Ultrasonically enhanced rifampin activity against internalized Staphylococcus aureus

Effects of low-frequency ultrasound combined with anti-MRSA agents on the mouse model of pulmonary infection

The treatment of methicillin-resistant Staphylococcus aureus (MRSA)-induced pneumonia with antibiotics alone poses considerable challenges. To address these challenges, low-frequency ultrasound (LFU) emerges as a promising approach. In this study, a mouse pneumonia model was established through intratracheal injection of MRSA to investigate the therapeutic efficacy of LFU in combination with antibiotics. Minimal inhibitory concentration was assessed, and the distribution of antibiotics in the lung and plasma was determined using liquid chromatography coupled with mass spectrometry. Various parameters, including the survival rate, histopathology, lung bacterial clearance, and the expressions of cytokines and inflammation-related genes, were evaluated before and after treatment. Compared with the infection group, both the antibiotic-alone groups [vancomycin (VCM), linezolid, and contezolid (CZD)] and the groups in combination with LFU demonstrated an improvement in the survival status of mice. The average colony-forming units of lung tissue in the LFU combination groups were lower compared with the antibiotic-alone groups. While no significant changes in C-reactive protein and procalcitonin in plasma and bronchoalveolar lavage fluid were observed, histopathological results revealed reduced inflammatory damage in LFU combination groups. The secretion of interleukin-6 and tumor necrosis factor-alpha was decreased by the combination treatment, particularly in the VCM + LFU group. Furthermore, the expressions of MRSA virulence factors (hla and agrA) and inflammation-related genes (Saa3, Cxcl9, and Orm1) were further reduced by the combinations of LFU and antibiotics. Additionally, LFU treatment facilitated the distribution of VCM and CZD in mouse lung tissue at 30 and 45 min, respectively, after dosage.IMPORTANCETreating pneumonia caused by methicillin-resistant Staphylococcus aureus (MRSA) with antibiotics alone poses significant challenges. In this in vivo study, we present compelling evidence supporting the efficacy of low-frequency ultrasound (LFU) as a promising approach to overcome these obstacles. Our findings demonstrated that LFU enhanced the effectiveness of vancomycin, linezolid, and contezolid in an MRSA pneumonia model. The combination of LFU with anti-MRSA agents markedly improved the survival rate of mice, accelerated the clearance of pulmonary bacteria, reduced inflammatory injury, inhibited the production of MRSA endotoxin, and enhanced the distribution of antibiotics in lung tissue. The application of LFU in the treatment of pulmonary infections held substantial significance. We believe that readers of your journal will find this topic of considerable interest.

Synergistic effect of low-frequency ultrasound and antibiotics on the treatment of Klebsiella pneumoniae pneumonia in mice

The antibiotic‐resistant Klebsiella pneumoniae (Kp) has become a significant crisis in treating pneumonia. Low‐frequency ultrasound (LFU) is promising to overcome the obstacles. Mice were infected with bioluminescent Kp Xen39 by intratracheal injection to study the therapeutic effect of LFU in combination with antibiotics. The counts per second (CPS) were assessed with an animal biophoton imaging system. Bacterial clearance, histopathology, and the concentrations of cytokines were determined to evaluate the therapeutic effect. LC–MS/MS was used to detect the distribution of antibiotics in the lung and plasma. LFU in combination with meropenem (MEM) or amikacin (AMK) significantly improved the behavioural state of mice. The CPS of the LFU combination group were more significantly decreased compared with those of the antibiotic alone groups. The average colony‐forming units of lung tissue in the LFU combination groups were also lower than those of the antibiotic groups. Although no significant changes of cytokines (IL‐6 and TNF‐α) in plasma and bronchoalveolar lavage fluid were observed, LFU in combination with antibiotics showed less inflammatory damage from histopathological results compared with the antibiotic‐alone groups. Moreover, 10 min of LFU treatment promoted the distribution of MEM and AMK in mouse lung tissue at 60 and 30 min, respectively, after dosage. LFU could enhance the effectiveness of MEM and AMK in the treatment of Kp‐induced pneumonia, which might be attributed to the fact that LFU could promote the distribution of antibiotics in lung tissue and reduce inflammatory injury.

Staphylococcus aureus vs. Osteoblast: Relationship and Consequences in Osteomyelitis

Bone cells, namely osteoblasts and osteoclasts work in concert and are responsible for bone extracellular matrix formation and resorption. This homeostasis is, in part, altered during infections by Staphylococcus aureus through the induction of various responses from the osteoblasts. This includes the over-production of chemokines, cytokines and growth factors, thus suggesting a role for these cells in both innate and adaptive immunity. S. aureus decreases the activity and viability of osteoblasts, by induction of apoptosis-dependent and independent mechanisms. The tight relationship between osteoclasts and osteoblasts is also modulated by S. aureus infection. The present review provides a survey of the relevant literature discussing the important aspects of S. aureus and osteoblast interaction as well as the ability for antimicrobial peptides to kill intra-osteoblastic S. aureus, hence emphasizing the necessity for new anti-infectious therapeutics.

Ultrasound microbubbles enhance human β-defensin 3 against biofilms

BACKGROUND

The infection of orthopedic implantation devices with Staphylococcus has been a serious concern within the biomaterial community. Treatments are not always successful because of antibiotic-resistant bacteria biofilm infection. Recent studies have shown that combination of antibiotics with low-frequency ultrasound (US) can enhance the bactericidal activity effectively against the formation of biofilms in vitro pilot study. Meanwhile, microbubbles evolved as targeted drug-delivery agents can provide nuclei for inertial cavitation and lower the threshold for US-induced cavitation. Human β-defensin 3 (HBD-3) is a cationic antimicrobial peptide considered particularly promising for future bactericidal employment and has effect on antibiotic-resistant Staphylococcus biofilms. But the effect has not been reported when combined with US-targeted microbubble destruction (UTMD) in vivo.

METHODS

In this study, we evaluated the effect of HBD-3 combined with UTMD on two tested Staphylococcus by the spread plate method, crystal violet staining, confocal laser scanning microscopy, scanning electron microscopy, and real-time polymerase chain reaction.

RESULTS

In the study, we found that the biofilm densities, the percentage of live cells, and the viable counts of two tested Staphylococcus that recovered from the biofilm on the titanium surface in mice were significantly decreased in the group of the HBD-3 combined with UTMD, compared with those of other groups. Furthermore, in the experiment, we found out that UTMD could enhance HBD-3 activity, which inhibits the biofilm-associated genes expression of icaAD and the methicillin-resistance genes expression of MecA by promoting the icaR expression simultaneously.

CONCLUSIONS

The combination of HBD-3 with UTMD can play a significant role on the elimination of the antibiotic-resistant Staphylococcus biofilms in vivo.