Clinical and microbiologic features of <i>Achromobacter</i> species: a 10-year, multicenter experience

<i>Achromobacter</i> species are Gram-negative bacilli that predominantly affect individuals with cystic fibrosis or those with immunocompromising conditions. Clinical and microbiologic data on <i>Achromobacter</i> species are limited due to the rarity of these organisms and challenges with species-level identification. We conducted a 10-year retrospective analysis (1 January 2013 to 14 March 2023) of all bloodstream and non-bloodstream <i>Achromobacter</i> isolates identified at three tertiary-care Mayo Clinic locations (Minnesota, Arizona, and Florida). Additionally, we examined clinical characteristics of adult patients with <i>Achromobacter</i> bloodstream isolates. A total of 1,598 <i>Achromobacter</i> isolates, encompassing 1,545 non-bloodstream isolates and 53 bloodstream isolates, were identified. The most frequently identified species was <i>Achromobacter xylosoxidans</i>, though species-level identification was not possible for many isolates. Among adult patients with <i>Achromobacter</i> bloodstream infection, the mean age was 58.3 years (standard deviation ± 16.7), 73.1% had a central venous catheter, and 59.6% were immunocompromised. All-cause mortality was 10.2% at 30 days and 18.4% at 90 days. Bloodstream isolates exhibited greater than 90% susceptibility to meropenem, piperacillin-tazobactam, and trimethoprim-sulfamethoxazole. The respiratory tract was the most common source of non-bloodstream isolates (57.5%). Non-bloodstream isolates showed high susceptibility to imipenem (94.6%), piperacillin-tazobactam (92.8%), trimethoprim-sulfamethoxazole (92.1%), and meropenem (87.5%) while demonstrating significant resistance to fluoroquinolones and aminoglycosides. Our findings support the use of piperacillin-tazobactam, carbapenems, or trimethoprim-sulfamethoxazole as initial therapy for <i>Achromobacter</i> infections. Further research is needed to better define the clinical and microbiologic characteristics of <i>Achromobacter</i> infections.IMPORTANCE<i>Achromobacter</i> is a rare but important genus of bacteria that tends to cause infection in those with cystic fibrosis, recurrent healthcare exposures, and/or an immunocompromising condition. There is limited data on the clinical profile of <i>Achromobacter</i> infections as well as optimal antibiotic selection for affected patients. We conducted a retrospective study to improve understanding of the microbiologic and clinical characteristics of <i>Achromobacter</i>. Our study consists of a 10-year survey of all <i>Achromobacter</i> isolates processed by three Mayo Clinic tertiary-care centers in Minnesota, Florida, and Arizona from 2013 to 2023. We report multiple findings, including the clinical characteristics of patients with <i>Achromobacter</i> bloodstream infection, the number of different <i>Achromobacter</i> species identified, and the sources of isolates not obtained from blood cultures. We additionally present antimicrobial susceptibility results for <i>Achromobacter</i> isolates. Our study provides guidance to clinicians treating <i>Achromobacter</i> infections and, it is hoped, will facilitate ongoing study of <i>Achromobacter</i>.