Environmental Stress Affects the Formation of Staphylococcus aureus Persisters Tolerant to Antibiotics

Abstract

The ability to form persisters has been observed in many microorganisms, including Staphylococcus aureus, mainly in the context of chronic infections and the pathogenicity of these microbes. In our research, we have demonstrated that salt or oxidative stress could play a role in the formation of S. aureus persisters outside the host's intracellular interface. We pre-exposed planktonic growing bacterial culture to an oxidative or salt stress and monitored the dynamics of persister formation after ciprofloxacin and gentamicin treatment. In parallel, using the quantitative PCR (qPCR) approach, we determined the expression level of the stress sigma factor SigB. The pre-exposure of bacteria to salt stress caused a 1-2.5 order of magnitude increase in persister formation in the bacterial population after antibiotic exposure, depending on the type and concentration of the antibiotic used. In contrast, oxidative stress only minimally influenced the formation of persisters, without correlation to the antibiotic type and concentration. We have demonstrated that both stress and antibiotic exposure increase the expression of sigB in bacterial populations from very early on. And that the expression level of sigB differs with the type of antibiotic and stress, but no correlation was observed between persister formation and sigB expression. The method used could be helpful in testing the ability that strains can have, to form persisters.

A Quantitative Survey of Bacterial Persistence in the Presence of Antibiotics: Towards Antipersister Antimicrobial Discovery

“…A different source of cells that survive the presence of high concentrations of antibiotics are bacteria that find themselves under the eventual shortage of nutrients or have various other sources of stress, also denoted as type I persisters [ 137 , 138 ]. While type II persisters can be regarded as deploying bet-hedging strategies, type I persisters are cells that deploy strongly evolutionarily selected responses against expected stress pressures [ 32 , 108 , 139 , 140 , 141 , 142 ]. A well-known case among the latter is nutrient scarcity and the associated responses [ 40 , 58 , 139 , 143 ], such as what occurs in the case of the stationary growth phase of a bacterial batch culture, which we showed here generates approximately 30-fold more persisters than do the exponentially growing populations.…”

“…A selection of 847 primary publications deemed relevant to the theme of antibiotic bacterial persisters were manually surveyed for quantitative data from work carried out in planktonic cultures. Numerical data were finally extracted from 187 articles [ 3 , 4 , 7 , 8 , 11 , 12 , 36 , 39 , 40 , 49 , 51 , 52 , 55 , 56 , 57 , 58 , 61 , 66 , 67 , 68 , 89 , 115 , 116 , 117 , 119 , 121 , 122 , 126 , 133 , 141 , 142 , 143 , 150 , 163 , 173 , 177 , 184 , 185 , 186 , 187 , 188 , 189 , 190 , 191 , 192 , 193 , 194 , 195 , 196 , 197 , 198 ,…”

The general stress response of Staphylococcus aureus promotes tolerance of antibiotics and survival in whole human blood

“…Furthermore, whilst several different stress-response mechanisms have been linked to antibiotic tolerance, a phenomenon that is independent of antibiotic resistance, the contribution of σB to the survival of bacteria exposed to antibiotics is not characterized [6,45]. This is despite several different antibiotics triggering σB activity [46][47][48].…”

Fostering Innovation in the Treatment of Chronic Polymicrobial Cystic Fibrosis-Associated Infections Exploring Aspartic Acid and Succinic Acid as Ciprofloxacin Adjuvants

“…In turn, persister cells represent about 1% of the population that survive to antibiotic treatments despite not being antibiotic resistant (Conlon et al, 2015;Fisher et al, 2017). Both VBNC and persister cells can be induced by stressful conditions, such as an antibiotic treatment (Kubistova et al, 2017;Ayrapetyan et al, 2018) and biofilms (Pasquaroli et al, 2013;Ayrapetyan et al, 2018;Soares et al, 2019). The detection of dormant cells should be preferentially performed using advanced techniques, such as flow cytometry (Ruger et al, 2014), but the high viscosity of ASM and its components (e.g., eDNA, mucin, salts) demands an extensive optimization of the ASM preparation (before flow cytometry analysis) that we have not yet concluded in our laboratory.…”