A 17-month-old girl, born full term and with no significant past medical history, was admitted to our hospital for persistent fevers and positive blood cultures. Prior to admission, she had travelled with her family to western India for 26 days in early 2020. While abroad, she was hospitalized for 2 days with non-bloody, non-bilious emesis and non-bloody diarrhoea. Testing revealed a negative malarial parasite smear and C-reactive protein (CRP) of 18 mg l−1 [normal range (N): <5.0 mg l−1]. She was discharged on oral cefixime and a probiotic containing 2 billion spores per capsule (Enterogermina; Sanofi-Aventis S.p.A.), which she continued for 4 days. She had intermittent fevers (highest temperature 38.3 °C) for the remainder of her trip. She presented to our paediatric emergency department 1 day after return to the USA for evaluation of persistent fevers; however, on arrival, she was afebrile and haemodynamically stable, with a normal physical exam. Laboratory testing revealed a white blood cell (WBC) count of 14 510 µl−1 (N: 6000–17 000 µl−1), platelet count of 586 000 µl−1 (N: 150 000–400 000 µl−1), CRP of 10.1 mg l−1 and erythrocye sedimentation rate (ESR) of 51 mm h–1 (N: 0–20 mm h–1). Urinalysis was negative. Respiratory viral panel (RVP) testing of a nasopharyngeal swab revealed Coronavirus (non-SARS-CoV-2) infection. Blood cultures grew a Gram-positive bacillus after 2 days of incubation, so empiric ceftriaxone was initiated. The organism was identified as by matrix-assisted laser desorption/ionization-time of flight MS (Beckman Coulter) and was confirmed by the state reference laboratory. She had 19 blood cultures growing during her 31-day hospitalization. Empiric ceftriaxone was switched to ampicillin, due to reports of ampicillin’s efficacy against []. Antimicrobial susceptibility was derived using Clinical and Laboratory Standards Institute guidelines – the isolate was susceptible to ceftriaxone, gentamicin, levofloxacin and vancomycin () []. Persistent bacteraemia prompted addition of levofloxacin, with gentamicin added for synergy. Ampicillin was discontinued after further sensitivity testing was indeterminate and replaced with intravenous vancomycin, while continuing gentamicin and levofloxacin. Oral vancomycin was added to target bacteria from germinating intraluminal spores. She had an extensive evaluation for source and risk factors predisposing to persistent bacteraemia. Urine cultures revealed no growth. Repeat RVP testing was negative. Multiple trans-thoracic echocardiograms were negative for endocarditis. Abdominal ultrasound was unremarkable. Magnetic resonance imaging (MRI) of chest/abdomen/pelvis revealed no acute abnormalities, with patent arterial and venous vasculature. Brain MRI was unremarkable. Lower extremity ultrasound was negative for deep vein thrombosis. Positron emission tomography scanning did not reveal a source of infection. Vitamin A and zinc levels were normal; however, zinc/multivitamin supplementation was started to prevent micronutrient deficiency and bacterial translocation. Immunology was consulted to rule out underlying immunodeficiency. Evaluation revealed normal quantitative immunoglobulins and protective titres to tetanus, diphtheria, measles, mumps, rubella and (consistent with normal humoral immunity). Assessment of cellular immunity revealed a normal lymphocyte immunophenotype (normal CD4+ and CD8+ T cells and CD19+ B cells) and normal lymphocyte function (based on phytohaemagglutinin/pokeweed mitogen response). Complement assays including total complement (CH50), alternate pathway (AH50) and mannose binding lectin were normal. Phagocytic evaluation revealed normal dihydrorhodamine (DHR), glucose-6-phosphate-dehydrogenase and myeloperoxidase staining. Toll-like receptor testing was not performed due to laboratory error. A genetic panel of 207 primary immunodeficiency genes revealed heterozygous variants of uncertain significance: CHD7 c.5066T>C (p.Val1689Ala), RMRP n.228C>T (RNA change), RTEL1 c.1189C>G (p.Gln397Glu), which were not consistent with her phenotype. She was discharged on oral vancomycin and levofloxacin to complete a 14-day course. During outpatient follow-up, she remained clinically stable without antibiotics. grew in surveillance blood cultures drawn 1 week, 5 weeks and 11 weeks from hospital discharge. Her CRP levels remained undetectable, with minimally elevated ESR (22 mm h–1) and unremarkable haematological, renal and hepatic laboratory parameters. By 12 and 16 weeks after hospital discharge, blood cultures were sterile. We performed a comprehensive literature review in the Medline and Google Scholar bibliographic databases for English language articles with the search terms ‘ bacteraemia’ and ‘probiotics bacteraemia’. We identified seven prior cases of bacteraemia occurring in patients with underlying co-morbidities () [].