Evaluation of a synergistic combination between the non-antibiotic microbicides diclofenac and trifluoperazine

Repositioning of non-antibiotic drugs as an alternative to microbial resistance: a systematic review

The global spread of microbial resistance coupled with high costs and slow pace in the discovery of a new antibiotic have made drug repositioning an attractive and promising alternative in the treatment of infections caused by multidrug resistant (MDR) microorganisms. The reuse involves the production of compounds with lower costs and development time, using diversified production technologies. The present systematic review aimed to present a selection of studies published in the last 20 years, which report the antimicrobial activity of non-antibiotic drugs that are candidates for repositioning, which could be used against the current microbial multidrug resistance. A search was performed in the PubMed, SciELO and Google Scholar databases using the following search strategies: [(drug repurposing) OR (drug repositioning) OR (repositioning) AND (non-antibiotic) AND (antibacterial activity) AND (antimicrobial activity)]. Overall, 112 articles were included, which explored the antimicrobial activity in antidepressants, antihypertensives, anti-inflammatories, antineoplastics, hypoglycemic agents, among other drugs. It was concluded that they have significant antimicrobial activity in vitro and in vivo, against standard strain and clinical isolates (Gram-negative and Gram-positive) and fungi. When associated with antibacterials, most of these drugs had their antibacterial activity enhanced. It was also a consensus of the studies included in this review that the presence of aromatic rings in the molecular structure contributes to antimicrobial activity. This review highlights the potential repositioning of several classes of non-antibiotic drugs as promising candidates for repositioning in the treatment of severe bacterial infections of MDR bacteria, extensively resistant (XDR) and pan-resistant (PDR) to drugs.

Alterations in the transcriptome and antibiotic susceptibility of Staphylococcus aureus grown in the presence of diclofenac

Background

Diclofenac is a non-steroidal anti-inflammatory drug (NSAID) which has been shown to increase the susceptibility of various bacteria to antimicrobials and demonstrated to have broad antimicrobial activity. This study describes transcriptome alterations in S. aureus strain COL grown with diclofenac and characterizes the effects of this NSAID on antibiotic susceptibility in laboratory, clinical and diclofenac reduced-susceptibility (Dc^RS) S. aureus strains.

Methods

Transcriptional alterations in response to growth with diclofenac were measured using S. aureus gene expression microarrays and quantitative real-time PCR. Antimicrobial susceptibility was determined by agar diffusion MICs and gradient plate analysis. Ciprofloxacin accumulation was measured by fluorescence spectrophotometry.

Results

Growth of S. aureus strain COL with 80 μg/ml (0.2 × MIC) of diclofenac resulted in the significant alteration by ≥2-fold of 458 genes. These represented genes encoding proteins for transport and binding, protein and DNA synthesis, and the cell envelope. Notable alterations included the strong down-regulation of antimicrobial efflux pumps including mepRAB and a putative emrAB/qacA-family pump. Diclofenac up-regulated sigB (σ^B), encoding an alternative sigma factor which has been shown to be important for antimicrobial resistance. Staphylococcus aureus microarray metadatabase (SAMMD) analysis further revealed that 46% of genes differentially-expressed with diclofenac are also σ^B-regulated. Diclofenac altered S. aureus susceptibility to multiple antibiotics in a strain-dependent manner. Susceptibility increased for ciprofloxacin, ofloxacin and norfloxacin, decreased for oxacillin and vancomycin, and did not change for tetracycline or chloramphenicol. Mutation to Dc^RS did not affect susceptibility to the above antibiotics. Reduced ciprofloxacin MICs with diclofenac in strain BB255, were not associated with increased drug accumulation.

Conclusions

The results of this study suggest that diclofenac influences antibiotic susceptibility in S. aureus, in part, by altering the expression of regulatory and structural genes associated with cell wall biosynthesis/turnover and transport.

Activity of diclofenac used alone and in combination with streptomycin against Mycobacterium tuberculosis in mice

The non-steroidal anti-inflammatory drug diclofenac (DCL) shows noteworthy in vitro and in vivo antimycobacterial activity. The aim of this study was to ascertain whether DCL used in combination with the first-line antitubercular antibiotic streptomycin (STM) synergistically augments its efficacy in vitro as well as in a murine tuberculosis infection model. In vitro minimum inhibitory concentrations (MICs) and synergistic activities of the drugs with respect to standard strains and clinical isolates of Mycobacterium tuberculosis were determined. Swiss albino male mice were intravenously infected with 2.3x10(7) M. tuberculosis H37Rv. Mice were treated with DCL or STM alone as well as in combination for 4 weeks to determine the survival rate, spleen weight and colony-forming unit (CFU) counts in the lungs and spleen. DCL was bactericidal at 40 microg/mL (4xMIC) against M. tuberculosis H37Rv and was synergistic with STM in vitro (fractional inhibitory concentration index 0.37). A dose of 10 microg/g/day DCL or 150 microg/g/day STM for 4 weeks, administered from 1 day post infection, significantly (P<0.05) lowered bacterial counts and reduced mean spleen weight of mice compared with untreated animals. Simultaneous administration of both agents further decreased CFU counts (P<0.05) in the lungs and spleen compared with mice receiving STM alone. Thus, the ability of extended antibiotic therapy may be improved with the help of this synergistic drug pair in murine tuberculosis, and further investigations may throw light on new directions to combat multidrug-resistant tuberculosis infections in humans.

Antibacterial property of the antipsychotic agent prochlorperazine, and its synergism with methdilazine

The antipsychotic drug prochlorperazine was screened in vitro for possible antimicrobial property against 157 strains of bacteria, belonging to gram positive and gram negative genera. The minimum inhibitory concentration (MIC) of prochlorperazine was determined by agar dilution method, which ranged from 25 to 200 microg/ml with respect to most of the strains. Based on such findings, a further study was undertaken to determine whether the efficacy of this drug could be enhanced in the presence of an antihistaminic agent methdilazine, reported to have remarkable antimicrobial action. Four bacterial strains, sensitive to prochlorperazine as well as to three antibacterial chemotherapeutics, viz., methdilazine, fluphenazine and thioridazine were chosen. Disc diffusion tests with prochlorperazine and methdilazine revealed marked synergism between the combination, compared to their individual effects. The synergism was found to be statistically significant (p<0.01). To assess the degree of synergism, the checkerboard analysis was performed. The FIC index of this combination turned out to be 0.37, which confirmed synergism. Therefore, this synergistic drug combination might open a new therapeutic approach to combat drug-resistance in bacterial infections.

Evaluation of synergism between the aminoglycoside antibiotic streptomycin and the cardiovascular agent amlodipine

Amlodipine, a cardiovascular drug, exhibited remarkable antibacterial action in vitro against 504 bacterial strains belonging to both Gram positive and Gram negative genera, as well as in vivo against a mouse-virulent bacterium. Based on such findings, the present study was undertaken to determine whether the efficacy of this non-antibiotic drug could be enhanced in the presence of any antibiotic. Twelve bacterial strains, sensitive to amlodipine as well as to 6 antibiotics, viz., benzyl penicillin, streptomycin, chloramphenicol, tetracycline, erythromycin and ciprofloxacin were chosen. Disc diffusion test with amlodipine and streptomycin revealed marked synergism between the combination, compared with their individual effects. The synergism was found to be statistically significant (p<0.01). To assess the degree of synergy, the checkerboard analysis was performed. The fractional inhibitory concentration (FIC) index of this combination turned out to be 0.24, which confirmed synergism. This antibiotic-non-antibiotic pair was then administered to mice, challenged with S. typhimurium to determine whether this was effective in vivo. Statistical analysis of the mouse protection tests suggested that the combination was highly synergistic (p<0.001), according to Student's t-test. This synergistic drug combination may help us in enhancing the scope of prolonged antibiotic therapy in various types of infections, and might open a new therapeutic approach to combat drug resistance in bacterial diseases.

In Vitro and In Vivo Synergism between Tetracycline and the Cardiovascular Agent Oxyfedrine HCl against Common Bacterial Strains

The cardiovascular drug oxyfedrine HCl revealed noteworthy in vitro antibacterial action against 501 strains of Gram positive and Gram negative bacteria. It also offered significant protection to mice challenged with a mouse-virulent bacterial strain. Prompted by such results, the present study was carried out to ascertain whether this drug could augment the efficiency of an antibiotic when used in combination with it. For this purpose, ten bacterial strains were selected, which were sensitive to oxyfedrine as well as to six antibiotics, like benzyl penicillin, chloramphenicol, ciprofloxacin, erythromycin, streptomycin and tetracycline. Distinct and statistically significant (p<0.01) synergism was observed between oxyfedrine and tetracycline by disc diffusion tests, compared with their individual effects. The fractional inhibitory concentration (FIC) index of this combination, evaluated by checkerboard analysis, was 0.37, which confirmed synergism between the pair. This synergistic drug duo was further dispensed to infected mice. The results of the mouse-protection tests advocated that the combination was significantly synergistic (p<0.0001), according to Student's 't' test. Hence, the capacity of extended antibiotic therapy in several microbial diseases may be improved with the help of this synergistic drug pair, and the study might throw light on newer directions to contest drug-resistant bacterial infections.