Susceptibility to -lactams and quinolones of Enterobacteriaceae isolated from urinary tract infections in outpatients

The antibiotic susceptibility profile was evaluated in 71 Enterobacteriaceae isolates obtained from outpatient urine cultures in July 2010 from two health institutions in Santa Fe, Argentina. The highest rates of antibiotic resistance were observed for ampicillin (AMP) (69%), trimethoprim/sulfametho-xazole (TMS) (33%), and ciprofloxacin (CIP) (25%). Meanwhile, 21 % of the isolates were resistant to three or more tested antibiotics families. Thirty integron-containing bacteria (42.3%) were de-tected, and a strong association with TMS resistance was found. Third generation cephalosporin re-sistance was detected in only one Escherichia coli isolate, and it was characterized as a blaCMY-2 carrier. No plasmid-mediated quinolone resistance (PMQR) was found. Resistance to fluoroquino-lone in the isolates was due to alterations in QRDR regions. Two mutations in GyrA (S83L, D87N) and one in ParC (S80I) were observed in all CIP-resistant E. coli. It was determined to be the main phylogenetic groups in E. coli isolates. Minimum Inhibitory Concentration (MIC) values against nalidixic acid (NAL), levofloxacin (LEV), and CIP were determined for 63 uropathogenic E. coli iso-lates as MIC50 of 4 g/mL, 0.03125 g/mL, and 0.03125 g/mL, respectively, while the MIC90 val-ues of the antibiotics were determined as 1024 g/mL, 64 g/mL, and 16 g/mL, respectively. An association between the phylogenetic groups, A and B1 with fluoroquinolone resistance was ob-served. These results point to the importance of awareness of the potential risk associated with empir-ical treatment with both the families of antibiotics. Key words: urine tract infection, outpatient, -lactam resistance, fluoroquinolone resistance, inte-grons