Evaluation of photodynamic therapy effect along with colistin on pandrug-resistant Acinetobacter baumannii

Effect of photodynamic therapy on multidrug-resistant Acinetobacter baumannii: A scoping review

BACKGROUND

Acinetobacter baumannii is a Gram-negative, non-fermenting coccobacillus of the Moraxellaceae family. It is an opportunistic pathogen responsible for several hospital-acquired infections (HAIs) associated with skin and tissue infections at surgical sites, catheter-associated urinary tract infections, and central line catheters. Multidrug-resistant (MDR) A. baumannii has caused hospital outbreaks that are difficult to eradicate and represent one of the leading producers of HAIs. MDR-A. baumannii presents a broad range of resistance to different antimicrobials, including carbapenems. Due to the low sensitivity to conventional antibiotic therapies, it is necessary to identify other therapeutic options. Antimicrobial photodynamic therapy (aPDT) is a promising alternative and complementary approach to address the shortage of antimicrobials in MDR-A. baumannii. APDT combines a photosensitizer agent, light, and oxygen to achieve a bactericidal/bacteriostatic effect. The effect is given by producing reactive oxygen species (ROS) that produce photooxidative stress over bacterial structures, such as the envelope and the DNA.

METHODS

This study aims to systematically collect bibliographic information from databases such as PubMed, Scopus, and google scholar to analyze the relevant articles critically.

RESULTS

An increasing body of evidence demonstrates the efficacy of photodynamic inactivation in eliminating A. baumannii strains, both in vitro and in vivo.

CONCLUSIONS

The evidence supports that photodynamic inactivation is an alternative capable of eliminating strains of Acinetobacter baumannii and may considerably improve the treatment of MDR strains. Although they do exist, aPDT studies on MDR strains of A. baumannii are scarce and should increase since it is on these strains that photodynamic therapy becomes attractive.

Colistin Resistance and Management of Drug Resistant Infections

Colistin resistance is a globalized sensible issue because it has been considered a drug of the last-line resort to treat drug-resistant bacterial infections. The product of the mobilized colistin resistance (mcr) gene and its variants are the significant causes of colistin resistance, which is emerging due to the frequent colistin use in veterinary, and these genes circulate among the bacterial community. Apart from mcr genes, some other intrinsic genes and proteins are also involved in colistin resistance. Researchers focus on the most advanced genomics (whole genome sequencing), proteomics, and bioinformatics approaches to explore the question of colistin resistance. To combat colistin resistance, researchers developed various strategies such as the development of newer drugs, the repurposing of existing drugs, combinatorial treatment by colistin with other drugs, a nano-based approach, photodynamic therapy, a CRISPRi-based strategy, and a phage-based strategy. In this timeline review, we have discussed the development of colistin resistance and its management in developing countries.

Photodynamic therapy for treatment of infected burns

Burns are among the most debilitating and devastating forms of trauma. Such injuries are influenced by infections, causing increased morbidity, mortality, and healthcare costs. Due to the emergence of multidrug-resistant infectious agents, efficient treatment of infections in burns is a challenging issue. Antimicrobial photodynamic therapy (aPDT) is a promising approach to inactivate infectious agents, including multidrug-resistant. In this review, studies on PubMed were gathered, aiming to summarize the achievements regarding the applications of antimicrobial photodynamic therapy for the treatment of infected burns. A literature search was carried out for aPDT published reports assessment on bacterial, fungal, and viral infections in burns. The collected data suggest that aPDT could be a promising new approach against multidrug-resistant infectious agents. However, despite important results being obtained against bacteria, experimental and clinical studies are necessary yet on the effectiveness of aPDT against fungal and viral infections in burns, which could reduce morbidity and mortality of burned patients, mainly those infected by multidrug-resistant strains.

Factors mediating Acinetobacter baumannii biofilm formation: Opportunities for developing therapeutics

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A. baumannii rapidly acquires antimicrobial resistance and causes biofilm associated infections.

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Strategies to target intrinsic factors mediating A. baumannii biofilm formation offer therapeutic prospects.

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Antimicrobial polymers and coating medical devices with antibiofilm agents may prevent biofilm associated infections.

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Biofilm matrix or regulatory mechanisms such as quorum sensing are potential targets for treating chronic infections.

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Phage therapy, photodynamic therapy and nanoparticle therapy are novel promising approaches for treating biofilm associated infections.

Acinetobacter baumannii has notably become a superbug due to its mounting risk of infection and escalating rates of antimicrobial resistance, including colistin, the last-resort antibiotic. Its propensity to form biofilm on biotic and abiotic surfaces has contributed to the majority of nosocomial infections. Bacterial cells in biofilms are resistant to antibiotics and host immune response, and pose challenges in treatment. Therefore current scenario urgently requires the development of novel therapeutic strategies for successful treatment outcomes. This article provides a holistic understanding of sequential events and regulatory mechanisms directing A. baumannii biofilm formation. Understanding the key factors functioning and regulating the biofilm machinery of A. baumannii will provide us insight to develop novel approaches to combat A. baumannii infections. Further, the review article deliberates promising strategies for the prevention of biofilm formation on medically relevant substances and potential therapeutic strategies for the eradication of preformed biofilms which can help tackle biofilm-associated A. baumannii infections. Advances in emerging therapeutic opportunities such as phage therapy, nanoparticle therapy and photodynamic therapy are also discussed to comprehend the current scenario and future outlook for the development of successful treatment against biofilm-associated A. baumannii infections.

Antimicrobial photodynamic therapy against Acinetobacter baumannii

Acinetobacter baumannii (A. baumannii) has emerged as a pathogen of global importance able to cause opportunistic infections on the skin, urinary tract, lungs, and bloodstream, being frequently involved in hospital outbreaks. Such bacterium can resist a variety of environmental conditions and develop resistance to different classes of antibiotics. Antimicrobial photodynamic therapy (aPDT) has been considered a promising approach to overcome bacterial resistance once it does not cause selective environmental pressure on bacteria. In this review, studies on aPDT were accessed on PubMed, and their findings were summarized regarding its efficacy against A. baumannii. The data obtained from the literature show that exogenous photosensitizers belonging to different chemical classes are effective against multidrug-resistant A. baumannii strains. However, most of such data is from in vitro studies, and additional studies are necessary to evaluate if the exogenous photosensitizers may induce selective pressure on A. baumannii and the effectiveness of such photosensitizers in clinical practice.

Photodisinfection effects of silver sulfadiazine nanoliposomes doped-curcumin on Acinetobacter baumannii: a mouse model

Aim: To evaluate the antimicrobial effects of photoexcited silver sulfadiazine nanoliposomes (AgSD-NLs) doped by curcumin (AgSD-NLs@Cur) on Acinetobacter baumannii. Materials & methods: Following characterization, the cytotoxic and hemolytic activities of AgSD-NLs@Cur were evaluated. The antimicrobial activities of AgSD-NLs@Cur-mediated antimicrobial photodynamic therapy (aPDT) were determined. Histopathological examination of the burn wound sites of infected mice treated with photoexcited AgSD-NLs@Cur was assessed. Results: No significant cytotoxic and hemolytic activities were observed. There was a decrease in the Acinetobacter baumannii count in planktonic and biofilm forms and the gene expression level using AgSD-NLs@Cur-aPDT (p < 0.05). Histopathological analysis indicated the epidermis developed markedly and the bacterial load decreased significantly after aPDT. Conclusion: Photoexcited AgSD-NLs@Cur has an antimicrobial potential against A. baumannii.

Considerations and Caveats in Combating ESKAPE Pathogens against Nosocomial Infections

ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) are among the most common opportunistic pathogens in nosocomial infections. ESKAPE pathogens distinguish themselves from normal ones by developing a high level of antibiotic resistance that involves multiple mechanisms. Contemporary therapeutic strategies which are potential options in combating ESKAPE bacteria need further investigation. Herein, a broad overview of the antimicrobial research on ESKAPE pathogens over the past five years is provided with prospective clinical applications.

Using Colistin as a Trojan Horse: Inactivation of Gram-Negative Bacteria with Chlorophyllin

Colistin (polymyxin E) is a membrane-destabilizing antibiotic used against Gram-negative bacteria. We have recently reported that the outer membrane prevents the uptake of antibacterial chlorophyllin into Gram-negative cells. In this study, we used sub-toxic concentrations of colistin to weaken this barrier for a combination treatment of Escherichia coli and Salmonella enterica serovar Typhimurium with chlorophyllin. In the presence of 0.25 µg/mL colistin, chlorophyllin was able to inactivate both bacteria strains at concentrations of 5-10 mg/L for E. coli and 0.5-1 mg/L for S. Typhimurium, which showed a higher overall susceptibility to chlorophyllin treatment. In accordance with a previous study, chlorophyllin has proven antibacterial activity both as a photosensitizer, illuminated with 12 mW/cm2, and in darkness. Our data clearly confirmed the relevance of the outer membrane in protection against xenobiotics. Combination treatment with colistin broadens chlorophyllin's application spectrum against Gram-negatives and gives rise to the assumption that chlorophyllin together with cell membrane-destabilizing substances may become a promising approach in bacteria control. Furthermore, we demonstrated that colistin acts as a door opener even for the photodynamic inactivation of colistin-resistant (mcr-1-positive) E. coli cells by chlorophyllin, which could help us to overcome this antimicrobial resistance.