Synergistic Effect of Tazobactam on Amikacin MIC in Acinetobacter baumannii Isolated from Burn Patients in Tehran, Iran

Synergistic Antibacterial Activity of 1-Methyl Ester-Nigericin and Methyl 5-(Hydroxymethyl) Furan-2-Carboxylate Against Proteus spp

<b>Background and Objective:</b> Synergistic combinations of antimicrobial agents with different mechanisms of action are successful approaches for combating bacterial infections. This study aimed to evaluate the synergistic effect of 1-methyl ester-nigericin <b>(1)</b> and methyl 5-(hydroxymethyl) furan-2-carboxylate <b>(2)</b> against <i>Proteus</i> spp., isolates. <b>Materials and Methods:</b> The synergistic antimicrobial activity of the compounds was tested by the checkerboard method and time-kill curves. To estimate the interaction between the compounds, the Fractional Inhibitory Concentration Index (FICI) of the combination was calculated. The cytotoxic activity of the compounds in combination was determined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay on LLC-MK2 cell lines. The reduction percentage of biofilms was obtained using the colourimetric method. <b>Results:</b> The MIC values for compounds <b>1</b> and <b>2</b> against test bacteria ranged from 39.06-78.12 μg mL<sup>1</sup> and from 78.12-156.25 μg mL<sup>1</sup>, respectively. The MIC was reduced to 1-8th as a result of the combination of compounds <b>1</b> and <b>2</b>. After 4-24 hrs of treatment with ½ MIC of compounds <b>1</b> and <b>2</b>, the killing rate (in CFU mL<sup>1</sup>) increased to a greater degree than observed with either test compound alone. The combination of compounds <b>1</b> and <b>2</b> showed a synergistic effect with FICI of 0.50 and 0.28. The synergistic combination of compounds <b>1</b> and <b>2</b> was effective on the biofilm reduction of <i>Proteus</i> <i>vulgaris</i> NP16 (85.72%) and NP47 (89.14%). <b>Conclusion:</b> This study recommends compounds <b>1</b> and <b>2</b> in combination as a potential alternative treatment agent for <i>Proteus</i> spp. infections.

Virulence Potential and Treatment Options of Multidrug-Resistant (MDR) Acinetobacter baumannii

Acinetobacter baumannii is an opportunistic pathogen which is undoubtedly known for a high rate of morbidity and mortality in hospital-acquired infections. A. baumannii causes life-threatening infections, including; ventilator-associated pneumonia (VAP), meningitis, bacteremia, and wound and urinary tract infections (UTI). In 2017, the World Health Organization listed A. baumannii as a priority-1 pathogen. The prevalence of A. baumannii infections and outbreaks emphasizes the direct need for the use of effective therapeutic agents for treating such infections. Available antimicrobials, such as; carbapenems, tigecycline, and colistins have insufficient effectiveness due to the appearance of multidrug-resistant strains, accentuating the need for alternative and novel therapeutic remedies. To understand and overcome this menace, the knowledge of recent discoveries on the virulence factors of A. baumannii is needed. Herein, we summarized the role of various virulence factors, including; outer membrane proteins, efflux pumps, biofilm, penicillin-binding proteins, and siderophores/iron acquisition systems. We reviewed the recent scientific literature on different A. baumannii virulence factors and the effective antimicrobial agents for the treatment and management of bacterial infections.