Which one of the following is true regarding bacterial exotoxins?
Correct Answer A:
Exotoxins and endotoxins:
Exotoxins are secreted by bacteria where as endotoxins are only released following lysis of the cell.
Exotoxins: Exotoxins are generally released by Gram positive bacteria with the notable exceptions of Vibrio cholerae and some strains of E. coli. There may be classified into a number of different groups:
Superantigens (bridge the MHC class II protein on antigen-presenting cells with the T cell receptor on the surface of T cells):
AB toxins - ADP ribosylating:
Lockjaw is caused by Clostridium tetani neurotoxin (tetanospasmin).
Endotoxins:
A 76-year-old woman with a history of atrial fibrillation presents with abdominal pain and bloody diarrhoea. On examination her temperature is 37.8ºC, pulse 102 / min and respiratory rate 30 / min. Her abdomen is tender with generalized guarding. Blood tests reveal the following:
What is the most likely diagnosis?
Correct Answer B: The low bicarbonate points to a metabolic acidosis - highly suggestive of mesenteric ischaemia.
Mesenteric ischaemia: Mesenteric ischaemia is primarily caused by arterial embolism resulting in infarction of the colon. It is more likely to occur in areas such as the splenic flexure that are located at the borders of the territory supplied by the superior and inferior mesenteric arteries.
Predisposing factors:
Features:
Management:
A 65-year-old man with a history of dyspepsia is found to have a gastric MALT lymphoma on biopsy.
What treatment should be offered?
Correct Answer E: Gastric MALT lymphoma - eradicate H. pylori.
Gastric MALT lymphoma: Overview:
A 34-year-old HIV positive man is referred to gastroenterology due to jaundiced sclera. Liver function tests are as follows:
Correct Answer E: The LFTs clearly show a cholestatic picture. Given the background of HIV the most likely cause is sclerosing cholangitis.
HIV: biliary and pancreatic disease: The most common cause of biliary disease in patients with HIV is sclerosing cholangitis due to infections such as CMV, Cryptosporidium and Microsporidia.
Pancreatitis in the context of HIV infection may be secondary to anti-retroviral treatment (especially didanosine) or by opportunistic infections e.g. CMV.
A 23-year-old nurse is reviewed in occupational health following a needle stick injury from a man known to be a carrier of hepatitis B.
Which one of the following would appear first during acute hepatitis B infection?
Hepatitis B serology:
Interpreting hepatitis B serology is a dying art form which still occurs at regular intervals in medical exams. It is important to remember a few key facts:
Example results:
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