The First Case of Community-Acquired Pneumonia Due to Capsular Genotype K2-ST86 Hypervirulent Klebsiella pneumoniae in Okinawa, Japan: A Case Report and Literature Review

Hypervirulent Klebsiella pneumoniae (HV-KP) typically causes pyogenic liver abscess and bacteremia with metastatic infections. Community-acquired pneumonia (CAP) due to HV-KP is uncommon and details of its clinical and microbiological features are limited. We report the first case of CAP due to capsular genotype K2-ST86 HV-KP in Okinawa, Japan and review infections caused by the K2-ST86 strain. A 79-year-old woman presenting with fever and productive cough persisting for the past three days was admitted to hospital. Her vital signs indicated septic shock. Lung examination by auscultation revealed holo-crackle and lobar pneumonia in chest radiography, and Streptococcus pneumoniae was suspected. However, sputum and blood cultures revealed Gram-negative coccus identified as K. pneumoniae. Genetic analysis identified the isolated strain as the K2 serotype harboring rmpA, iutA, entB, and mrkD. Therefore, we identified the isolated strain as hypervirulent. The isolate belonged to ST86 as determined by multilocus sequence typing. The case was not complicated by predisposing factors such as diabetes mellitus and malignancy related to HV-KP infection; thus, this CAP-causing HV-KP strain may differ from the typical HV-KP strain that induces liver abscess. A literature review identified only nine cases with CAP due to HV-KP. In all cases, the disease mainly occurred in older males with diabetes mellitus, which makes the present case unusual, and had high rates of septic shock and death. No case, including ours, was complicated by metastatic infection, suggesting that CAP due to HV-KP poses little distant metastasis risk, even in patients with bloodstream infection. In our review, consistent with our case, K2-ST86 was the most common strain of HV-KP in patients with CAP. Therefore, studies are needed to elucidate the clinical and microbiological features of HV-KP CAP, with a focus on the K2-ST86 strain. Physicians should always consider K. pneumoniae in cases of sepsis CAP with lobar pneumonia.