Marsh P D, West A A, Keevil C W
Bacterial Metabolism Research Laboratory, PHLS Centre for Applied Microbiology and Research, Salisbury, Wiltshire.
J Med Microbiol. 1987 Nov;24(3):259-62. doi: 10.1099/00222615-24-3-259.
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.
在之前的一项研究中，从20名成年志愿者中的9人的唾液中分离出了少量能够在添加了40毫克/升阿莫西林的琼脂上生长的细菌。所有这些细菌都被鉴定为血链球菌，尽管在传统测试中没有菌株产生葡聚糖。然而，使用一种特定的检测方法发现，所有耐药菌株都能分泌葡糖基转移酶（GTF），即合成这些细胞外多糖的酶；合成葡聚糖的酶GTF-S的产量比抗生素敏感对照菌株低22%-43%。葡聚糖引物显著抑制了耐药菌和敏感菌的酶产生。耐阿莫西林的细菌对其他青霉素也耐药；它们对红霉素的耐药性各不相同，但对头孢噻吩和克林霉素均敏感。由于葡聚糖的产生被认为是血链球菌等细菌在受损心脏瓣膜上定殖的关键因素，这些高耐药性细菌可能不会对易感个体构成威胁。
