Evaluation of Staphylococcus aureus Antibiotic Tolerance Using Kill Curve Assays

2021 ◽  
pp. 45-54
Author(s):  
Jessica N. Brandwein ◽  
Kelly C. Rice
Keyword(s):  
Staphylococcus Aureus ◽  
Antibiotic Tolerance ◽  
Kill Curve

scholarly journals Trans-Cinnamaldehyde Exhibits Synergy with Conventional Antibiotic against Methicillin-Resistant Staphylococcus aureus

2021 ◽  
Vol 22 (5) ◽  
pp. 2752
Author(s):  
Shu Wang ◽  
Ok-Hwa Kang ◽  
Dong-Yeul Kwon
Keyword(s):  
Staphylococcus Aureus ◽  
Methicillin Resistant Staphylococcus Aureus ◽  
Synergistic Effects ◽  
Regulatory Gene ◽  
Western Blot Assay ◽  
Methicillin Resistant ◽  
Wide Range ◽  
Kill Curve ◽  
Conventional Antibiotics ◽  
Time Kill

Methicillin-resistant Staphylococcus aureus (MRSA) is a major nosocomial pathogen worldwide and has acquired multiple resistance to a wide range of antibiotics. Hence, there is a pressing need to explore novel strategies to overcome the increase in antimicrobial resistance. The present study aims to investigate the efficacy and mechanism of plant-derived antimicrobials, trans-cinnamaldehyde (TCA) in decreasing MRSA’s resistance to eight conventional antibiotics. A checkerboard dilution test and time–kill curve assay are used to determine the synergistic effects of TCA combined with the antibiotics. The results indicated that TCA increased the antibacterial activity of the antibiotics by 2-16-fold. To study the mechanism of the synergism, we analyzed the mecA transcription gene and the penicillin-binding protein 2a level of MRSA treated with TCA by quantitative RT-PCR or Western blot assay. The gene transcription and the protein level were significantly inhibited. Additionally, it was verified that TCA can significantly inhibit the biofilm, which is highly resistant to antibiotics. The expression of the biofilm regulatory gene hld of MRSA after TCA treatment was also significantly downregulated. These findings suggest that TCA maybe is an exceptionally potent modulator of antibiotics.

scholarly journals Author Correction: Reactive oxygen species induce antibiotic tolerance during systemic Staphylococcus aureus infection

2020 ◽  
Vol 5 (3) ◽  
pp. 526-526 ◽  
Author(s):  
Sarah E. Rowe ◽  
Nikki J. Wagner ◽  
Lupeng Li ◽  
Jenna E. Beam ◽  
Alec D. Wilkinson ◽  
...  
Keyword(s):  
Reactive Oxygen Species ◽  
Staphylococcus Aureus ◽  
Reactive Oxygen ◽  
Antibiotic Tolerance ◽  
Oxygen Species ◽  
Aureus Infection

Peroxynitrite Induces Antibiotic Tolerance in Staphylococcus aureus

2020 ◽  
Vol 159 ◽  
pp. S38-S39
Author(s):  
Jenna Beam ◽  
John Shook ◽  
Nikki Wagner ◽  
Edward Moreira Bahnson ◽  
Sarah Rowe ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Antibiotic Tolerance

scholarly journals Gel-Entrapped Staphylococcus aureus Bacteria as Models of Biofilm Infection Exhibit Growth in Dense Aggregates, Oxygen Limitation, Antibiotic Tolerance, and Heterogeneous Gene Expression

2016 ◽  
Vol 60 (10) ◽  
pp. 6294-6301 ◽  
Author(s):  
Breana Pabst ◽  
Betsey Pitts ◽  
Ellen Lauchnor ◽  
Philip S. Stewart
Keyword(s):  
Staphylococcus Aureus ◽  
Fluorescent Protein ◽  
Specific Growth ◽  
Matrix Material ◽  
Antibiotic Tolerance ◽  
Glass Capillary ◽  
Host Matrix ◽  
Content Type ◽  
Biofilm Infection

ABSTRACTAn experimental model that mimicked the structure and characteristics ofin vivobiofilm infections, such as those occurring in the lung or in dermal wounds where no biomaterial surface is present, was developed. In these infections, microbial biofilm forms as cell aggregates interspersed in a layer of mucus or host matrix material. This structure was modeled by filling glass capillary tubes with an agarose gel that had been seeded withStaphylococcus aureusbacteria and then incubating the gel biofilm in medium for up to 30 h. Confocal microscopy showed that the bacteria formed in discrete pockets distributed throughout the gel matrix. These aggregates enlarged over time and also developed a size gradient, with the clusters being larger near the nutrient- and oxygen-supplied interface and smaller at greater depths. Bacteria entrapped in gels for 24 h grew slowly (specific growth rate, 0.06 h−1) and were much less susceptible to oxacillin, minocycline, or ciprofloxacin than planktonic cells. Microelectrode measurements showed that the oxygen concentration decreased with depth into the gel biofilm, falling to values less than 3% of air saturation at depths of 500 μm. An anaerobiosis-responsive green fluorescent protein reporter gene for lactate dehydrogenase was induced in the region of the gel where the measured oxygen concentrations were low, confirming biologically relevant hypoxia. These results show that the gel biofilm model captures key features of biofilm infection in mucus or compromised tissue: formation of dense, distinct aggregates, reduced specific growth rates, local hypoxia, and antibiotic tolerance.

scholarly journals Interruption of the tricarboxylic acid cycle in Staphylococcus aureus leads to increased tolerance to innate immunity

2021 ◽  
Vol 7 (4) ◽  
pp. 513-527
Author(s):  
Alexis M. Hobbs ◽  
◽  
Kennedy E. Kluthe ◽  
Kimberly A. Carlson ◽  
Austin S. Nuxoll
Keyword(s):  
Staphylococcus Aureus ◽  
Immune System ◽  
Innate Immune System ◽  
Tricarboxylic Acid Cycle ◽  
Fold Increase ◽  
Tca Cycle ◽  
Tricarboxylic Acid ◽  
Innate Immune ◽  
Antibiotic Tolerance ◽  
Males And Females

<abstract> <p><italic>Staphylococcus aureus</italic> is widely known for its resistance and virulence causing public health concerns. However, antibiotic tolerance is also a contributor to chronic and relapsing infections. Previously, it has been demonstrated that persister formation is dependent on reduced tricarboxylic acid (TCA) cycle activity. Persisters have been extensively examined in terms of antibiotic tolerance but tolerance to antimicrobial peptides (AMPs) remains largely unexplored. AMPs are a key component of both the human and <italic>Drosophila</italic> innate immune response. TCA cycle mutants were tested to determine both antibiotic and AMP tolerance. Challenging with multiple classes of antibiotics led to increased persister formation (100- to 1,000-fold). Similarly, TCA mutants exhibited AMP tolerance with a 100- to 1,000-fold increase in persister formation when challenged with LL-37 or human β-defensin 3 (hβD3). The ability of TCA cycle mutants to tolerate the innate immune system was further examined with a <italic>D. melanogaster</italic> model. Both males and females infected with TCA cycle mutants exhibited increased mortality and had higher bacterial burdens (1.5 log) during the course of the infection. These results suggest increasing the percentage of persister cells leads to increased tolerance to components of the innate immune system.</p> </abstract>

scholarly journals Antimicrobial activities of widely consumed herbal tea’s alone or in combination with antibiotics: An in vitro study

2016 ◽  
Author(s):  
Mayram Tuysuz ◽  
Sibel Dosler ◽  
Ayse Seher Birteksoz Tan ◽  
Gulten Otuk
Keyword(s):  
Escherichia Coli ◽  
Staphylococcus Aureus ◽  
In Vitro Study ◽  
Antimicrobial Activities ◽  
Combination Studies ◽  
Kill Curve ◽  
Time Kill ◽  
Microbroth Dilution ◽  
Antagonistic Interactions

Background: Because of increasing antibiotic resistance, herbal teas are the most popular natural alternatives, which are gaining even more importance. We examined the antimicrobial activities of 31 herbal teas both alone and in combination with antibiotics or antifungals against the standard and clinical isolates of Pseudomonas aeruginosa, Acinetobacter baumannii, Escherichia coli, Klebsiella pneumoniae, Enterococcus faecalis, methicillin susceptible/resistant Staphylococcus aureus and Candida albicans. Methods: The antimicrobial activities of the teas were determined by using the disk diffusion and microbroth dilution methods, and the combination studies were examined by using the microbroth checkerboard and time killing curve methods. Results: Rosehip, rosehip bag, pomegranate blossom, thyme, wormwood, mint, echinacea bag, cinnamon, black, and green teas were active against most of the studied microorganisms. In the combination studies, we characterized all the expected effects (synergistic, additive, and antagonistic) between the teas and the antimicrobials. While synergy was observed more frequently between ampicillin, ampicillin-sulbactam, or nystatine, and the various tea combinations, most of the effects between the ciprofloxacin, erythromycin, cefuroxime, or amikacin and various tea combinations, particularly rosehip, rosehip bag, and pomegranate blossom teas, were antagonistic. The results of the time kill curve analyses showed that none of the herbal teas were bactericidal in their usage concentrations; however, in combination they were. Discussion: Some herbal teas, particularly rosehip and pomegranate blossom should be avoided because of antagonistic interactions during the course of antibiotic treatment or should be consumed alone.

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