scholarly journals Differential Effects of Linezolid and Ciprofloxacin on Toxin Production by Bacillus anthracis in anIn VitroPharmacodynamic System

2011 ◽  
Vol 56 (1) ◽  
pp. 513-517 ◽  
Author(s):  
Arnold Louie ◽  
Brian D. VanScoy ◽  
Henry S. Heine ◽  
Weiguo Liu ◽  
Terry Abshire ◽  
...  

ABSTRACTBacillus anthraciscauses anthrax. Ciprofloxacin is a gold standard for the treatment of anthrax. Previously, using the non-toxin-producing ΔSterne strain ofB. anthracis, we demonstrated that linezolid was equivalent to ciprofloxacin for reducing the total (vegetative and spore) bacterial population. With ciprofloxacin therapy, the total population consisted of spores. With linezolid therapy, the population consisted primarily of vegetative bacteria. Linezolid is a protein synthesis inhibitor, while ciprofloxacin is not. Since toxins are produced only by vegetativeB. anthracis, the effect of linezolid and ciprofloxacin on toxin production is of interest. The effect of simulated clinical regimens of ciprofloxacin and linezolid on the vegetative and spore populations and on toxin production was examined in anin vitropharmacodynamic model over 15 days by using the toxin-producing Sterne strain ofB. anthracis. Ciprofloxacin and linezolid reduced the total Sterne population at similar rates. With ciprofloxacin therapy, the total Sterne population consisted of spores. With linezolid therapy, >90% of the population was vegetativeB. anthracis. With ciprofloxacin therapy, toxin was first detectable at 3 h and remained detectable for at least 5 h. Toxin was never detected with linezolid therapy. Ciprofloxacin and linezolid reduced the total Sterne population at similar rates. However, theB. anthracispopulation was primarily spores with ciprofloxacin therapy and was primarily vegetative bacteria with linezolid therapy. Toxin production was detected for at least 5 h with ciprofloxacin therapy but was never detected with linezolid treatment. Linezolid may have an advantage over ciprofloxacin for the treatment ofB. anthracisinfections.

2011 ◽  
Vol 56 (3) ◽  
pp. 1229-1239 ◽  
Author(s):  
Arnold Louie ◽  
Brian D. VanScoy ◽  
David L. Brown ◽  
Robert W. Kulawy ◽  
Henry S. Heine ◽  
...  

ABSTRACTBacillus anthracis, the bacterium that causes anthrax, is an agent of bioterrorism. The most effective antimicrobial therapy forB. anthracisinfections is unknown. Anin vitropharmacodynamic model ofB. anthraciswas used to compare the efficacies of simulated clinically prescribed regimens of moxifloxacin, linezolid, and meropenem with the “gold standards,” doxycycline and ciprofloxacin. Treatment outcomes for isogenic spore-forming and non-spore-forming strains ofB. anthraciswere compared. Against spore-formingB. anthracis, ciprofloxacin, moxifloxacin, linezolid, and meropenem reduced theB. anthracispopulation by 4 log10CFU/ml over 10 days. Doxycycline reduced the population of thisB. anthracisstrain by 5 log10CFU/ml (analysis of variance [ANOVA]P= 0.01 versus other drugs). Against an isogenic non-spore-forming strain, meropenem killed the vegetativeB. anthracisthe fastest, followed by moxifloxacin and ciprofloxacin and then doxycycline. Linezolid offered the lowest bacterial kill rate. Heat shock studies using the spore-producingB. anthracisstrain showed that with moxifloxacin, ciprofloxacin, and meropenem therapies the total population was mostly spores, while the population was primarily vegetative bacteria with linezolid and doxycycline therapies. Spores have a profound impact on the rate and extent of killing ofB. anthracis. Against spore-formingB. anthracis, the five antibiotics killed the total (spore and vegetative) bacterial population at similar rates (within 1 log10CFU/ml of each other). However, bactericidal antibiotics killed vegetativeB. anthracisfaster than bacteriostatic drugs. Since only vegetative-phaseB. anthracisproduces the toxins that may kill the infected host, the rate and mechanism of killing of an antibiotic may determine its overallin vivoefficacy. Further studies are needed to examine this important observation.


2012 ◽  
Vol 56 (10) ◽  
pp. 5401-5405 ◽  
Author(s):  
Melissa J. Karau ◽  
Ashenafi Y. Tilahun ◽  
Suzannah M. Schmidt ◽  
Chad R. Clark ◽  
Robin Patel ◽  
...  

ABSTRACTSuperantigens (SAg), the potent activators of the immune system, are important determinants ofStaphylococcus aureusvirulence and pathogenicity. Superior response to SAg in human leukocyte antigen (HLA)-DR3 transgenic mice rendered them more susceptible than C57BL/6 mice to pneumonia caused by SAg-producing strains ofS. aureus. Linezolid, a bacterial protein synthesis inhibitor, was superior to vancomycin in inhibiting SAg production byS. aureusin vitroand conferred greater protection from pneumonia caused by SAg-producing staphylococci.


2013 ◽  
Vol 58 (2) ◽  
pp. 909-915 ◽  
Author(s):  
Julia Mallegol ◽  
Prabhavathi Fernandes ◽  
Roberto G. Melano ◽  
Cyril Guyard

ABSTRACTThe activity of solithromycin was evaluated against clinicalLegionella pneumophilaserogroup 1 (Lp1) isolates (n= 196) collected in Ontario, Canada, from 1980 to 2011. Itsin vitroactivity was compared to that of azithromycin (AZM) using the broth microdilution method. Solithromycin had a MIC50of ≤0.015 μg/ml and a MIC90of 0.031 μg/ml, making its activity at least 8-fold to 32-fold higher than that of AZM (MIC50and MIC90, 0.125 μg/ml and 1 μg/ml, respectively). Ninety-nine percent of the isolates had MICs for solithromycin ranging from ≤0.015 μg/ml to 0.031 μg/ml, whereas 83.6% of the isolates showed MICs for AZM ranging from 0.062 μg/ml to 0.25 μg/ml. Interestingly, 96.7% (30 out of 31 clinical isolates) identified with higher AZM MICs (0.5 μg/ml to 2 μg/ml) belonged to the clinically prevalent sequence type 1. To investigate the intracellular activity of solithromycin,in vitroinvasion assays were also performed against a subset of representative Lp1 isolates internalized within human lung epithelial cells. Solithromycin and AZM both inhibited growth of all intracellular Lp1 isolates at 1× or 8× MICs, displaying bacteriostatic effects, as would be expected with protein synthesis inhibitor rather than bactericidal activity. Solithromycin demonstrated the highestin vitroand intracellular potency against all Lp1 isolates compared to AZM. Given the rapid spread of resistance mechanisms among respiratory pathogens and the reported treatment failures in legionellosis, the development of this new fluoroketolide, already in phase 3 oral clinical studies, constitutes a promising alternative option for the treatment of legionellosis.


2000 ◽  
Vol 93 (5) ◽  
pp. 845-851 ◽  
Author(s):  
Shinsaku Nishio ◽  
Masatoshi Yunoki ◽  
Zong-Fu Chen ◽  
Matthew J. Anzivino ◽  
Kevin S. Lee

Object. Ischemic neuronal damage associated with neurological and other types of surgery can have severe consequences for functional recovery after surgery. Hypothermia administered during and/or after ischemia has proved to be clinically beneficial and its effects often rival or exceed those of other therapeutic strategies. In the present study the authors examined whether transient hypothermia is an effective preconditioning stimulus for inducing ischemic tolerance in the brain.Methods. Adult rats were subjected to a 20-minute period of hypothermic preconditioning followed by an interval ranging from 6 hours to 7 days. At the end of this interval, the animals were subjected to transient focal ischemia induced by clamping one middle cerebral artery and both carotid arteries for 1 hour. The volume of cerebral infarction was assessed 1 or 7 days postischemia. In the first series of experiments, hypothermic preconditioning (28.5°C) with a postconditioning interval of 1 day reduced the extent of cerebral infarction measured 1 and 7 days postischemia. In the second series, hypothermic preconditioning (31.5°C) with postconditioning intervals of 6 hours, 1 day, or 2 days (but not 7 days) reduced the extent of cerebral infarction measured 1 day postischemia. Treatment with the protein synthesis inhibitor anisomycin blocked the protective effect of hypothermic preconditioning. In a final series of experiments, in vitro brain slices prepared from hypothermia-preconditioned (nonischemic) animals were shown to tolerate a hypoxic challenge better than slices prepared from unconditioned animals.Conclusions. These findings indicate that hypothermic preconditioning induces a form of delayed tolerance to focal ischemic damage. The time course over which tolerance occurs and the ability of a protein synthesis inhibitor to block tolerance suggest that increased expression of one or more gene products is necessary to establish tissue tolerance following hypothermia. The attenuation of hypoxic injury in vitro following in vivo preconditioning indicates that tolerance is due, at least in part, to direct effects on the brain neuropil. Hypothermic preconditioning could provide a relatively low-risk approach for improving surgical outcome after invasive surgery, including high-risk neurological and cardiovascular procedures.


2016 ◽  
Vol 61 (2) ◽  
Author(s):  
Derek Fleming ◽  
Laura Chahin ◽  
Kendra Rumbaugh

ABSTRACT The persistent nature of chronic wounds leaves them highly susceptible to invasion by a variety of pathogens that have the ability to construct an extracellular polymeric substance (EPS). This EPS makes the bacterial population, or biofilm, up to 1,000-fold more antibiotic tolerant than planktonic cells and makes wound healing extremely difficult. Thus, compounds which have the ability to degrade biofilms, but not host tissue components, are highly sought after for clinical applications. In this study, we examined the efficacy of two glycoside hydrolases, α-amylase and cellulase, which break down complex polysaccharides, to effectively disrupt Staphylococcus aureus and Pseudomonas aeruginosa monoculture and coculture biofilms. We hypothesized that glycoside hydrolase therapy would significantly reduce EPS biomass and convert bacteria to their planktonic state, leaving them more susceptible to conventional antimicrobials. Treatment of S. aureus and P. aeruginosa biofilms, grown in vitro and in vivo, with solutions of α-amylase and cellulase resulted in significant reductions in biomass, dissolution of the biofilm, and an increase in the effectiveness of subsequent antibiotic treatments. These data suggest that glycoside hydrolase therapy represents a potential safe, effective, and new avenue of treatment for biofilm-related infections.


2013 ◽  
Vol 58 (2) ◽  
pp. 672-677 ◽  
Author(s):  
Amira A. Bhalodi ◽  
Mao Hagihara ◽  
David P. Nicolau ◽  
Joseph L. Kuti

ABSTRACTThe effects of prior vancomycin exposure on ceftaroline and daptomycin therapy against methicillin-resistantStaphylococcus aureus(MRSA) have not been widely studied. Humanized free-drug exposures of vancomycin at 1 g every 12 h (q12h), ceftaroline at 600 mg q12h, and daptomycin at 10 mg/kg of body weight q24h were simulated in a 96-hin vitropharmacodynamic model against three MRSA isolates, including one heteroresistant vancomycin-intermediateS. aureus(hVISA) isolate and one VISA isolate. A total of five regimens were tested: vancomycin, ceftaroline, and daptomycin alone for the entire 96 h, and then sequential therapy with vancomycin for 48 h followed by ceftaroline or daptomycin for 48 h. Microbiological responses were measured by the changes in log10CFU during 96 h from baseline. Control isolates grew to 9.16 ± 0.32, 9.13 ± 0.14, and 8.69 ± 0.28 log10CFU for MRSA, hVISA, and VISA, respectively. Vancomycin initially achieved ≥3 log10CFU reductions against the MRSA and hVISA isolates, followed by regrowth beginning at 48 h; minimal activity was observed against VISA. The change in 96-h log10CFU was largest for sequential therapy with vancomycin followed by ceftaroline (−5.22 ± 1.2,P= 0.010 versus ceftaroline) and for sequential therapy with vancomycin followed by ceftaroline (−3.60 ± 0.6,P= 0.037 versus daptomycin), compared with daptomycin (−2.24 ± 1.0), vancomycin (−1.40 ± 1.8), and sequential therapy with vancomycin followed by daptomycin (−1.32 ± 1.0,P> 0.5 for the last three regimens). Prior exposure of vancomycin at 1 g q12h reduced the initial microbiological response of daptomycin, particularly for hVISA and VISA isolates, but did not affect the response of ceftaroline. In the scenario of poor vancomycin response for high-inoculum MRSA infection, a ceftaroline-containing regimen may be preferred.


2020 ◽  
Vol 64 (12) ◽  
Author(s):  
Iris H. Chen ◽  
David P. Nicolau ◽  
Joseph L. Kuti

ABSTRACT Combination therapy may enhance imipenem/cilastatin/relebactam’s (I/R) activity against Pseudomonas aeruginosa and suppress resistance development. Human-simulated unbound plasma concentrations of I/R at 1.25 g every 6 h (h), colistin at 360 mg daily, and amikacin at 25 mg/kg daily were reproduced alone and in combination against six imipenem-nonsusceptible P. aeruginosa isolates in an in vitro pharmacodynamic model over 24 h. For I/R alone, the mean reductions in CFU ± the standard errors by 24 h were −2.52 ± 0.49, −1.49 ± 0.49, −1.15 ± 0.67, and −0.61 ± 0.10 log10 CFU/ml against isolates with MICs of 1/4, 2/4, 4/4, and 8/4 μg/ml, respectively. Amikacin alone also resulted in 24 h CFU reductions consistent with its MIC, while colistin CFU reductions did not differ. Resistant subpopulations were observed after 24 h in 1, 4, and 3 I/R-, colistin-, and amikacin-exposed isolates, respectively. The combination of I/R and colistin resulted in synergistic (n = 1) or additive (n = 2) interactions against three isolates with 24-h CFU reductions ranging from −2.62 to −4.67 log10 CFU/ml. The combination of I/R and amikacin exhibited indifferent interactions against all isolates, with combined drugs achieving −0.51- to −3.33-log10 CFU/ml reductions. No resistant subpopulations were observed during I/R and colistin combination studies, and when added to amikacin, I/R prevented the emergence of amikacin resistance. Against these six multidrug-resistant P. aeruginosa, I/R alone achieved significant CFU reductions against I/R-susceptible isolates. Combinations of I/R plus colistin resulted in additivity or synergy against some P. aeruginosa, whereas the addition of amikacin did not provide further antibacterial efficacy against these isolates.


mSphere ◽  
2019 ◽  
Vol 4 (6) ◽  
Author(s):  
Olivia A. Todd ◽  
Mairi C. Noverr ◽  
Brian M. Peters

ABSTRACT Candida albicans and Staphylococcus aureus are common causes of nosocomial infections with severe morbidity and mortality. Murine polymicrobial intra-abdominal infection (IAI) with C. albicans and S. aureus results in acute mortality dependent on the secreted cytolytic effector alpha-toxin. Here, we confirmed that alpha-toxin is elevated during polymicrobial growth compared to monomicrobial growth in vitro. Therefore, this study sought to unravel the mechanism by which C. albicans drives enhanced staphylococcal alpha-toxin production. Using a combination of functional and genetic approaches, we determined that an intact agr quorum sensing regulon is necessary for enhanced alpha-toxin production during coculture and that a secreted candidal factor likely is not implicated in elevating agr activation. As the agr system is pH sensitive, we observed that C. albicans raises the pH during polymicrobial growth and that this correlates with increased agr activity and alpha-toxin production. Modulation of the pH could predictably attenuate or activate agr activity during coculture. By using a C. albicans mutant deficient in alkalinization (stp2Δ/Δ), we confirmed that modulation of the extracellular pH by C. albicans can drive agr expression and toxin production. Additionally, the use of various Candida species (C. glabrata, C. dubliniensis, C. tropicalis, C. parapsilosis, and C. krusei) demonstrated that those capable of raising the extracellular pH correlated with elevated agr activity and alpha-toxin production during coculture. Overall, we demonstrate that alkalinization of the extracellular pH by the Candida species leads to sustained activation of the staphylococcal agr system. IMPORTANCE Candida albicans and Staphylococcus aureus are commonly coisolated from central venous catheters and deep-seated infections, including intra-abdominal sepsis. Thus, they represent a significant cause of nosocomial morbidity and mortality. Yet how these organisms behave in the context of polymicrobial growth remains poorly understood. In this work, we set out to determine the mechanism by which activation of the staphylococcal agr quorum sensing system and production of its major virulence effector alpha-toxin is enhanced during coculture with C. albicans. Surprisingly, we likely ruled out that a secreted candidal factor drives this process. Instead, we demonstrated that alkalinization of the extracellular milieu by C. albicans and other Candida species correlated with elevated agr activity. Thus, we propose a mechanism where modulation of the extracellular pH by fungal opportunists can indirectly alter virulence of a bacterial pathogen. Uncovering molecular events that drive interkingdom pathogenicity mechanisms may enhance surveillance and treatment for devastating polymicrobial infections.


1993 ◽  
Vol 10 (1) ◽  
pp. 7-13 ◽  
Author(s):  
M Angervo ◽  
P Leinonen ◽  
R Koistinen ◽  
M Julkunen ◽  
M Seppälä

ABSTRACT The growth-regulating actions of IGFs are modulated by their binding proteins (IGFBPs). The serum concentration of IGFBP-1 is down-regulated by insulin, and in-vitro studies have demonstrated that IGFBP-1 secretion from various tissues and cells can be stimulated by theophylline, forskolin, oestrogen and progesterone. We have studied the effects and mechanisms of thyroid hormone action on IGFBP-1 gene expression and secretion by human hepatoma cells in vitro. Tri-iodothyronine dose-dependently enhanced IGFBP-1 secretion in serum-free HepG2 cell cultures after 24–48 h of exposure, as measured by a specific immunofluorometric assay. This was accompanied by an increase (+ 50%) in the amount of IGFBP-1 mRNA, which could be prevented by cycloheximide, a protein synthesis inhibitor. Cycloheximide transiently enhanced (+ 200%) the accumulation of IGFBP-1 mRNA at 3–12 h of incubation, when no effect of tri-iodothyronine was observed. It is concluded that thyroid hormone stimulates IGFBP-1 secretion slowly by enhancing IGFBP-1 gene expression by a protein mediator. The acute stimulation of IGFBP-1 gene transcription by cycloheximide associates this gene with a number of growth-related genes encoding growth- and tumour-associated peptides.


2012 ◽  
Vol 56 (6) ◽  
pp. 3174-3180 ◽  
Author(s):  
Ashley D. Hall ◽  
Molly E. Steed ◽  
Cesar A. Arias ◽  
Barbara E. Murray ◽  
Michael J. Rybak

ABSTRACTDaptomycin MICs for enterococci are typically 1- to 2-fold higher than those forStaphylococcus aureus, and there is an imminent need to establish the optimal dose for appropriate treatment of enterococcal infections. We investigated the bactericidal activity of daptomycin at various dose exposures compared to that of linezolid against vancomycin-resistant enterococcus (VRE) in anin vitropharmacokinetic/pharmacodynamic model utilizing simulated endocardial vegetations over 96 h. Daptomycin at doses of 6, 8, 10, and 12 mg/kg of body weight/day and linezolid at a dose of 600 mg every 12 h were evaluated against two clinical vancomycin-resistantEnterococcus faeciumstrains (EFm11499 and 09-184D1051), one of which was linezolid resistant (09-184D1051), and one clinical vancomycin-resistantEnterococcus faecalisstrain (EFs11496). Daptomycin MICs were 4, 2, and 0.5 μg/ml for EFm11499, 09-184D1051, and EFs11496, respectively. Bactericidal activity, defined as a ≥3 log10CFU/g reduction from the initial colony count, was demonstrated against all three isolates with all doses of daptomycin; however, bactericidal activity was not sustained with the daptomycin 6- and 8-mg/kg/day regimens. Linezolid was bacteriostatic against EFm11499 and displayed no appreciable activity against 09-184D1051 or EFs11496. Concentration-dependent killing was displayed with more sustained reduction in colony count (3.58 to 6.46 and 5.89 to 6.56 log10CFU/g) at 96 h for the simulated regimen of daptomycin at doses of 10 and 12 mg/kg/day, respectively (P≤ 0.012). NoE. faeciummutants with reduced susceptibility were recovered at any dosage regimen; however, theE. faecalisstrain developed reduced daptomycin susceptibility with daptomycin at 6, 8, and 10 but not at 12 mg/kg/day. Daptomycin displayed a dose-dependent response against three VRE isolates, with high-dose daptomycin producing sustained bactericidal activity. Further research is warranted.


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