Objective: Following the isolation of a Marseillevirus from the stool of a healthy young Senegalese and a Mimivirus from a Tunisian patient with pneumonia, we attempted to isolate other giant viruses of amoebae from a large human stool collection.
Methods: During the period 2010-2011, a total of 1,605 stool samples, including 115 from Tunisian patients with pneumonia, were cultured on amoebae. We used a recently developed high-throughput isolation system to detect amoebae plaque lysis on agar plates; this method allows for the testing of 100 samples per plate per week. The giant virus was identified by sequencing of genes conserved in Megavirales.
Results: A single giant virus, called Shan, was isolated from the stool of a Tunisian patient with pneumonia who responded poorly to antibiotics. This virus has an icosahedral shape typical of members of the family Mimiviridae and a size of 640 ± 10 nm. Phylogenetic analyses showed that Shan virus was classified as a member of Mimivirus lineage C that infects amoebae.
Conclusion: Only one isolate was obtained in this study, suggesting that giant viruses of amoebae are rare in human stool. The isolation of Shan virus from a patient with pneumonia brings into question the etiological role of this virus and its subsequent release in stool.