title: Recovery of mutans streptococci on MSB, SB-20 and SB-20M agar media.
abstract: OBJECTIVE
  The recovery of mutans streptococci in saliva and dental biofilm samples depends, in part, on the culture medium used. In this study, we compared (i) the culture media Sucrose-Bacitracin agar (SB-20), Modified SB-20 (SB-20M) and Mitis Salivarius Bacitracin agar (MSB) in the count of colony forming units (cfu) of mutans streptococci and (ii) in the morphological and biochemical differentiation between Streptococcus mutans and Streptococcus sobrinus.
  
  
  METHODS
  Samples of non-stimulated saliva from 20 children were plated on SB-20, SB-20M and MSB, and incubated in microaerophilia at 37°C for 72h. Identification of microorganisms was based on analysis of colony morphology under stereomicroscopy. The biochemical identification of colonies was done by biochemical tests using sugar fermentation, resistance to bacitracin and hydrogen peroxide production.
  
  
  RESULTS
  There was no significant difference (p>0.05) in the number of cfu of mutans streptococci recovered on SB-20 and SB-20M agar. Comparing the media, SB-20 and SB-20M yielded a larger number of mutans streptococci colonies (p<0.05) and were more effective than MSB in the identification of S. sobrinus (p<0.05), but not of S. mutans (p>0.05).
  
  
  CONCLUSIONS
  There was no significant difference between SB-20 and SB-20M culture media in the count of mutans streptococci, demonstrating that the replacement of sucrose by coarse granular cane sugar did not alter the efficacy of the medium. Compared with MSB, SB-20 and SB-20M allowed counting a larger number of mutans streptococci colonies and a more effective morphological identification of S. sobrinus.
authors.affiliation: Department of Preventive Dentistry, School of Dentistry, National University of Tucumán, T4000, San Miguel de Tucumán, Argentina.
authors.forename: Marta Estela
authors.initials: ME
authors.lastname: Saravia
authors.forename: Paulo
authors.initials: P
authors.lastname: Nelson-Filho
authors.forename: Raquel Assed Bezerra
authors.initials: RA
authors.lastname: Silva
authors.forename: Andiara
authors.initials: A
authors.lastname: De Rossi
authors.forename: Gisele
authors.initials: G
authors.lastname: Faria
authors.forename: Léa Assed Bezerra
authors.initials: LA
authors.lastname: Silva
authors.forename: Claes-Göran
authors.initials: CG
authors.lastname: Emilson
mesh_terms: D000362:Agar / Q000145:classification*; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001414:Bacitracin / Q000494:pharmacology; D058491:Bacterial Load; D015373:Bacterial Typing Techniques; D001431:Bacteriological Techniques; D018441:Biofilms; D002648:Child; D002675:Child, Preschool; D003470:Culture Media / Q000145:classification*; D024881:Drug Resistance, Bacterial; D005285:Fermentation; D006801:Humans; D012463:Saliva / Q000382:microbiology; D013295:Streptococcus mutans / Q000302:isolation & purification*; D016986:Streptococcus sobrinus / Q000302:isolation & purification*; D013395:Sucrose / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D003470:Culture Media; D001414:Bacitracin; D013395:Sucrose; D000362:Agar