After testing the potency of different β-lactamase inhibitors against purified OXA-M290 enzyme, the antimicrobial activity of combinations of β-lactam antibiotics and β-lactamase inhibitors is tested against the E. coli KGH1 strain that produces OXA-M290. The results of these studies can be used to identify the best antibiotic to treat an infection caused by this E. coli strain. Broth microdilution tests are carried out with a panel of β-lactam antibiotics and β-lactamase inhibitors to determine their MICs against E. coli KGH1. These tests are carried out in a 96-well microplate. Three β-lactam antibiotics (amoxicillin, ceftazidime, and ertapenem) and three β-lactamase inhibitors (sulbactam, tazobactam, and vaborbactam) are tested. The rows in the microplate correspond to the following antibiotics and inhibitors: Row A: amoxicillinRow B: amoxicillin + sulbactamRow C: ceftazidimeRow D: ceftazidime + sulbactamRow E: ertapenemRow F: ertapenem + sulbactamRow G: ertapenem + tazobactamRow H: ertapenem + vaborbactam The different columns of the microplate contain different antibiotic concentrations: Column 1: 64 μg/mLColumn 2: 32 μg/mLColumn 3: 16 μg/mLColumn 4: 8 μg/mLColumn 5: 4 μg/mLColumn 6: 2 μg/mLColumn 7: 1 μg/mLColumn 8: 0.5 μg/mLColumn 9: 0.25 μg/mLColumn 10: 0.13 μg/mLColumn 11: 0.06 μg/mL After using a multichannel pipette to add bacteria, liquid media, and antibiotics to the wells, the plate is incubated overnight at 37 °C. The following day, the growth of bacterial cells in each well is measured using a microplate reader, based on the absorbance of the wells at 600 nm (remember: bacterial growth can be measured by turbidimetry, as described in Module 1). If the absorbance value for a well is zero, this means that the bacteria did not grow in this well. The wells in column 12 were used as a control. These wells only contain liquid media, and no bacteria were added to these wells before the plate was incubated overnight. This experiment generates the following results: , 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 A, 0.38, 0.41, 0.45, 0.42, 0.51, 0.39, 0.45, 0.51, 0.46, 0.45, 0.52, 0.00 B, 0.00, 0.00, 0.39, 0.42, 0.51, 0.50, 0.49, 0.49, 0.45, 0.51, 0.49, 0.00 C, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.43, 0.46, 0.51, 0.46, 0.58, 0.00 D, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.43, 0.51, 0.46, 0.00 E, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.37, 0.41, 0.39, 0.45, 0.00 F, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.36, 0.44, 0.00 G, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.37, 0.00 H, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.37, 0.35, 0.00 a. What is the MIC value for each antibiotic and antibiotic/inhibitor combination? b. Based on these MIC values, which antibiotic (or combination of antibiotic and β-lactamase inhibitor) would you recommend be used to treat an infection caused by E. coli KGH1? Why?
After testing the potency of different β-lactamase inhibitors against purified OXA-M290 enzyme, the antimicrobial activity of combinations of β-lactam antibiotics and β-lactamase inhibitors is tested against the E. coli KGH1 strain that produces OXA-M290. The results of these studies can be used to identify the best antibiotic to treat an infection caused by this E. coli strain.
Broth microdilution tests are carried out with a panel of β-lactam antibiotics and β-lactamase inhibitors to determine their MICs against E. coli KGH1. These tests are carried out in a 96-well microplate.
Three β-lactam antibiotics (amoxicillin, ceftazidime, and ertapenem) and three β-lactamase inhibitors (sulbactam, tazobactam, and vaborbactam) are tested. The rows in the microplate correspond to the following antibiotics and inhibitors:
Row A: amoxicillin
Row B: amoxicillin + sulbactam
Row C: ceftazidime
Row D: ceftazidime + sulbactam
Row E: ertapenem
Row F: ertapenem + sulbactam
Row G: ertapenem + tazobactam
Row H: ertapenem + vaborbactam
The different columns of the microplate contain different antibiotic concentrations:
Column 1: 64 μg/mL
Column 2: 32 μg/mL
Column 3: 16 μg/mL
Column 4: 8 μg/mL
Column 5: 4 μg/mL
Column 6: 2 μg/mL
Column 7: 1 μg/mL
Column 8: 0.5 μg/mL
Column 9: 0.25 μg/mL
Column 10: 0.13 μg/mL
Column 11: 0.06 μg/mL
After using a multichannel pipette to add bacteria, liquid media, and antibiotics to the wells, the plate is incubated overnight at 37 °C. The following day, the growth of bacterial cells in each well is measured using a microplate reader, based on the absorbance of the wells at 600 nm (remember: bacterial growth can be measured by turbidimetry, as described in Module 1). If the absorbance value for a well is zero, this means that the bacteria did not grow in this well.
The wells in column 12 were used as a control. These wells only contain liquid media, and no bacteria were added to these wells before the plate was incubated overnight.
This experiment generates the following results:
, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12
A, 0.38, 0.41, 0.45, 0.42, 0.51, 0.39, 0.45, 0.51, 0.46, 0.45, 0.52, 0.00
B, 0.00, 0.00, 0.39, 0.42, 0.51, 0.50, 0.49, 0.49, 0.45, 0.51, 0.49, 0.00
C, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.43, 0.46, 0.51, 0.46, 0.58, 0.00
D, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.43, 0.51, 0.46, 0.00
E, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.37, 0.41, 0.39, 0.45, 0.00
F, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.36, 0.44, 0.00
G, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.37, 0.00
H, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.37, 0.35, 0.00
a. What is the MIC value for each antibiotic and antibiotic/inhibitor combination?
b. Based on these MIC values, which antibiotic (or combination of antibiotic and β-lactamase inhibitor) would you recommend be used to treat an infection caused by E. coli KGH1? Why?
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