Full Length Research Paper

Detection of Pseudomonas aeruginosa in sputum samples by modified fluorescent in situ hybridization

Saeed Tajbakhsh¹*, Michael Hogardt², Jürgen Heesemann², Cordula Grzonka² and Kristin Adler²

¹Department of Microbiology and Parasitology, Faculty of Medicine, Bushehr University of Medical Sciences, P. O. Box 3631, Bushehr, Iran.

²Max von Pettenkofer-Institut für Hygiene und Medizinische Mikrobiologie, Ludwig-Maximilians University, Munich, Germany.

*Corresponding author. E-mail:tajbakhshsaeed@yahoo.com. Fax: +98-771-2531933. Tel: +98-917-7746164.

Accepted 18 January, 2008

Pseudomonas aeruginosa is the most common and dominant infectious agent that causes chronic pneumonia in patients with cystic fibrosis (CF). Fluorescent in situ hybridization (FISH) is a powerful molecular method for the specific and rapid diagnosis of bacteria, including the detection of P. aeruginosa in sputum samples from CF patients. High background fluorescence of viscous sputum samples obtained from CF patients may impede detection of microorganisms by FISH. The aim of this study was to test the application of biotin during FISH technique to reduce unspecific background fluorescence in sputum samples to facilitate and improve detection of P. aeruginosa. Sixty-three sputum samples from CF patients were tested by FISH to detect P. aeruginosa. All the 63 samples were also examined by a modified FISH procedure including biotin treatment. The FISH results were compared with those of conventional culture method. The specificity of FISH was 100%. The sensitivity of FISH for detection of P. aeruginosa from samples without biotin treatment was 83.3%, whereas in biotin-treated samples was 88.1%. Biotin reduced background fluorescence of 12 sputum samples of CF patients and it did not show any adverse effect on FISH results of the remaining sputum samples. Therefore, using of biotin in FISH procedure seems to facilitate and improve the detection of respiratory tract infections by P. aeruginosa in this population.

Key words: Pseudomonas aeruginosa, fluorescent in situ hybridization, FISH, biotin.