Synergistic Combination of Carbapenems and Colistin against P. aeruginosa and A. baumannii

Abstract

Background: Intubated patients are particularly at risk of developing infections caused by these pathogens, specifically, P. aeruginosa and A. baumannii. In the past fifteen years, Carbapenems were known to be the drugs of choice for these bacteria. With the increase in the use and misuse of antibiotics, these bacteria became highly resistant, and almost all available antibiotics, including Carbapenems, became inefficient. Synergistic combination therapy may be a useful strategy in slowing as well as overcoming the emergence of resistance. The aim of this study was to evaluate the antibacterial activity on P. aeruginosa and A. baumannii of the combination of two antibiotics: Colistin and a Carbapenem (Meropenem or Imipenem). Methods: The antibacterial activity was assessed by determining the MIC. Then, the effect of combining the antibiotics was studied using the Checkerboard Technique described by White et al., 1996. The Fractional Inhibitory Concentration (FIC) for each strain was then calculated and classified as synergy, additive, indifference or antagonism. 11 strains of A. baumannii and 11 strains of P. aeruginosa were tested in the presence of Meropenem combined with Colistin or Imipenem combined with Colistin. Results: For the combination of Meropenem and Colistin, 6 strains of A. baumannii and 3 strains of P. aeruginosa showed synergy while 5 strains of A. baumannii and 7 strains of P. aeruginosa showed additive effect, only 1 strain of P. aeruginosa showed antagonism. For Imipenem and Colistin, only 1 strain of A. baumannii and 3 strains of Pseudomonas showed synergy while 8 strains of Acinetobacter and 8 strains of Pseudomonas showed additive effect. Conclusion: The "in vitro" combination Colistin-Carbapenem is associated with an improvement in MIC. In the majority of the cases, this improvement suggests a synergistic combination or an additive effect.

Effect of Antibiotic Combinations on the Sensitivity of Carbapenem Resistant Acinetobacter baumannii Strains

“…On the other hand, (13%) of A. baumannii isolates showed synergistic effect to imipenem/colistin combination and (87%) showed an additive effect. These results are consistent with results obtained by Daoud et al where (54.5%) of A. baumannii isolates showed synergistic effect to meropenem/colistin combination and (45.5%) showed an additive effect [41]. While, (11%) of A. baumannii isolates showed synergistic effect to imipenem/colistin combination and (89%) showed an additive effect.…”

Aerobic bacteriological profile and antimicrobial susceptibility pattern of pus isolates from tertiary care hospital in India

“…Colistin acts on outer membrane of cell wall and creates pores allowing the other drugs to enter into the bacterial cell. Meropenem has bactericidal activity and binds to PBP of cell wall and inhibits cell wall synthesis [26,27].…”

Intravenous Colistin Use for Multidrug-Resistant Gram-Negative Infections in Pediatric Patients

“…The ultimate antibacterial activity and the synergy were regarded with the combination of colistin and meropenem therapy (26), for this reason carbapenem was the most frequently used antibiotic in our study. However in some cases because of different indications, we had to use quinolones despite we did not use preferential this agent under 18 years old.…”