Bacteriocinogeny and Antibiotic Resistance of Naturally Occurring Strains of Streptococcus mutans

Abstract

We studied bacteriocinogenies and antibiotic resistances of naturally occurring strains of Streptococcus mutans isolated from different sources.It was found that naturally occurring strains from humans and rats were distinguished by their bacteriocin susceptibilities and production.We had a few incidences of tetracycline resistant strains only among those isolated from rats.It is quite interesting that none of the resistant strains we collected produced bacteriocins.Streptococcus mutans is well known for its cariogenicity ( 1,3,16). It is classified into seven serological types (12,19), and DNA analysis also indicated its heterogeneity (2), but little work has been reported on fresh isolates of this bacterium except for serotypings.We were planning to perform some genetic studies on the fresh isolates of this bacterium, and as the first step, we examined their non-physiological properties, such as bacteriocinogeny (10, 13), lysogeny (5) and antibiotic resistance. There are some reports on each of these properties (4,7,11,14,15,18), but all except Rogers (14) worked exclusively with established strains, and no comparative studies were carried out for all of these properties simultaneously. MATERIALS AND METHODSStrains employed We isolated naturally occurring fresh strains from oral cavities of man and rats with gelatin agar medium containing 2% gelatin, 1% meat extract, 0.1% glucose, 30% sucrose and 2% agar (pH 7.2). Colonies which appeared on the plates after 48 hr of incubation were selected according to their morphological characteristics, purified on brain heart infusion (BHI) agar (Difco) after five sub-cultures, and identified by their cell-morphologies according to Gram stains, hemolytic activities, sugar fermenation, and adherence to the wall of a test tube containing sucrose-broth. These isolates were maintained on Todd-Hewitt agar (BBL) and were periodically checked for typical growth on mitis-salivarius agar (Difco). All incubations were carried out anaerobically using the BBL Gas Pak system at 37 C.

Antimicrobial susceptibility of 1042 strains of Streptococcus mutans and Streptococcus sobrinus: comparison from 1985 to 1989

“…Considering the variadons expected for a study of this type, the MIC were found to be very similar to those observed by other authors (1, 3, 7). No strains requiring high concentrations of antibiotics to achieve inhibition were detected, as has previously been indicated in other studies, particularly in reference to tetracycline (6). Excluding the behavior of several strains to spiramycin and acetyl spiramycin, the remaining antibiotics tested in this study inhibit 100%) of the strains at a concentration of < 2 /ig/ml.…”

“…Differences in suscepdbility have been reported to exist between different serotypes (7), which would imply that anatomic and physiological factors exist at the cell wall level. Certain cases of resistance to tetracycline seem to be caused by transposons (5,6). The aim of this study was to examine the evolution of sensidvity in S. tnutans and S. sobrinus over a 5-year period.…”

Biology, immunology, and cariogenicity of Streptococcus mutans.

“…Eleven of 17 human strains and 7 of 16 rat strains of S. mutans, all of which are nonlysogenic, produce mutacins. Most of the nonmutacinogenic rat strains are tetracycline resistant (290).…”

“…The only information available on the mechanism of action of bacteriocins of streptococci indicates an inhibition of DNA, RNA, and protein synthesis (512). No involvement of a plasmid in mutacinogeny has been reported, although extensive surveys have been made (102,225,226,290,294).…”