00
^!#&*^&^*#!(FG*T!^&*#*((*!#&()#_)#!*&$!*#)(!*##(*0Portage_Learning_BIO171_Lab_Notebook__5.docx.pdf*&!#%#&&!%%#^#^&^!#&*^&^*#!(FG*T!^&*#*((*!#&()#_)#!
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https://www.cliffsnotes.com//study-notes/16611924 5:42:03 AM*&!#%#&&!%%#^#^&^!#&*^&^*#!(FG*T!^&*#*((*!#&()#_)#!*&$!*#)(!*##(*0Portage_L
