A case of death within 72 hours after community-acquired bloodstream infection caused by klebsiella variicola

Klebsiella subspecies infection is widely misdiagnosed and underestimated in clinic. We report a patient who was admitted to hospital due to unknown high fever. Bacterial culture only revealed the klebsiella pneumonia. Broad-spectrum antibiotics failed to improve patient's symptoms, although these antibiotics are sensitive to klebsiella pneumonia according to the drug susceptibility results. Patient rapidly entered sepsis and subsequent sepsis shock, and died within 72 hours. The delayed PMseq-DNA Pro high throughput gene detection revealed the mixed infection of klebsiella pneumoniae and klebsiella variicola. This is a very rare case that patient suffered so rapid deterioration and died from bacterial infection within short period of time. Klebsiella variicola could contribute to rapid illness progression, while it was revealed by gene detection rather than classic laboratory methods. Which suggests that early genetic detection should be recommended in cases of complex infection.


Introduction
The klebsiella causing infection is a well-known type of infection with its high incidence and mortality. It causes outbreaks of nosocomial infections and even drug resistance, and can lead to infection in the community among health-care patients or people with underlying immunode ciency [1] . Based on genetic analysis, the klebsiella pneumoniae (K. pneumoniae) contains three polygroups: klebsiella pneumoniae (KpI), K.quasipneumoniae (KpII) and K.variicola(KpIII) [2]. Previous research illustrated that KpI was the most frequent group, followed by KpIII and KpII [1,3]. It's di cult to distinguish KpI from KpII and KpIII using classic clinical laboratory examinations [4]. Currently, the clinical importance of KpII and KpIII is overlooked , whilst approximately 20% of human isolates assumed to be K. pneumoniae are in fact K. variicola/ or K. quasipneumoniae [1]. Clinically, Klebsiella pneumoniae is usually de ned as classic klebsiella (Ck) and hypervirulent klebsiella (Hvkp) based on its invasiveness or virulence. The genetic research revealed two fatal virulence strains embedded in KpII (ST604 wcaG) and KpIII(ST616, wcaG ), which links the relationship between bacteria virulence and its gene structure strain [5,6] .
Although the K.pneumoniae infection exists worldwide, no clinical case reported that a mixed infection caused by klebsiella pneumoniae and klebsiella variicola would lead to patient death within a very short period. Here we report a rare case of a community-acquired bloodstream mixed infection caused by klebsiella pneumoniae and klebsiella variicola leading to mortality within 72 hours. This case highlights a signi cant warning to community physicians and ICU clinicians to unexplained high fever, cough, or rapid deterioration of vital signs calling for vigilance against Klebsiella pneumoniae infection or mixed infection of klebsiella pneumoniae and klebsiella variicola.

Case Presentation
A 52-year old male was admitted to Jinyang Hospital at 21:20 on November 8, 2020 with unexplained fever, bellyache and headache for half hour. He had no medical history other than 5 years of history of type 2 diabetes and 7 years of history of Gout, and irregularly taking metformin, piroxicam and butazodine to treat diabetes and gout respectively. On admission, Doctors excluded the possibility of drug or food poisoning because the patient and his family members stated he had not taken any drugs or special food. Physical examinations revealed: Temperature of 38.7℃; blood pres sure 125/76 mmHg; heart rate 104/min; respiratory rate 20/min; pulse oxygen saturation 95% on room air; with no other physical signs presented. Laboratory data showed an abnormal of blood routine examination results (white blood cell (WBC) count of 5.46 x 10 9 /L,87.3% neutrophils, 11.4% lymphocytes and 0.8% monocytes), the mildly increased C-reaction protein (CRP) and normal hepatorenal function parameters (Table 1 Table 2); The main treatments included physical cooling, anti-in ammation with intravenous Ceftazidime (1gram per 8 hours).
However all treatments failed to improve the patient's symptoms. By 18 00 on November 9, 2020, the patient presented a high fever (41℃), diarrhea, and confusion. He was subsequently transferred to Intensive Care Unit of Guizhou Provincial People's Hospital. Physical examinations showed bleeding points scattered on abdomen, back and lower limbs, and lung wet rales were found. Laboratory examinations revealed there were the deteriorated hepatorenal function, clotting function and increased in ammation parameters such as C-reactive protein (CRP), Procalcitonin (PCT) and count of White blood cell ( Table 3,Table 4 Table 5). The electrocardiogram and abdominal ultrasonography showed no signi cant abnormality (Figure1 2), and the Chest radiograph showed the manifestations of in ammatory response ( Figure 3).These laboratory examinations also excluded the diagnosis of infection of virus, mycobacteria, mycoplasma/chlamydia and autoimmune disease (Table 6). Classical bacteria culture of blood was examined after admission and showed the bacterial of klebsiella pneumonia (Table 7). After admission, the initial diagnosis considered immunity-acquired infection, and treatments included anti-in ammation (intravenous Vancomycin 1gram per 8hours + intravenous Meropenem 1gram per 6hours + intravenous caspofungin 70 milligrams/initial dose), plasma exchange were immediately implemented on admission. Four hours later after admission, patient's conditions deteriorated, with a decreased blood pressure and dyspnea with reduced oxygen saturation. Life support therapies including mechanical ventilation and vasoactive drugs were then conducted. During these treatments, other examinations (classical bacteria culture of blood, bone marrow biopsy and PMseq-DNA Pro High throughput gene detection) were conducted on second day after transfer. However, the patient's condition was further aggravated within following few hours, and at 13:00 on November 11, 2020, the patient suffered cardiac arrest and was declared clinically dead after several rescue efforts. The PMseq-DNA Pro High throughput gene detection was conducted on second day after transferring, results was acquired on November 13, 2020 and revealed the mixed infection of klebsiella pneumoniae and klebsiella variicola ( Figure 4). The bone marrow biopsy was examined on second day after transferring and supported the severe bacterial infection ( Figure 5). Based on all parameters, we considered the diagnosis of severe community-acquired bloodstream mixed infection caused by klebsiella pneumoniae and klebsiella variicola.

Discussion
Klebsiella is a Gram-negative bacterium within the enterobacteriaceae family. It usually causes the opportunistic nosocomial infection or community-required infection among hospitalized patients or community people. Klebsiella pneumoniae is mainly colonized in human gut but also has been isolated from other body surfaces such as hand, face, and skin, even from other sources including water, plants and soil [1,7] . Klebsiella pneumoniae infection has led to signi cant concerns because of its increasing incidence, varied manifestation and resultant mortality [8]. It contains several subspecies manifesting with varied clinical performances. Recently, some severe infections caused by polygroups of klebsiella pneumoniae have raised signi cant questions for clinicians. As in this case study, a rare of mixed infection caused by klebsiella pneumoniae and Klebsiella variicola brings patient the fatal effect within a very short period.
In this case, we excluded the possibility of poisoning of drugs and food. Moreover, the following laboratory examinations did not support the infection of virus, chlamydia, mycoplasma, fungal and parasite. We de ned this case as community-required infection disease because the patient had no the history of hospitalization within several months. The bacteria culture of blood sample showed klebsiella pneumoniae bloodstream infection, while the PMseq-DNA Pro High throughput gene detection for blood sample further revealed the infection sources including two phenotypes of genus klebsiella, klebsiella pneumoniae and Klebsiella variicola. Therefore we considered the case as the mixed bloodstream infection of klebsiella pneumoniae and Klebsiella variicola. Klebsiella bacteria colonization in human gut can cause infection when individual presents with immunode ciency. Recent research revealed the diabetes is a signi cant risk factor for hypervirulent Klebsiella pneumoniae infection and for causing serious complications [9][10][11]. In this case, patient had the medical history of diabetes and gout, and treatments with piroxicam and butazodine to gout. His medical history could contribute to his underlying immunode ciency and was possibly responsible for mixed bloodstream infection. Although there are more sequence numbers of klebsiella pneumoniae than klebsiella variicola from the blood sample detected, we consider that the klebsiella variicola played the more viral role to this disease progression and patient's prognosis in this case because the klebsiella variicola associated with the more frequent cause of bloodstream infection and higher mortality [3,4].
For clinicians, the current commonly method used to nd infection pathogens is bacterial culture of sputum, urine, blood and other specimens. However, it is di cult to distinguish Klebsiella pneumoniae and its subspecies, which may delay diagnosis and treatment [4]. As shown in this case, Klebsiella pneumoniae was found in blood culture and was sensitive to antibiotics used, but treatment did not respond well. Gene detection of blood sample identi ed Klebsiella pneumoniae and its subspecies. However, gene detection was performed on second day after the patient transferring (The third day after symptom onset, normally it needs 24-48 hours to acquire the test results), and patient's condition progressed rapidly, thus it did not provide a guide to treatment. This case suggests that early use of genetic detection may be helpful in determining infection pathogens and guiding treatment for complex infection diseases.
To date there is no consensus on the effective treatment of hypervirulent klebsiella infection. Recent clinical observations showed tigecycline and polymyxin display higher rates of treatment success than other antibacterial drugs such as carbapenem [12]. Moreover, the combination of treatments is preferred to monotherapy in cases of severe infections [13,14]. Lacking the evidences of klebsiella variicola during the initial period in this case, the anti-infection treatments implemented for this patient contained antifungal, anti-virus and antibacterial drug across a broad-spectrum. As shown in this case and previous researches, treatments based on clinical experiences and classical methods displayed a poor clinical effect, although bacterial culture results showed klebsiella pneumoniae are sensitive to antibiotics used. Thus, this case further suggests that early introduction of genetic detection method may be more useful in diagnosing and instructing treatment for severe infection. In addition, tigecycline or polymyxin, or combination treatment of tigecycline and polymyxin should be tried in health-care patients who presented with suspected and severe community-acquired Klebsiella pneumoniae infection.

Conclusion
Klebsiella pneumoniae subspecies can cause severe infection and bring the fast and fatal in uence to health-care patients. When community-acquired infections occur in patients requiring health care and progress rapidly, we should consider the possibility of infection caused by Klebsiella pneumoniae subspecies or their con uence. Comparing to classic clinical laboratory methods, early introduction of genetic test is more bene cial to diagnosis and treatment. In addition, routine broad-spectrum antibacterial drugs may not be effective to the suspected pneumoniae subspecies infection, thus, tigecycline or polymyxin, or their combination strategy should be conducted as soon as possible to prevent its fatal effects.

Statement of Ethics
This case report was conducted according to the ethical guidelines of the Helsinki Declaration and was approved by the Human Ethics Committee of Guizhou Provincial People's Hospital. Written informed consent was obtained from the family members of patient for publication of this case report and any accompanying images.

Con ict of Interest
We con rm that the manuscript has been read and approved by all named authors, and the order of authors listed in the manuscript has been approved by all of us. All authors declare that they have no competing interests.

Availability of data and material
The datasets generated during and/or analysed during the current study are available from the corresponding author on reasonable request. Tables   Tables 1-7  The electrocardiogram on November 8, 2020. The electrocardiogram was performed after admission in Jinyang Hospital, results showed that Sinus tachycardia 140/min and mild change of T wave. The Chest radiograph on November 8, 2020. After admission in Jinyang Hospital, chest radiograph was performed, results showed that the manifestations of bilateral lung in ammation: The fuzzy bilateral lung markings, multiple patchy and patchy hyperdense shadows. The PMseq-DNA Pro high throughput gene detection from blood sample. To identify the pathogenic bacteria for bloodstream, the blood sample was collected on second day after patient transferring from Jinyan Hospital to Guizhou Provincial People's Hospital. And the gene detection of blood sample was performed. Results showed that the bacterial type is the G-, bacterial genera is Klebsiella, and there are 68405 of sequences number. Also, results revealed that there are two species of klebsiella: klebsiella pneumoniae and klebsiella variicola, their sequence number are 243747 and 543 respectively.