Dataset Information

Combination Susceptibility Testing of Common Antimicrobials in Vitro and the Effects of Sub-MIC of Antimicrobials on Staphylococcus aureus Biofilm Formation.

ABSTRACT: The current study was conducted to evaluate the antibacterial combination efficacies, and whether the sub-inhibitory concentrations (sub-MIC) of antibiotics can influent on the biofilm formation of S. aureus. The minimum inhibitory concentration (MIC) of common antibacterial drugs was determined in vitro against clinical isolates of Staphylococcus aureus (S. aureus), Escherichia coli (E. coli), and Pasteurella multocida (P. multocida) alone and in combination with each other by using the broth microdilution method and the checkerboard micro-dilution method analyzed with the fractional inhibitory concentration index (FICI), respectively. Regarding these results, antibacterial drug combinations were categorized as synergistic, interacting, antagonistic and indifferent, and most of the results were consistent with the previous reports. Additionally, the effects of sub-MIC of seven antimicrobials (kanamycin, acetylisovaleryltylosin tartrate, enrofloxacin, lincomycin, colistin sulfate, berberine, and clarithromycin) on S. aureus biofilm formation were determined via crystal violet staining, scanning electron microscopy (SEM) and real-time PCR. Our results demonstrate that all antibiotics, except acetylisovaleryltylosin tartrate, effectively reduced the S. aureus biofilm formation. In addition, real-time reverse transcriptase PCR was used to analyze the relative expression levels of S. aureus biofilm-related genes such as sarA, fnbA, rbf, lrgA, cidA, and eno after the treatment at sub-MIC with all of the six antimicrobials. All antibiotics significantly inhibited the expression of these biofilm-related genes except for acetylisovaleryltylosin tartrate, which efficiently up-regulated these transcripts. These results provide the theoretical parameters for the selection of effective antimicrobial combinations in clinical therapy and demonstrate how to correctly use antibiotics at sub-MIC as preventive drugs.

SUBMITTER: Yang B

PROVIDER: S-EPMC5671985 | biostudies-literature | 2017

REPOSITORIES: biostudies-literature

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Combination Susceptibility Testing of Common Antimicrobials in Vitro and the Effects of Sub-MIC of Antimicrobials on Staphylococcus aureus Biofilm Formation.

Yang Bing B Lei Zhixin Z Zhao Yishuang Y Ahmed Saeed S Wang Chunqun C Zhang Shishuo S Fu Shulin S Cao Jiyue J Qiu Yinsheng Y

Frontiers in microbiology 20171101

The current study was conducted to evaluate the antibacterial combination efficacies, and whether the sub-inhibitory concentrations (sub-MIC) of antibiotics can influent on the biofilm formation of S. aureus. The minimum inhibitory concentration (MIC) of common antibacterial drugs was determined in vitro against clinical isolates of Staphylococcus aureus (S. aureus), Escherichia coli (E. coli), and Pasteurella multocida (P. multocida) alone ...[more]

PMID: 29163415

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Project description:Biofilm-associated polymicrobial infections, particularly those involving fungi and bacteria, are responsible for significant morbidity and mortality and tend to be challenging to treat. Candida albicans and Staphylococcus aureus specifically are considered leading opportunistic fungal and bacterial pathogens, respectively, mainly due to their ability to form biofilms on catheters and indwelling medical devices. However, the impact of mixed-species biofilm growth on therapy remains largely understudied. In this study, we investigated the influence of C. albicans secreted cell wall polysaccharides on the response of S. aureus to antibacterial agents in biofilm. Results demonstrated significantly enhanced tolerance for S. aureus to drugs in the presence of C. albicans or its secreted cell wall polysaccharide material. Fluorescence confocal time-lapse microscopy revealed impairment of drug diffusion through the mixed biofilm matrix. Using C. albicans mutant strains with modulated cell wall polysaccharide expression, exogenous supplementation, and enzymatic degradation, the C. albicans-secreted ?-1,3-glucan cell wall component was identified as the key matrix constituent providing the bacteria with enhanced drug tolerance. Further, antibody labeling demonstrated rapid coating of the bacteria by the C. albicans matrix material. Importantly, via its effect on the fungal biofilm matrix, the antifungal caspofungin sensitized the bacteria to the drugs. Understanding such symbiotic interactions with clinical relevance between microbial species in biofilms will greatly aid in overcoming the limitations of current therapies and in defining potential new targets for treating polymicrobial infections.The fungus Candida albicans and the bacterium Staphylococcus aureus are important microbial pathogens responsible for the majority of infections in hospitalized patients and are often coisolated from a host. In this study, we demonstrated that when grown together, the fungus provides the bacterium with enhanced tolerance to antimicrobial drugs. This process was mediated by polysaccharides secreted by the fungal cell into the environment. The biofilm matrix formed by these polysaccharides prevented penetration by the drugs and provided the bacteria with protection. Importantly, we show that by inhibiting the production of the fungal polysaccharides, a specific antifungal agent indirectly sensitized the bacteria to antimicrobials. Understanding the therapeutic implications of the interactions between these two diverse microbial species will aid in overcoming the limitations of current therapies and in defining new targets for treating complex polymicrobial infections.

Project description:Staphylococcus aureus is a major human pathogen, a potential "Super-bug" and a typical biofilm forming bacteria. With usage of large amount of antibiotics, the residual antibiotics in clinical settings further complicate the colonization, pathogenesis and resistance of S. aureus. This study aimed at investigating the phenotypical and global gene expression changes on biofilm formation of a clinical S. aureus isolate treated under different types of antibiotics. Firstly, an isolate Guangzhou-SAU749 was selected from a large sale of previously identified S. aureus isolates, which exhibited weak biofilm formation in terms of biomass and viability. Secondly, 9 commonly prescribed antibiotics for S. aureus infections treatment, together with 10 concentrations ranging from 1/128 to 4 minimum inhibitory concentration (MIC) with 2-fold serial dilution, were used as different antibiotic stress conditions. Then, biofilm formation of S. aureus Guangzhou-SAU749 at different stages including 8 h, 16 h, 24 h, and 48 h, was tested by crystal violet and MTS assays. Thirdly, the whole genome of S. aureus Guangzhou-SAU749 was investigated by genome sequencing on PacBio platform. Fourthly, since enhancement of biofilm formation occurred when treated with 1/2 MIC tetracycline (TCY) and 1/4 MIC streptomycin (STR) since 5 h, the relevant biofilm samples were selected and subjected to RNA-seq and bioinformatics analysis. Last, expression of two component system (TCS) and biofilm associated genes in 4 h, 8 h, 16 h, 24 h, and 48 h sub-MIC TCY and STR treated biofilm samples were performed by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Although most antibiotics lowered the biomass and cell viability of Guangzhou-SAU749 biofilm at concentrations higher than MIC, certain antibiotics including TCY and STR promoted biofilm formation at sub-MICs. Additionally, upon genome sequencing, RNA-seq and RT-qPCR on biofilm samples treated with sub-MIC of TCY and STR at key time points, genes lytR, arlR, hssR, tagA, clfB, atlA and cidA related to TCS and biofilm formation were identified to contribute to the enhanced biofilm formation, providing a theoretical basis for further controlling on S. aureus biofilm formation.

Dataset Information

Combination Susceptibility Testing of Common Antimicrobials in Vitro and the Effects of Sub-MIC of Antimicrobials on Staphylococcus aureus Biofilm Formation.

Publications

Combination Susceptibility Testing of Common Antimicrobials <i>in Vitro</i> and the Effects of Sub-MIC of Antimicrobials on <i>Staphylococcus aureus</i> Biofilm Formation.

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