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6216802 
Book/Book Chapter 
17 - Examination of faeces for bacterial pathogens 
Gillespie, SH 
1994 
Butterworth-Heinemann 
Medical Microbiology Illustrated 
192-210 
Publisher Summary The diverse range of pathogens that may affect the gastrointestinal tract, together with the large number of individual species that form the normal flora of the gastrointestinal tract, means that the investigation of feces could be extremely time consuming unless selective methods are employed. This chapter discusses the major bacterial pathogens causing diarrheal disease. The fecal specimen should be examined macroscopically for the presence of blood, pus, or mucous exudate and consistency. Microscopic examination for bacterial pathogens such as salmonellas and shigellas does not yield useful information as these organisms are morphologically identical to the normal fecal flora. In patients with AIDS, mycobacteria can be demonstrated by Ziehl–Neelsen (ZN) staining. Microscopic examination is essential for the diagnosis of parasitic infections of the gastrointestinal tract. A fecal smear can be stained by the Ziehl–Neelsen or auramine techniques and examined for the presence of cysts of Cryptosporidium parvum and Isospora belli. The formol–ether concentration technique can be used to improve the quality of the specimen by clearing fat and removing fecal debris as well as concentrating the ova and cysts before the examination of an unstained preparation. 
Gillespie, S. H.