A 79-year-old Japanese non-drinker woman with a history of dementia and primary aldosteronism was admitted to our hospital presenting with fever and a productive cough persisting for the past three days and respiratory distress. Despite the advanced age, the score of performance status was 2 (ambulatory and capable of all self-care but unable to carry out any work activities; up and about more than 50% of waking hours). She had never been a resident in a nursing home or an extended-care ward. She also did not receive antimicrobial agents and was not hospitalized in the preceding 90 days, and had no history of overseas travel. All these factors were indicative of her infection being community acquired.
Upon admission (day 1), her general condition was severe, and vital signs indicated sepsis; blood pressure was 89/60 mmHg; heart rate, 130 beats/min; body temperature, 38.5  C; respiratory rate, 25 breaths/min; and oxygen saturation, 92% in room air. A physical examination revealed crackles on both lateral lung fields upon auscultation. Blood tests showed elevated white blood cell count (16,400 cells/muL; neutrophil 88%) and C-reactive protein (42.81 mg/dL). A chest X-ray revealed lobar pneumonia on both lung fields, and computed tomography (CT) revealed multiple consolidations with air-bronchogram, nodules, and ground-glass opacities, particularly in both lower lobes (Figure 1). Although, radiological findings indicated pneumonia due to S. pneumoniae, Gram staining of sputum samples revealed no predominant microorganism. A commercially available urine antigen test for detecting S. pneumoniae and Legionella pneumophila and the rapid influenza virus test were also negative. The case was diagnosed as severe CAP with septic shock, and fluid resuscitation for septic shock and administration of meropenem (MEPM) were started immediately. The following day, both sputum and two sets of blood cultures confirmed only Gram-negative coccus. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry revealed the isolate as K. pneumoniae. Colonies on sheep blood agar demonstrated hypermucoviscosity, and the string test:a semiquantitative phenotypic estimation that determines hypermucoviscosity by stretching a bacterial colony on an agar plate using an inoculation needle:was positive (the string reached over 5 mm in length, which is consistent with the characteristics of HV-KP). A biochemical test confirmed that the isolated organism was K. pneumoniae. Multiplex PCR (magA, iutA, allS, kfu, rmpA, entB, mrkD, and ybtS) and multilocus sequence typing (MLST) were performed according to previously described methods. Genetic analysis identified this strain as the K2 serotype harboring rmpA, iutA, entB, and mrkD (Figure 2). Therefore, we identified the isolated strain as hypervirulent. The isolate belonged to ST 86 (ST86) as determined by MLST.
Additionally, urinalysis, urine culture, lumbar puncture, ultrasonography, and CT of the abdomen and head were performed to determine if the patient had complicating disseminated HV-KP infection, because treatment duration depends on the site and extent of infection. Metastatic infections, such as liver abscess, meningitis, brain abscess, or ocular infection, were all absent. The isolate was susceptible to all routinely tested antibiotics except ampicillin. MEPM was stopped and the patient was placed on ceftriaxone (CTRX) as a definitive therapy, because the usual dose of CTRX is given once a day, which could avoid intravascular over volume in the elderly. The patient received 2 weeks of intravenous antibiotics, recovered gradually, without recurrence, and was discharged on day 20.