Cat scratch disease without skin lesions: a case report of fatal underdiagnosed ST1 Bartonella henselae bacteremia

Bartonella henselae , the causative agent of cat scratch disease, is primarily transmitted to humans when skin lesions are in physical contact with flea feces contaminated with the pathogen. Such lesions are typically caused by scratches or bites from cats or dogs. However, some infected individuals may not exhibit visible skin lesions, hence not prompting clinical suspicion. This report describes a case of underdiagnosed B. henselae bacteremia in an immunocompetent woman, retrospectively confirmed by molecular detection from a blood culture initially deemed negative after 5 days of incubation. The patient first presented to the emergency department with persistent fever but was afebrile upon examination and had no visible skin lesions. She was admitted and treated for urosepsis and discharged. Two months later, she returned with complaints of shortness of breath and succumbed to fulminant atypical pneumonia. The suspicion of a fastidious pathogen prompted the decision to extend the incubation period of her initial blood culture, which subsequently yielded colonies after 14 days. PCR identified the etiological agent as B. henselae , and multi-locus sequence typing revealed the isolate belonged to sequence type 1 (ST1), a widespread clone detected across multiple countries and continents. This case highlights the diagnostic challenges of vector-borne infections and underscores the importance of considering extended culture periods and advanced molecular techniques in identifying elusive pathogens, such as B. henselae .