Abstract

Background: The growing incidence of multidrug resistant (MDR) bacterial infections has become a public health crisis. This work aims to evaluate the in-vitro activity of silver nanoparticles (AgNPs), alone and in combination with the antimicrobials amikacin and ceftazidime, against MDR Gram-negative bacilli (GNB) isolated from clinical cases in Zagazig University Hospitals. Methods: In a cross sectional study, MDR GNB were isolated from different clinical specimens and were tested to determine the minimal inhibitory concentration (MIC), minimal bactericidal concentration (MBC) and bactericidal activity of AgNPs using broth microdilution method. The effect of combining subMIC levels of AgNPs (MIC/2 and MIC/4) with amikacin and ceftazidime, was also determined by broth microdilution. Results: A total of 63 MDR GNB was obtained during the study period (22 E. coli, 17 Klebsiella, 15 Pseudomonas aeruginosa and 9 Acinetobacter isolates). AgNPs demonstrated a bactericidal effect on all tested isolates with an MBC/MIC ratio of less than 4. When combined with amikacin, a synergistic effect was demonstrated on all tested E.coli and Klebsiella isolates at AgNPs MIC/2 and on 45.4%, 40% and 77.8% of E.coli, P.aeruginosa and Acinetobacter isolates, respectively at MIC/4. In combination with ceftazidime, AgNPs exhibited a synergistic effect on 100% of E. coli and 88.2% Klebsiella at both MIC/2 and MIC/4 and on 40% of P. aeruginosa isolates at AgNPs MIC/4. Conclusions: AgNPs exert a bactericidal activity on MDR GNB as well as a synergistic effect when combined with amikacin and ceftazidime suggesting them as a new weapon in the war against MDR GNB.

Highlights

  • Antimicrobial resistance in bacteria, especially in Gram negative bacilli (GNB), is a frightening problem that threatens the treatment and outcome of healthcare acquired infections increasing mortality rates and causing massive economic loss to both patient and nation [1]

  • Among metallic NPs, silver NPs (AgNPs) gained much of interest owing to their powerful antimicrobial properties [8]. As data concerning this issue is limited in our hospital, this study aims to evaluate the in-vitro activity of AgNPs, alone and in combination with other antimicrobials, against multidrug resistant (MDR) Gram-negative bacilli (GNB) isolated from clinical cases in Zagazig University Hospitals

  • This study aimed to detect the antibacterial activity of spherical AgNPs with an average size of 20±5 nm against MDR GNB isolates from nosocomial infections in Zagazig University Hospitals and to investigate the effect of combination between AgNPs and two antibiotics against the isolated MDR GNB

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Summary

Introduction

Antimicrobial resistance in bacteria, especially in Gram negative bacilli (GNB), is a frightening problem that threatens the treatment and outcome of healthcare acquired infections increasing mortality rates and causing massive economic loss to both patient and nation [1]. AgNPs MIC/2 (S1) ranged between 1 and 8 μg/ml, while MIC/4 (S2) ranged between 0.5 and 4 μg/ml. *FICI; Fractional inhibitory concentration index, IN; indifference, PS; partially synergistic, S; synergistic, AD; additive

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