Minimal Bactericidal Concentration for Biofilms (MBC-B)
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A biofilm is a multicellular consortium of surface associated microbes surrounded by a hydrated, extracellular polymer matrix. The biofilm matrix plays a critical role in preventing desiccation, acquiring nutrients, and provides community protection from environmental assaults. Importantly, biofilms are significantly more resistant to antimicrobials relative to their free-swimming counterparts. The level of antimicrobial tolerance is influenced by a number of factors, including genetic/adaptive resistance mechanisms, stage of biofilm development, and pharmacokinetics of the antibiotic. Here, we describe an in vitro microtiter-based assay to quantify the minimal bactericidal concentration for biofilms (MBC-B) for short exposure times (2 h). This exposure period is significantly shorter than standard over-night and 24-hour treatments described in traditional protocols. This assay was developed to approximate the time an antibiotic is available during a one-time treatment before it is metabolized, sequestered by host proteins, or digested.Keywords:
Minimum bactericidal concentration
Multidrug tolerance
Extracellular polymeric substance
This paper presented the influence of Al(III) on biodegradability, micromorphology, composition and functional groups characteristics of the biofilm extracellular polymeric substances (EPS) during different growth phases. The sequencing batch biofilm reactors were developed to cultivate biofilms under different Al(III) dosages. The results elucidated that Al(III) affected biofilm development adversely at the beginning of biofilm growth, but promoted the biofilm mass and improved the biofilm activity with the growth of the biofilm. The micromorphological observation indicated that Al(III) led to a reduction of the filaments and promotion of the EPS secretion in growth phases of the biofilm, also Al(III) could promote microorganisms to form larger colonies for mature biofilm. Then, the analysis of EPS contents and components suggested that Al(III) could increase the protein (PN) of tightly bound EPS (TB-EPS) which alleviated the metal toxicity inhibition on the biofilm during the initial phases of biofilm growth. The biofilm could gradually adapt to the inhibition caused by Al(III) at the biofilm maturation moment. Finally, through the Fourier transform infrared spectroscopy, it was found that Al(III) was beneficial for the proliferation and secretion of TB-EPS functional groups, especially the functional groups of protein and polysaccharides.
Extracellular polymeric substance
Bacterial growth
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Extracellular polymeric substance
Biofouling
Extracellular polysaccharide
Divalent
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Biofilms are composed of multicellular communities of microbial cells and their self-secreted extracellular polymeric substances (EPS). The viruses named bacteriophages can infect and lyze bacterial cells, leading to efficient biofilm eradication. The aim of this study was to analyze how bacteriophages disrupt the biofilm structure by killing bacterial cells and/or by damaging extracellular polysaccharides, proteins, and DNA. The use of colorimetric and spectrofluorimetric methods and confocal laser scanning microscopy (CLSM) enabled a comprehensive assessment of phage activity against E. faecalis biofilms. The impact of the phages vB_Efa29212_2e and vB_Efa29212_3e was investigated. They were applied separately or in combination on 1-day and 7-day-old biofilms. Phages 2e effectively inhibited the growth of planktonic cells with a limited effect on the biofilm. They did not notably affect extracellular polysaccharides and proteins; however, they increased DNA levels. Phages 3e demonstrated a potent and dispersing impact on E. faecalis biofilms, despite being slightly less effective than bacteriophages 2e against planktonic cells. Phages 3e reduced the amount of extracellular polysaccharides and increased eDNA levels in both 1-day-old and 7-day-old biofilm cultures. Phage cocktails had a strong antimicrobial effect on both planktonic and biofilm-associated bacteria. A significant reduction in the levels of polysaccharides, proteins, and eDNA in 1-day-old biofilm samples was noted, which confirms that phages interfere with the structure of E. faecalis biofilm by killing bacterial cells and affecting extracellular polymer levels.
Extracellular polymeric substance
Enterococcus faecalis
Extracellular polysaccharide
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The azithromycin tablet in Bangladesh maintains standard MIC and MBC. But how much is this assumption is true; this will be evaluated through this research work. This is a cross sectional study to determine the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of selected azithromycin tablet. The collected samples were analyzed according to USP specification. The MICs of azithromycin were determined by broth dilution method. MBCs were determined by the drop plate method from the tubes, where apparently no visible growth found. This study showed that MIC & MBC values of azithromycin tablet found highest against Pseudomonas spp., Shigella spp. and E. coli were > 64.0 mg/ml (micro gram per milliliter) and lowest against B. pumillus was 1.0/2.0 mg/ml. MIC and MBC values higher than that of the peak serum concentration of azithromycin must have chance of therapeutic failure and development of azithromycin tolerance and resistance to the bacteria tested. To evaluate the efficiency of antibiotic there are two factors2. Which influence potential utility of a antibiotics in a specific clinical situation. The first is the measure of potency of the antibiotic for the pathogen in question minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC). The second is relationship between the concentration time profile and potency of the antibiotics. This research work will play an important role to determine the MIC and MBC of selected azithromycin tablet in Bangladesh.
Minimum bactericidal concentration
Serial dilution
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Minimum bactericidal concentration
Disinfectant
Table (database)
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A novel ‘dilution tube method’ (DTM) which is a modification of the ‘dilution method’ (DM) is hereby described for the determination of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). This new DTM uses only broth medium in tubes and the required antibiotic. MIC and MBC for Escherichia coli, Klebsiella pneumoniae and Staphylococcus aureus were determined in tubes by double diluting (or higher dilutions), broths containing gentamicin concentrations that inhibit bacterial growth, and incubating at 37°C for 18 to 24 h. The tube for MIC showed growth and appeared turbid after incubation while that for MBC remained clear. The results obtained using DTM agrees completely with those obtained with DM. The advantages of this novel DTM include the elimination of extra stress, time and costs associated with preparing and inoculating agar medium as done in DM. Key words: Antibiotics, minimum inhibitory concentration, minimum bactericidal concentration, dilution tube method, dilution method.
Minimum bactericidal concentration
Serial dilution
Dilution
Agar dilution
Agar Dilution Method
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The effects of Fe(III) on the biofilm mass and activity, the biofilm micromorphology as well as the composition and functional groups characteristics of extracellular polymeric substances (EPS) in biofilm were investigated in laboratory-scale fixed bed biofilm reactors. The results showed that 2 mg/L of Fe(III) promoted the biofilm mass and improved the biofilm activity, but 16 mg/L of Fe(III) adversely affected biofilm development. Scanning electron microscopy (SEM) study indicated a high concentration (16 mg/L) of Fe(III) led to significant reduction of the filaments, great promotion of the EPS secretion in biofilm. The result of the EPS composition suggested 2 mg/L of Fe(III) increased soluble EPS and loosely bound EPS which contributed to the microbial aggregation, while 16 mg/L of Fe(III) promoted tightly bound EPS production unfavourable for substrate mass transfer. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analysis demonstrated that Fe(III) exerted a significant influence on the -CONH- groups of proteins and the C-O groups of polysaccharides in EPS. This study reveals that Fe(III) influences biofilm development and activity not only by directly impacting the microbial physiology but by indirectly affecting the EPS constituents, and it helps to provide theoretical guidance for iron ion containing wastewater treatment.
Extracellular polymeric substance
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Sloughing
Extracellular polymeric substance
Extracellular polysaccharide
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Through adding different concentration of Cu2+ in the biofilm reactor, the relationship between extracellular polymeric substance(EPS) secreted by biofilm and efficiency of copper removal by biofilm was studied. Biofilm tolerance of Cu2+ was better than activated sludge, but a high concentration of Cu2+ rapidly poisoned the biofilm. When Cu2+2 mg·L?1, Cu2+ inhibited biofilm secretion of EPS. Concentration of 2 mg·L?1Cu2+5 mg·L?1, Cu2+ would increase the amount of EPS, while Cu2+5 mg?L?1, the biofilm system displayed serious instability. Comparing proteins/polysaccharide(PN/PS) value showed that the biofilm suffered inhibition by Cu2+. The biofilm would inhibit more extracellular polysaccharide secretion, and the biofilm resistance of Cu2+ indicated that the biofilm would secrete more extracellular protein. The amount of EPS had a good correlation with the enrichment ratio of Cu2+.
Extracellular polymeric substance
Extracellular polysaccharide
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The presented protocol outlines a comprehensive assessment of the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values for bacterial cell cultures. These experiments are vital for screening bacterial susceptibility to antibiotics and substances with potential antibacterial properties. The protocol not only covers the necessary preparatory steps but also introduces the application of the widely recognized Gompertz model. The protocol ensures a smooth execution of the assessment through thorough preparation and step-by-step instructions. The user-friendly instructions provided enable researchers to easily follow the protocol, facilitating the implementation of the assessment. By adhering to the outlined procedures, researchers can acquire a deeper understanding of bacterial susceptibility, evaluate the efficacy of antimicrobial agents through MIC and MBC values, and contribute to the advancement of antibacterial strategies.
Minimum bactericidal concentration
Broth microdilution
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