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Pathology - Gastrointestinal infections
Campylobacter, Salmonella, Shigella, Escherichia coli • Prevalent bacterial etiologies of gastrointestinal infections. Mucosal biopsies typically reveal acute colitis characterized by the presence of neutrophils in the lamina propria and inside crypts.
Enterotoxigenic E. coli (ETEC) is a prevalent etiological agent of diarrhea in travelers. ETEC has fimbriae that enable the bacteria to attach to small bowel epithelial cells and secrete toxins, resulting in significant fluid loss.
Enterohaemorrhagic E. coli synthesizes a cytotoxin, resulting in haemorrhagic necrosis of the intestinal mucosa and bloody diarrhea. Vulnerable individuals, especially children, are at risk of developing thrombotic microangiopathy, resulting in hemolysis and acute renal failure (hemolytic uremic syndrome).
Clostridium difficile • A significant etiology of colitis frequently linked to the administration of broad-spectrum antibiotics in hospitalized individuals. The clinical presentation is diverse, spanning from mild diarrhea to severe colitis with potential for perforation and mortality. • Macroscopically, colitis results in the development of cream-colored pseudomembranes on the colonic mucosal surface. • Microscopically, crypts filled with neutrophils and mucus are enveloped by pseudomembranes consisting of fibrin and neutrophils.
Mycobacterium avium • Notable opportunistic pathogen in immunocompromised individuals. • A disseminated infection affecting the small and large intestine results in persistent diarrhea. Mucosal biopsy reveals significant infiltration of the lamina propria by macrophages with acid-fast bacilli.
Rotavirus is the predominant etiological agent of severe diarrhea in newborns and young children. • Transmission occurs via the faecal-oral route. • Immunity is acquired in childhood, rendering adult infections uncommon.
Norovirus • A prevalent etiological agent of epidemic gastroenteritis outbreaks. • Highly contagious, transmitted via contaminated food or drink, direct person-to-person interaction, and surface contamination. • Frequently observed in confined populations such as institutions, hospitals, and cruise ships.
Cytomegalovirus • Typically linked to immunocompromised states. Cytomegalovirus (CMV) infection significantly contributes to abrupt clinical decline in immunosuppressed individuals with inflammatory bowel disease. • Microscopically, the alterations range from modest inflammation to profound ulceration. CMV inclusions are present in endothelial and stromal cells.
Giardia lamblia • Protozoan transmitted through the use of water contaminated with the organism's cysts. The developed pathogen adheres to the brush edge of the epithelial cells of the upper small intestine. The inflammatory response induces a mild diarrheal condition that persists for approximately one week before resolution. Immunocompromised persons may experience persistent infections.
Entamoeba histolytica • Prevalent protozoal infection impacting around 10% of the global population. • Symptoms vary from mild diarrhea and stomach discomfort to severe fulminant colitis. The infection may spread to several areas, including the liver, and, infrequently, massive inflammatory tumors known as amoebomas may develop. • Mild instances exhibit neutrophilic infiltration only, but more severe cases are linked to profound ulceration of the gut. The organisms are spherical entities featuring a bean-shaped nucleus and a frothy cytoplasm that contains engulfed red blood cells.
Enterobius vermicularis Nematode pinworm transmitted via hand-to-mouth transfer of ova. • Larvae develop into adult organisms, primarily inhabiting the caecum. During nocturnal hours, female organisms travel to the anus to lay eggs, resulting in significant perianal pruritus.
Necator americanus with Ancylostoma duodenale Nematode hookworms that adhere to the jejunal mucosa. A pump mechanism is employed to extract blood and interstitial fluid from the host. Elevated worm burdens can result in substantial cumulative blood loss. Hookworm infection is the predominant cause of iron deficiency anemia globally.
Campylobacter, Salmonella, Shigella, Escherichia coli • Prevalent bacterial etiologies of gastrointestinal infections. Mucosal biopsies typically reveal acute colitis characterized by the presence of neutrophils in the lamina propria and inside crypts.
Enterotoxigenic E. coli (ETEC) is a prevalent etiological agent of diarrhea in travelers. ETEC has fimbriae that enable the bacteria to attach to small bowel epithelial cells and secrete toxins, resulting in significant fluid loss.
Enterohaemorrhagic E. coli synthesizes a cytotoxin, resulting in haemorrhagic necrosis of the intestinal mucosa and bloody diarrhea. Vulnerable individuals, especially children, are at risk of developing thrombotic microangiopathy, resulting in hemolysis and acute renal failure (hemolytic uremic syndrome).
Clostridium difficile • A significant etiology of colitis frequently linked to the administration of broad-spectrum antibiotics in hospitalized individuals. The clinical presentation is diverse, spanning from mild diarrhea to severe colitis with potential for perforation and mortality. • Macroscopically, colitis results in the development of cream-colored pseudomembranes on the colonic mucosal surface. • Microscopically, crypts filled with neutrophils and mucus are enveloped by pseudomembranes consisting of fibrin and neutrophils.
Mycobacterium avium • Notable opportunistic pathogen in immunocompromised individuals. • A disseminated infection affecting the small and large intestine results in persistent diarrhea. Mucosal biopsy reveals significant infiltration of the lamina propria by macrophages with acid-fast bacilli.
Rotavirus is the predominant etiological agent of severe diarrhea in newborns and young children. • Transmission occurs via the faecal-oral route. • Immunity is acquired in childhood, rendering adult infections uncommon.
Norovirus • A prevalent etiological agent of epidemic gastroenteritis outbreaks. • Highly contagious, transmitted via contaminated food or drink, direct person-to-person interaction, and surface contamination. • Frequently observed in confined populations such as institutions, hospitals, and cruise ships.
Cytomegalovirus • Typically linked to immunocompromised states. Cytomegalovirus (CMV) infection significantly contributes to abrupt clinical decline in immunosuppressed individuals with inflammatory bowel disease. • Microscopically, the alterations range from modest inflammation to profound ulceration. CMV inclusions are present in endothelial and stromal cells.
Giardia lamblia • Protozoan transmitted through the use of water contaminated with the organism's cysts. The developed pathogen adheres to the brush edge of the epithelial cells of the upper small intestine. The inflammatory response induces a mild diarrheal condition that persists for approximately one week before resolution. Immunocompromised persons may experience persistent infections.
Entamoeba histolytica • Prevalent protozoal infection impacting around 10% of the global population. • Symptoms vary from mild diarrhea and stomach discomfort to severe fulminant colitis. The infection may spread to several areas, including the liver, and, infrequently, massive inflammatory tumors known as amoebomas may develop. • Mild instances exhibit neutrophilic infiltration only, but more severe cases are linked to profound ulceration of the gut. The organisms are spherical entities featuring a bean-shaped nucleus and a frothy cytoplasm that contains engulfed red blood cells.
Enterobius vermicularis Nematode pinworm transmitted via hand-to-mouth transfer of ova. • Larvae develop into adult organisms, primarily inhabiting the caecum. During nocturnal hours, female organisms travel to the anus to lay eggs, resulting in significant perianal pruritus.
Necator americanus with Ancylostoma duodenale Nematode hookworms that adhere to the jejunal mucosa. A pump mechanism is employed to extract blood and interstitial fluid from the host. Elevated worm burdens can result in substantial cumulative blood loss. Hookworm infection is the predominant cause of iron deficiency anemia globally.
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