April 1991, Volume 41, Issue 4

Original Article


K. Zaman  ( International Centre for Diarrhoeal Disease Research, Dhaka, Bangladesh. )
MD. Yunus  ( International Centre for Diarrhoeal Disease Research, Dhaka, Bangladesh. )
A. H. Baqui  ( International Centre for Diarrhoeal Disease Research, Dhaka, Bangladesh. )
K. M. B. Hossain  ( International Centre for Diarrhoeal Disease Research, Dhaka, Bangladesh. )


Over a period of 10 years 35,620 patients, admitted from a defined surveillance area, had a rectal swab culture done at a rural diarrhoea treatment centre in Bangladesh. Shigella spp. were isolated from 3,440 (9.7%) cases. Marked year to year variations were observed in isolation rates of Shigella spp. ranging from 5.7% to 16.7%. Sh. flexneri was the predominant isolate between 1978 to 1982 (56%-67%), Sh. dysenteriae type 1 predominated from i 983 to 1985 (45%-50%), and again Sh.flexneri became predominant in 1986 (55%) and 1987(61%). Shigella were most commonly isolated from children aged 1-4 years followed by children 5-9 years and elderly people aged 45+ years. Sh. flexneri was isolated most frequently during August - January and Sh.dysenteriae type 1 during June to July. The overall case fatality rate in patients with shigellosis was 0.96%. It was 1.10% in children under 5 years of age. Prevalence of multiple antibiotic resistant strains increased over the years and at present most strains are resistant to commonly used antibiotics such as ampicillin and cotrimoxazole. Nalidixic acid is currently the drug of choice for Shigella infection in this area (JPMA41: 75, 1991).


In Bangladesh, as in most developing countries, shigellosis causes considerable of morbidity and mor­tality particularly in young children1-2. Epidemics of shigellosis have occurred in the developed countries as well3, and claimed thousands of lives4. The Shigella isolation rate at Dhaka Hospital of the International Centre for Diarrhoeal Disease Research, Bangladesh (JCDDR,B) increased from 0.5% in 1970 to 12% in 19815. In the ICDDR, B rural treatment centre at Matlab, Shigella was isolated 5%-6% of admitted cases during 1977-786. Emergence of multiple antibiotic resistance has been reported from Bangladesh and other countries7-10. Case fatality rate in Dhaka Hospital ranged from 3-13%5. To understand the epidemiologic pattern of shigellosis in rural Bangladesh, we reviewed the clinical and laboratory records of patients admitted at the Matlab Treatment Centre between 1978-87.


ICDDR, B operates a diarrhoea treatment centre at Matlab, arural area of Bangladesh, which lies 45km south east of Dhaka. Since 1963 a demographic surveillance system (DSS) which consists of regular cross sectional census and longitudinal registration of vital events has been maintained in the area. Details of the study area, its people and field research procedures have been reported elsewhere11.  From February 1978, rectal swab, stool specimens were obtained from all admitted DSS (about 35% of total admissions) registered patients and cultured for Shigel­lae, Yibrio cholerae and Salmonellae using standard procedures12. The clinical and microbiological records of all DSS patients admitted between February, 1978 and December1987 were reviewed to obtain the age distribu­tion, seasonality, antibiotic sensitivity patterns and mor­tality information of Shigella patients. During 1977-7913 and 1983-8414 Shigella strains were tested for sensitivity to tetracycline, ampicillin, chloramphenicol, kenamycin, gentamycin, streptomycin and cotriffioxazole by tIle Bauer-Kirby technique15. In 1987, these were tested only against ampicillin, cotrimoxazole and nalidixic acid. The Shigella isolation techniques remained same for the whole period of study.


The total number of DSS patients admitted between 1978 and 1987 was 35,620. The admission sharply fell I 1979 because some of the areas were excluded from the DSS in October, 1978. Shigellae were isolated from 3,440 (9.7%) patients. Marked year to year variations were observed in isolation rates of Shigella spp. ranging from 5.7% to 16.7% (Table-I).

The distribution of Shigella spp. isolated in different years is shown in Table II

Sh.flexneri was predominant between 1978 to 1982 (56% - 67) and Sh.dysentcriae type I from 1983 to 1985 (45% - 50%), Sh.felxneri again became predominant during 1986 and 1987 (55% and 61%). Sh.boydii, Sh.sonnei and Sh.ysenteriae type (2-10) were isolated in all years, but were never predominant. The age distribution of the patients and Shigella species isolation rates are shown in Table III.

Shigellae were most commonly isolated in children aged 1-4 years, followed by children between 5 - 9 years and elderly people aged 45 years and above. Sh.flexneri was isolated most frequently in younger children (1 -4 year) and Sh. dysenteriae type 1 in older children (5 - 9 year). The lowest isolation was found in infants. Sh.fiexneri was isolated most frequently during August-january. Sh.dysenteriae type 1 isolation usually peaked in june-july (Figure-).

The overall case fatality rate in patients with shigellosis was 0.96% (33/3440). Highest fatality (2.1%) was observed in children aged 5-9 years (Table-IV).

The resistance pattern of Shigellae to antibiotics is shown in Table-V.

Five percent of Sh.dysentenae type 1 isolates were resistant to ampicillin in 1977-79, 4% in 1983-84; while 91% were resistant in 1987. Resistance to cotrimoxazole was also 5% in 1977-79 but increased to 96% in 1983-84 and 94% in 1987. 7% of Sh.flexneri isolates were resistant to ampicillin in 1977-79 and increased to 53% in 1987. During the same period resistance to cotrimoxazole also increased from 0% to 22%. Both Sh.dysentenae type 1 and Sh.flexneri were highly (97%) sensitive to nalidixic acid in 1987.


In the developed countries the predominant species of shigella is Sh.sonnei16. At Matlab Sh.flexneri was most common in all the years studied except 1983-85 when multiresistant Sh.dysenteriae type I epidemic swept through Bangladesh and India17,18. Our lowest isolation rates were in infants. This is similar to results obtained in earlier studies and might be due to less exposure and/or protective effect of breast eeding19-21. Cotrimoxazole and ampicilim were equally effec­tive against Shigella in 197913. But during 1983-84 most (96) isolates of Sh. dysenteriae type 1 were resistant to cotriqoxazole while there was also a marked increase in Sh.dyenteriae type 1 isolation. However, at that time sensitivity particularly of Sh.dysenteriae type 1 to ampicil­lin was sill very high (96%) and the drug was being used effectively By the year 1987 more than 90% of Sh.dysenteiae type 1 isolates were resistant to ampicillin and cotrumxazole, 53% of Sh.flexneri isolates were resistant to ampicillin and 22% to cotrimoxazole. Nalidixic acid iecame the drug of choice for treating all kinds of shigelae. We observed only 3% of Shigella isolates were resistant to nalidixic acid. In Teknaf, another rural arear)f Bangladesh resistance to nalidixic acid has been observed as high as 86% of Shigella isolates22. Frequent use of antibiotics in subtherapeutic doses and for illnesses which they are not indicated has been observed in Matlal area23. This is generally true for other areas of Banglades!. Such abuse and over use of antibiotic may have contributed to the increase in antibiotic resistant strains in rural Bangladesh. Because this overuse is still continuting the situation must be monitored. The case facality rate in our was much lower than that of Dhaka hospital. 5. This may be due to difference in case mix at these tv0 facilities. All our patients are from a defined surveillane area, and many of them report to our hospital early and often with mild illness. Dhaka hospital draws patients from a much larger catchment area and serves as a referal centre for complicated cases of diarrhoea. We conclude that shigellosis still remains a major health problem in rural Bangladesh. Research should be continued to identify alternative antimicrobias for the treatment of shigellosis and to identify the risk factors associated with acquiring resistant Shigella infections. Preventive measures such as hand washing24, need be promoted and intensified for better control of the disease.


The authors are grateful to Dr. Dilip Mahalanabis and Dr. Andre Briend for theft valuable comments in reviewing the manuscript.


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