Direct detection of Acinetobacter baumannii by loop-mediated isothermal amplification in patients with respiratory tract infection

Background
Rapid detection and treatment of Acinetobacter baumannii which is a health-care-associated pathogen that causes outbreaks and frequently encountered in ICU patients on mechanical ventilation is very important.


Aim
The present study aimed to detect the frequency of A. baumannii in sputum sample by loop-mediated isothermal amplification (LAMP) assay in comparison with the different culture methods.


Patients and methods
In all, 200 sputum samples and 100 tracheal aspirates (TA) were included to detect the frequency of Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, A. baumannii, Pseudomonas aeruginosa, and Enterobacter spp. (ESKAPE) pathogens by cultural methods and to detect A. baumannii from sputum sample by LAMP assay comparing its results with CHROMagar Acinetobacter and conventional culture methods referring to the rate of multidrug-resistant A. baumannii.


Results
By conventional culture, positive culture was reported in 228/300 (76%) of all samples. A. baumannii and Klebsiella spp. were the most identified pathogens as they were detected in 27/145 (18.6%) and 19/145 (13%) of sputum samples and 19/83 (22%) and 43/83 (51.8%) of TA. Regarding culture on CHROMagar 46 isolates were identified as A. baumannii, 27 were from sputum sample, and 19 from TA. Out of 46 A. baumannii isolates multidrug-resistant A. baumannii were detected in 9/27 (33.3%) and 15/19 (78.9%) in sputum samples and TA, respectively. DNA of A. baumannii was detected in 28/200 (14%) by LAMP assay from sputum samples. Sensitivity and specificity of LAMP assay were 100 and 99.5% when compared with the conventional culture.


Conclusion
CHROMagar Acinetobacter and LAMP assay are cost-efficient methods in comparison to conventional culture. LAMP assay is distinguished from the others for its simplicity and rapid detection of pathogens.