The Use of Combinations of Antimicrobial Drugs

Comparative Study on the Synergistic Action of Differentially Synthesized Silver Nanoparticles with β-Cephem Antibiotics and Chloramphenicol

“…In our study nonhydrophilic nature of nanosilver facilitates the transport of antibiotics (cefazolin, cephalothin, and chloramphenicol) to the cell membrane which consists of phospholipids and glycoprotein ( Figure 9) which are all hydrophobic groups and the synergistic effect may be caused by the bonding reaction between hydroxyl and amido groups of antibiotics and nanosilver; then the antibiotic-silver nanoparticle combination may attach on the cell membrane and result in the lysis of cell wall of bacteria, which was followed by the entry of Ag NPantibiotic combination into the cell and may result in the DNA unwinding and cell death ( Figure 9). Some of the previous work also reported the mechanism of DNA unwinding by the attachment of ampicillin-Ag NP combination on bacterial cell [8]. The effect induced by the silver nanoparticles alone indicated that their antimicrobial effect is not as good as the combination of Ag NPs and antibiotics and the combination of silver nanoparticles are found to be effective at lower concentration.…”

“…Moreover, high surface to volume ratio of silver nanoparticles may contribute to their enhanced antimicrobial properties by increasing the contact surface of silver nanoparticles with the microorganisms. Several studies also suggest that silver nanoparticles, which are well known to have broad spectrum antimicrobial activity against bacteria, virus, and eukaryotic microorganisms [4], interact with the cell membrane and some of them will penetrate the bacterial cell wall, thereby causing the death of bacteria [5,6] Synergistic action is now commonly used to describe an interaction of two antimicrobial agents or occasionally more than two [7], in which the effect produced by the drugs in combination is greater than the sum of their individual effects when the antibiotics are used alone [8]. In another study, Vivekanandan et al proposed that the silver nanoparticles have the ability to destroy the stability of lipopolysacchrides allowing increase in permeability of outer membrane and the peptidoglycan structure, which was recognized and captured by antibiotics (e.g., cephalexin) immediately, and the conjugation of antibiotics with silver nanoparticles makes the resistant strain to become sensitive to cephalexin [9].…”

Synergism of Vancomycin-Gentamicin and Vancomycin-Streptomycin Against Enterococci

“…Briefly, a culture grown ovemight in TSB was diluted with TSB to give approximately 105 to 106 colony-forming units per ml and incubated with different antibiotics in a water bath at 37 C. The final concentrations of antibiotics were as follows: streptomycin, 10 4g/ml; gentamicin, 4 jig/ml; vancomycin, 5 ,ug/ml; vancomycin, 10 1g/ml; vancomycin, 10 Ag/ml, with gentamicin, 4 gg/ml; vancomycin, 5 gg/ml, with gentamicin, 4 Ag/ml; vancomycin, 10 ,g/ml, with streptomycin, 10 ,g/ml; and vancomycin, 5 jig/ml, with streptomycin, 10 1sg/ml. At 6,24, and 48 h of incubation, viable colony-forming units were enumerated by the pour-plate technique with the use of TSA. Colonies on TSA were counted after incubation at 37 C for 48 h.…”

The Demonstration and Significance of Synergism Between -Lactam Antibiotics

“…These aspects will be considered in detail before a discussion of the problem of possible clinical applications of the phenomenon. Synergism is a much-used and much-defined word, and a great deal of controversy exists as to its true meaning, and how best it may be demonstrated (Jawetz, 1968). A merely additive effect seems to be ruled out here by the results of the isobolograms, and the fact that no zones were observed whenever one ,f3-lactam compound was tested against itself (i.e., the same solution-at MNIC-put into all four wells of a paired-hole plate).…”