OBJECTIVE. Evaluation of the in vitro activity of new fluoroquinolones, cephalosporins and carbapenems against gram-negative bacteria. MATERIAL AND METHOD. A total of 569 clinical isolates were obtained from inpatients at São Paulo Hospital - UNIFESP/EPM in June and July of 1992. The species distribution was as follows: Enterobacter sp. (62), Escherichia coli (308), Klebsiella pneumoniae (27), Klebsiella sp. (9), Proteus mirabilis (23), Pseudomonas aeruginosa (88), Pseudomonas sp. (4), Serratia sp. (30) and other gram-negatives (7). Susceptibility tests were performed by broth microdilution. The antimicrobials agents tested were: ciprofloxacin, ofloxacin, levofloxacin, grepafloxacin, DU 6859-a, ceftazidime, cefepime, FK 037, imipenem, meropenem and biapenem. RESULTS. DU 6859-a showed the highest antimicrobial activity among the fluoroquinolones. It was two- to four-fold more active than ciprofloxacin against some species. The potency and antimicrobial spectrum were similar between the fourth-generation cephalosporins against Enterobacteriaceae, except for Enterobacter sp. strains which were more susceptible to cefepime than they were to cefetazidime or FK 037. When testing Pseudomonas aeruginosa, ceftazidime was slightly more active than the other cephalosporins. Against Enterobacteriaceae and Pseudomonas aeruginosa strains, meropenem was more active than imipenem or biapenem. In addition, the percentage of strains, susceptible to meropenem was higher than the percentage susceptible to the other cerbapenems against these species. CONCLUSION. The new antimicrobial agents demonstrated in vitro activity higher than that of agents commercially avaliable. However, more studies are necessary to further evaluate the in vivo activity and the clinical benefit of these compounds.
In vitro activity; Gram-negative bacteria; Fluoroquinolones; Cephalosporins; Carbapenems
