Shigella isolation in Vellore, south India (1997-2001).

Shigellosis has been a major cause of dysentery for many years at Vellore, south India. In the last two years the number of Shigella being isolated from samples of faeces from patients with diarrhoea has decreased (5% isolation rate in 1997 to 3.9% in 2001), although the microbiological methods and media used have not changed. Also, the nalidixic acid (NA) resistance has increased for S. sonnei (now 94%). This is noteworthy, since NA has been recommended for the empirical treatment of patients suspected to have shigellosis and this concept needs to be reconsidered based on available data.