Ayala Juan, Quesada Alberto, Vadillo Santiago, Criado Jerónimo, Píriz Segundo
`'Severo Ochoa'' Molecular Biology Centre, CSIC-UAM, 28049 Cantoblanco, Madrid, Spain 2,3Biochemistry, Molecular Biology and Genetics Department2, and Medicine and Animal Health Department3, University of Extremadura, 10071 Cáceres, Spain.
J Med Microbiol. 2005 Nov;54(Pt 11):1055-1064. doi: 10.1099/jmm.0.45930-0.
In this study penicillin-binding proteins (PBPs) of Bacteroides fragilis and the resistance mechanisms of this micro-organism to 11 beta-lactam antibiotics were analysed. The study focused on the role of PBP2Bfr and metallo-beta-lactamase in the mechanism of resistance to imipenem. The mechanism of beta-lactam resistance in B. fragilis was strain dependent. The gene encoding the orthologue of Escherichia coli PBP3 gene (pbpBBfr, which encodes the protein PBP2Bfr) was sequenced in five of the eight strains studied, along with the ccrA (cfiA) gene in strain 119, and their implications for resistance were examined. Differences were found in the amino-acid sequence of PBP2Bfr in strains AK-2 and 119, and the production of beta-lactamases indicated that these differences may be involved in the mechanism of resistance to imipenem. In vitro binding competition assays with membrane extracts using imipenem indicated that the PBP that bound imipenem with the highest affinity was PBP2Bfr, and that increased affinity in strain 7160 may be responsible for the moderate susceptibility of this strain to imipenem. In the same way, the importance of the chromosomal class A beta-lactamase CepA in the resistance mechanism of the B. fragilis strains NCTC 9344, 7160, 2013E, AK-4, 0423 and R-212 was studied. In these strains this is the principal resistance mechanism to antimicrobial agents studied other than imipenem.
在本研究中，分析了脆弱拟杆菌的青霉素结合蛋白（PBPs）以及该微生物对11种β-内酰胺抗生素的耐药机制。该研究聚焦于PBP2Bfr和金属β-内酰胺酶在对亚胺培南耐药机制中的作用。脆弱拟杆菌中β-内酰胺耐药机制具有菌株依赖性。在所研究的8个菌株中的5个菌株中，对编码大肠杆菌PBP3基因直系同源物的基因（pbpBBfr，其编码蛋白PBP2Bfr）进行了测序，同时对菌株119中的ccrA（cfiA）基因进行了测序，并研究了它们对耐药性的影响。在菌株AK-2和119中发现了PBP2Bfr氨基酸序列的差异，β-内酰胺酶的产生表明这些差异可能参与了对亚胺培南的耐药机制。使用亚胺培南对膜提取物进行的体外结合竞争试验表明，与亚胺培南结合亲和力最高的PBP是PBP2Bfr，菌株7160中亲和力的增加可能是该菌株对亚胺培南中度敏感的原因。同样，研究了染色体A类β-内酰胺酶CepA在脆弱拟杆菌菌株NCTC 9344、7160、2013E、AK-4、0423和R-212耐药机制中的重要性。在这些菌株中，这是除亚胺培南外所研究抗菌药物的主要耐药机制。
