[The application of loop-mediated isothermal amplification for detection of common pathogenic bacteria in lower respiratory tract infections].

OBJECTIVE

To investigate the spectrum of common pathogenic bacteria of low respiratory tract infection by loop-mediated isothermal amplification (LAMP) of nucleic acid test and to prove the clinical significance of this method.

METHODS

A total of 289 qualified sputum samples from patients with lower respiratory tract infections in Fujian Province were detected by LAMP technique, and then the distribution of pathogenic bacteria was analyzed. The positive cases (the patients whose specific bacterial copies in their sputum samples > 1×10(3) copies/ml) were divided into 2 groups according to whether their treatment had covered this pathogen or not. The underlying diseases, duration of anti-bacterial treatment, the hospital days, and the effectiveness of initial treatment and cure rate were compared.

RESULTS

The culture method in the 289 patients showed that 44 (15.2%) were positive. Tests by the LAMP method with a bacteria concentration > 1×10(3) copies/ml as cutoff value, showed positive results in 124 patients (43.0%). The lower respiratory tract pathogens included 144 strains of bacteria (77.8%), and 41 strains of atypical pathogens (22.2%). Gram-negative bacteria were the predominant pathogens, such as Pseudomonas aeruginosa, H. influenzae, Klebsiella pneumoniae, and Streptococcus pneumoniae. In 95 cases the initial therapy had covered the pathogens, while in 29 cases the initial therapy had not. The effectiveness of the initial treatment (χ(2) = 31.0, P < 0.01) and the total days of hospital stay (t = -2.083, P = 0.039) in the group whose antibiotics had covered the pathogens were significantly higher than those of the other group. However, there were no significant difference in duration of anti-bacterial treatment (t = -1.073, P = 0.285)and cure rates (χ(2) = 0.6, P = 0.4) between the 2 groups.

CONCLUSIONS

LAMP method can detect the nuclear acid of the bacteria in the sputum much more rapidly and sensitively than the routine culture method. LAMP technique may be helpful to know the pathogenic bacteria before treatment, and therefore may improve the choice of initial antibiotic therapy.