Allovahlkampfia spelaea Causing Keratitis in Humans

Citation: Tolba MEM, Huseein EAM, Farrag HMM, Mohamed HED, Kobayashi S, Suzuki J, et al. (2016) Allovahlkampfia spelaea Causing Keratitis in Humans. PLoS Negl Trop Dis 10(7): e0004841. doi:10.1371/journal.pntd.0004841
Published: July 14, 2016

Clare-314Background: Free-living amoebae are present worldwide. They can survive in different environment causing human diseases in some instances. Acanthamoeba sp. is known for causing sight-threatening keratitis in humans. Free-living amoeba keratitis is more common in developing countries. Amoebae of family Vahlkampfiidae are rarely reported to cause such affections. A new genus, Allovahlkampfia spelaea was recently identified from caves with no data about pathogenicity in humans. We tried to identify the causative free-living amoeba in a case of keratitis in an Egyptian patient using morphological and molecular techniques.
Methods: Pathogenic amoebae were culture using monoxenic culture system. Identification through morphological features and 18S ribosomal RNA subunit DNA amplification and sequencing was done. Pathogenicity to laboratory rabbits and ability to produce keratitis were assessed experimentally.
Results: Allovahlkampfia spelaea was identified as a cause of human keratitis. Whole sequence of 18S ribosomal subunit DNA was sequenced and assembled. The Egyptian strain was closely related to SK1 strain isolated in Slovenia. The ability to induce keratitis was confirmed using animal model.
Conclusions: This the first time to report Allovahlkampfia spelaea as a human pathogen. Combining both molecular and morphological identification is critical to correctly diagnose amoebae causing keratitis in humans. Use of different pairs of primers and sequencing amplified DNA is needed to prevent misdiagnosis.

Author Summary: Free-living amoebae are present worldwide. Some species are known to cause chronic keratitis in human. Amoebic chronic keratitis is sight-threatening disease occurring in both developing and well-developed countries. Allovahlkampfia spelaea is a newly discovered free-living amoeba. We report the first human case of chronic keratitis due to that amoeba. For correct identification, both morphological and molecular techniques should be combined.


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