Epidemiology and Molecular Genetics of Macrolide Resistance in Staphylococcus aurous.

金黄色葡萄球菌对大环内酯类抗生素的耐药类型分为A、B、c 3组。A组菌株对大环内酯类抗生素(M)、林肯胺类抗生素(L)、链霉素类B型抗生素(S)具有组成性耐药。C组菌株对MLS具有诱导抗性。B组菌株对14元大环内酯类和s具有诱导抗性，我们将这种表型称为PMS。1978年至1989年期间，匈牙利分离出413株耐pms的金黄色葡萄球菌菌株。他们还对青霉素（99%）、四环素（79%）和氯霉素（63%）耐药。绝大多数（94%）属于52相复合体，表明它们是同源的。进一步检测43株菌株，发现PMS表型的决定因素位于3种质粒中的一种，该质粒也编码β -内酰胺酶产生和抗镉离子，但不编码抗砷酸盐。四环素耐药和氯霉素耐药由DNA大小分别为4.4kb和2.9kb的独立质粒编码。PMS质粒的DNA大小分别为50kb、23.8kb和16.8kb。23.8kb和50kb的质粒也携带抗汞基因。pms质粒的不亲和性包括pI258，编码A类大环内酯类耐药。用限制性内切酶检测PMS质粒23.8kb和16.8kb DNA的片段模式。PMS质粒与pI258之间编码β -内酰胺酶和复制的DNA区域相同，但两者之间的片段差异较大。pI258的非同源10kb区域被称为A组MLS决定子位点，PMS质粒上的4kb区域是PMS决定子位点。16.8kb PMS质粒缺乏抗汞基因，其余区域与23.8kb质粒相同。

Types of macrolide resistance in Staphylococcus aureus are classified into 3 groups, A, B and C. Group A strains are constitutively resistant to macrolides (M), lincosamides (L), and streptogramin Type B antibiotics (S). Group C strains are inducibly resistant to MLS. Group B strains are inducibly resistant to 14-member macrolides and S. We referred to this phenotype as PMS.During a period from 1978 to 1989, 413 PMS-resistant S. aurous strains were isolated in Hungary. They were also resistant to penicillin (99%), tetracycline (79%) and chloramphenicol (63%). Most of them (94%) belonged to the phase type 52-complex, suggesting that they are from the same origin. 43 strains were further examined, and we found that the determinant for PMS phenotype was located on one of 3 kinds of plasmid, which also encoded beta-lactamase production and cadmium ion resistance, but not arsenate resistance. Tetracycline and chloramphenicol resistances were encoded by independent plasmids whose DNA size were 4.4kb and 2.9kb respectively. The DNA size of PMS plasmids was 50kb, 23.8kb or 16.8kb. 23.8kb and 50kb plasmids also carried genes for mercury resistance.The incompatibility of the PMS-plasmids was incl as pI258, which encodes group A macrolide resistance. 23.8kb and 16.8kb DNA of PMS plasmids were examined for their fragment pattern by restriction enzymes. The DNA areas encoding beta-lactamase and replication were the same between PMS plasmids and pI258, but fragments between the 2 areas were quite different. Non-homologous 10kb area of pI258 is known as the site of group A MLS determinants, and 4kb area on PMS plasmids is the site of PMS determinants. 16.8kb PMS plasmid lacked mercury resistance genes, but other area was the same as that of 23.8kb plasmid.