Interactions Between ATP Production, Growth Rate, and Antibiotic Lethality Determine the Inoculum Effect in β-lactamase-expression Escherichia coli
Abstract
Antibiotic resistance is a global threat, claiming approximately five million lives annually and impacting nations worldwide. In the U.S.A., this issue is significant, with 2.8 million diagnosed cases leading to 35,000 deaths each year. One way that bacteria can resist antibiotic treatment is through the inoculum effect (IE). IE explains how the concentration of antibiotics required to kill a population of bacteria increases as a function of bacterial density. Recently it was found that increasing ATP production/growth rate decreases the strength of IE. However, we do not know if this relationship can predict IE in bacteria that express β-lactamases as the expression of such enzymes has been previously shown to impact both ATP production and growth rate. To investigate this, we conducted ATP assays, growth rate assays, and MIC assays using Escherichia coli that express the NDM-1 β-lactamase. Changing the amount of β-lactamase expressed by E. coli altered the strength of the inoculum effect, ATP production, and growth rate. Furthermore, for a given β-lactamase expression level, we found a biphasic relationship between ATP production/growth rate and the strength of IE. Our mathematical model affirmed this relationship, attributing it to the concentration of ATP, β-lactamase expression, antibiotic lethality, and growth. Our mechanism represents the first attempt to understand how and why IE arises during treatment with a β-lactamase. In the long term, our findings may lead to a novel approach to systematically reduce the occurrence of IE in the clinic, potentially saving millions of lives annually worldwide.
Faculty Sponsors
Dr. Robert P. Smith
Project Type
Event
Location
Alvin Sherman Library
Start Date
4-3-2024 12:30 PM
End Date
4-4-2024 1:30 PM
Interactions Between ATP Production, Growth Rate, and Antibiotic Lethality Determine the Inoculum Effect in β-lactamase-expression Escherichia coli
Alvin Sherman Library
Antibiotic resistance is a global threat, claiming approximately five million lives annually and impacting nations worldwide. In the U.S.A., this issue is significant, with 2.8 million diagnosed cases leading to 35,000 deaths each year. One way that bacteria can resist antibiotic treatment is through the inoculum effect (IE). IE explains how the concentration of antibiotics required to kill a population of bacteria increases as a function of bacterial density. Recently it was found that increasing ATP production/growth rate decreases the strength of IE. However, we do not know if this relationship can predict IE in bacteria that express β-lactamases as the expression of such enzymes has been previously shown to impact both ATP production and growth rate. To investigate this, we conducted ATP assays, growth rate assays, and MIC assays using Escherichia coli that express the NDM-1 β-lactamase. Changing the amount of β-lactamase expressed by E. coli altered the strength of the inoculum effect, ATP production, and growth rate. Furthermore, for a given β-lactamase expression level, we found a biphasic relationship between ATP production/growth rate and the strength of IE. Our mathematical model affirmed this relationship, attributing it to the concentration of ATP, β-lactamase expression, antibiotic lethality, and growth. Our mechanism represents the first attempt to understand how and why IE arises during treatment with a β-lactamase. In the long term, our findings may lead to a novel approach to systematically reduce the occurrence of IE in the clinic, potentially saving millions of lives annually worldwide.
