Multisystem Infections

Abstract

Many bacterial infections can cause multisystem or metastatic infection, commonly through haematogenous spread, with preferred sites or tropism depending upon specific organism. For example, Staphylococcus aureus is a well-recognized cause of infective endocarditis, joint infection, and vertebral osteomyelitis. Klebsiella pneumoniae can cause endogenous endophthalmitis in association with a pyogenic liver abscess, a syndrome well described in East Asia. Streptococcus pneumoniae typically causes lower respiratory tract infections or bacterial meningitis. The combination of meningitis, pneumonia, and endocarditis is called ‘Austrian syndrome’ and is strongly associated with hyposplenism or alcohol abuse. Other examples of bacteria that disseminate and cause multisystem infection are covered elsewhere. C. albicans or non-albicans species in the blood can metastasize to the eye (causing chorioretinitis or endophthalmitis) or to the heart (causing infective endocarditis). The primary sites of infection are commonly the GI tract or intravascular catheters, and high-risk groups include patients who have recently undergone abdominal surgery, received multiple courses of intravenous antibiotics, and are receiving total parenteral nutrition. Empirical treatment is with either IV liposomal amphotericin or an echinocandin before stepping down to an oral azole, commonly fluconazole at a dose of 400mg od. Because of the risk of metastatic spread, minimum duration is normally two weeks after the first negative blood culture. Cryptococcosis is caused by one of two species: Cryptococcus neoformans or Cryptococcus gattii. Unlike C. neoformans, C. gattii can cause infection in immunocompetent people. The clinical syndrome, Cryptococcosis, is an opportunistic infection for AIDS, but other conditions that predispose to infection are lymphoma, sarcoidosis, liver cirrhosis, and corticosteroids. Following inhalation, cryptococci can disseminate to the cerebrospinal fluid (CSF) and cause meningitis. Occasionally, Cryptococcoma—umbilicated papules on the skin— can occur. Symptoms are often subacute and include fever and dry cough. Following dissemination to the CSF, headache and confusion can occur. Diagnosis is based upon detection of capsular antigen by latex particle agglutination or culture, typically from blood or CSF. For meningitis, treatment consists of three phases. The induction phase is two weeks of IV liposomal amphotericin and flucytosine, followed by consolidation with eight weeks of oral fluconazole 800mg once daily, then finally secondary prophylaxis, 200mg orally once daily.