Oshima T, Miyachi H, Fusegawa H, Masukawa A, Ikeda M, Ando Y
Central Clinical Laboratory, Tokai University Hospital, Isehara.
Rinsho Byori. 1993 Jul;41(7):773-8.
In the treatment of methicillin-resistant Staphylococcus aureus (MRSA) infection, rapid detection of MRSA is extremely important. The mecA gene codes the new drug resistant polypeptides called penicillin-binding protein 2a (PBP2a) or 2'(PBP2'), which mediates the clinically relevant resistance to all beta-lactam antibiotics. This gene could be beneficial in the detection of MRSA using the polymerase chain reaction (PCR). However, the identical mecA gene has been found in both coagulase-positive and coagulase-negative Staphylococcus with the appropriate methicillin-resistant phenotype. The second gene related to the expression of methicillin-resistance has been called femA. In this study, we amplified both mecA and femA genes by PCR in 97 strains and 32 clinical specimens. The mecA gene was positive in all 63(100%) MRSA strains and 2(6%) of the 34 methicillin-sensitive Staphylococcus aureus (MSSA) strains. Two strains with the methicillin-sensitive phenotype and the mecA gene resulted in methicillin-resistance when cultured on an agar plate containing 4.5% NaCl. The mecA gene was also present in all 10(100%) coagulase-negative Staphylococcus strains with the methicillin-resistant phenotype. The femA gene was positive in all 97(100%) MRSA and MSSA strains. On the other hand, the femA gene was absent from coagulase -negative Staphylococcus strains with the methicillin-resistant phenotype. Although the mechanism by which the product of femA gene influences the expression of methicillin-resistance is unknown, the gene appears to be restricted only in coagulase-positive Staphylococcus, regardless of methicillin-resistance. In conclusion, in vitro enzymatic amplification of both mecA and femA genes would lead to rapid and definite diagnosis of the MRSA infection.
在耐甲氧西林金黄色葡萄球菌（MRSA）感染的治疗中，快速检测MRSA极为重要。mecA基因编码名为青霉素结合蛋白2a（PBP2a）或2'（PBP2'）的新型耐药多肽，该多肽介导对所有β-内酰胺类抗生素的临床相关耐药性。该基因在利用聚合酶链反应（PCR）检测MRSA方面可能具有重要作用。然而，在具有适当耐甲氧西林表型的凝固酶阳性和凝固酶阴性葡萄球菌中均发现了相同的mecA基因。与耐甲氧西林表达相关的第二个基因被称为femA。在本研究中，我们通过PCR对97株菌株和32份临床标本中的mecA和femA基因进行了扩增。在所有63株（100%）MRSA菌株以及34株甲氧西林敏感金黄色葡萄球菌（MSSA）菌株中的2株（6%）中，mecA基因呈阳性。两株具有甲氧西林敏感表型且mecA基因阳性的菌株，在含有4.5%氯化钠的琼脂平板上培养时表现出甲氧西林耐药性。在所有10株（100%）具有耐甲氧西林表型的凝固酶阴性葡萄球菌菌株中也存在mecA基因。femA基因在所有97株（100%）MRSA和MSSA菌株中均呈阳性。另一方面，具有耐甲氧西林表型的凝固酶阴性葡萄球菌菌株中不存在femA基因。尽管femA基因产物影响耐甲氧西林表达的机制尚不清楚，但该基因似乎仅局限于凝固酶阳性葡萄球菌中，无论其是否耐甲氧西林。总之，体外酶促扩增mecA和femA基因将有助于快速、明确地诊断MRSA感染。
