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 significant 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 significant 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 defined 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 immunodeficiency. Recent research revealed the diabetes is a significant risk factor for hypervirulent Klebsiella pneumoniae infection and for causing serious complications [9-11]. 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 immunodeficiency 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 find infection pathogens is bacterial culture of sputum, urine, blood and other specimens. However, it is difficult 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 identified 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 anti-fungal, 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.