Comparison of genospecies and antimicrobial resistance profiles of isolates in the Acinetobacter calcoaceticus-Acinetobacter baumannii complex from various clinical specimens.

This study was conducted to compare the prevalences of antimicrobial resistance profiles of clinical isolates in the Acinetobacter calcoaceticus-Acinetobacter baumannii complex from sterile and nonsterile sites and to further study the relationship of antimicrobial resistance profiles and genospecies by amplified rRNA gene restriction analysis (ARDRA). A total of 1,381 isolates were tested with 12 different antibiotics to show their antimicrobial susceptibility profiles. A total of 205 clinical isolates were further analyzed by ARDRA of the intergenic spacer (ITS) region of the 16S-23S rRNA gene. It was found that the overall percentage of isolates from nonsterile sites (urine, sputum, pus, or catheter tip) that were resistant to the 12 antibiotics tested was significantly higher than that of isolates from sterile sites (cerebrospinal fluid [CSF], ascites fluid, and bloodstream) (46% versus 22%; P < 0.05). After ARDRA, it was found that 97% of the 62 isolates resistant to all antibiotics tested were the A. baumannii genospecies, which was identified in only 31% of the isolates susceptible to all antibiotics tested. More genospecies diversity was identified in the isolates susceptible to all antibiotics tested, including genospecies of 13TU (34%), genotype 3 (29%), and A. calcoaceticus (5%). Furthermore, as 91% (10/11) of the isolates from CSF were susceptible to all antibiotics tested, the A. calcoaceticus-A. baumannii complex isolates with multidrug resistance could be less invasive than the more susceptible isolates. This study also indicated current emergence of carbapenem-, fluoroquinolone-, aminoglycoside-, and cephalosporin-resistant A. calcoaceticus-A. baumannii complex isolates in Taiwan.