الملخص

ABSTRACT Detection of β–lactamases was conducted in Rhizobium leguminosarum biovar viciae isolated from root nodules of Vicia faba L.. Acidimetric method was used to detect the occurrence of β–lactamases in general, the isolate gave a positive result. Detection of extended–spectrum β–lactamase (ESBLs) was also performed using two methods; double disk synergy method and the method of National Committee for Clinical Laboratory Standards (NCCLS). The isolate gave a positive results too. R. leguminosarum biovar viciae also showed a resistance to cefoxitin, which consider a primary evidence for being a potential producer of AmpC β–lactamase. The results clearly indicated the occurrence of more than one type of β–lactamases in the tested isolate, which might be used as a defensive mean for survival and resisting β–lactams antibiotics in the surrounding soil.