The in-vitro activity of ciprofloxacin, imipenem and rifampicin, singly, and in two and three drug combinations was evaluated against 16 isolates of Pseudomonas cepacia. All 16 isolates were resistant to rifampicin; nine isolates were susceptible to ciprofloxacin; six were susceptible and seven had intermediate susceptibility to imipenem. The imipenem and rifampicin combination was synergistic for one of 16, imipenem and ciprofloxacin synergistic for seven of 16 and the three antibiotic combination was synergistic for 12 of 16 isolates. The three antibiotic combination demonstrated synergism with two isolates which were resistant to all three drugs. Combinations of two and three antibiotics resulted in enhanced killing of P. cepacia in this in-vitro study.
The in vitro susceptibility of Haemophilus influenzae type b to rifampin, cefotaxime, ceftazidime, ceftriaxone and cefuroxime was examined at inocula of 10(5) and 10(7) CFU/ml. Time-kill curves were then obtained using antibiotic concentrations at one-half the MIC for each drug at the two inocula with combinations of rifampin plus each of the cephalosporins. There was a pronounced inoculum effect with all of the cephalosporins except for cefuroxime, but the MIC values were also higher for the latter drug. The rare failure of some cephalosporins to promptly sterilize the cerebrospinal fluid in meningitis should encourage investigation of the relationship between the inoculum effect, minimum bactericidal concentration and cerebrospinal fluid antibiotic levels in these clinical situations. A marked synergistic effect was noted for most of the isolates, and therefore, cephalosporin-rifampin combinations might show clinical utility.
For 16 isolates of Pseudomonas cepacia from patients with cystic fibrosis, synergism was determined by the killing curve method, utilizing various combinations of antibiotics [ticarcillin (Ti), rifampin (Ri), tobramycin (To), imipenem (Im), ofloxacin (Of), polymyxin B (PB), and trimethoprim/sulfamethoxazole (SxT)]. All 16 isolates were resistant to Ti, To, Ri, and PB; 11 were sensitive to S x T, 13 were sensitive to Im, and 2 were sensitive to Of. The combination of Im/Ri was synergistic for 8 isolates. Several combinations (Ti/Ri/Im), (Ti/Im/To), (Ri/Im/To) also demonstrated synergism for these 8 isolates. The Im/Ri combination did not demonstrate synergism against the other 8 isolates. The Ti/Im/To combination was synergistic for 6 of these. The Ri/ Im/To combination was synergistic for 5 and the Ti/Im/Ri combination was synergistic for 3. Synergism could also be demonstrated with several 4-drug combinations. This study suggests that multi-drug combinations may have a role in the treatment of P. cepacia infections if proven in clinical studies.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.