The susceptibility of non-replicating populations of bacteria to killing by bactericidal antibiotics Open Access

Shah, Nilang (Spring 2018)

Permanent URL: https://etd.library.emory.edu/concern/etds/ff3655282?locale=en
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Abstract

Non-growing populations of bacteria are known to be phenotypically refractory to antibiotics to which they are genetically susceptible.  Here, we consider three classes of non-growing planktonic bacteria: (1) Stationary phase, when the concentration of the limiting resource is too low to allow for replication; (2) Minority subpopulations of non- or slowly replicating bacteria, known as persisters; (3) Populations exposed to bacteriostatic antibiotics that prevent their replication and kill them slowly. Using experimental populations of Staphylococcus aureus Newman and Escherichia coli K12 and bactericidal antibiotics of 10 and 8 classes, respectively, we address the quantitative question of how refractory non-growing and slowly dying populations of these different types are susceptible to antibiotics and the rates at which different concentrations of these drugs kill them. Contrary to the common belief that non-growing bacteria are refractory to antibiotic-mediated killing, all three classes of non-growing populations of these Gram-positive and Gram-negative bacteria are killed by one or more bactericidal antibiotics and some of these drugs kill non-growing bacteria at relatively low concentrations. Lastly, we investigate the relationship between persistence and bacteriostasis by examining the ability of these non-growing states to support the replication of bacteriophage.

Table of Contents

Table of Contents

Abstract.............................................................................................................................. 1

Introduction........................................................................................................................ 1

Materials and Methods....................................................................................................... 2

Results................................................................................................................................ 4

Table 1: Antibiotics Used .................................................................................................. 5

Figure 1: Time kill for exponentially replicating bacteria..................................................... 5

Figure 2: Dynamics of hipA7 persister formation................................................................ 7

Figure 3: Effect of antibiotics on stationary phase bacteria................................................. 8

Figure 4: Effect of antibiotics on E. coli hipA7 persisters...................................................... 9

Figure 5: Susceptibility of S. aureus persisters to antibiotics.............................................. 10

Figure 6: Effect of antibiotic treatment on bacteriostatic persisters................................... 11

Discussion......................................................................................................................... 12

Figure 7: Effect of phage treatment on E. coli hipA7 persisters.......................................... 13

Figure 8: Effect of phage treatment on E. coli bacteriostatic persisters.............................. 14

Supplemental Information................................................................................................. 15

Table S1: Phage Used...................................................................................................... 14

Figure S1: Antibiotic N(24)/N(0) for exponentially growing bacteria.................................. 14

References........................................................................................................................ 17

 

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