Author(s)

Cheguri H. Swathi¹, Sudhaharan Sukanya², Vemu Lakshmi^2,3, Kamaraju Saipriya¹, Venkataraman Sritharan^1,4

¹Department of Molecular Diagnostics & Biomarkers, Global Medical Education & Research Foundation (GMERF), Hyderabad, India.
²Nizam’s Institute of Medical Sciences (NIMS), Hyderabad, India.
³Kamineni Academy of Medical Sciences and Research Center, Hyderabad, India.
⁴Department of Molecular Diagnostics & Biomarkers, Gleneagles Global Hospital, Hyderabad, India.

Currently, available phenotyping and commercial methods report A. baumannii only as Acinetobacter calcoaceticus-baumannii complex (ACB) and do not identify individual members of the complex. This is a single blind study aimed to evaluate certain commonly used species-specific genetic markers namely, Intergenic Transcribed Spacer region in 16S rRNA of A. baumannii (Ab-ITS) and gyrB, for identification of ACB members. These molecular targets were first validated on clinical isolates (n = 200) and subsequently on uncultured tracheal aspirates (n = 172). Among the clinical isolates, 183/200 (91.5%) were positive for Ab-ITS. The clinical isolates 17 (17/200) which are failed to amplify in Ab-ITS PCR were subsequently diagnosed by gyrB PCR as A. calcoaceticus (n = 2), A. pitti (n = 6) and A. nosocomialis (n = 9) but not A. baumannii. Among the tracheal aspirates, 62 samples were reported as sterile in Advanced Expert System of VITEK-2, among the remaining 110 samples, 68.1% (75/110) samples contained Ab-ITS target. Twenty-five of the sterile samples (25/62) were found to contain Ab-ITS target sequence. Since, our sample processing method enabled identification of all the species of ACB complex by PCR even in uncultured tracheal aspirates, adaptation of our protocol would enable same day (6 - 8 h) reporting and help the clinician make evidence based therapeutic decision quickly.

Acinetobacter baumannii, ACB Complex, Ab-ITS, gyrB, PCR, Tracheal Aspirates

Swathi, C. , Sukanya, S. , Lakshmi, V. , Saipriya, K. and Sritharan, V. (2020) A Simple Method for Direct Detection and Discrimination of A. baumannii in Tracheal Aspirates without Culture Isolation. Advances in Infectious Diseases, 10, 148-159. doi: 10.4236/aid.2020.102012.