Orthopedic infections associated with distinct Acinetobacter strains in rural area of Qingdao, China

Introduction Acinetobacter baumannii poses a profound global health threat because of multidrug resistance and its association with nosocomial infections. However, standard clinical diagnostics often report it together with other Acinetobacter species as A. baumannii-calcoaceticus complex (ABC), which unavoidably conceals the attribution of non- A. baumannii species. This study reported orthopedic infection cases associated with different Acinetobacter species and characterized the genomes of the culture isolates to evaluate their potential impact on the clinical treatment. Methods Nine in-patients with A. baumannii-calcoaceticus complex identified by culture during hospitalization were enrolled by the Orthopedics Department from a local hospital in Qingdao, China. Their clinical data were reviewed. One ABC isolate from each patient was tested for drug susceptibility and subjected for whole-genome sequencing, followed by bioinformatic analyses. Results Through whole-genome analysis, nine ABC isolates were identified as six A. baumannii , two A. pittii , and one A. soli with distinct antibiotic resistance profiles and phylogenetic characteristics, indicating progressing pathogen transmission across broad geographic regions in One Health perspective. All A. baumannii and A. pittii strains carried multidrug resistance genes, while A. soli bore only amvA and rsmA . Phenotypically, eight isolates were susceptible to almost all the antibiotics tested, with only one A. baumannii being multidrug resistant. Despite this, eight patients received cephalosporins following positive reports of A. baumannii-calcoaceticus complex. Conclusion Our study highlighted the limitation of current clinical diagnostic approaches for non- A. baumannii cases, which tended to be overtreated, and suggested that Acinetobacter etiology landscape should be explored further beyond A. baumannii to avoid antibiotic misuse.