Microbiological replacement associated with recurrent pneumonia during chemotherapy for Hodgkin lymphoma: a case report

Background: Persistent or recurrent pneumonia during antimicrobial therapy in patients receiving chemotherapy can be difficult to interpret. It may reflect persistence of the initial pathogen, inadequate antimicrobial exposure, noninfectious mimics, aspiration, superinfection or acquisition of a new respiratory pathogen. We report a case illustrating the clinical importance of repeat microbiological assessment when pneumonia persists or worsens despite apparently appropriate antimicrobial treatment. Case presentation: A man in his 80s with advanced classical Hodgkin lymphoma and chronic obstructive pulmonary disease developed pneumonia during chemotherapy. The initial sputum culture yielded cefepime-susceptible Klebsiella oxytoca. Cefepime produced transient defervescence, but oxygen requirements and radiographic abnormalities persisted, and fever recurred from day 18 with radiographic progression by day 19. Repeat sputum obtained on day 23 subsequently yielded extended-spectrum beta-lactamase-producing Klebsiella pneumoniae resistant to piperacillin/tazobactam and cefepime but susceptible to carbapenems. The isolate showed a positive string test, consistent with a hypermucoviscous phenotype. Doripenem was started after the resistant isolate was reported; however, the patient later developed progressive bilateral pulmonary infiltrates and respiratory failure and died. The interpretation of microbiological replacement remained presumptive because the organisms were recovered from expectorated sputum and molecular characterization was unavailable. Conclusion: This case highlights presumptive microbiological replacement as a clinically important consideration when pneumonia persists or worsens during chemotherapy. Repeat respiratory culture and updated susceptibility testing can materially alter antimicrobial management. A positive string test should be interpreted as a supplementary microbiological clue rather than proof of hypervirulence, metastatic infection or causality for death.