Antibiotic regimen based on population analysis of residing persister cells eradicates Staphylococcus epidermidis biofilms

Abstract

Biofilm formation is a major pathogenicity strategy ofBacteria employ a variety of strategies to escape killing by antibiotics, including mutation, phenotypic variation, and change to a biofilm growth mode 1-3 . One form of phenotypic variation, known as persistence, is characterised by the presence of a subset of antibiotic-tolerant cells within a bacterial population. Persister cells pre-exist in most bacterial populations, including cultures at mid-log phase, stationary phase, and in biofilms [4][5][6] . The prevalence of persister cells in a population depends on its growth mode, the age of inocula, strain background, growth medium, and time course chosen for selection [6][7][8] . Persister cells display heterogeneity in growth rates and tolerance to various antibiotics 6,9,10 , though multidrug tolerance is not a consistent trait 11 . Transcriptome analysis suggests that persister cells have reduced expression of genes involved in metabolic pathways, biosynthesis pathways, and energy production 12,13 , which often leads to a dormancy status of cells. However, being entirely dormant is not necessarily a prerequisite for the formation of persister subpopulations [14][15][16] .In clinical settings, bacteria grow predominantly as biofilms, following attachment and accumulation on biotic or abiotic surfaces; and they present group dynamics [17][18][19] . Bacteria within biofilms are highly tolerant to antibiotics, but the exact mechanisms behind this tolerance are complex and no single factor can fully account for this specific trait [20][21][22] . Persister cells are more prevalent in biofilms than in log-planktonic cultures and are thought to be responsible for the recalcitrance of many chronic infections, such as cystic fibrosis and chronic wound infections,

Efficient Killing of Planktonic and Biofilm-Embedded Coagulase-Negative Staphylococci by Bactericidal Protein P128

“…In addition to the physical factors associated with biofilms, the physiological state of bacteria in biofilms contributes to antibiotic tolerance (12). Thus, apart from the issues of the permeability barrier of a biofilm matrix, the presence of a high percentage of a persister cell population has been thought to be the reason behind the tolerance of biofilms to antibiotics (11,18 cells result from the fact that it can inhibit growing and nongrowing cells equally well, and biofilm matrix probably does not act as a permeability barrier against P128. Given the variability of biofilm matrix compositions in CoNS (43,44), it is likely that the strains used in this study will form biofilms with matrices containing carbohydrates, DNA, and proteins in various proportions.…”

“…A recent study has demonstrated that ATP depletion and expression of stationary-phase markers lead the bacterial cell into a physiological state in which it becomes tolerant to the action of antibiotics (14). It has been demonstrated that biofilms formed by S. epidermidis, S. haemolyticus, and S. lugdunensis in vitro are tolerant to the action of high concentrations of most of the antibiotics (15)(16)(17)(18). Obviously, to control CoNS infections, there is a need to develop new therapeutics, especially those with good antibiofilm activity and the ability to kill persister cells.…”

Effect of clpP and clpC deletion on persister cell number in Staphylococcus aureus

“…Antibiotic concentrations and exposure time used in this study were 80 times the MIC for 16-17 h to minimize the survival of spontaneous antibiotic-resistant mutants and ensure eradication of tolerant but killable cells (Yang et al, 2015). The antibiotic concentrations used in this study were as follows: oxacillin, 30 µg ml…”

“…At least three TA modules exist in S. aureus including mazEF, axe1-txe1 and axe2-txe2 (Donegan & Cheung, 2009;Yoshizumi et al, 2009). Donegan et al (2010) examined the proteolytic regulation of TA systems by ClpPC in S. aureus and found that ClpP is essential for the degradation of all known S. aureus antitoxins.…”

“…Antibiotic concentrations of 80 times the MIC were chosen for this study to minimize the survival of spontaneous antibiotic-resistant mutants and ensure eradication of tolerant but killable cells (Yang et al, 2015). MICs were performed with a 96-well microtitre plate.…”