Which nonfermenting gram-negative rod is rarely isolated in the United States?

Which nonfermenting gram-negative rod is rarely isolated in the United States?

• A. Pseudomonas aeruginosa
• B. Stenotrophomonas maltophilia
• C. Burkholderia mallei
• D. Burkholderia cepacia

Answer: (C)

Nonfermenting gram-negative rods vary a lot in how often they appear in clinical labs, and geography or host associations often explain those differences. In the United States, several of these organisms are commonly encountered: Pseudomonas aeruginosa is a frequent hospital and CF-related pathogen; Stenotrophomonas maltophilia is an increasingly seen nosocomial Gram-negative rod; and Burkholderia cepacia complex is well known, especially in cystic fibrosis patients. Burkholderia mallei, however, is traditionally associated with glanders in horses and is extremely rare in humans in the U.S. due to geographic and animal-health controls. Because of this limited occurrence, Burkholderia mallei is the nonfermenting rod you would least expect to see isolated in routine U.S. clinical practice, making it the correct choice for this question.

Nonfermenting gram-negative rods vary a lot in how often they appear in clinical labs, and geography or host associations often explain those differences. In the United States, several of these organisms are commonly encountered: Pseudomonas aeruginosa is a frequent hospital and CF-related pathogen; Stenotrophomonas maltophilia is an increasingly seen nosocomial Gram-negative rod; and Burkholderia cepacia complex is well known, especially in cystic fibrosis patients. Burkholderia mallei, however, is traditionally associated with glanders in horses and is extremely rare in humans in the U.S. due to geographic and animal-health controls. Because of this limited occurrence, Burkholderia mallei is the nonfermenting rod you would least expect to see isolated in routine U.S. clinical practice, making it the correct choice for this question.