Probable primary bloodstream infection caused by multidrug-resistant Achromobacter piechaudii in an apparently immunocompetent child: a case report

Background Achromobacter piechaudii is an extremely rare opportunistic pathogen in humans. Previous reports of clinical infection have mostly involved adults with underlying conditions such as malignancies or immunocompromised states.This report describes the probable first case of primary, multidrug-resistant Achromobacter piechaudii bloodstream infection in an apparently immunocompetent child. Case presentation A previously healthy 10-year-10-month-old boy with no known immunodeficiency or chronic disease was admitted with intermittent headache and fever for 4 days, accompanied by chills, vomiting, and lethargy.He had no recent travel, sick contacts, or known exposure to contaminated water. Complete blood count showed elevated white blood cell count and neutrophil percentage. C-reactive protein and procalcitonin were markedly elevated. Empirical treatment with ceftriaxone was started on admission. On day 2 of hospitalization, blood culture indicated growth of Gram-negative bacilli. On day 3, the isolate was identified as Achromobacter piechaudii by MALDI-TOF MS (score > 2.3). Cerebrospinal fluid examination was normal, confirming primary bloodstream infection. Antimicrobial susceptibility testing showed a multidrug-resistant phenotype. The antibiotic regimen was switched to piperacillin-tazobactam after resistance to ceftriaxone was confirmed.The patient’s fever resolved, clinical symptoms disappeared, and the outcome was favorable. Conclusion To our knowledge, this is the probable first case report of primary multidrug-resistant Achromobacter piechaudii bloodstream infection in an apparently immunocompetent child.This case suggests that clinicians should consider rare Achromobacter species when managing pediatric bloodstream infection without obvious immunodeficiency. The multidrug-resistant phenotype highlights the need for accurate species identification and susceptibility-guided therapy.