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- Shigellosis
- Swapan Kumar Niyogi
- J. Microbiol. 2005;43(2):133-143.
- DOI: https://doi.org/2172 [pii]
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Abstract
- Shigellosis is a global human health problem. Four species of Shigella i.e. S. dysenteriae, S. flexneri, S. boydii and S. sonnei are able to cause the disease. These species are subdivided into serotypes on the basis of O-specific polysaccharide of the LPS. Shigella dysenteriae type 1 produces severe disease and may be associated with life-threatening complications. The symptoms of shigellosis include diarrhoea and/or dysentery with frequent mucoid bloody stools, abdominal cramps and tenesmus. Shigella spp. cause dysentery by invading the colonic mucosa. Shigella bacteria multiply within colonic epithelial cells, cause cell death and spread laterally to infect and kill adjacent epithelial cells, causing mucosal ulceration, inflammation and bleeding. Transmission usually occurs via contaminated food and water or through person-to-person contact. Laboratory diagnosis is made by culturing the stool samples using selective/differential agar media. Shigella spp. are highly fragile organism and considerable care must be exercised in collecting faecal specimens, transporting them to the laboratories and in using appropriate media for isolation. Antimicrobial agents are the mainstay of therapy of all cases of shigellosis. Due to the global emergence of drug resistance, the choice of antimicrobial agents for treating shigellosis is limited. Although single dose of norfloxacin and ciprofloxacin has been shown to be effective, they are currently less effective against S. dysenteriae type 1 infection. Newer quinolones, cephalosporin derivatives, and azithromycin are the drug of choice. However, fluoroquinolone-resistant S. dysenteriae type 1 infection have been reported. Currently, no vaccines against Shigella infection exist. Both live and subunit parenteral vaccine candidates are under development. Because immunity to Shigella is serotype-specific, the priority is to develop vaccine against S. dysenteriae type 1 and S. flexneri type 2a. Shigella species are important pathogens responsible for diarrhoeal diseases and dysentery occurring all over the world. The morbidity and mortality due to shigellosis are especially high among children in developing countries. A recent review of literature (Kotloff et al.,1999) concluded that, of the estimated 165 million cases of Shigella diarrhoea that occur annually, 99% occur in developing countries, and in developing countries 69% of episodes occur in children under five years of age. Moreover, of the ca.1.1 million deaths attributed to Shigella infections in developing countries, 60% of deaths occur in the under-five age group. Travellers from developed to developing regions and soldiers serving under field conditions are also at an increased risk to develop shigellosis.
- The Value of Submitting Multiple Sputum Specimens for Accurate Diagnosis of Pulmonary Tuberculosis
- Ozgul Kisa , Ali Albay , Orhan Baylan , Levent Doganci
- J. Microbiol. 2002;40(4):301-304.
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Abstract
- Is a multiple number of sputum specimens necessary for the diagnosis of pulmonary tuberculosis? To answer this question, 6844 respiratory specimens obtained from previously untreated patients suspected of having pulmonary tuberculosis between 1998 and 2001 were evaluated retrospectively. All of the specimens were evaluated by acid fast bacilli smear and BACTEC 460 TB culture system. A total of 785 (11%) specimens from 353 patients were positive for Mycobacterium tuberculosis complex. For 76% (270/353) of these patients the organism was detected from sputum specimens collected sequentially for daily basis. Mycobacterium tuberculosis was isolated in the first, second and third samples of the majority (98%, 195/199) of patients who had three or more sputum samples sent to the laboratory. Our results indicate that, we could carry out Mycobacterium tuberculosis isolation in the first, second and third sputum samples of the overwhelming majority of the patients and the diagnostic value of four or more sputum specimens submitted to the laboratory was very low (2%). We recommend that, for definitive and cost-effective diagnosis of pulmonary tuberculosis at least three sequential sputum specimens be collected for all patients suspected pulmonary tuberculosis.
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