Turbidity and Colony Count of Acinetobacter baumannii suspensions after meropenem-based antibiotic combination exposure

Background: Carbapenems are the treatment of choice for
multidrug-resistant (MDR) A. baumannii infection but are inadequate for
carbapenem-resistant A.baumannii (CRAB) infections. Combination therapy
came into the spotlight in the last decade. This study compares the colony
count reduction after exposure to meropenem-based antibiotics in
clinically achieved concentration with the time-kill test. Results: A
bactericidal effect was achieved in isolates that were intermediate to
ampicillin sulbactam at the administration of meropenem and
ampicillin-sulbactam with a 2 MIC + 2 MIC. The combination of meropenem
and ampicillin-sulbactam showed a bacteriostatic effect in isolates
resistant to both antibiotics. The bactericidal effect was not achieved
when meropenem and amikacin were administered to isolates that were
intermediate or resistant to meropenem and amikacin. Conclusion: There is
a significant difference in the colony count reduction between groups of
A. baumannii isolates after exposure to antibiotic combinations.