L. Saiman et al., Identification and antimicrobial susceptibility of Alcaligenes xylosoxidans isolated from patients with cystic fibrosis, J CLIN MICR, 39(11), 2001, pp. 3942-3945
In the past decade, potential pathogens, including Alcaligenes species, hav
e been increasingly recovered from cystic fibrosis (CF) patients. Accurate
identification of multiply antibiotic-resistant gram-negative bacilli is cr
itical to understanding the epidemiology and clinical implications of emerg
ing pathogens in CF. We examined the frequency of correct identification of
Alcaligenes spp. by microbiology laboratories affiliated with American CF
patient care centers. Selective media, an exotoxin A probe for Pseudomonas
aeruginosa, and a commercial identification assay, API 20 NE, were used for
identification. The activity of antimicrobial agents against these clinica
l isolates was determined. A total of 106 strains from 78 patients from 49
CF centers in 22 states were studied. Most (89%) were correctly identified
by the referring laboratories as Alcaligenes xylosoxidans. However, 12 (11%
) strains were misidentified; these were found to be P. aeruginosa (n = 10)
, Stenotrophomonas maltophilia (n = 1), and Burkholderia cepacia (n = 1). M
inocycline, imipenem, meropenem, piperacillin, and piperacillin-tazobactam
were the most active since 51, 59, 51, 50, and 55% of strains, respectively
, were inhibited. High concentrations of colistin (100 and 200 mug/ml) inhi
bited 92% of strains. Chloramphenicol paired with minocycline and ciproflox
acin paired with either imipenem or meropenem were the most active combinat
ions and inhibited 40 and 32%, respectively, of strains. Selective media an
d biochemical identification proved to be useful strategies for distinguish
ing A. xylosoxidans from other CF pathogens. Standards for processing CF sp
ecimens should be developed, and the optimal method for antimicrobial susce
ptibility testing of A. xylosoxidans should be determined.