Abstract
BackgroundShigellosis or bacillary dysentery, an acute bloody diarrhoea, is a major public health burden in developing countries. In the absence of prompt and appropriate treatment, the infection is often fatal, particularly in young malnourished children. Here, we describe a new diagnostic test for rapid detection, in stool, at the bedside of patients, of Shigella flexneri 2a, the most predominant agent of the endemic form of the disease.Methodology/Principal FindingsThe test is based on the detection of S.flexneri 2a lipopolysaccharide (LPS) using serotype 2a-specific monoclonal antibodies coupled to gold particles and displayed on one-step immunochromatographic dipstick. A concentration as low as 20 ng/ml of LPS is detected in distilled water and in reconstituted stools in under 15 minutes. The threshold of detection corresponds to a concentration of 5×107 CFU/ml of S. flexneri 2a, which provides an unequivocal positive reaction in three minutes in distilled water and reconstituted stools. The specificity is 100% when tested with a battery of Shigella and unrelated strains, in culture. When tested in Vietnam, on clinical samples, the specificity and sensitivity were 99.2 and 91.5%, respectively. A decrease of the sensitivity during the evaluation on stool samples was observed after five weeks at room temperature and was due to moistening of the dipsticks caused by the humidity of the air during the fifth week of the evaluation. This drawback is now overcome by improving the packaging and providing dipsticks individually wrapped in waterproof bags.ConclusionThis simple dipstick-bases test represents a powerful tool for case management and epidemiological surveys.
Highlights
Shigellosis, an acute bloody diarrhea caused by the Gram negative entero-invasive bacterium Shigella spp, represents a major public health burden in many developing countries [1]
S. dysenteriae type 1 is associated with the most severe form of the disease and high mortality rate when epidemics occur, most of the deaths are attributable to the endemic form of the disease, which is most often caused by S. flexneri
Dysenteric patients have a more severe form of shigellosis with a clinical spectrum ranging from watery diarrhea to diarrhea with mucus and frank bloody diarrhea
Summary
Shigellosis, an acute bloody diarrhea caused by the Gram negative entero-invasive bacterium Shigella spp, represents a major public health burden in many developing countries [1]. According to a reference study published in 1999, which provided projections derived from literature-based data [2], the annual number of Shigella episodes throughout the world was estimated to be about 164.7 million, with 99% occurring in developing countries. A decrease of the sensitivity during the evaluation on stool samples was observed after five weeks at room temperature and was due to moistening of the dipsticks caused by the humidity of the air during the fifth week of the evaluation. This drawback is overcome by improving the packaging and providing dipsticks individually wrapped in waterproof bags. This simple dipstick-bases test represents a powerful tool for case management and epidemiological surveys
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