Fulminant Aeromonas caviae bacteremia with migratory myalgia: a case report of a CTX-M-3-producing multidrug-resistant strain

Aeromonas caviae is an emerging waterborne pathogen of increasing clinical concern, particularly regarding antimicrobial resistance. While extended-spectrum β-lactamase (ESBL) genes such as bla CTX−M are well-documented in Enterobacterales, they remain uncommon in A. caviae . We report a rare case of fulminant A. caviae bacteremia with atypical clinical manifestations and a complex genomic resistome. A 71-year-old man without formal immunodeficiency but with predisposing vulnerabilities (advanced age, prior subtotal gastrectomy) presented with fulminant bacteremia progressing to septic shock and unusual migratory myalgia following a minor paddy field injury. Initial empirical ertapenem therapy at a referring hospital was clinically ineffective. Blood cultures isolated A. caviae with multidrug resistance. Whole-genome sequencing (WGS)–based phylogenomic analysis confirmed species identity (clustering with A. caviae type strain NCTC 12244; bootstrap 100%; average nucleotide identity 98.09%), distinguishing it from closely related species ( A. dhakensis , A. hydrophila , A. veronii ). WGS identified ESBL genes bla CTX−M−3 , bla TEM−1B , and bla OXA−10 , alongside aac(6’)-Ib-cr and tet(A) . The isolate remained susceptible to amikacin and representative carbapenems (imipenem, meropenem). Therapy was successfully switched to biapenem, achieving rapid clinical recovery and microbiological clearance. A. caviae, an environmental organism, can harbor clinically significant ESBL genes and cause life-threatening infections even in individuals without formal immunodeficiency. Ertapenem failure despite carbapenem class susceptibility suggests that pharmacokinetic/pharmacodynamic factors may contribute to treatment failure in critically ill patients with hypoalbuminemia and acute kidney injury, although direct evidence is lacking. These findings highlight the need for integrated One Health surveillance to monitor antimicrobial resistance gene flow between environmental and human populations, though confirmation through prospective multicentre studies is warranted.