A 66-year-old female presents with severe watery diarrhoea and a fever of 38.5°C. She is currently on a day 5 of a 10-day course of clindamycin for leg cellulitis.
Which ONE of the following statements is TRUE regarding Clostridium difficile (C. difficile)- associated diarrhoea?
Answer: D: Antibiotic-associated diarrhoea is defined as otherwise unexplained diarrhoea that occurs in association with the administration of antibiotics.
Infection with C. difficile causes a toxin-mediated enteric disease that can result in:
Although infection with C. difficile accounts for only 10–20% of the cases of antibiotic-associated diarrhoea, it accounts for the majority of cases of colitis associated with antibiotic therapy.
Antibiotic-associated enterocolitis caused by C. difficile is unique in that the organism is normally present in the colon and it causes illness primarily during or after the administration of antimicrobial agents. Symptoms may appear during the course of antimicrobial therapy or commonly up to 3–4 weeks after discontinuation of antibiotics. Clindamycin, cephalosporins, and penicillins are the antibiotics most frequently associated with C. difficile diarrhoea, although they also cause diarrhoea that is unrelated to this organism.
The rates of diarrhoea associated with parenterally administered antibiotics are similar to rates associated with orally administered agents.
Spontaneous resolution usually occurs within 48–72 hours after discontinuing the offending antibiotic. If not, treatment should be commenced with metronidazole or vancomycin. The usual duration of therapy is 10 days. Indications for oral vancomycin, as opposed to metronidazole, are pregnancy, lactation, ANSWERS 185 intolerance of metronidazole, or failure to respond to metronidazole after 3–5 days of treatment.
Ideally, all antibiotic treatment should be oral since C. difficile is restricted to the lumen of the colon. If intravenous treatment is required, only metronidazole (and not vancomycin) is effective, since this approach will still result in moderate concentrations of the drug in the colon. Intravenous vancomycin generally is not effective because it does not reach effective intraluminal concentrations.
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A 19-year-old man presents with violent vomiting, abdominal cramps and mild diarrhoea 2 hours after the consumption of leftover fried rice and meat.
Which ONE of the following is the MOST likely responsible organism?
Answer: C: Both Staphylococcus and Bacillus cereus (B. cereus) produce preformed toxins and therefore the onset of symptoms will occur early, within 1–6 hours, after ingestion of contaminated food. However, Staphylococcus food poisoning is associated with the consumption of protein-rich food, including eggs, potato salad and mayonnaise, whereas B. cereus food poisoning is commonly caused by the ingestion of fried rice.
B. cereus foodborne illness is mostly due to improper holding temperatures for cooked food. The heat-resistant spores survive boiling and then germinate when boiled foods such as fried rice are left unrefrigerated, producing the toxin. Flash-frying or brief rewarming of the food before serving often is not sufficient to destroy the preformed, heat-stable emetic toxin.
Food contamination with Staphylococcus is extremely common and the organism can be isolated from the hands of about 50% of the population. The bacterium itself is killed by high cooking temperatures but the enterotoxin is heat-stable. Therefore, once it is present in food, reheating or even boiling will not prevent illness.
Clostridium perfringens (C. perfringens) and Vibrio produces toxins only after colonisation and therefore symptoms usually occur after a longer period (6–24 hours). Illness with C. perfringens is caused by the ingestion of meat or poultry heavily contaminated with C. perfringens. Typically, the food is cooked more than 24 hours before consumption, allowed to cool slowly at room temperature, and then served either cool or rewarmed. During this period of incubation, spores that survived cooking germinate, and clostridia multiply to reach sufficient numbers to constitute an infectious inoculum. Ingestion of live organisms is required to produce disease, but illness is not caused by infection; rather, it is from an enterotoxin produced by sporulation of the organism in the GIT. Symptoms usually start after an incubation period of 6–24 hours and is characterised by acute onset abdominal cramps and watery diarrhoea. Vibrio is associated with the ingestion of seafood, particularly raw shell fish. Symptoms start after 24–48 hours with diarrhoea and abdominal cramps.
Regarding the clinical features of inflammatory bowel disease (IBD), which ONE of the following statements is FALSE?
Answer: C: Diarrhoea is a frequent complaint in patients with IBD. Bloody diarrhoea, mucus, tenesmus and rectal complaints are more common in UC. The symptoms of CD are more heterogenous and include abdominal pain, diarrhoea and weight loss. Additionally, systemic symptoms of malaise, anorexia or fever are more common with CD.
Extraintestinal manifestations occur in both CD and UC, although they are more common in CD. Nearly half of patients with CD will have extraintestinal manifestations. Extraintestinal manifestations often involve the musculoskeletal system, skin and eyes:
1. Musculoskeletal
2. Skin
3. Eyes
Similarly, fistulae and abscesses occur in both UC and CD but are much more common in CD. Both CD and UC are associated with an equivalent increased risk of colonic carcinoma.
A 26-year-old male has known IBD. He presents with a fever of 38°C, increased stool frequency and abdominal pain. Regarding exacerbations and complications in patients with IBD, which ONE of the following statements is TRUE?
Answer: A: Patients with IBD presenting to the ED should be assessed to determine the activity/severity of the disease as well as the presence of complications. The Truelove and Witts’ classification is commonly used to establish disease severity in patients with ulcerative colitis (table below):
The Crohn’s Disease Activity Index is a useful score in determining the disease severity of CD and uses the following parameters in the assessment:
Plain abdominal and chest radiographs are essential to detect free gas with perforation, dilated bowel loops and air-fluid levels with obstruction, or dilated transverse colon >6 cm with toxic megacolon. A dilated transverse colon >12 cm indicates imminent perforation, causing peritonitis and septicaemia with subsequent high mortality rate. The effect of NSAIDs in exacerbating IBD is still unclear. However, it seems like non-selective NSAIDs may exacerbate IBD, whereas non-selective NSAIDs most likely do not exacerbate IBD. NSAIDs should therefore be avoided if possible.
Stool microscopy, culture and C. difficile toxin assay should be performed as part of the initial assessment because pseudomembranous colitis can complicate or mimic severe ulcerative colitis. C. difficile has a higher prevalence in patients with IBD through unknown mechanisms and is associated with increased mortality.
A 42-year-old female presents late at night to the ED with right upper quadrant (RUQ) pain. You perform a focused ultrasound of the RUQ to look for biliary disease. Regarding ultrasonographic assessment of the biliary system, which ONE of the following is FALSE?
Answer: B: A focused ED ultrasound of the gallbladder is useful to confirm the presence or absence of:
Finding both gallstones and a sonographic Murphy’s on bedside ultrasound has a 92.2% positive predictive value (PPV) for diagnosing cholecysitis, whereas the absence of both these signs have an NPV of 95.2%. A sonographic Murphy’s sign refers to pain on compression of the fundus of the gallbladder with the probe tip and is probably the most specific sign of inflammation. Other common sonographic findings include gallbladder wall thickening and pericholecystic fluid. The anterior wall of the gallbladder should be measured, as the acoustic enhancement artifact will obscure an accurate picture of the posterior wall. Gallbladder wall thickness >3 mm is regarded as abnormal.
A dilated common bile duct (CBD) demonstrates obstruction. A normal CBD typically measures <6 mm in the transverse diameter and should be measured from inner wall to inner wall. The CBD diameter can increase with age but, in general, a diameter >8 mm is regarded as abnormal (in the absence of previous cholecystectomy).
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