Prolonged Helicobacter canis Bacteremia in an Infant: A Case Report

To the Editors: We report the case of a 1.5-month-old full-term male infant, admitted with mild fever and diarrhea. Temperature rose from 37.5°C (day 0, D0) to 38.3°C (D1), with nonbloody, nondehydrating diarrhea and 1 vomiting episode. Clinical examination was unremarkable except for mild nasal congestion. Initial workup showed elevated C-reactive protein (CRP; 36 mg/L at D1, 119 mg/L at D2), normal leukocyte count (15 G/L, neutrophils: 8 G/L), and negative urine and stool cultures. Multiplex PCR FilmArray Respiratory Panel 2 plus (bioMérieux, Marcy-l'Étoile, France) detected human coronavirus 229E. The infant improved spontaneously. A blood culture BD BACTEC Peds Plus (BD, Franklin Lakes, NJ) drawn at D0 became positive after 4 days 3 hours, revealing thin, curved Gram-negative bacilli (Figure, Supplemental Digital Content 1, https://links.lww.com/INF/G586). Blood culture drawn at D5 became positive after 4 days 1 hour, while CRP had decreased to 28 mg/L. Blood cultures at D15 and D20 showed bacteremia persistence at D15 (time to positivity 3 days 10 hours) and negativity at D20, while CRP normalized (<1 mg/L) by D15. Intravenous cefotaxime 100 mg/kg/d was started at D20 for 10 days. Blood cultures at D24 and D39 remained negative (Figure, Supplemental Digital Content 2, https://links.lww.com/INF/G587). Echocardiography, abdominal ultrasound and immunologic workup [lymphocyte immunophenotyping, immunoglobulin (Ig)G, IgM, IgA] were normal. The family owned a healthy cat. The clinical outcome was favorable, without recurrence. Subcultures from blood cultures grew only on Columbia blood agar incubated at 35°C under microaerophilic conditions after 48 hours. Matrix-assisted laser desorption ionization-time of flight mass spectrometry Biotyper (Bruker Daltonics, Bremen, Germany) and Vitek MS (bioMérieux) failed to provide reliable identification. Whole-genome sequencing (iSeq100, Illumina, San Diego, CA) identified Helicobacter canis, with average nucleotide identity and DNA–DNA hybridization values of 95.6% and 75.7%, respectively, versus reference strain CCUG-32756T. Antimicrobial susceptibility testing by E-test (bioMérieux) on Mueller–Hinton agar with 10% horse blood under microaerophilic conditions showed low minimum inhibitory concentrations for all tested agents (Table 1), interpreted using PK/PD or Helicobacter pylori breakpoints (Comité de l'Antibiogramme de la Société Française de Microbiologie/European Committee on Antimicrobial Susceptibility Testing guidelines 2025 v1.1). TABLE 1. - Minimal Inhibitory Concentrations (MICs) Determined by E-test for Helicobacter canis Strains From Previous Reports and the Present Case Lardinois et al1 Mihevc et al2 Leemann et al3 Charazac et al (Current report) AST* (mg/L) AMP = 0.064 (S)A/C = 0.047 (S)CRO = 0.075 (S)MP < 0.002 (S)MZ < 0.016 CM = 2 (R)CI > 32 (R)TC < 0.016 (S)RI < 0.002 (S) A/C = 0.016 (S)CTX = 0.125 (S)CRO = 0.25 (S) MP = 0.25 (S)GM = 0.064 (S) AM = 0.38 (S)A/C = 0.094 (S)CRO = 0.75 (S)P/T = 1 (S) IMI = 0.047 (S)MZ = 0.064CM = 0.094 (S) AM = 0,5 (S)CTX = 0,5 (S)GM = 0,5 (S)CL = 0,023 (S) LE = 0,012 (S)TC = 0,094 (S)RI = 0,023 (S)MZ = 0,38 *AST: antimicrobial susceptibility testing interpreted according to EUCAST/CASFM guidelines (2025 v1.1). Metronidazole could not be categorized. (S): use with caution; (R): should not be used. A/C, amoxicillin–clavulanate; AM, amoxicillin; AMP, ampicillin; CI, ciprofloxacin; CL, clarithromycin; CM, clindamycin; CRO, ceftriaxone; CTX, cefotaxime; GM, gentamicin; IMI, imipenem; LE, levofloxacin; MP, meropenem; MZ, metronidazole; P/T, piperacillin-tazobactam; RI, rifampicin; TC, tetracycline. Helicobacter canis is a rare zoonotic enterohepatic Helicobacter, mainly reported in immunocompromised adults, with dog or cat exposure.1 Pediatric infections are exceptional, with few cases of bacteremia or gastroenteritis, frequently associated with intercurrent infections and no underlying immunodeficiency (Table, Supplemental Digital Content 3, https://links.lww.com/INF/G588).4–6 In our patient, bacteremia persisted for 15 days despite rapid clinical improvement and CRP normalization, suggesting H. canis infection may be pauci-symptomatic and persistent,1 with absent or minimal biologic inflammatory response.5,6 Viral or bacterial co-infections, including human coronavirus 229E in this case, may facilitate infection in immunocompetent hosts. Slow growth, demanding culture requirements and limited matrix-assisted laser desorption ionization-time of flight databases, likely contribute to underdiagnosis and scarce minimum inhibitory concentration data (Table 1). Reliable identification relies on 16S rDNA, gyrA gene or whole-genome sequencing.1,7 Favorable outcomes have been reported with ceftriaxone, cefuroxime or doxycycline plus metronidazole, whereas ampicillin plus gentamicin and amoxicillin–clavulanate have been associated with recurrences. A treatment course of at least 2 weeks is recommended to prevent relapse.1 In conclusion, immunocompetent children with pet exposure and intercurrent infections may represent an emerging target for H. canis. Systematic blood cultures, appropriate microaerophilic conditions and sequencing-based identification are essential to recognize this underdiagnosed zoonosis and guide therapy. ACKNOWLEDGMENTS The authors thank Jeffrey Arsham, a native English speaker, for his reviewing of the English-language manuscript.