Achromobacter

Background

• Genus of aerobic, afermentative Gram-negative bacilli within the family Alcaligenaceae and order Burkholderiales
• Oxidase-positive, catalase-positive, indole-negative, urease-negative, and DNase-negative
• May be misidentified as other afermentative Gram-negative bacilli
• Most notable species of clinical significance is Achromobacter xylosoxidans
• Other species that have been isolated from clinical specimens include Achromobacter denitrificans, Achromobacter ruhlandii, Achromobacter piechaudii, Achromobacter animicus, Achromobacter mucicolens, Achromobacter pulmonis, Achromobacter insolitus, Achromobacter spanius, Achromobacter deleyi, Achromobacter aegreficans, Achromobacter insuavis, Achromobacter anxifer, Achromobacter dolens, and Achromobacter marplatensis

Clinical Manifestations

• Commonly found causing chronic lung infections in patients with cystic fibrosis
• Can also cause pneumonia and bacteremia, often associated with indwelling hardware
• Rarely cause skin and soft tissue infections, urinary tract infection, intraabdominal infection, CNS infection, eye infection, and ear infection
• Very rarely cause endocarditis and osteomyelitis

Management

• Intrinsically resistant to cephalosporins, aztreonam, azithromycin, and aminoglycosides
• The most reliable agents are TMP-SMX, ceftazidime, piperacillin, and carbapenems (imipenem more than meropenem)
  • However, there is increasingly resistant to carbapenems due to efflux pumps and metallo-beta-lactamases
• May be susceptible to ticarcillin, cefepime, fluoroquinolones, doxycycline, tigecycline, and colistin
• For MDR isolates, consider cefiderocol or eravacycline
  • Less evidence for meropenem-vaborbactam and plazomicin, but may also work

Further Reading

• Achromobacter Infections and Treatment Options. Antimicrob Agents Chemother. 2020. doi: 10.1128/AAC.01025-20