Obtaining Muramic Acid from Staphylococcus aureus: A Simple Strategy for Axenic Isolation of Tannerella forsythia

<b>Background:</b> The periodontal pathogen <i>Tannerella forsythia</i> is auxotrophic for muramic acid (MurNAc), a key component of bacterial peptidoglycan, and dependent on an external supply of MurNAc to maintain pure laboratory cultures. The focus of this study was to find a source of muramic acid and peptidoglycan fragments from a <i>Staphylococcus aureus</i> strain. This would facilitate the isolation of <i>T. forsythia</i> by incorporating peptidoglycan into conventional anaerobic media. <b>Methods:</b> The <i>S. aureus</i> strain ATCC 29213 was chosen as the source. The standardization and quantification of the method included verifying concentrations via spectrophotometry and developing a linear regression model with standard curves for muramic acid and lactic acid. The resulting lysate was used to seed Fastidious Anaerobe Agar (FAA) plates, which were inoculated with strain <i>T. forsythia</i> (ATCC 43037) and incubated in an anaerobic chamber for seven days. <b>Results:</b> The resulting lysate had an optical density ranging from 0.061 to 0.083, which corresponds to a muramic acid concentration of approximately 12 µg/mL. Pure cultures of <i>T. forsythia</i> could then be obtained on FAA plates supplemented with muramic acid (MurNAc) (FAA-Mur). The viability of the axenic <i>T. forsythia</i> culture was confirmed using muramic acid/peptidoglycan fragments of microbial origin. <b>Conclusions:</b> The method presented improves the growth of <i>T. forsythia</i>. Consequently, <i>T. forsythia</i> is available for further investigation into the regular performance of sensitivity tests in periodontics and the routine generation of growth curves for quantitative polymerase chain reaction (qPCR) analysis.