Discussion

We present the case of invasive liver abscess syndrome with endogenous endophthalmitis caused by the K2 serotype of K. pneumoniae extending to complete ablepsia despite improvement of the pathophysiology of severe sepsis. One systematic review reported K. pneumoniae had been the most common causative organism (27 %) in endogenous bacterial endophthalmitis. Following other organisms were Staphylococcus aureus (10 %), Pseudomonas aeruginosa (6 %), Group B streptococci (6 %), and Neisseria meningitidis (5 %) [10]. Therefore, use of broad-spectrum antibiotics must be considered until identification of causative microorganism.

This case of a primary liver abscess caused by the definite K2 serotyping of K. pneumoniae is the first adult case in Japan. This invasive syndrome caused by K. pneumoniae serotypes K1 or K2 has been reported mainly in Southeast Asian countries, especially in Taiwan. We found around 50 cases with liver abscess caused by K. pneumoniae serotype K2 all over the world [11, 12]. However, in Japan, only three cases—two in elderly men infected with the K1 serotype and one in a 7-year-old child with the K2 serotype—have been reported [46], when we searched PubMed and the Igaku Chuo Zasshi databases for papers published between Jun 01, 1970, and Dec 31, 2015, by using combinations of the following keywords: “Klebsiella pneumoniae,” “liver abscess,” “K1” or “K2,” except minutes and selected articles about this invasive syndrome published by Japanese authors.

Almost 30 cases of primary liver abscess caused by K. pneumoniae with endogenous endophthalmitis have been reported in Japan (all reports in Japanese); we conducted a search of the medical literature published using the Igaku Chuo Zasshi database and “liver abscess,” “endophthalmitis,” and “Klebsiella pneumoniae” as search terms. In addition, we could find two more Japanese literatures related to invasive liver abscess syndrome when we searched Igaku Chuo Zasshi database by using following keywords: “Klebsiella pneumoniae,” “liver abscess,” and “rmpA” [13, 14]. The K1 and K2 serotype were suspected in all cases because of the clinical features, but examination of the serotype has never been reported. Therefore, an invasive liver abscess caused by the K1 or K2 serotype of K. pneumoniae may not be rare in Japan.

The virulence-associated gene rmpA was positive in our case. rmpA is not an independent factor contributing to a liver abscess, but it aids in capsule synthesis. One report showed that all K. pneumoniae strains that cause liver abscesses and abscesses at other sites are rmpA-positive. rmpA has been confirmed as a gene that regulates capsular polysaccharide synthesis [15]. Thus, in our case, rmpA was probably associated with liver abscess formation.