Breakthrough and persistent bacteremia due to serotype K1 Klebsiella pneumoniae in an immunocompetent patient

Herein, we report a case of breakthrough and persistent bacteremia due to serotype K1 Klebsiella pneumoniae in an immunocompetent 53- year-old man. He was diagnosed with pyogenic spondylitis owing to back pain and based on magnetic resonance imaging findings. On admission, several imaging studies were taken to search for other abscesses and infective endocarditis; however, there were no significant findings. Additionally, blood cultures were negative. Upon treatment with intravenous ampicillin/sulbactam, the patient’s symptoms improved. However, eleven days after admission, the patient experienced a fever and worsening back pain. Blood cultures were taken again, and K. pneumoniae was detected, which showed sensitivity to ampicillin/sulbactam. Fourteen days after admission, K. pneumoniae was detected again, suggesting breakthrough and persistent bacteremia with K. pneumoniae. The source of the K. pneumoniae infection was unknown. The antimicrobial regimen was changed to a combination of ceftriaxone and gentamicin. Sixty days after admission, the patient was discharged without any sequelae. The isolated K. pneumoniae strains were found to carry rmpA and were confirmed as serotype K1; thus, detected hypervirulent K. pneumoniae (HvKP). HvKP is an increasingly recognized pathotype of K. pneumoniae characterized clinically by its ability to cause organ- or life-threatening infections in healthy persons. To the best of our knowledge, our case is the first report of spondylitis due to confirmed HvKP. Moreover, HvKP caused breakthrough and persistent bacteremia on an immunocompetent patient.