Comparison of OmpA Gene-Targeted Real-Time PCR with the Conventional Culture Method for Detection of Acinetobacter baumanii in Pneumonic BALB/c Mice

Abstract

Background: Acinetobacter baumannii is an important pathogen in health care and is responsible for severe nosocomial and community-acquired pneumonia. To design novel therapeutic agents, a mouse model for A. baumannii pneumonia is essential.

Methods: We described a mouse model of A. baumannii using clinical and 19606R standard strains for developing a quantitative real-time PCR (qRT-PCR) for rapid identification of A. baumannii infection from lung tissues of BALB/c mice.

Results: To infect the mice, three doses of bacteria (0.5 × 108, 1 × 108, and 1.5 × 108 cfu/ml) were used. Lung tissues were cultured and compared with ompA gene. Clinical isolates had better positive results at day three with the highest dose than 19606 strain either in culture (4 versus 3) or in qRT-PCR (5 versus 4). However, qRT-PCR detection was 100%, the specificity was 70%, and the positive predictive value was 27%.

Conclusion: The qRT-PCR detection of A. baumannii in the BALB/c mice model has a higher sensitivity than the culture method.

Keywords: Acinetobacter baumanii; OmpA; qRT-PCR Pneumonia; BALB/c mice.

Fig. 1

Positive results of A.baumannii in the samples of lung tissues of pneumonic mice. Mice were inoculated with three different doses of clinical isolate and standard strain (19606R), and numbers of colonies and OmpA genes were measured on days 1, 2, and 3 post inoculation. (A); Number of colonies detected in the traditional tissue culture. (B); Number of OmpA gene detected by qRT-PCR directly from lung tissue. Twenty mice were used for each dose of bacteria, and five mice were used in each group (total 180 mice). ^* and ^** represent p < 0.05 and p < 0.01, respectively