Non-contact induction heating and SAAP-148 eliminate persisters within MRSA biofilms mimicking a metal implant infection

Abstract

Implant-associated infections are the primary cause of complications following orthopaedic surgery. Due to biofilm and persister formation, current treatments, i.e. surgical debridement followed by antibiotics, often fail. There is an urgent need for alternative strategies to combat such infections. Therefore, the present study investigated the effects of non-contact induction heating (NCIH), the antimicrobial peptide SAAP-148 and combinations thereof on bacterial counts in 7 d mature biofilms and in persister-enriched biofilms of methicillin-resistant Staphylococcus aureus (MRSA) on titanium-aluminium-niobium (TAN) discs. Enrichment of persisters was achieved by daily exposure of mature biofilms to high doses of rifampicin and ciprofloxacin for 3 consecutive days. To heat up the TAN discs, a miniaturised induction heater was built and successfully validated. Using this apparatus, NCIH resulting in surface temperatures up to 85 °C eradicated all the bacteria in immature biofilms but not in mature biofilms, whereas persisters were already eliminated at surface temperatures ≥ 70 °C. SAAP-148 at concentrations > 25.6 µmol/L reduced the persister counts in antibiotics-exposed, mature biofilms. As surface temperatures > 60 °C can have detrimental effects on the surrounding tissues, the maximum temperature of NCIH used in combination with SAAP-148 on persisters was set to 60 °C. Results revealed that this combination was slightly more effective than the peptide or NCIH alone in eliminating biofilm-embedded persisters. NCIH and SAAP-148 can be applied both invasively and non-invasively in various treatment scenarios. Together, combinations of NCIH and SAAP-148 might be a promising treatment strategy to combat metal-implant-associated infections.

Novel Antibacterial Agents SAAP-148 and Halicin Combat Gram-Negative Bacteria Colonizing Catheters

“…SAAP-148 and halicin were effective against these persisters derived from the antibiotic-exposed mature biofilms of the four bacterial strains tested in a dose-dependent manner. This is in agreement with earlier findings that SAAP-148 effectively reduced bacterial counts within antibiotic-exposed mature biofilms of MRSA [37,38]. Herein, we provided proof for the first time that SAAP-148 possesses a potent anti-persister effect against GNB strains.…”

“…In a study by de Breij et al [28], the peptide SAAP-148 was highly efficient in killing a panel of planktonic multidrug-resistant (MDR) bacteria, including colistin-resistant E. coli, K. pneumoniae, and A. baumannii. Further studies have also shown the efficacy of this peptide against biofilms [28,36] and persister cells [28,37,38]. de Breij et al [28] investigated the mode of action of SAAP-148 and showed that the formation of pores in cell walls led to the permeabilization of the membrane, followed by the destruction of the bacterial cells.…”

“…Moreover, it was suggested that the compound kills bacteria by dissipating the transmembrane electrochemical gradient, ∆pH, after binding with iron [39,41]. The effect of either SAAP148 or halicin on Gram-positive bacteria, especially S. aureus, has been extensively studied [28,[36][37][38]40,[42][43][44][45][46][47][48][49][50]. However, few reports on their effects on GNBs are available [28,36,39,40,[46][47][48][49]51], and none of the studies tested strains isolated directly from medical devices and using both agents against GNBs.…”

Bacteriophage ISP eliminates Staphylococcus aureus in planktonic phase, but not in the various stages of the biofilm cycle

“…Second, 100 µL of mid-logarithmic phase MRSA and MSSA at 10 7 CFU/mL in BHI broth was added on top of medical grade titanium-7% aluminum-6% niobium [TAN; iso5832/11 discs, handled as described previously 30 ] in 96-wells flat-bottom polystyrene plates. After 1 h, TAN discs were washed twice with 0.9% saline to remove non-adherent bacteria and transferred to a 96-wells flat-bottom polystyrene plate with 100 µL of ISP at final concentrations ranging from 10 1 –10 8 PFU/mL.…”

Bacterial Biofilms: A Current Clinical Dilemma and a Promising Therapeutic Target

“…Many other compounds have been found to possess anti-persister activity, including synthetic peptides like SAAP-148 and natural analogs like Pexiganan 106,107 .…”