Characterisation of and polysaccharide production by amoxycillin-resistant streptococci.
Small numbers of bacteria capable of growing on agar supplemented with amoxycillin 40 mg/L were isolated from the saliva of 9 out of 20 adult volunteers in a previous study. All the bacteria were identified as Streptococcus sanguis although no strains produced dextran in conventional tests. However, using a specific assay, all the antibiotic-resistant strains were found to secrete glucosyltransferases (GTF), the enzymes that synthesise these extracellular polysaccharides; the production of GTF-S, the enzyme that synthesizes dextran, was 22-43% less than that of an antibiotic-sensitive control strain. Enzyme production by both antibiotic-resistant and sensitive bacteria was markedly inhibited by dextran primer. The amoxycillin-resistant bacteria were resistant to other penicillins; their resistance to erythromycin was variable but they were uniformly sensitive to cephalothin and clindamycin. As dextran production has been proposed as a key factor in the colonisation of damaged heart valves by bacteria such as S. sanguis, these highly resistant bacteria may not pose a threat to the susceptible individual.
D000658:Amoxicillin / Q000494:pharmacology*; D004352:Drug Resistance, Microbial; D005964:Glucosyltransferases / Q000378:metabolism; D006602:Hexosyltransferases / Q000378:metabolism; D011135:Polysaccharides, Bacterial / Q000096:biosynthesis*; D012463:Saliva / Q000382:microbiology; D013291:Streptococcus / Q000187:drug effects / Q000378:metabolism*; D001426:Bacterial Proteins
D000658:Amoxicillin; D005964:Glucosyltransferases; D006602:Hexosyltransferases; D011135:Polysaccharides, Bacterial; C021451:inulosucrase; D001426:Bacterial Proteins