Comparison of three methods for culturing throat swabs from cystic fibrosis patients.

In patients with cystic fibrosis who do not produce sputum, deep throat swabs are cultured for potential respiratory pathogens. Usually these swabs are directly streaked onto selective agar media. In a study of 50 pediatric cystic fibrosis patients, we compared this traditional method using rayon swabs with two methods having quantitative modifications: calcium alginate swabs eluted in Ringer's lactate and rayon swabs eluted in normal saline. The eluates were then processed quantitatively (three-step dilution series). The yield of potential pathogens was significantly higher with the two quantitative methods. Overall, the combination of alginate with Ringer's lactate was superior to the combination of rayon with saline, although only some of these differences achieved statistical significance.