Fusobacterium nucleatum: a rare cause of pyogenic liver abscess
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While pyogenic liver abscesses are uncommon, they are associated with significant mortality and morbidity. Most pyogenic liver abscesses are polymicrobial and are caused by enteric bacteria and anaerobes. Rarely, mono-microbial infections may occur, typically in immunocompromised individuals. We report the unusual case of a 69 year-old immunocompetent female who developed a pyogenic liver abscess due to Fusobacterium nucleatum infection, likely from a dental source. Poor oropharyngeal hygiene seems to have a major role in infection from this organism and therefore F. nucleatum should be considered as a differential for causes of pyogenic liver abscess in such patients. Drainage of the abscess and antibiotic therapy are the mainstays of therapy.
KeywordsPyogenic liver abscess Fusobacterium Poor dental hygiene Immunocompromised state
Pyogenic liver abscess
right upper quadrant
abdominal aortic aneurysm
Worldwide, amebic liver abscess remains the most common form of liver abscess, but in the United States pyogenic liver abscess (PLA) is the most common form (Wong et al. 2002). The incidence of pyogenic liver abscesses is estimated at about 2.3 per 100,000 patients (Huang et al. 1996; Kaplan et al. 2004) and mortality is estimated at 2–12% (Mohsen et al. 2002; Rahimian et al. 2004) despite advances in antibiotic therapy and investigation and management of these abscesses over the years.
Due to its rich blood supply from the portal and systemic circulations, the liver is a common site of metastatic disease and also the most common site of visceral abscesses. According to a large case series, an estimated 48% of intra-abdominal abscesses involve the liver (Altemeier et al. 1973). Intra-abdominal infections, particularly those involving the biliary tract are more likely to lead to the formation of a PLA (Huang et al. 1996; Rahimian et al. 2004). Bacteria may also spread through the portal vein or from hematogenous seeding from bacteremia from other sources (Huang et al. 1996), with periodontal disease being increasingly recognized as a potential source (Crippin and Wang 1992; Ohyama et al. 2009). Most PLA are polymicrobial and mixed enteric and anaerobic species are common pathogens, with one case series identifying anaerobes in up to 45% cases (Nozawa et al. 2011). However, monomicrobial infections are also possible.
Fusobacterium is an anaerobic bacterium that is found in the oropharyngeal cavity and is believed to be strongly associated with the formation of dental plaque (Bolstad et al. 1996). PLA secondary to F. nucleatum has rarely been reported previously, and mostly in immunodeficient hosts with the exception of a few (Tweedy and White 1987; Scoular et al. 1992; Etienne et al. 2001; Ala et al. 2001; Wells et al. 2005; Schattner and Gotler 2014; Dahya et al. 2015; Ahmed et al. 2015). We report the case of a 69 year-old immunocompetent female who was found to have a pyogenic liver abscess secondary to Fusobacterium nucleatum.
A 69 year-old female presented with a 2-month history of vague right upper quadrant (RUQ) pain, intermittent fevers and chills. Her pain was dull in nature and was slightly worse with deep inspiration. Her past medical and surgical histories were significant for emphysema, well controlled diabetes mellitus, known pancreatic and renal cysts and an infra-renal abdominal aortic aneurysm (AAA) endovascular repair a few years ago.
Differential diagnoses for a liver hypodensity seen on imaging can be broad and can include an amebic or pyogenic liver abscess, primary or metastatic malignancy (especially colonic). Since the suspicion for PLA was high based on the ultrasound, the patient was started on broad spectrum antibiotic coverage with Vancomycin and Meropenem. The oral cavity was considered as a potential source of infection due to the patient’s poor dental hygiene. However, hematogenous spread of infection leading to PLA, especially from an oropharyngeal source is extremely uncommon and F. nucleatum was not initially suspected as the causative organism.
Immunodeficient patients tend to develop opportunistic and superimposed infections, occasionally with rare organisms. Among the sixteen cases of PLA due to F. nucleatum that have been reported (including current case), only five patients (31.25%) had documented immunocompetence. Out of these five patients, four (80%) were found to have dental disease and the remaining one patient had evidence of a tonsil infection (Mémain et al. 2001). This probably implies that F. nucleatum leading to distant infection and abscess formation is very likely to have originated from the oropharyngeal region and likely secondary to poor dental hygiene leading to dental disease. Other rare organisms that have been known to cause PLA are Citrobacter koseri (Gupta et al. 2013), Gemella morbillorum (Borro et al. 2014) and Streptococcus milleri (Chen et al. 2012), which is especially known for its underlying association with colorectal neoplasia.
The liver is a major site of intraabdominal abscesses (Altemeier et al. 1973). However, it is not clear why the liver seems to be preferentially affected over other visceral organs by F. nucleatum. While this could just be due to the liver’s dual blood supply which is derived from the portal as well as systemic circulations, it is also possible that the formation of liver abscesses in Fusobacterium bacteremia represents an early stage of infection and if left untreated, it might lead to involvement of other organs as well. Organism (F. nucleatum) and organ (Liver) specific interaction and factors that are still unknown, might have a role to play as well.
Early identification and treatment of PLA is very essential, given the high likelihood of fatality in untreated cases (Stroup et al. 2007). Known risk factors for mortality are presence of anaerobic infection, abscess greater than 5 cm in size and the need for open surgical drainage (Yang et al. 2004; Lok et al. 2008; Chen et al. 2012). Treatment consists of abscess drainage as well as appropriate antibiotic therapy. Like other infections, collection of cultures should ideally be performed prior to initiation of antibiotic therapy.
We report an unusual case of a PLA due to F. nucleatum infection which seems to be an emerging causative organism for PLA. In this case the infection was likely from a dental source and the host was immunocompetent. Poor oropharyngeal hygiene seems to have a major role in infection from this organism and therefore F. nucleatum should be considered as a differential of PLA in patients with poor dental hygiene, especially with a known history of immunodeficiency. Radiology guided drainage of the abscess and antibiotic therapy (including anerobic coverage) are the mainstays of therapy and patients rarely require invasive surgery for PLA (Heneghan et al. 2011; Pang et al. 2011).
SJSN, DM and PP all acquired and interpreted the data and wrote the manuscript. PP also supervised the entire manuscript draft and SJSN made final revisions. All authors read and approved the final manuscript.
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Competing interests The authors declare that they have no competing interests.
Ethics, consent and permissions Consent to publish was obtained from the participant to report individual patient data.
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