Methodology for improving the detection rate of sputum with invasive Aspergillus fumigatus

Objective To investigate a method for improving the isolation rate of invasive aspergillus fumigatus in sputum by modifying the culture medium.Methods Collected the frequently occurring in sputum specimen including Candida albicans and analyzed their drug resistance.Then mixed these as bacteria with Aspergillus fumigatus spore in various proportions to simulate the mixed infection sputum specimen,and observed their mutual interference.Then appropriate antibiotics were added into the culture medium to enhance the selective growth of Aspergillus fumigatus via inhibiting the growth of interference bacteria.Results When the concentration of Pseudomonas aeruginosa was greater or equal to 104 CFU/ mL,growth of Aspergillus fumigatus(103 CFU/mL) would be totally inhibited.Staphylococcus aureus and Escherichia coli needed a level of 105 CFU/mL to totally inhibit the growth of Aspergillus fumigatus.Candida albicans needed a mixing with aspergillus fumigatus at a ratio of 100∶1.In accordance with the drug resistance specificity of the interference bacteria,imipenem and vancomycin were added to the culture medium and it was shown that the growths of abovementioned three were effectively inhibited.Addition of fluconazole 5 μg/mL could inhibit the growth of candida albicans.The above-mentioned three antibiotics had no effects on the growth of Aspergillus fumigatus.Conclusions The detection rate of invasive Aspergillus fumigatus could be enhanced by adding appropriate antibiotics to culture medium to inhibit the growth of interference bacteria.