Shigellosis is an important intestinal infection
of public health concern, accounting for 140 million cases globally per
year and 60,000 deaths annually of which 60% occur in children below 5
years of age . The disease can occur as sporadic, epidemic and
pandemic forms. The disease has a short incubation period. In 1969-1970,
an epidemic of shigellosis caused by multi-drug resistant
S.dysenteriae type 1 occurred in Central America and rapidly spread
to different parts of Africa and Asia. The epidemic was seen in
Bangladesh in 1970s and in Eastern India in 1974 . The disease is
characterized by fever, loose stools mixed with blood and mucus,
tenesmus and abdominal cramps. Dehydration is not generally a
conspicuous feature. Shigellosis is caused by four species of
Shigella viz., S.sonnei, S.flexneri, S. boydii and
S.dysenteriae. S.sonnei causes mild dysentery in developed
countries, while S. dysenteriae type 1 causes severe dysentery in
developing countries in patients with poor hygiene, sanitation and
improper disposal of human and animal waste and overcrowding.
Shigellosis can occur in high risk populations, viz., displaced
populations, travellers, in the military and day-care centers. Each of
them are sub-divided into several serotypes, e.g., S.flexneri
1-6, S. boydii 1-18, S.sonnei phase I and phase II, and
S. dysenteriae 1-12. Three strains are responsible for causing
majority of shigellosis cases, viz., S. sonnei, S. flexneri 2a
and S. dysenteriae Type 1.
In the article on school outbreak of S. sonnei
infection in China in this issue of the journal , S. sonnei
strains exhibited high degree of drug resistance. Usually, shigellosis
caused by S. dysenteriae type 1 is characterized by multiple drug
resistance and high morbidity and mortality particularly in children
below 5 years of age . S. dysenteriae type 1 may be associated
with a number of complications like rectal prolapse, leukemoid reaction,
convulsions and hemolytic uremic syndrome (HUS). In this study, the
shigella strains were sensitive to ciprofloxacin and third generation
cephalosporins. In view of the reported cartilage toxicity of
fluroquinolones in animal model, the drug was not used in China where it
is prohibited for use in children. However, in many countries,
fluroquinolones are used in children successfully for the treatment of
infections, without any cartilage toxicity being reported [3,6]. High
rate of antimicrobial resistance as well as high prevalence of class 2
integrons among S. sonnei species was observed in this study. The
authors suggest that it is mandatory to continuously monitor the local
antibiotic resistance patterns of Shigella species . However,
it is imperative to keep in mind that stool cultures are often negative,
more so, if the sample has been processed long after collection.
Hand washing with plenty of water with soap or mud,
improvement of environmental sanitation, water supply and avoidance of
overcrowding are required for prevention of the disease, particularly in
slums and refugee camps. Vaccine development for shigellosis is a
formidable task as it can be caused by a number of serotypes and
immunity to Shigella is serotype specific. Several attempts have
been made to develop a safe and effective vaccine against shigellosis,
but none is yet available for public use.
Competing interests: None; Funding: Nil.
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