Molecular characterization of resistance to fluoroquinolones in Bartonella henselae and Bartonella quintana.

Only the plasmid from the human E. coli isolate differed in RFLP fingerprint pattern from the other blaCTX-M-2-carrying plasmids. Southern blot hybridization with a blaCTX-M-2 probe revealed a .10 kb EcoRI fragment in the plasmids from the porcine and broiler E. coli isolates and from the Salmonella Virchow CODA-1 isolate. Two EcoRI fragments of 6 and 10 kb were found in the plasmid from the human E. coli isolate and in the plasmid from the Salmonella Virchow 142-1 isolate. For the blaCTX-M-15-carrying plasmids, results of RFLP analysis were identical except for the plasmid from the human E. coli strain. For the animal strains, Southern blot hybridization with a blaCTX-M-15 probe revealed two EcoRI fragments of 6.5 and 7 kb and one 5 kb PstI fragment. The plasmid from the human E. coli strain showed 5 and .10 kb EcoRI fragments and a 5.5 kb PstI fragment. The Southern blot results suggest the existence of two copies of the tested ESBLs on their 150 kb plasmids. The differences seen in the RFLP analyses for the blaCTX-M-2and blaCTX-M-15-carrying plasmids may possibly reflect the rapid evolution of these plasmids as they were exposed to different environmental stresses. The human, porcine and poultry environments may be experienced by bacteria in different ways. In summary, ESBL resistance plasmids appear to move readily between different microorganisms and different ecosystems. TEM-52-carrying cephalosporin-resistant organisms may have been transmitted from food animals to humans, or vice versa. For the CTX-M-2or CTX-M-15-carrying cephalosporinresistant organisms, exchange between food animals and humans, however, remains unclear, mainly due to the unknown plasticity and evolutionary speed of the plasmids carrying them.