Faculty Bibliography

The ability of physiological amounts of lysozyme to de-chain two serotype c strains of Streptococcus mutans was determined. Both human and hen lysozymes were equally effective in chain breakage of S. mutans DPR and S. mutans DJR. De-chaining did not affect growth of cultures, but resulted in finely dispersed suspensions, at stationary phase, which were visibly different from untreated cultures. Less than 50 micrograms lysozyme per ml culture medium reduced chain length to virtually all diplococci and single cells, and this chain disruption increased total viable cell count. De-chaining required an active enzyme indicating that a degree of hydrolysis of the peptidoglycan occurred at the septae of the streptococci. De-chained S. mutans did not survive as well as streptococci of normal chain length when incubated under acidic conditions (pH 5.5), but gross cellular lysis was not apparent. The reduced aciduric property of the disrupted chains may have been due to a participation of autolysins or to a lethal triggered by the lysozyme-damaged peptidoglycan. De-chaining may be a mechanism by which lysozyme could regulate the levels of S. mutans in acidogenic plaque samples.

The specificity of lysozyme determinations in human parotid and submandibular-sublingual salivas of two subjects was assessed by comparison of lysozyme concentrations in native acidified salivas with purified enzyme obtained by immunoadsorbent fractionation of the salivas. Lysozyme concentrations were measured by the turbidimetric catalytic method and by a newly developed enzyme-linked immunosorbent assay (ELISA). The validity of the assays was established by comparing assay results with enzyme concentration values determined from optical density-extinction coefficient calculations of the purified lysozyme peak. Values for purified enzyme were found to be similar, irrespective of the assay used to determine lysozyme concentrations, and were in agreement with extinction coefficient calculations. Based on the ELISA technique, recoveries of lysozyme from both parotid and submandibular-sublingual salivas were greater than 75 and 90%, respectively. Similar recoveries were noted for parotid saliva when determinations were based on the turbidimetric assay. However, the ELISA and turbidimetric assays differed with respect to lysozyme levels in submandibular-sublingual saliva because of the apparent presence of an enhancement factor which gave rise to higher lysozyme values in the catalytic assay and therefore resulted in low recoveries of purified enzyme. This catalytic enhancement factor was present in the nonadsorbed fraction of both subjects, as higher lysozyme activities were noted when nonadsorbed fractions were added to affinity-purified lysozymes. Lysozyme levels were also determined in the parotid and submandibular-sublingual salivas of caries-resistant and -susceptible adults. In general, levels of lysozyme in parotid saliva were lower in comparison to submandibular -sublingual saliva; however, significant differences in enzyme concentration were not evident between the caries-resistant and caries-susceptible subjects.