Monoclonal antibodies for enumeration and identification of mutans streptococci in epidemiological studies

Two members of the mutans streptococci, Streptococcus mutans and Strep. sobrinus, are often found in human dental plaque. Different cariogenic characteristics between these species have been reported and therefore these species should be detected and identified separately. Identification of mutans streptococci based on sugar fermentation is troublesome and easily leads to erroneous conclusions. Furthermore, the recovery for the two species differs on selective media. This causes incorrect enumeration of Strep. mutans and Strep. sobrinus in clinical samples. The aim of this study was to develop an improved method for simultaneous identification and enumeration of Strep. mutans and Strep. sobrinus in dental plaque and saliva samples. The immunoblot technique described is based on growth of the microorganisms on non-selective media, followed by immunological detection with specific monoclonal antibodies. With the immunoblot significantly more plaque samples containing Strep. sobrinus were detected than on the selective medium TYCSB (p less than 0.01). The number of plaque samples harbouring Strep. mutans was equal on TYCSB and immunoblot. However, the numbers of c.f.u. of Strep. mutans and Strep. sobrinus detected with the blot were significantly higher than those obtained on TYCSB (p less than 0.01). The recovery of Strep. sobrinus on primary isolations on TYCSB appeared to be inhibited in 29 out of the 45 Strep. sobrinus-containing plaque samples. False-positive and false-negative reactions with the immunoblot were not found. The results indicate that the presence and numbers of Strep. sobrinus and Strep. mutans can be studied reliably using the immunoblot technique.