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Polymicrobial Liver Abscess — SCE Infectious Diseases MCQ

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ModerateHealthcare-Associated InfectionsPolymicrobial Liver AbscessSCE Infectious Diseases

A 55-year-old man develops right upper quadrant pain and fever. CT shows a multiloculated liver abscess with gas formation. Percutaneous aspirate yields foul-smelling pus. Culture grows Bacteroides fragilis and Streptococcus anginosus. What is the most likely source?

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Correct answer: E — Biliary or colonic source (ascending cholangitis, diverticular disease, or appendicitis with portal pyaemia)

A polymicrobial liver abscess containing B. fragilis and S. anginosus (milleri group) with gas formation indicates a biliary or colonic source. Portal pyaemia from intra-abdominal pathology (diverticulitis, appendicitis, cholangitis) is the most common mechanism. CT abdomen/pelvis should be performed to identify the source. Treatment requires percutaneous drainage PLUS IV antibiotics covering aerobes and anaerobes (Ceftriaxone plus Metronidazole, or Piperacillin/Tazobactam). Duration is typically 4–6 weeks. Amoebic abscess is typically solitary without gas and grows no bacteria.

Reference: BSAC 2017 – Intra-abdominal infections; BSG 2021 – Hepatic abscess