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Photodynamic therapy with methylene blue effectively kills antibiotic resistant bacteria from pediatric patients with
Korry T Wirth1,2, Eric Y Wang3, Darrian S Hawryluk2
1Division of Pediatric Surgery, Department of Surgery, University of Rochester Medical Center, Rochester, NY, USA.
Insights
Photodynamic therapy (PDT) effectively reduced bacteria from perforated appendicitis cases, including antibiotic-resistant strains. This suggests PDT could be a valuable addition to standard antimicrobial treatments for pediatric intra-abdominal infections.
Area of Science:
- Microbiology
- Biomedical Engineering
- Pediatric Surgery
Background:
- Perforated appendicitis (PA) is a leading cause of intra-abdominal abscesses in children, resulting in increased healthcare costs and poorer outcomes.
- Current treatments for PA often involve antibiotics, but rising antibiotic resistance poses a significant challenge.
Purpose of the Study:
- To evaluate the efficacy of photodynamic therapy (PDT) in eliminating bacteria isolated from pediatric patients with perforated appendicitis.
- To determine if PDT is effective against antibiotic-resistant bacterial strains commonly found in PA infections.
Main Methods:
- Bacterial isolates from peritoneal fluid of 30 pediatric PA patients were cultured.
- Cultures were treated with methylene blue (MB) and a 665 nm laser for PDT.
- Bacterial log reductions were compared between PDT and control groups (MB alone, laser alone, no treatment).
Main Results:
- Bacteria were isolated from 93.3% of specimens, with 86.7% being polymicrobial. Common isolates included E. coli, Streptococcus anginosus group, Bacteroides fragilis, and Pseudomonas aeruginosa.
- MB-PDT achieved significant log reductions for E. coli (5.86 ± 0.39), S. anginosus (5.91 ± 0.88), and P. aeruginosa (2.23 ± 0.64) compared to controls (p < 0.001).
- PDT demonstrated comparable efficacy against antibiotic-resistant and pan-susceptible isolates for E. coli, S. anginosus, and P. aeruginosa.
Conclusions:
- Photodynamic therapy with methylene blue achieved >99.9% bacterial kill for most isolated strains from perforated appendicitis, irrespective of antibiotic susceptibility.
- PDT shows promise as an adjunctive therapy to conventional antimicrobial treatments for pediatric perforated appendicitis.
Abstract:
Perforated appendicitis (PA) is the most common cause of intra-abdominal abscess in children and is associated with higher costs, extended hospitalizations, and worse postoperative outcomes compared to uncomplicated appendicitis. Photodynamic therapy (PDT) utilizes a photosensitizer and light to generate cytotoxic reactive species that are efficacious against bacteria. We sought to determine whether PDT could effectively eliminate bacteria isolated from the peritoneal cavities of pediatric patients with perforated appendicitis. After IRB approval, bacterial subcultures from 30 pediatric surgical patients with PA were developed as planktonic monocultures. Samples were derived from standard clinical collection of peritoneal fluid in patients undergoing surgery for PA. Cultures were incubated with the photosensitizer methylene blue (MB) and exposed to a 665 nm laser to perform PDT. Control conditions were MB alone, laser alone, or no MB and no laser. Log reductions in bacterial growth between groups were compared using two-way ANOVA. Bacteria were isolated from 28 (93.3%) specimens, and 26 (86.7%) were polymicrobial. The most prevalent organisms included Escherichia coli (76.7%), the Streptococcus anginosus group (56.7%), Bacteroides fragilis (46.6%), and Pseudomonas aeruginosa (26.7%), with antibiotic resistance common among E. coli isolates. For E. coli, MB-PDT caused a 5.86 ± 0.39 log10 reduction compared to the no-treatment control (p < 0.001). For S. anginosus and P. aeruginosa, MB-PDT resulted in reductions of 5.91 ± 0.88 log10 and 2.23 ± 0.64 log10, respectively (all p < 0.001). PDT showed comparable efficacy in isolates with multiple antibiotic resistance relative to those that were antibiotic pan-susceptible for E. coli (p = 0.760), S. anginosus group (p > 0.999), and P. aeruginosa (p = 0.991). PDT application to bacterial isolates from patients with perforated appendicitis achieved > 99.9% bacterial kill in all isolated strains other than P. aeruginosa, regardless of antibiotic susceptibility, suggesting that PDT may be a viable adjunct to in vivo antimicrobial therapy.
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