Enhanced Isolation of Influenza Virus in Conventional Plate Cell Cultures by Using Low-Speed Centrifugation from Clinical Specimens

To determine whether low-speed centrifugation as a means of amplifying viral adsorption to target cells can enhance the sensitivity of conventional techniques for the isolation of influenza virus from clinical specimens, the authors conducted a simultaneous comparison between two conventional plate cell cultures—one with and one without centrifugation (700 X g , 60 minutes). Of 26 influenza virus isolates obtained from 528 clinical specimens, 17 were more efficiently isolated by the centrifugation assay compared with conventional culture methods. Centrifugation-assisted methods were found to be efficient in the recovery of 17 of 20 isolates (85%) not identified on first passage by conventional techniques. The number of isolates obtained with centrifugation was 1.5 times as high as that obtained with no centrifugation after three passages. The two assays were significantly different in the isolation of influenza virus ( P < 0.01). Since lowspeed centrifugation may increase the infectivity of influenza virus in cell culture, this technique may prove useful in the efficient and rapid isolation of this virus from clinical specimens.