Fig. 4

Detection of S. pneumoniae with Spn-FLUO in human sputum. (A) Aliquots of sputum were DNA extracted and used as templates in qPCR reactions targeting the lytA gene. Other aliquots were stained with Spn-FLUO, and the presence of S. pneumoniae was scored. The graphic shows the pneumococcal genome equivalent (GenEq)/ml in all samples (overall), or categorized as moderate (scored +, and ++), or abundant (scored +++). Statistical significance of differences in bacterial density was assessed using the Student’s t-test. ns = no significant difference. (B-D) Sputum specimens stained with Spn-FLUO and observed under (B) epifluorescence in the green channel or (C) bright field. Panel (D) shows the merged epifluorescence and bright field channels. Arrows point out S. pneumoniae identified by Spn-FLUO, while arrowheads signal staphylococcus-like microcolonies, which were not stained by Spn-FLUO but were observed in the bright field channels