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Published on: October 27, 2013
Surveillance of Amoebic Keratitis-Causing Acanthamoebae for Potential Bacterial Endosymbionts in Ontario, Canada
Nessika Karsenti1, Andrew Purssell2, Rachel Lau3
1Schulich School of Medicine & Dentistry, London, ON N6A 5C1, Canada.
Abstract:
Acanthamoeba spp. are the causative pathogens of several infections, including amoebic keratitis (AK), a vision-threatening infection. Acanthamoebae from corneal specimens of patients with AK harbor bacterial endosymbionts, which may increase virulence. We sought to understand the spectrum of bacterial endosymbionts present in clinical isolates of Acanthamoeba spp. identified in our reference parasitology laboratory. Isolates of Acanthamoeba spp. obtained from our biobank of anonymized corneal scrapings were screened for potential endosymbionts by PCR using primer pairs detecting bacteria belonging to orders Chlamydiales, Rickettsiales, or Legionellales and pan16S primers. Three primer pairs specific to the 18s rRNA gene of Acanthamoeba spp. were used for the amplification of Acanthamoeba DNA used for sequencing. Sanger sequencing of all PCR products was performed, followed by BLAST analysis for species identification. We screened 26 clinical isolates of Acanthamoeba spp. for potential endosymbionts. Five isolates (19%) were found to contain bacterial DNA belonging to Legionellales. Three (11%) contained members of the Rickettsiales and Pseudomonas genticulata was detected in a Rickettsia-positive sample. One strain (4%) contained Neochlamydia hartmannellae, a member of the Chlamydiales order. Bacterial endosymbionts are prevalent in clinical strains of Acanthamoeba causing AK isolated from corneal scrapings. The demonstration of these organisms in clinical Acanthamoeba isolates supports a potential exploration of anti-endosymbiont therapeutics as an adjuvant therapy in the treatment of AK.
Insights
Bacterial endosymbionts are common in Acanthamoeba strains causing eye infections. Identifying these bacteria in Acanthamoeba isolates may lead to new treatments for amoebic keratitis.
Area of Science:
- Microbiology
- Ophthalmology
- Parasitology
Background:
- Acanthamoeba species cause serious eye infections like amoebic keratitis (AK).
- Bacterial endosymbionts within Acanthamoeba may enhance its virulence.
- Understanding these endosymbionts is crucial for AK treatment.
Purpose of the Study:
- To identify the range of bacterial endosymbionts in clinical Acanthamoeba isolates from AK patients.
- To investigate the prevalence of specific bacterial orders (Chlamydiales, Rickettsiales, Legionellales) within these isolates.
Main Methods:
- Screening of 26 clinical Acanthamoeba isolates from corneal scrapings using PCR.
- Utilized primer pairs specific for Chlamydiales, Rickettsiales, Legionellales, and pan16S rRNA.
- Sanger sequencing and BLAST analysis for bacterial and Acanthamoeba species identification.
Main Results:
- Bacterial DNA was detected in 19% (Legionellales), 11% (Rickettsiales), and 4% (Chlamydiales) of isolates.
- Pseudomonas genticulata was found in a Rickettsia-positive sample.
- Neochlamydia hartmannellae was identified in one isolate.
Conclusions:
- Bacterial endosymbionts are frequently found in clinical Acanthamoeba strains causing AK.
- The presence of these endosymbionts suggests potential for developing anti-endosymbiont therapies.
- Targeting endosymbionts could offer an adjunctive treatment strategy for amoebic keratitis.
