Shigella infections among children in Andaman--an archipelago of tropical islands in Bay of Bengal.

Shigellosis is common among children in the Andaman and Nicobar islands. Our experience showed two distinct features of shigellosis within a span of 3 years in 1994-6: (i) changing patterns of serotype or subtype specific shigellosis and (ii) emergence of multidrug resistant isolates with changing R-patterns. The rate of isolation was 10.4-27.9% with the rate of isolation of Shigella flexneri interchanging with S. dysenteriae alternately. In 1994, S. flexneri superseded S. dysenteriae (48.6% vs. 33.3%; P < 0.05) while S. dysenteriae dominated over S. flexneri in 1995 (54.7% vs. 34.0%; P < 0.05). The picture reversed again in 1996 (63.0% vs. 22.2%; P < 0.05). Among shigellae isolates, the commonest serotypes were S. dysenteriae type 1 and S. flexneri type 2a. Isolated shigellae were of multidrug resistant type. Seven R-patterns were observed in 1994, while 8R-patterns were observed during the next year with the emergence of nalidixic acid resistance. In 1996, emergence of gentamicin resistance was also observed. All isolates were resistant to ampicillin and sensitive to quinolones. The MIC of nalidixic acid and gentamicin are > or = 128 microg/ml and > or = 64 microg/ml respectively. These changing trends in shigellosis has important public health significance.