Grepafloxacin against penicillin-resistant pneumococci in the rabbit meningitis model

Grepafloxacin, a new fluoroquinolone, produced bactericidal activity comparable to that of vancomycin and ceftriaxone in the treatment in rabbits of meningitis caused by a pneumococcal strain highly resistant to penicillin (MIC 4 mg/L) (triangle uplog(10) cfu/mL*h for grepafloxacin, -0.32 +/- 0.15; dose, 15 mg/kg iv; triangle uplog(10) cfu/mL*h for vancomycin, -0.39 +/- 0.18; dose, 2 x 20 mg/kg iv; triangle uplog(10) cfu/mL*h for ceftriaxone, -0.32 +/- 0. 12; dose, 125 mg/kg iv). Higher doses of grepafloxacin (30 mg/kg and 2 x 50 mg/kg) did not improve the killing rates. The combination of grepafloxacin with vancomycin was not significantly superior to monotherapies (P > 0.05). In vitro, grepafloxacin was bactericidal at concentrations above the MIC. Using concentrations around the MIC, addition of vancomycin to grepafloxacin showed synergic activity.

Synergy between trovafloxacin and ceftriaxone against penicillin-resistant pneumococci in the rabbit meningitis model and in vitro

The bactericidal activities of monotherapy with trovafloxacin (-0.37 +/- 0.15 Delta log(10) CFU/ml. h), vancomycin (-0.32 +/- 0.12 Delta log(10) CFU/ml. h), and ceftriaxone (-0.36 +/- 0.19 Delta log(10) CFU/ml. h) for the treatment of experimental meningitis in rabbits due to a clinical penicillin-resistant pneumococcal strain (MIC, 4 mg/liter) were similar. The combination of ceftriaxone with trovafloxacin considerably improved the killing rates (-0.67 +/- 0.16 Delta log(10) CFU/ml. h) and was slightly superior to ceftriaxone with vancomycin (killing rate, -0.53 +/- 0. 22 Delta log(10) CFU/ml. h), the regimen most commonly used in clinical practice. In vitro, synergy was demonstrated between ceftriaxone and trovafloxacin by the checkerboard method (fractional inhibitory concentration index, 0.5) and by time-killing assays over 8 h.

Evaluation of cefepime alone and in combination with vancomycin against penicillin-resistant pneumococci in the rabbit meningitis model and in vitro

Cefepime, a broad-spectrum, fourth-generation cephalosporin, showed excellent CSF penetration with levels ranging between 10 and 16 mg/L after two intravenous injections (100 mg/kg). The bactericidal activity of cefepime (-0.60 +/- 0.28 Deltalog(10) cfu/mL/h) was superior to that of ceftriaxone (-0.34 +/- 0.23 Deltalog(10) cfu/mL/h, P < 0.05) and vancomycin (-0.39 +/- 0.19 Deltalog(10) cfu/mL/h, P < 0.05) in the treatment of rabbits with meningitis caused by an isolate highly resistant to penicillin (MIC of penicillin G: 4 mg/L). The addition of vancomycin to both cephalosporins did not significantly increase the killing rate compared with monotherapies (P > 0.05). Similar results were obtained in time-killing experiments in vitro.

Trovafloxacin in combination with vancomycin against penicillin-resistant pneumococci in the rabbit meningitis model

Trovafloxacin, a new fluoroquinolone, produced bactericidal activity (-0.33 +/- 0.13 delta log10 CFU/ml.h; intravenously [i.v.] administered dose, 15 mg/kg) comparable to that of vancomycin (-0.39 +/- 0.18 delta log10 CFU/ml.h; i.v. admininistered dose, 20 mg/kg) in the treatment of experimental meningitis in rabbits due to a pneumococcal strain highly resistant to penicillin (MIC of penicillin G, 4 micrograms/ml). The combination of both drugs significantly increased (P < 0.05) the killing rate (-0.60 +/- 0.23 delta log10 CFU/ml.h) compared to that produced by either monotherapy. These results were also confirmed in vitro.

Foxo-mediated Bim transcription is dispensable for the apoptosis of hematopoietic cells that is mediated by this BH3-only protein

The BH3-only protein Bim is a critical initiator of apoptosis in hematopoietic cells. Bim is upregulated in response to growth factor withdrawal and in vitro studies have implicated the transcription factor Foxo3a as a critical inducer. To test the importance of this regulation in vivo, we generated mice with mutated Foxo-binding sites within the Bim promoters (Bim(ΔFoxo/ΔFoxo)). Contrary to Bim-deficient mice, Bim(ΔFoxo/ΔFoxo) mice had a normal hematopoietic system. Moreover, cytokine-dependent haematopoietic cells from Bim(ΔFoxo/ΔFoxo) and wt mice died at similar rates. These results indicate that regulation of Bim by Foxo transcription factors is not critical for the killing of hematopoietic cells.

Efficacy of taurolidine against periodontopathic species--an in vitro study

The antimicrobial effect of taurolidine was tested against periodontopathic species in comparison to chlorhexidine digluconate in the presence or absence of serum. Minimal inhibitory concentrations (MIC), microbiocidal concentrations (MBC), as well as killing were determined against 32 different microbial strains including 3 Porphyromonas gingivalis, 3 Aggregatibacter actinomycetemcomitans, and 15 potentially superinfecting species with and without 25% v/v human serum. The MIC(50) of taurolidine against the tested microbial strains was 0.025% and the MIC(90) 0.05%. The respective values for the MBCs were 0.05% and 0.1%. Addition of 25% serum (heat-inactivated) did not change the MIC and MBC values of taurolidine. In contrast, MICs and MBCs of chlorhexidine (CHX) increased by two steps after addition of serum. Taurolidine killed microorganisms in a concentration and time-dependent manner, the killing rate of 1.6% taurolidine was 99.08% ± 2.27% in mean after 2 h. Again, killing activity of taurolidine was not affected if serum was added, whereas addition of inactivated serum clearly reduced the killing rate of all selected bacterial strains by CHX. Therefore, taurolidine possesses antimicrobial properties which are not reduced in the presence of serum as a main component in gingival crevicular fluid and wound fluid. Taurolidine may have potential as an antimicrobial agent in non-surgical and surgical periodontal treatment.

Effect of ozone on periodontopathogenic species--an in vitro study

The in vitro study was aimed to determine the effect of ozone on periodontopathogenic microorganisms. Ozone was generated for 6 s-2 × 24 s (corresponding to 0.56 mg-2 × 2.24 mg of ozone) against 23 mainly anaerobic periodontopathogenic species. Agar diffusion test was used as a screening method. Then, the killing activity was tested in a serum-free environment and with 25% v/v inactivated serum. Further, the effect of ozone on bactericidal activity of native serum was analyzed against Fusobacterium nucleatum, Porphyromonas gingivalis, and Aggregatibacter actinomycetemcomitans. Agar diffusion test showed a high efficacy of ozone against microorganisms, especially against Porphyromonas gingivalis. This result was confirmed by the killing tests; most of the strains in a concentration of 10(5) were completely eliminated after twofold 18-s application of ozone. Only four of the six potentially "superinfecting" species (Staphylococcus aureus, Enterococcus faecalis, Enterobacter cloacae, Candida albicans) survived in part. Addition of heat-inactivated serum reduced the killing rate of ozone by 78% after 6-s and by 47% after twofold 18-s exposures; no strain was completely eradicated after any application of ozone. The bactericidal effect of native serum was enhanced after application of ozone; no effect was visible on the included A. actinomycetemcomitans strain which was found to be completely resistant to the bactericidal action of serum. In conclusion, (a) ozone has a strong antibacterial activity against putative periodontopathogenic microorganisms, and (b) the bactericidal effect is reduced in the presence of serum. Ozone may have potential as an adjunctive application to mechanical treatment in periodontitis patients.

Efficacy of gatifloxacin alone and in combination with cefepime against penicillin-resistant Streptococcus pneumoniae in a rabbit meningitis model and in vitro

Gatifloxacin penetrated well into cerebrospinal fluid (CSF) (49 +/- 11%), measured by comparison of AUC(CSF)/AUC(serum), and showed good bactericidal activity (leading to a decrease of 0.75 +/- 0.17 log10 cfu/mL/h) in the treatment of experimental meningitis in rabbits caused by a penicillin-resistant pneumococcal strain (MIC 4 mg/L). It was significantly more effective than the standard regimen, ceftriaxone with vancomycin, which led to a decrease of 0.53 +/- 0.17 log10 cfu/mL/h. The addition of cefepime to gatifloxacin slightly improved the killing rates (giving a decrease of 0.84 +/- 0.14 log10 cfu/mL/h). In vitro, synergy was demonstrated between cefepime and gatifloxacin by the chequerboard method (fractional inhibitory concentration index = 0.5) and by viable counts over 8 h.

Virulence and genotype-associated infectivity of interferon-treated macrophages by porcine reproductive and respiratory syndrome viruses.

The polarization into M1 and M2 macrophages (MΦ) is essential to understand MΦ function. Consequently, the aim of this study was to determine the impact of IFN-γ (M1), IL-4 (M2) and IFN-β activation of MΦ on the susceptibility to genotype 1 and 2 porcine reproductive respiratory syndrome (PRRS) virus (PRRSV) strains varying in virulence. To this end, monocyte-derived MΦ were generated by culture during 72h and polarization was induced for another 24h by addition of IFN-γ, IL-4 or IFN-β. MΦ were infected with a collection of PRRSV isolates belonging to genotype 1 and genotype 2. Undifferentiated and M2 MΦ were highly susceptible to all PRRSV isolates. In contrast, M1 and IFN-β activated MΦ were resistant to low pathogenic genotype 1 PRRSV but not or only partially to genotype 2 PRRSV strains. Interestingly, highly virulent PRRSV isolates of both genotypes showed particularly high levels of infection compared with the prototype viruses in both M1 and IFN-β-treated MΦ (P<0.05). This was seen at the level of nucleocapsid expression, viral titres and virus-induced cell death. In conclusion, by using IFN-γ and IFN-β stimulated MΦ it is possible to discriminate between PRRSV varying in genotype and virulence. Genotype 2 PRRSV strains are more efficient at escaping the intrinsic antiviral effects induced by type I and II IFNs. Our in vitro model will help to identify viral genetic elements responsible for virulence, an information important not only to understand PRRS pathogenesis but also for a rational vaccine design. Our results also suggest that monocyte-derived MΦ can be used as a PRRSV infection model instead of alveolar MΦ, avoiding the killing of pigs.

CXCL14 Displays Antimicrobial Activity against Respiratory Tract Bacteria and Contributes to Clearance of Streptococcus pneumoniae Pulmonary Infection

CXCL14 is a chemokine with an atypical, yet highly conserved, primary structure characterized by a short N terminus and high sequence identity between human and mouse. Although it induces chemotaxis of monocytic cells at high concentrations, its physiological role in leukocyte trafficking remains elusive. In contrast, several studies have demonstrated that CXCL14 is a broad-spectrum antimicrobial peptide that is expressed abundantly and constitutively in epithelial tissues. In this study, we further explored the antimicrobial properties of CXCL14 against respiratory pathogens in vitro and in vivo. We found that CXCL14 potently killed Pseudomonas aeruginosa, Streptococcus mitis, and Streptococcus pneumoniae in a dose-dependent manner in part through membrane depolarization and rupture. By performing structure-activity studies, we found that the activity against Gram-negative bacteria was largely associated with the N-terminal peptide CXCL141-13. Interestingly, the central part of the molecule representing the β-sheet also maintained ∼62% killing activity and was sufficient to induce chemotaxis of THP-1 cells. The C-terminal α-helix of CXCL14 had neither antimicrobial nor chemotactic effect. To investigate a physiological function for CXCL14 in innate immunity in vivo, we infected CXCL14-deficient mice with lung pathogens and we found that CXCL14 contributed to enhanced clearance of Streptococcus pneumoniae, but not Pseudomonas aeruginosa. Our comprehensive studies reflect the complex bactericidal mechanisms of CXCL14, and we propose that different structural features are relevant for the killing of Gram-negative and Gram-positive bacteria. Taken together, our studies show that evolutionary-conserved features of CXCL14 are important for constitutive antimicrobial defenses against pneumonia.

Pharmacodynamics of antibiotics in experimental bacterial meningitis--two sides to rapid bacterial killing in the cerebrospinal fluid

In bacterial meningitis, several pharmacodynamic factors determine therapeutic success--when defined as sterilization of the cerebrospinal fluid (CSF); (i) local host defense deficits require the use of bactericidal antibiotics; (ii) CSF antibiotic concentrations that are at least 10-fold above the MBC are necessary for maximal bactericidal activity; (iii) high CSF peak concentrations that lead to rapid bacterial killing appear more important than prolonged suprainhibitory concentrations, probably because very low residual levels in the CSF prevent bacterial regrowth even during relatively long dosing intervals; (iv) penetration of antibiotics into the CSF is significantly impaired by the blood-brain barrier, thus requiring high serum levels to achieve the CSF concentrations necessary for rapid bacterial killing. Beyond these principles, recent data suggest that rapid lytic killing of bacteria in the CSF may have harmful effects on the brain because of the release of biologically active bacterial products. The conflict between the need for rapid CSF sterilization and the harmful consequences of bacterial lysis must be addressed in the therapy of meningitis.

Killing of bacteria by copper surfaces involves dissolved copper

Bacteria are rapidly killed on copper surfaces. However, the mechanism of this process remains unclear. Using Enterococcus hirae, the effect of inactivation of copper homeostatic genes and of medium compositions on survival and copper dissolution was tested. The results support a role for dissolved copper ions in killing.