A 44-year-old woman was admitted to the emergency department of the affiliated hospital of Guizhou Medical University, with complaints of coughing, vomiting, tightness in the chest, shortness of breath, abdominal pain, chills and fevers in the morning and at night that had persisted for half a month and worsened over the past three days. She was subsequently hospitalized into nephrology department with diagnosis of chronic renal failure (CRF). The patient had a medical history of type 2 diabetes mellitus and had been treated for CRF during the last two years. She was taking Euthyrox for treatment of hypothyroidism converted from hyperthyroidism that was diagnosed 20 years ago. Her surgical traumas included caesarean section and inferior vena cava filter placement for venous thrombosis. The physical examination the next day revealed moist rales in both lungs and serum measurement found neutrophilic leukocytosis (WBC count 11.14x109/L with 96.40% neutrophils), high interleukin-6 (IL-6, 251.20 pg/mL) and procalcitonin (PCT, 100 ng/L). Ceftizoxime was administrated for anti-infection treatment, which was replaced by meropenem after microbial detection of Klebsiella pneumoniae from the blood and urine isolates. The patient was discharged after 23 days of treatment when the acute symptoms disappeared and serum parameters returned to normal.
Twelve days later, the patient was re-admitted into the emergency department with a complaint of >10 hours of diarrhoea and >3 hours of impaired consciousness. Soon the patient was sent to the intensive care unit (ICU) due to her condition deteriorating into severe consciousness disorders. The vital signs and physical parameters on admission were the following: body temperature 37.2 C, hypotensive blood pressure 84/47 mmHg, heavy and moist rales in both lungs audible through auscultation, no abnormal bulge/depression or pulsation in the precordial area, no obvious pathological murmur heard by auscultation in all the cardiac valve areas and no oedema in the lower extremities. Laboratory analysis indicated neutrophilic leukocytosis (WBC count 35.22x109/L with 96.80% neutrophils) and suspicion of sepsis (interleukin-6 5000 pg/mL and PCT higher than 100 ng/L in serum). Computed tomography (CT) of the chest showed a large pleural effusion and abdominal effusion.
The emergency treatments included phlegm removal, sedation, analgesia, vasoactive drugs, anti-inflammation, and anti-infection drug imipenem. A closed drainage of the right thoracic cavity was performed to improve the right pneumothorax. The patient had to be subsequently submitted to orotracheal intubation and an invasive ventilator due to severe hypoxia. Despite all these treatments, her general condition deteriorated. A cardiac ultrasound exam revealed a significantly enlarging pericardial effusion (Figure 1).
Pericardiocentesis drainage was immediately employed, and 150 mL of purulent liquid was withdrawn. Bacterial identification and drug sensitivity test were conducted using MicroScan WalkAway 96 plus automatic analysis system. The drug susceptibility results were verified later by broth microdilution method. A Klebsiella pneumoniae strain was confirmed and cultured from the pericardial effusion, which was resistant to multiple antibiotics, especially carbapenems (Table 1). Therefore, the patient was diagnosed with purulent pericarditis caused by CR-KP. CR-KP were also detected in the patient's blood, ascites, and urine. 
Within one to two hours after the pericardiocentesis drainage, the patient's heart rate gradually dropped to 40 bpm. The patient failed to regain consciousness despite active resuscitation (ACDCRP) and eventually died, likely from multiorgan failure associated with sustained septic shock.
Five isolates (blood cultures, urine, ascites, pericardial effusion, and sputum) collected from this patient were positive for ST11 Klebsiella pneumoniae, confirmed by PCR screening and DNA sequencing analysis of the seven house-keeping genes of KB (rpoB, phoE, gapA, infB, mdh, tonB, and pgi) according to the Institut Pasteur Multilocus Sequence Typing (MLST) databases (https://bigsdb.pasteur.fr/klebsiella/). Using the primers described previously for PCR, the capsular serotype of all the isolates was confirmed to be K64, which was validated by whole-genome sequencing. All isolates demonstrated hypermucoviscosity as shown by string length >5 mm in the string test (Figure 2). Common carbapenem resistance genes and virulence genes were identified by PCR using primers reported in the literature. All isolates presented beta-lactam resistance gene blaKPC but were negative for other carbapenemases including OXA-48, IMP, NDM and VIM. The KP strain from all five isolates possessed virulence factor plasmids rmpA, mrkD, entB and ybtS, which are related to mucoid phenotype, type-3 fimbrial adhesin, enterobactin and yersiniabactin, respectively.
The bacterial genome sequencing data obtained from pericardial effusion culture was compared against the Comprehensive Antibiotic Resistance Database (CARD) and Virulence Factor Database (VFDB). A total of 27 putative resistance genes were identified (Table 2), associated with three main resistance mechanisms: 1. The antibiotic efflux pump systems, prominently genes belonging to the ATP-binding cassette (ABC) and the major facilitator superfamily (MFS), 2. antibiotic inactivation or reduced permeability to target, which is induced by beta-lactamase gene amplification and porin disruption, such as blakpc-1, blaTEM-1 and blaCTX-M-65 and 3. alteration in the target sites of antibiotics by rmtB gene encoding the aminoglycoside-modifying 16S rRNA methylase and sul2 gene encoding altered forms of dihydropteroate synthase that are not inhibited by the sulfonamides. Furthermore, 31 virulence-associated genes were predicted, which suggested the employment of several iron uptake mechanisms in the patient isolate, including production of aerobactin (iuc), enterobactin (entB, entA, fepC, etc.) and secretion of yersiniabactin (ybtS, ybtE, irp1, 1rp2, etc.) (Table 3).  
Based on the evidence of carbapenem resistance, the hypervirulence determinants, and the mucoid phenotype of the bacteria, we conclude that the infective agent identified in the isolates is sequence type 11 (ST11) capsular serotype K64 carbapenem-resistant hypervirulent Klebsiella pneumoniae (CR-hvKP).
The serum survival of the CR-hvKP strain from the pericardial effusion, blood and ascites isolates was tested according to the previous description. As shown in Figure 3, the colony-forming unit (CFU) recovery of all isolates was inhibited by the human serum time-dependently. After three hours of incubation, barely any CFU colony was visible in two samples and no colony growth was observed by the next day (Figure 3A and B), indicating a susceptibility of the KP strain to normal human serum.