Shigellosis in children remains an import-ant health problem in developing countries. Increased incidence of resistance to antimi-crobial agents among Shigella spp. presents a major threat in the control of Shigellosis(1). Moreover, shift in the prevalent serogroups and changing pattern of antimicrobial susceptibilities among Shigellae isolates makes it difficult to recommend a drug of choice for Shigellosis(2). We report the distribution of serogroups of Shigella and their antimicrobial resistance pattern among childhood diarrhea cases in Calcutta.

During January to December 1997, a total of 230 samples were collected from children under 5 years of age suffering from acute diarrhea attending the Diarrhea Treatment Unit at Dr. B.C. Roy Memorial Hospital for Children, Calcutta. Fecal samples were cultured for Shigella spp. using standard microbiological techniques(3). Shigella strains identified were tested for susceptibility to the commonly used antimicrobial agents using disk diffusion technique according to the standard procedure outlined in National Committee for Clinical Laboratory Standard guidelines(4).

Shigella spp. were isolated as the sole pathogen from 11 of 230 (4.5%) stool samples. Shigella flexneri was the predominant species isolated (63.6%) followed by Shigella sonnei (36.4%). Sixty three per cent children presented with watery diarrhea and thirty seven per cent with blood and mucus (dysentery). Isolation rate of Shigella from watery diarrhea and dysentery cases were 2% and 9.3%, respectively. The Shigellae strains were resistant to co-trimoxazole (91%), tetracycline (73%) and furazolidone (91%). The organisms were sensitive to gentamicin, cefuroxime, nalidixic acid and newer quinolone derivatives in 91, 82, 91 and 100 per cent of cases, respectively. Almost 73% of the isolated strains of Shigellae were multidrug resistant.

Shigella strains are particularly noted for their multiple drug resistance which may result from the selection of resistant mutants through the widespread use of anti-microbial agents. Plasmid-mediated resistance in shigella species is well documented(5). Multidrug resistant Shigella have been reported from different parts of India(6,7). In our study about 73% of the isolated strains of shigellae were multidrug resistant. An increased trend of development of resistance to nalidixic acid was reported from Calcutta(8,9). Presently, signifi-cantly low resistance to nalidixic acid (9%) was observed in the present study. However, the development of resistance to furazolidone steadily increased over the past few years(9) and markedly high resistance (91%) to furazolidone was noted in our study.

In 1984, multi-drug resistance Shigella dysenteriae type 1 strains were isolated during an epidemic in West Bengal(6). After the epidemic, Shigella dysenteriae strains were replaced by various serotypes of Shigella flexneri. We observed Shigella flexneri to be the prevalent serogroup in Calcutta, typical of endemic shigellosis in a developing country. Ciprofloxacin was found to be in vitro active against all the isolates. Although, the safety of fluoroquinolone in young children is controver-sial, several reports about the safe usage in childhood have been published(10). Cipro-floxacin may be a good alternative in the treatment of multi-drug resistant strians. Efforts should be made to evaluate newer drugs for the treatment of childhood shigellosis. Continuous monitoring of the susceptibility patterns of Shigella spp. is important to notice the emergence of drug resistance as also for decid-ing periodically the appropriate antimicrobial therapy for Shigellosis.

S.K.Niyogi
P. Dutta,
U. Mitra,

Division of Microbiology and Clinical Medicine,
National Institute of Cholera and Enteric Diseases,
P 33 CIT Road Schm XM,
P.O. Beliaghata, Calcutta 700 010, India.

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