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Ultrastructural polymicrobial Staphylococcus aureus-Pseudomonas aeruginosa interactions and antimicrobial resistance
Sanchita Mitra1, Nagapriya Banka2, Soumyava Basu3
1Consultant Microbiologist, Jhaveri Microbiology Centre, LV Prasad Eye Institute, Kallam Anji Reddy Campus, Hyderabad, 500034, India.
Abstract:
Aim: To investigate antagonistic interactions among pathogens, in ex vivo donor corneas infected with monomicrobial or polymicrobial combinations of antibiotic susceptible and resistant clinical isolates of Staphylococcus aureus (MSSA, MRSA) and Pseudomonas aeruginosa (S-PA, MDR-PA).Materials & methods: Scanning electron microscopy and antimicrobial susceptibility testing (AST, broth microdilution for minimum inhibitory and bactericidal concentrations [MIC/MBC]) pre-and post-polymicrobial interactions, in infected donor corneas.Results: MSSA lost viability with S-PA/MDR-PA, while MRSA formed larger cells, biofilm and lower MIC (teicoplanin) with S-PA, but lost viability with MDR-PA. S-PA had lower MIC (ceftazidime, meropenem, chloramphenicol) with MSSA, and lower MBC (cefoperazone, ciprofloxacin) and fewer cells with MRSA. MDR-PA had abundant cells and no change in AST with MSSA or MRSA.Conclusion: Significant antagonistic interactions occur in ocular polymicrobial infections, affecting antibiotic susceptible isolates more than resistant ones.
Insights
Polymicrobial eye infections show antagonistic interactions. Antibiotic-susceptible pathogens like Staphylococcus aureus (MSSA) and Pseudomonas aeruginosa (S-PA) were more affected than resistant strains (MRSA, MDR-PA).
Area of Science:
- Ocular Microbiology
- Antimicrobial Resistance
- Infectious Diseases
Background:
- Ocular infections can involve single or multiple pathogens.
- Understanding pathogen interactions is crucial for effective treatment, especially with rising antibiotic resistance.
Purpose of the Study:
- To investigate antagonistic interactions between Staphylococcus aureus (MSSA, MRSA) and Pseudomonas aeruginosa (S-PA, MDR-PA) in ex vivo donor corneas.
- To assess how these interactions affect antimicrobial susceptibility.
Main Methods:
- Infection of ex vivo donor corneas with monomicrobial and polymicrobial combinations.
- Utilized scanning electron microscopy to visualize interactions.
- Performed antimicrobial susceptibility testing (AST), including MIC and MBC, before and after co-culturing.
Main Results:
- Methicillin-susceptible Staphylococcus aureus (MSSA) showed reduced viability when co-infected with susceptible Pseudomonas aeruginosa (S-PA) or multidrug-resistant Pseudomonas aeruginosa (MDR-PA).
- Methicillin-resistant Staphylococcus aureus (MRSA) exhibited altered growth and reduced teicoplanin MIC when interacting with S-PA, but lost viability with MDR-PA.
- S-PA demonstrated reduced susceptibility (lower MIC/MBC) to certain antibiotics when interacting with MSSA or MRSA, while MDR-PA showed no significant changes in AST.
Conclusions:
- Significant antagonistic interactions occur in polymicrobial ocular infections.
- These interactions disproportionately impact antibiotic-susceptible bacterial isolates compared to resistant ones.
- Findings highlight the complexity of treating polymicrobial eye infections and the need to consider pathogen dynamics.
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