Q1. Correct Answer: A
This is an example of Yersinia infection. Transmission of yersiniosis is largely foodborne.
Risk factors associated with yersiniosis include consumption of undercooked or raw pork products and exposure to untreated water. Y. enterocolitica infection has also been associated with iron-overload states (such as hemochromatosis) and blood transfusions, because iron likely promotes virulence of this organism. The incubation period for yersiniosis is typically 4-6 days. Clinical manifestations of acute yersiniosis include diarrhea, abdominal pain, and fever; nausea and vomiting may also occur. Localization of abdominal pain to the right lower quadrant is also a diagnostic clue for yersiniosis. However, both Yersinia and Campylobacter can present with right lower quadrant pain that may be confused as appendicitis (pseudo appendicitis). Another diagnostic clue is pharyngitis, which may be an accompanying symptom. Yersinia causes diarrhea through penetration of the mucosa and proliferation in the submucosa. Pathogenic Y. enterocolitica pass through the stomach, adhere to gut epithelial cells, invade the gut wall, localize in lymphoid tissue within the gut wall and in regional mesenteric lymph nodes, and evade the host’s cell-mediated immune response. Vibrio cholerae and enterotoxigenic E. coli (ETEC) secrete enterotoxins that stimulate secretion and/or impair absorption.
Some bacteria produce toxins in contaminated food; when ingested, the toxins cause acute symptoms, usually nausea and vomiting. Examples of these are Staphylococcus aureus and Bacillus cereus. Enteropathogenic E. coli (EPEC) and enterohemorrhagic E. coli (EHEC) adhere to the intestinal mucosa, where they attach and cause effacement of the microvilli. Shigella, enteroinvasive E. coli, and Campylobacter jejuni penetrate the mucosa, spread, and cause mucosal damage with erosions and ulcers.
1. Cover TL, Aber RC. Yersinia enterocolitica. N Engl J Med. Jul 6 1989;321(1):16-24.