Loss of penicillin tolerance by inactivating the carbon catabolite repression determinant CcpA in Streptococcus gordonii

Objectives Antibiotic tolerance is a phenomenon allowing bacteria to withstand drug-induced killing. Here, we studied a penicillin-tolerant mutant of Streptococcus gordonii (Tol1), which was shown to be deregulated in the expression of the arginine deiminase operon (arc). arc was not directly responsible for tolerance, but is controlled by the global regulator CcpA. Therefore, we sought whether CcpA might be implicated in tolerance. Methods The ccpA gene was characterized and subsequently inactivated by PCR ligation mutagenesis in both the susceptible wild-type (WT) and Tol1. The minimal inhibitory concentration and time-kill curves for the strains were determined and the outcome of penicillin treatment in experimental endocarditis assessed. Results ccpA sequence and expression were similar between the WT and Tol1 strains. In killing assays, the WT lost 3.5 ± 0.6 and 5.3 ± 0.6 log10 cfu/mL and Tol1 lost 0.4 ± 0.2 and 1.4 ± 0.9 log10 cfu/mL after 24 and 48 h of penicillin exposure, respectively. Deletion of ccpA almost totally restored Tol1 kill susceptibility (loss of 2.5 ± 0.7 and 4.9 ± 0.7 log10 cfu/mL at the same endpoints). In experimental endocarditis, penicillin treatment induced a significant reduction in vegetation bacterial densities between Tol1 (4.1 log10 cfu/g) and Tol1ΔccpA (2.4 log10 cfu/g). Restitution of ccpA re-established the tolerant phenotype both in vitro and in vivo. Conclusions CcpA, a global regulator of the carbon catabolite repression system, is implicated in penicillin tolerance both in vitro and in vivo. This links antibiotic survival to bacterial sugar metabolism. However, since ccpA sequence and expression were similar between the WT and Tol1 strains, other factors are probably involved in toleranc

Ceftriaxone acts synergistically with levofloxacin in experimental meningitis and reduces levofloxacin-induced resistance in penicillin-resistant pneumococci

Ceftriaxone acted synergistically with levofloxacin in time-killing assays in vitro over 8 h against two penicillin-resistant pneumococcal strains (WB4 and KR4; MIC of penicillin: 4 mg/L). Synergy was confirmed with the chequerboard method, showing FIC indices of 0.25. In the experimental rabbit meningitis model, ceftriaxone (1× 125 mg/kg) was slightly less bactericidal (-0.30 Δlog10 cfu/mL.h) compared with levofloxacin (-0.45 Δlog10 cfu/mL.h) against the penicillin-resistant strain WB4. The combination therapy (levofloxacin and ceftriaxone) was significantly superior (-0.64 Δlog10 cfu/mL.h) to either monotherapy. In cycling experiments in vitro, the addition of ceftriaxone at a sub-MIC concentration (1/16 MIC) reduced levofloxacin-induced resistance in the two strains KR4 and WB4. After 12 cycles with levofloxacin monotherapy, the MIC increased 64-fold in both strains versus a 16-fold increase with the combination (levofloxacin + ceftriaxone 1/16 MIC). In both strains, levofloxacin-induced resistance was confirmed by mutations detected in the genes parC and gyrA, encoding for subunits of topoisomerase IV and gyrase, respectively. The addition of ceftriaxone suppressed mutations in parC but led to a new mutation in parE in both strain

Meropenem Prevents Levofloxacin-Induced Resistance in Penicillin-Resistant Pneumococci and Acts Synergistically with Levofloxacin in Experimental Meningitis

The aim of the present study was to investigate the potential synergy between meropenem and levofloxacin in vitro and in experimental meningitis and to determine the effect of meropenem on levofloxacin-induced resistance in vitro. Meropenem increased the efficacy of levofloxacin against the penicillin-resistant pneumococcal strain KR4 in time-killing assays in vitro and acted synergistically against a second penicillin-resistant strain WB4. In the checkerboard, only an additive effect (FIC indices: 1.0) was observed for both strains. In cycling experiments in vitro, levofloxacin alone led to a 64-fold increase in the MIC for both strains after 12 cycles. Addition of meropenem in sub-MIC concentrations (0.25×MIC) completely inhibited the selection of levofloxacin-resistant mutants in WB4 after 12 cycles. In KR4, the addition of meropenem led to just a twofold increase in the MIC for levofloxacin after 12 cycles. Mutations detected in the genes encoding for topoisomerase IV (parC) and gyrase (gyrA) confirmed the levofloxacin-induced resistance in both strains. Addition of meropenem was able to completely suppress levofloxacin-induced mutations in WB4 and led to only one mutation in parE in KR4. In experimental meningitis, meropenem, given in two doses (2×125mg/kg), produced a good bactericidal activity (−0.45 Δlog10 cfu/ml·h) comparable to one dose (1×10mg/kg) of levofloxacin (−0.44 Δlog10 cfu/ml·h) against the penicillin-resistant strain WB4. Meropenem combined with levofloxacin acted synergistically (−0.93 Δlog10 cfu/ml·h), sterilizing the CSF of all rabbit

Efficacy of daptomycin in the treatment of experimental endocarditis due to susceptible and multidrug-resistant enterococci.

OBJECTIVES: Daptomycin was tested in vitro and in rats with experimental endocarditis against the ampicillin-susceptible and vancomycin-susceptible Enterococcus faecalis JH2-2, the vancomycin-resistant (VanA type) mutant of strain JH2-2 (strain JH2-2/pIP819), and the ampicillin-resistant and vancomycin-resistant (VanB type) Enterococcus faecium D366. METHODS: Rats with catheter-induced aortic vegetations were treated with doses simulating intravenously kinetics in humans of daptomycin (6 mg/kg every 24 h), amoxicillin (2 g every 6 h), vancomycin (1 g every 12 h) or teicoplanin (12 mg/kg every 12 h). Treatment was started 16 h post-inoculation and continued for 2 days. RESULTS: MICs of daptomycin were 1, 1 and 2 mg/L, respectively, for strains JH2-2, JH2-2/pIP819 and D366. In time-kill studies, daptomycin showed rapid (within 2 h) bactericidal activity against all strains. Daptomycin was highly bound to rat serum proteins (89%). In the presence of 50% rat serum, simulating free concentrations, daptomycin killing was maintained but delayed (6-24 h). In vivo, daptomycin treatment resulted in 10 of 12 (83%), 9 of 11 (82%) and 11 of 12 (91%) culture-negative vegetations in rats infected with strains JH2-2, JH2-2/pIP819 and D366, respectively (P < 0.001 compared to controls). Daptomycin efficacy was comparable to that of amoxicillin and vancomycin for susceptible isolates. Daptomycin, however, was significantly (P < 0.05) more effective than teicoplanin against the glycopeptide-susceptible strain JH2-2 and superior to all comparators against resistant isolates. CONCLUSIONS: These results support the use of the newly proposed daptomycin dose of 6 mg/kg every 24 h for treatment of enterococcal infections in humans

Synergistic Interaction Between Phage Therapy and Antibiotics Clears Pseudomonas Aeruginosa Infection in Endocarditis and Reduces Virulence.

Increasing antibiotic resistance warrants therapeutic alternatives. Here we investigated the efficacy of bacteriophage-therapy (phage) alone or combined with antibiotics against experimental endocarditis (EE) due to Pseudomonas aeruginosa, an archetype of difficult-to-treat infection. In vitro fibrin clots and rats with aortic EE were treated with an antipseudomonas phage cocktail alone or combined with ciprofloxacin. Phage pharmacology, therapeutic efficacy, and resistance were determined. In vitro, single-dose phage therapy killed 7 log colony-forming units (CFUs)/g of fibrin clots in 6 hours. Phage-resistant mutants regrew after 24 hours but were prevented by combination with ciprofloxacin (2.5 × minimum inhibitory concentration). In vivo, single-dose phage therapy killed 2.5 log CFUs/g of vegetations in 6 hours (P < .001 vs untreated controls) and was comparable with ciprofloxacin monotherapy. Moreover, phage/ciprofloxacin combinations were highly synergistic, killing >6 log CFUs/g of vegetations in 6 hours and successfully treating 64% (n = 7/11) of rats. Phage-resistant mutants emerged in vitro but not in vivo, most likely because resistant mutations affected bacterial surface determinants important for infectivity (eg, the pilT and galU genes involved in pilus motility and LPS formation). Single-dose phage therapy was active against P. aeruginosa EE and highly synergistic with ciprofloxacin. Phage-resistant mutants had impaired infectivity. Phage-therapy alone or combined with antibiotics merits further clinical consideration

Unusual Spread of a Penicillin-Susceptible Methicillin-Resistant Staphylococcus aureus Clone in a Geographic Area of Low Incidence

We describe the unusual spread of a penicillin-susceptible methicillin-resistant Staphylococcus aureus (MRSA) clone in hospitals in western Switzerland, where the incidence of MRSA is usually low. During a 2-year period, this clone had been responsible for several outbreaks and had been isolated from >156 persons in 21 institutions. Molecular typing by pulsed-field gel electrophoresis (PFGE) demonstrated that all of these isolates belonged to the same clone. In 1 of the outbreaks, involving 30 cases, the clone was responsible for at least 17 secondary cases. In contrast, during the period of the latter outbreak, 9 other patients harboring different MRSA strains, as assessed by PFGE, were hospitalized in the same wards, but no secondary cases occurred. These observations suggest that this clone, compared with other MRSA strains, had some intrinsic factor(s) that contributed to its ability to disseminate and could thus be considered epidemi

Estudio de la adsorción de iones Cu (II) en un sorbente de base silícica en régimen estático mediante efectos mecánicos y sonorización

El presente trabajo expone las determinaciones que se efectuaron para determinar los procesos de sorción de iones Cu (II) en régimen estático con y sin impulsos ultrasónicos en un producto de base silícica con agua de comportamiento zeolítico en su estructura obtenido mediante un proceso de gelificación. Se escogieron dos fracciones con tamaños de partículas diferentes (0.071 y 0.125 mm de diámetro) a las cuales se les determinaron: densidad aparente, densidad aparente por aprisionamiento, densidad verdadera, compresibilidad, porosidad, factor de forma, superficie específica. El proceso de sorción de iones se lleva a cabo en determinadas condiciones de acidez, temperatura, pulso, concentración de iones Cu2+, diámetro de partícula y tiempo. Desde otro punto de vista se obtuvo el producto con iones cobre (II) con condiciones específicas de acidez, velocidad de agitación, diámetro de partícula, temperatura, concentraciones de iones Cu2+ y tiempo de contacto.The determinations ruling the processes of Cu2+ ions sorption in steady state with and without ultrasonic impulses in a silica base product with water of zeolitic-behaviour structure obtained by gelification, are introduced. Two fractions of different particle size are selected to determine its apparent density, confined apparent density, true density, compressibility, porosity, shape factor, specific surface. The sorption process is carried out in given acidity, temperature, pulse, Cu22+ concentration, particle diameter and time. From an alternative viewpoint, the product is obtained with Cu2+ ions in specific conditions of acidity, shake speed, particle diameter, temperature, Cu2+ concentration and contact time.Asociación Argentina de Energías Renovables y Medio Ambiente (ASADES

Estudio de la adsorción de iones Cu (II) en un sorbente de base silícica en régimen estático mediante efectos mecánicos y sonorización

El presente trabajo expone las determinaciones que se efectuaron para determinar los procesos de sorción de iones Cu (II) en régimen estático con y sin impulsos ultrasónicos en un producto de base silícica con agua de comportamiento zeolítico en su estructura obtenido mediante un proceso de gelificación. Se escogieron dos fracciones con tamaños de partículas diferentes (0.071 y 0.125 mm de diámetro) a las cuales se les determinaron: densidad aparente, densidad aparente por aprisionamiento, densidad verdadera, compresibilidad, porosidad, factor de forma, superficie específica. El proceso de sorción de iones se lleva a cabo en determinadas condiciones de acidez, temperatura, pulso, concentración de iones Cu2+, diámetro de partícula y tiempo. Desde otro punto de vista se obtuvo el producto con iones cobre (II) con condiciones específicas de acidez, velocidad de agitación, diámetro de partícula, temperatura, concentraciones de iones Cu2+ y tiempo de contacto.The determinations ruling the processes of Cu2+ ions sorption in steady state with and without ultrasonic impulses in a silica base product with water of zeolitic-behaviour structure obtained by gelification, are introduced. Two fractions of different particle size are selected to determine its apparent density, confined apparent density, true density, compressibility, porosity, shape factor, specific surface. The sorption process is carried out in given acidity, temperature, pulse, Cu22+ concentration, particle diameter and time. From an alternative viewpoint, the product is obtained with Cu2+ ions in specific conditions of acidity, shake speed, particle diameter, temperature, Cu2+ concentration and contact time.Asociación Argentina de Energías Renovables y Medio Ambiente (ASADES

Estudio de la adsorción de iones Cu (II) en un sorbente de base silícica en régimen estático mediante efectos mecánicos y sonorización

El presente trabajo expone las determinaciones que se efectuaron para determinar los procesos de sorción de iones Cu (II) en régimen estático con y sin impulsos ultrasónicos en un producto de base silícica con agua de comportamiento zeolítico en su estructura obtenido mediante un proceso de gelificación. Se escogieron dos fracciones con tamaños de partículas diferentes (0.071 y 0.125 mm de diámetro) a las cuales se les determinaron: densidad aparente, densidad aparente por aprisionamiento, densidad verdadera, compresibilidad, porosidad, factor de forma, superficie específica. El proceso de sorción de iones se lleva a cabo en determinadas condiciones de acidez, temperatura, pulso, concentración de iones Cu2+, diámetro de partícula y tiempo. Desde otro punto de vista se obtuvo el producto con iones cobre (II) con condiciones específicas de acidez, velocidad de agitación, diámetro de partícula, temperatura, concentraciones de iones Cu2+ y tiempo de contacto.The determinations ruling the processes of Cu2+ ions sorption in steady state with and without ultrasonic impulses in a silica base product with water of zeolitic-behaviour structure obtained by gelification, are introduced. Two fractions of different particle size are selected to determine its apparent density, confined apparent density, true density, compressibility, porosity, shape factor, specific surface. The sorption process is carried out in given acidity, temperature, pulse, Cu22+ concentration, particle diameter and time. From an alternative viewpoint, the product is obtained with Cu2+ ions in specific conditions of acidity, shake speed, particle diameter, temperature, Cu2+ concentration and contact time.Asociación Argentina de Energías Renovables y Medio Ambiente (ASADES