Oligonucleotide array-based identification of species in the Acinetobacter calcoaceticus-A. baumannii complex in isolates from blood cultures and antimicrobial susceptibility testing of the isolates.
Acinetobacter calcoaceticus, A. baumannii, Acinetobacter genomic species (gen. sp.) 3, and Acinetobacter gen. sp. 13TU, which are included in the A. calcoaceticus-A. baumannii complex, are difficult to distinguish by phenotypic methods. An array with six oligonucleotide probes based on the 16S-23S rRNA gene intergenic spacer (ITS) region was developed to differentiate species in the A. calcoaceticus-A. baumannii complex. Validation of the array with a reference collection of 52 strains of the A. calcoaceticus-A. baumannii complex and 137 strains of other species resulted in an identification sensitivity and specificity of 100%. By using the array, the species distribution of 291 isolates of the A. calcoaceticus-A. baumannii complex from patients with bacteremia were determined to be A. baumannii (221 strains [75.9%]), Acinetobacter gen. sp. 3 (67 strains [23.0%]), Acinetobacter gen. sp. 13TU (2 strains [0.7%]), and unidentified Acinetobacter sp. (1 strain [0.3%]). The identification accuracy of the array for 12 randomly selected isolates from patients with bacteremia was further confirmed by sequence analyses of the ITS region and the 16S rRNA gene. Antimicrobial susceptibility testing of the 291 isolates from patients with bacteremia revealed that A. baumannii strains were less susceptible to antimicrobial agents than Acinetobacter gen. sp. 3. All Acinetobacter gen. sp. 3 strains were susceptible to ampicillin-sulbactam, imipenem, and meropenem; but only 67.4%, 90%, and 86% of the A. baumannii strains were susceptible to ampicillin-sulbactam, imipenem, and meropenem, respectively. The observed significant variations in antimicrobial susceptibility among different species in the A. calcoaceticus-A. baumannii complex emphasize that the differentiation of species within the complex is relevant from a clinical-epidemiological point of view.
Ko
Wen-Chien
WC
Department of Internal Medicine, Center of Infection Control, National Cheng Kung University Hospital, Tainan, Taiwan.
Lee
Nan-Yao
NY
Su
Siou Cing
SC
Dijkshoorn
Lenie
L
Vaneechoutte
Mario
M
Wang
Li-Rong
LR
Yan
Jin-Jou
JJ
Chang
Tsung Chain
TC
D000151:Acinetobacter Infections / Q000175:diagnosis / Q000382:microbiology; D040981:Acinetobacter baumannii / Q000145:classification* / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification; D016954:Acinetobacter calcoaceticus / Q000145:classification* / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D016470:Bacteremia / Q000175:diagnosis / Q000382:microbiology; D015373:Bacterial Typing Techniques; D001769:Blood / Q000382:microbiology*; D003470:Culture Media; D004269:DNA, Bacterial / Q000032:analysis; D021903:DNA, Ribosomal Spacer; D006801:Humans; D008826:Microbial Sensitivity Tests / Q000379:methods; D020411:Oligonucleotide Array Sequence Analysis / Q000379:methods*; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012338:RNA, Ribosomal, 23S / Q000235:genetics; D012680:Sensitivity and Specificity; D017422:Sequence Analysis, DNA; D013045:Species Specificity
D000900:Anti-Bacterial Agents; D003470:Culture Media; D004269:DNA, Bacterial; D021903:DNA, Ribosomal Spacer; D012336:RNA, Ribosomal, 16S; D012338:RNA, Ribosomal, 23S