# Recent Advances in Bacterial Persistence Mechanisms
## 4 Treatment of Persisters  
Compared to resistance, the treatment of persistence has been newly thrown into the spotlight. Until now, there have been three main strategies (Table 1). First of all, we could directly target the existing persister cells. According to previous studies, bacterial membranes and cell walls are the main targets [70]. Increasing the proton motive force to energize cell membranes can help in the uptake of antibiotics [71]. For example, AM-0016 [72] and boromycin [73] are both membrane-targeted, acting as powerful drugs against Gram-positive bacteria. One conventional method is applying drug combinations. For the treatment of persistent methicillin-resistant _S. aureus_, daptomycin-based and ceftacline-based regimens showed a promising result as therapeutic options. In the presence of \(\beta\)-lactam, the surface charge of the net cell membrane was significantly increased, which improved daptomycin binding. Moreover, the \(\beta\)-lactam-mediated enhancement of innate immunity could also contribute to killing. Among multiple \(\beta\)-lactam antibiotics, daptomycin combined with ceftacline performed better [74]. Another possible anti-persister choice is treatment with anti-cancer drugs. Mitomycin C can eradicate persisters by causing the spontaneous cross-linking of DNA, which has been proven to be effective for _E. coli_, _S. aureus_, and _P. aeruginosa_[75]. Secondly, blocking the formation of persisters is also an alternative way, mainly interfering with the related pathways discussed before, such as the SOS response. For example, the engineered bacteriophage overexpresses the SOS response inhibitory factor LexA3, which attacks gene networks that are not directly targeted by antibiotics, and can enhance  
Figure 3: The main mechanisms of persister formation from biofilm, TA modules, ppGpp and SOS response. the killing of persister cells [76]. There have been reports of biofilm formation inhibitors with different mechanisms, which could be concluded to be anti-biofilm molecules or biofilm-dissolving substances [77]. Quercetin, a kind of flavonoid that affects quorum sensing, has been reported to act as an anti-biofilm compound against _S. aureus_. It inhibits alginate production, leading to a decline in adhesion during biofilm formation. It also reduces the production of extracellular polysaccharide substances (EPS) required for initial bacterial attachment [78]. Likewise, a glycoside hydrolase called Dispersin B can cleave certain EPS to prevent bacterial aggregation [79]. In addition, peptide 1018 can inhibit biofilm formation at the beginning, kill bacteria inside the biofilm at a specific concentration, and even disrupt mature biofilm [80]. Thus, the combination of antimicrobials and such anti-biofilm molecules may present a good performance in the treatment of persisters. Although we hope to inhibit persister formation from the first infection, the persisters may form at the very beginning. Indeed, besides stress-induced persistence, spontaneous persistence has long been observed. Therefore, vaccination might be the most practical preventive approach [4]. At last, resuscitating persisters to make them sensitive to conventional drugs is becoming an attractive method. It has been reported that the fatty acid signaling molecule cis-2-decenoic acid can increase metabolic activity in _E. coli_ and _P. aeruginosa_, turning persister cells into antibiotic-susceptible bacteria [81]. From another perspective, stimulating antibiotic influx could change the membrane permeabilization to improve the effectiveness of antibiotics [82]. The ability of silver to disrupt a variety of bacterial cellular processes, like disulfide bond formation, can also increase membrane permeability in Gram-negative bacteria. It has been reported that a combination of silver and antibiotics can eradicate bacterial persisters in vitro [83]. We hope that in the future there will be more practical strategies and drugs to treat persisters.