The applicability of the PNA FISH (peptide nucleic acid fluorescence in situ hybridization) method for detection of Streptococcus agalactiae (Group B streptococci - GBS) from swab samples was evaluated. Three swab sample processing protocols with different time-to-result (TTR) were compared, including (i) direct smearing of fresh swabs onto microscope slides (n = 153; TTR 2.5 h), (ii) further extraction and concentration of cells from these same swabs (n = 153; TTR 2.7 h), and (iii) short term LIM broth enrichment culture incubation (7 h, 37 degrees C) of fresh swabs (n = 120; TTR 9.5 h). Sensitivity, specificity, positive predictive value, and negative predictive value for GBS PNA FISH for sample processing procedures with TTR of 2.5 h, 2.7 h, and 9.5 h were 68%, 100%, 100%, 95%; 91% 100%, 100%, 98%; and 100%, 100%, 100%, 100% respectively. Improved test results were achieved by subjecting swabs to an extraction procedure or abbreviated LIM broth enrichment culture incubation prior to performing GBS PNA FISH.
