Combatting Planktonic and Biofilm Populations of Carbapenem-Resistant Acinetobacter baumannii with Polymyxin-Based Combinations (original) (raw)
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Antimicrobial agents and chemotherapy, 2016
Acinetobacter baumannii biofilms are difficult to eradicate. We investigated the effects of meropenem (2 mg/L), imipenem (2 mg/L), sulbactam (4 mg/L), colistin (2 mg/L), and tigecycline (2 mg/L), alone or in combination, on biofilm-embedded carbapenem-resistant and carbapenem-susceptible A. baumannii (CRAb and CSAb, respectively) as well as on the architecture of the biofilms. A. baumannii ATCC 15151(Ab15151), and its OXA-82 overproducing transformant, along with two clinical CSAb and two clinical CRAb isolates of differing clonalities were used. The minimal bactericidal concentrations for biofilm-embedded cell of the six tested isolates were more than 50-fold that for their planktonic cells. When used individually, meropenem exhibited higher killing effect than the other four antimicrobials on biofilm-embedded CSAb in the colony biofilm assay. For two clinical CRAb isolates, meropenem plus sulbactam or sulbactam plus tigecycline showed more than 100-fold the bactericidal effect exh...
Molecules
Polymyxin-based combination therapy is commonly used to treat carbapenem-resistant Acinetobacter baumannii (CRAB) infections. In the present study, the bactericidal effect of polymyxin B and minocycline combination was tested in three CRAB strains containing blaOXA-23 by the checkerboard assay and in vitro dynamic pharmacokinetics/pharmacodynamics (PK/PD) model. The combination showed synergistic or partial synergistic effect (fractional inhibitory concentration index ≤0.56) on the tested strains in checkboard assays. The antibacterial activity was enhanced in the combination group compared with either monotherapy in in vitro PK/PD model. The combination regimen (simultaneous infusion of 0.75 mg/kg polymyxin B and 100 mg minocycline via 2 h infusion) reduced bacterial colony counts by 0.9–3.5 log10 colony forming units per milliliter (CFU/mL) compared with either drug alone at 24 h. In conclusion, 0.75 mg/kg polymyxin B combined with 100 mg minocycline via 2 h infusion could be a pr...
The Brazilian Journal of Infectious Diseases, 2013
Acinetobacter baumannii is a major nosocomial pathogen and carbapenems are the mainstream agents against these organisms. 1 However, carbapenem-resistant A. baumannii (CRAB) isolates have become widely disseminated owing to the emergence of Class D carbapenemases, mainly OXA-23, which are highly prevalent in Brazil. Polymyxins B and colistin are often the last therapeutic options against CRAB isolates. 2 The combination of polymyxins with another antimicrobial has been proposed to overcome some shortcomings of polymyxins in monotherapy, including the potential for the emergence of hetero-resistant subpopulations and a possible limited bactericidal activity in vivo, considering recent pharmacokinetics studies. In vitro studies may provide some support defining that candidate antimicrobials would more likely present a beneficial effect when combined with polymyxins. We evaluated the combination of non-bactericidal concentrations of polymyxin B, which are also more likely to be clinically achieved, 2 with other antimicrobials in concentrations usually reached with common dosage regimes against OXA-23-producing A. baumannii isolates.
International Aquatic Research
The presence of organic matter in plankton cultures will lead to 10-to 1000-fold increases in bacterial density in less than 24 h. The presence of bacteria and fungi can damage cultivated phytoplankton and zooplankton. These microorganisms can also inhibit experiments investigating the role of these microorganisms in the community and in biological and ecological laboratory studies. The aim of this study was thus to evaluate the effect of penicillin ? streptomycin ? neomycin (antibiotics) in combination with nystatin (antifungal) to select an antimicrobial combination for the inhibition of biofilm bacteria and adherent fungi that is effective and also non-toxic to marine phytoplankton and zooplankton. Acartia tonsa was exposed to different antimicrobial treatments and application routes (culture medium, culture food, both) to evaluate the survival and egg and fecal pellet production endpoints. The same treatments were also applied to measure Amphibalanus improvisus survival and settlement and Conticribra weissflogii growth endpoints. We selected the most sensitive experimental organism and exposed it to some novel antimicrobial combinations. To evaluate the inhibition potential, biofilm bacteria and adherent fungi were exposed to the treatments that were safe for the bioindicator species. A tonsa was considered the most sensitive of all tested organisms. The treatment composed of 0.025 g L-1 penicillin G potassium ? 0.08 g L-1 streptomycin sulfate ? 0.04 g L-1 neomycin sulfate showed the best results for A. tonsa and C. weissflogii cultures. No differences were observed for A. improvisus between the treatments. A. tonsa survival rates showed no differences from the
Pathogens
Acinetobacter spp., the nosocomial pathogen, forms strong biofilms and is resistant to numerous antibiotics, causing persistent infections. This study investigates the antibacterial and anti-biofilm activity of polymyxin E alone and in combination with the cell-free supernatants (CFS) of the tested probiotic bacilli, Bacillus subtilis KATMIRA1933 and Bacillus amyloliquefaciens B-1895 against the selected Acinetobacter spp. starins. Three isolates of Acinetobacter spp., designated as Acinetobacter spp. isolate 1; Acinetobacter spp. isolate 2, and Acinetobacter spp. isolate 3, were collected from patients with burns, wounds, and blood infections, respectively. Bacterial identification and antibiotic susceptibility testing were conducted using the VITEK2 system. Auto-aggregation and coaggregation of the tested bacilli strains with the selected Acinetobacter spp. isolates were evaluated. A disk diffusion assay was used to identify the microorganism’s susceptibility to the selected antib...
Journal of Antimicrobial Chemotherapy, 2016
The pharmacodynamics of polymyxin/carbapenem combinations against carbapenem-resistant Acinetobacter baumannii (CRAB) are largely unknown. Our objective was to determine whether intensified meropenem regimens in combination with polymyxin B enhance killing and resistance suppression of CRAB. Methods: Time-kill experiments for meropenem and polymyxin B combinations were conducted against three polymyxin B-susceptible (MIC of polymyxin B ¼ 0.5 mg/L) CRAB strains with varying meropenem MICs (ATCC 19606, N16870 and 03-149-1; MIC of meropenem¼ 4, 16 and 64 mg/L, respectively) at 10 8 cfu/mL. A hollowfibre infection model was then used to simulate humanized regimens of polymyxin B and meropenem (2, 4, 6 and 8 g prolonged infusions every 8 h) versus N16870 at 10 8 cfu/mL over 14 days. New mathematical mechanismbased models were developed using S-ADAPT. Results: Time-kill experiments were well described by the mathematical mechanism-based models, with the presence of polymyxin B drastically decreasing the meropenem concentration needed for half-maximal activity against meropenem-resistant populations from 438 to 82.1 (ATCC 19606), 158 to 93.6 (N16870) and 433 to 76.0 mg/L (03-149-1). The maximum killing effect of combination treatment was similar among all three strains despite divergent meropenem MIC values (E max ¼2.13, 2.08 and 2.15; MIC of meropenem ¼4, 16 and 64 mg/L, respectively). Escalating the dose of meropenem in hollow-fibre combination regimens from 2 g every 8 h to 8 g every 8 h resulted in killing that progressed from a .2.5 log 10 cfu/mL reduction with regrowth by 72 h (2 g every 8 h) to complete eradication by 336 h (8 g every 8 h). Conclusion: Intensified meropenem dosing in combination with polymyxin B may offer a unique strategy to kill CRAB irrespective of the meropenem MIC.
African Journal of Microbiology Research, 2014
Acinetobacter baumannii is an opportunistic Gram negative coccobacillus that can grow easily in moist as well as dry conditions. During the last decade, A. baumannii emerged as one of the most resistant opportunistic pathogens responsible for nosocomial infections including ventilator associated pneumonia. The bug remains an important and difficult to treat pathogen whose pan-drug resistant nature has created a serious challenge. This has restricted the choice of treatment modalities. Currently, it appears as if all the available antibiotics are failing against this pathogen while single antibiotic therapy is certainly not working anymore. Thus, there is a strong need, thus, to explore new regimens to combat this resistant organism. A wide range of various combinations of drugs should therefore be tested for their synergistic activity against this pathogen. This study was aimed to find some effective combinations against extensively drug resistant (XDR) A. baumannii by combining various antibacterials. The microdilution checkerboard titration method was used for this purpose and fractional inhibitory concentrations (FICs) were calculated. In-vitro synergy was found in polymyxin Bcolistin (n = 3; 15%) and polymyxin B-rifampin (n = 3; 15%) combinations. Only additive effect was noted with polymyxin B-doxycycline (n = 12; 60%), polymyxin B-rifampin (n = 11; 55%), and polymyxin Bcolistin (n = 13; 65%). However, antagonism was detected in the polymyxin B-rifampin combination in one of the 20 strains evaluated for the purpose. Polymyxin B in combination with rifampin and colistin may be exploited against XDR A. baumannii. Synergy between polymyxin B and colistin have been demonstrated in only 15% of strains, this fully warrants the testing of more combinations.
Scientific reports, 2016
Polymyxins are last-resort antibiotics for treating infections of Gram-negative bacteria. The recent emergence of polymyxin-resistant bacteria, however, urgently demands clinical optimisation of polymyxin use to minimise further evolution of resistance. In this study we developed a novel combination therapy using minimal concentrations of polymyxin B. After large-scale screening of Streptomyces secondary metabolites, we identified a reliable polymixin synergist and confirmed as netropsin using high-pressure liquid chromatography, nuclear magnetic resonance, and mass spectrometry followed by in vitro assays using various Gram-negative pathogenic bacteria. To evaluate the effectiveness of combining polymixin B and netropsin in vivo, we performed survival analysis on greater wax moth Galleria mellonella infected with colistin-resistant clinical Acinetobacter baumannii isolates as well as Escherichia coli, Shigella flexineri, Salmonella typhimuruim, and Pseudomonas aeruginosa. The survi...
Simple fluorometric-based assay of antibiotic effectiveness for Acinetobacter baumannii biofilms
Scientific Reports
Despite strengthened antimicrobial therapy, biofilm infections of Acinetobacter baumannii are associated with poor prognosis and limited therapeutic options. Assessing antibiotics on planktonic bacteria can result in failure against biofilm infections. Currently, antibiotics to treat biofilm infections are administered empirically, usually without considering the susceptibility of the biofilm objectively before beginning treatment. For effective therapy to resolve biofilm infections it is essential to assess the efficacy of commonly used antibiotics against biofilms. Here, we offer a robust and simple assay to assess the efficacy of antibiotics against biofilms. In the present work, we carefully optimized the incubation time, detection range, and fluorescence reading mode for resazurin-based viability staining of biofilms in 96-well-plates and determined minimal biofilm eradication concentrations (MBECs) for A. baumannii isolates from patients with chronic infection. By applying this assay, we demonstrated that antibiotic response patterns varied uniquely within the biofilm formation of various clinical samples. MBEC-50 and 75 have significant discriminatory power over minimum inhibitory concentrations for planktonic suspensions to differentiate the overall efficiency of an antibiotic to eradicate a biofilm. The present assay is an ideal platform on which to assess the efficacy of antibiotics against biofilms in vitro to pave the way for more effective therapy. Every medical procedure that depends on antibiotics to fight infections can become compromised by antibiotic resistance. Bacteria have acquired increasing resistance to antibiotics since their introduction and this causes extensive illness and deaths worldwide. Among the bacteria that are alarmingly prevalent are multi-drug resistant Acinetobacter baumannii, which cause some 60% of hospital-acquired or nosocomial infections 1. These bacteria have become prevalent in communities, causing ventilator associated pneumonia, blood stream and a variety of skin and tissue infections, in both healthy and immune-compromised individuals 1,2. Indeed, the majority are chronic biofilm-associated infections that are highly resistant to antibiotic therapy, with 40-60% mortality rates 1,2. The biofilm structure makes it difficult for antibiotics to kill the bacteria that form biofilms, and subsequent infection can persist for up to weeks or months, and develop even greater resilience against antibiotics and spread to other organs 2-4. The biofilms can be impenetrable to antibiotics and immune cells, and bacteria in the deeper portions of the biofilms are in a state of slow growth, which acts as a structural and physiological barrier against
The Journal of antibiotics, 2015
Polymyxins, an old class of antibiotics, are currently used as the last resort for the treatment of multidrug-resistant (MDR) Acinetobacter baumannii. However, recent pharmacokinetic and pharmacodynamic data indicate that monotherapy can lead to the development of resistance. Novel approaches are urgently needed to preserve and improve the efficacy of this last-line class of antibiotics. This study examined the antimicrobial activity of novel combination of polymyxin B with anthelmintic closantel against A. baumannii. Closantel monotherapy (16 mg l(-1)) was ineffective against most tested A. baumannii isolates. However, closantel at 4-16 mg l(-1) with a clinically achievable concentration of polymyxin B (2 mg l(-1)) successfully inhibited the development of polymyxin resistance in polymyxin-susceptible isolates, and provided synergistic killing against polymyxin-resistant isolates (MIC ⩾4 mg l(-1)). Our findings suggest that the combination of polymyxin B with closantel could be pot...