Abstract
BackgroundFree-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.MethodsPathogenic 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.ResultsAllovahlkampfia 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.ConclusionsThis 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.
Highlights
Free-living amoebae (FLA) are present in different environments worldwide
A new genus, Allovahlkampfia spelaea was recently identified from caves with no data about pathogenicity in humans
Allovahlkampfia spelaea was identified as a cause of human keratitis
Summary
Free-living amoebae (FLA) are present in different environments worldwide. They can survive in soil, surface water, other aquatic environments and even desert[1,2]. The most commonly known genera are Acanthamoeba and Naegleria causing keratitis and primary amoebic meningoencephalitis[3,4]. Members of both families have vegetative form, the trophozoite, and quiescent form, the cyst, both can be used for morphological identification of different genera [5,6,7]. They can survive in different environment causing human diseases in some instances. We tried to identify the causative free-living amoeba in a case of keratitis in an Egyptian patient using morphological and molecular techniques
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