Saudi Journal of Gastroenterology
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ORIGINAL ARTICLE Table of Contents   
Year : 2007  |  Volume : 13  |  Issue : 3  |  Page : 129-132
Epidemiology of Shigella-associated diarrhea in Gorgan, north of Iran

1 Department of Microbiology, Golestan University of Medical Sciences, Iran
2 Pasteur Institute of Tehran, Iran

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Date of Submission10-Feb-2007
Date of Acceptance28-May-2007


Objective : Shigella is an important etiological agent for diarrhea and especially dysentery. Shigellosis is an intestinal infection that is a major public health problem in many developing countries. The aim of this study was to evaluate the prevalence of Shigella and its various species in diarrheal samples in Gorgan located in the north of Iran. Materials and Methods: Between January-December 2005, the epidemiology of Shigella- associated diarrhea was studied among 634 patients in Gorgan. The diarrheal samples accompanied with a questionnaire, which contained the demographic and main symptoms of the patients, were transported to the laboratory and inoculated in different culture media. Colonies suspected to be of Shigella were detected using differential biochemical tests and subsequently, the serotype of Shigella was defined using antisera.
Results : Shigella was isolated from 56/634 diarrheal samples) (8.8%) of which S. sonnei was the predominant species (55%). Occurrence of Schigella was highest in the 2-5 years' age group (70.9%) and highest in summer (73.2%) with the most frequent clinical manifestation being abdominal pain (67.8%). The prevalence of Shigella in males and females was 8 and 9.8% respectively, but this difference was not statistically significant. Conclusion: It has been shown that Shigella sonnei is the most common Shigella serogroup among 2-5 year-old children in Gorgan. It is therefore suggested that hygienic training be given to childcare attendants and the children themselves.

Keywords: Shigella , Diarrhea, serotype, epidemiology, Iran

How to cite this article:
Ghaemi EO, Aslani MM, Moradi AV, Dadgar T, Livani S, Mansourian AR, Nosrat SB, Ahmadi AR. Epidemiology of Shigella-associated diarrhea in Gorgan, north of Iran. Saudi J Gastroenterol 2007;13:129-32

How to cite this URL:
Ghaemi EO, Aslani MM, Moradi AV, Dadgar T, Livani S, Mansourian AR, Nosrat SB, Ahmadi AR. Epidemiology of Shigella-associated diarrhea in Gorgan, north of Iran. Saudi J Gastroenterol [serial online] 2007 [cited 2021 Sep 19];13:129-32. Available from:

Diarrhea is a generally unpleasant condition in which the sufferer has frequent watery, loose bowels. It is a major cause of childhood morbidity and mortality, especially in developing countries, [1] accounting for 5-8 million deaths annually. [2] Shigella is an important etiological agent for diarrhea, in particular, dysentery. The illness is also known as 'bacillary dysentery' and it is more severe than other forms of gastroenteritis. Shigellosis is a global human health problem. [3] A recent review of literature concluded that of the estimated 165 million cases of Shigella diarrhea that occur annually in the world, 99% occur in the developing world and the remaining 1% occurs in industrialized countries. In developing countries, 69% of these episodes occur in children under five years of age. Moreover, of the 1.1 million deaths attributed to Shigella infections in developing countries, 60% occur in the under-five age group in children. [4]

Prevention of Shigella infections has proven to be difficult, mainly due to the low inoculum needed to produce disease with infectious doses as low as 10-100 viable bacterial cells and inadequate empirical therapy options secondary to antimicrobial resistance. [5]

Shigellosis remains an important problem in developing countries. The purpose of this study was to evaluate the prevalence of Shigella and its various species in diarrheal samples in Gorgan located in the north of Iran.

   Materials and Methods Top

Sample population: Between January-December 2005, diarrheal samples were collected from individual patients aged ≤ 16 years, referring to the private or governmental laboratories. These samples were cultured for Shigella species. A diarrheal sample was defined as the occurrence of ≥ 3 unformed stools (or ≥ 1, if bloody) in a 24 hour period. We filled a questionnaire for each subject, which contained their demographic characteristics, time and frequency of diarrhea and signs of illness.

Laboratory tests: Standard microbiology laboratory techniques were used to isolate and identify Shigella . While an aliquot from a diarrheal sample was cultured directly on  Salmonella More Details-Shigella plates (SS1), XLD media and MacConkey Agar, another aliquot was inoculated in Salmonella-Shigella plates (SS 2 ) after 6-8 hours' enrichment in Selenit F (SF) broth. Shigella serogroups were determined using Iranian commercially available standard antisera (Tehran, Iran).

Statistical analyses : Data from all cases were entered into SPSS 11.5. Binary data analysis was performed using Chi-Square test.

   Results Top

Diarrheal samples of 634 patients were studied during 2005. Of these, 348 (54.8%) were male and all patients were ≤ 16 years of age. We isolated Salmonella species from five (0.79%) samples and Shigella species from 56 (8.8%) samples. Twenty-eight (4.4) of these 56 patients infected with Shigella were male, but the difference between the two groups was not statistically meaningful (P > 0.05) [Table - 1].

We found that the majority of bacillary dysentery cases occurred during the summer time-41 cases (73.2%), followed by ten (17.9%),four (7.1%)and only one case in autumn,winter and spring respectively [Table - 1].

The age distribution data revealed that Shigella sp. was isolated from 40 (70.9%) cases in the 2-5 year-old, 13 (23.6%) in the 6-12 year-old and three (5.5%) in ≤ one year-old age groups. Moreover, this difference was statistically significant ( P < 0.001), suggesting that the peak age of shigellosis was 2-5 years in children [Figure - 1]. The most common symptoms in our patients with Shigellosis were abdominal pain, tenesmus (69.6%) and fever (56.6%). However, these rates are not statistically different from those seen in the non Shigellosis population [Table - 2].

Out of 56 Shigella strains isolated during the surveillance period, S. sonnei (31 cases, 55%), S. flexneri (12 cases, 22%), S. dysenteriae (ten cases, 18%) and S. boydii (three cases, 5%) were detected [Figure - 2].

   Discussion Top

Our study showed that the prevalence of Shigella in diarrhea cases among children in Gorgan was 8.8%. However, other studies conducted in Iran reported prevalence rates of 3-21.7%. [6],[7],[8],[9] The reasons for this variation include behavioral and cultural differences and time of sampling. Prevalence of Shigella infection was 16% in Kenya [10] and 7.7% in Calcutta (India),[11] which is similar to the rate reported in our study.

We found that Shigellosis occurred mostly in children with a peak age of 2-6 years (70.9%). The risk of Shigella -associated diarrhea in children less than a year old is low (5.5%), this difference probably being due to their behavior and contact with different infected material. [4],[5],[12],[13],[14] Although it has been reported that the majority of Shigella isolates from developing countries are S. flexneri [4] (median 60%) which is also the case in some parts of Iran, [7],[9] we found that S. sonnei was the most common serogroup in our region. Similarly, other studies in Tehran showed that 58.9% of Shigella strains were S. sonnei . [12],[15] Thus, it can be predicted that development of a polyvalent vaccine that covers strains of S. sonnei and S. flexneri would provide protection against 77% of Shigella infections occurring in Gorgan in the north of Iran.

S. sonnei is mostly associated with crowding and poor sanitation in institutions such as schools, day-care and nursing centers and also among members of tour groups. [16] During a community-wide outbreak of S. sonnei , children younger than 6 years of age who attended day-care were found to be 2.4 times more likely to experience shigellosis than children who did not. [17] Due to this reason, more attention should be paid to the health of children less than 5 years of age in day-care centers. Educating child-care attendants and the children themselves regarding the importance of frequent hand washing is the key to prevent shigellosis. Also, because this infection is transmitted so easily from infected children to others, all symptomatic persons, employees and children with Shigella infection should be excluded from the daycare setting until diarrhea has ceased and stool cultures are negative for this bacteria.

Consistent with other studies, [4],[12],[18] the peak of Shigellosis in our region occurred during summer time.

In contrast to the study on Egyptian children, [5] our studies found that there are no statistical differences between diarrheal Shigellosis among males and females, indicating that the virulence of Shigella infections was not gender-related. [16]

   Conclusion Top

This study was conducted to determine the epidemiologic pattern of shigellosis in diarrheal samples in Gorgan. We may conclude that Shigella can be considered as an important agent of diarrhea among Iranian children living in Gorgan. The most common Shigella serogroup identified was S. sonnei in which age and season were significant risk factors for Shigella -associated diarrhea.

   Acknowledgment Top

We wish to thank all of our colleagues from the diagnostic laboratories in Gorgan and especially Khandandel M. R. and Behnam Npour for their sincere cooperation.

   References Top

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2.Kasper DL, Braunwald E, Fauci AS, Hauser SL, Longo DL, Jameson JL. Harrison's principles of internal medicine. McGraw-Hill: New York; 2005.  Back to cited text no. 2    
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4.Kotloff KL, Winickoff JP, Ivanoff B, Clemens JD, Swerdlow DL, Sansonetti PJ, et al . Global burden of Shigella infections: Implications for vaccine development and implementation of control strategies. Bull World Health Organ 1999;77:651-66.  Back to cited text no. 4  [PUBMED]  
5.Abu-Elyazeed RR, Wierzba TF, Frenck RW, Putnam SD, Rao MR, Savarino SJ, et al . Epidemiology of Shigella -associated diarrhea in rural Egyptian children. Am J Trop Med Hyg 2004;71:367-72.  Back to cited text no. 5  [PUBMED]  [FULLTEXT]
6.Soltan-Dallal MM, Moezardalan K. Frequency of Yersinia species infection in paediatric acute diarrhoea in Tehran. East Mediterr Health J 2004;10:152-8.  Back to cited text no. 6  [PUBMED]  
7.Moez Ardalan K, Zali MR, Dallal MM, Hemami MR, Salmanzadeh-Ahrabi S. Prevalence and pattern of antimicrobial resistance of Shigella species among patients with acute diarrhoea in Karaj, Tehran, Iran. J Health Popul Nutr 2003;21:96-102.  Back to cited text no. 7    
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10.Brooks JT, Ochieng JB, Kumar L, Okoth G, Shapiro RL, Wells JG, et al . Surveillance for Bacterial Diarrhea and Antimicrobial Resistance in Rural Western Kenya, 1997-2003. Clin Infect Dis 2006;43:393-401.  Back to cited text no. 10  [PUBMED]  [FULLTEXT]
11.Das AS, Mazumber DN, Pal D, Chattopadhyay VK. A study of nosocomial diarrhea in Calcutta. Indian J Gastroenterol 1996;15:12-3.  Back to cited text no. 11    
12.Ranjbar R. Study of the epidemiology of Shigella spp. in Tehran, Iran during 2002-2003. 14 th European Congress of Clinical Microbiology and Infectious Diseases. Prague / Czech Republic; 2004. p. 1-4.  Back to cited text no. 12    
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14.Ramiro Cruz J, Cano F, Bartlett AV, Mιndez H. Infection, diarrhea, and dysentery caused by Shigella species and Campylobacter jejuni among Guatemalan rural children. Pediatr Infect Dis J 1994;13:216-23.  Back to cited text no. 14    
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18.Wang X, Tao F, Xiao D, Lee H, Deen J, Gong Jian, et al . Trend and disease burden of bacillary dysentery in China (1991-2000). Bull World Health Organ 2006.  Back to cited text no. 18    

Correspondence Address:
Ezzat Ollah Ghaemi
Department of Microbiology, Golestan University of Medical Sciences, Gorgan
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/1319-3767.33464

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  [Figure - 1], [Figure - 2]

  [Table - 1], [Table - 2]

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