Can commensals alter pathogen's antibiotic resistance during co-culture?

Area of Science:

• Microbiology
• Infectious Diseases
• Antimicrobial Resistance

Background:

• Bacterial wound infections, particularly in burn wounds and diabetic foot ulcers, prolong hospitalization and worsen patient outcomes.
• Key pathogens include Pseudomonas aeruginosa and Staphylococcus aureus, but commensal bacteria like Staphylococcus epidermidis and Micrococcus luteus are also present.
• The impact of co-infection on the antibiotic resistance profiles of individual bacterial species remains largely uncharacterized.

Purpose of the Study:

• To investigate the influence of dual-species co-culture (commensal-pathogen) on the antibiotic resistance of each bacterial species.
• To assess how inter-species interactions within a co-culture environment affect antimicrobial susceptibility.

Main Methods:

• Commensal and pathogenic bacterial species were cultured individually and in dual-species co-cultures, with potential biofilm formation over 24 hours.
• Cultures were subsequently treated with antibiotics (ciprofloxacin or tobramycin).
• Minimum Biofilm Eradication Concentrations (MBECs) and bacterial viable counts were used to compare antibiotic resistance between single-species and co-culture conditions.

Main Results:

• Bacterial viability was reduced when species were co-cultured compared to single-species cultures.
• Co-culturing led to decreased antibiotic resistance, notably in Pseudomonas aeruginosa (lower MBECs).
• The antibiotic resistance of other species was influenced by specific inter-species effects.

Conclusions:

• The presence of commensal bacteria in co-culture with pathogens can reduce antibiotic resistance.
• Inter-species interactions within microbial communities significantly affect pathogen viability.
• Antimicrobial resistance assessment protocols should consider microbial community dynamics for more effective wound infection treatments.