In Vitro Bactericidal Effect of a β-lactam + Aminoglycoside Combination Against Multiresistant Pseudomonas aeruginosa and Acinetobacter baumannii

Abstract

Pseudomonas aeruginosa and Acinetobacter baumannii are frequently isolated in hospital outbreaks of nosocomial infections. In our hospital, among 1018 strains isolated one year in an intensive care unit, 84 strains (8.3%) of P. aeruginosa and 155 strains (15.2%) of A. baumannii were considered responsible for infections. The major problem related to these bacteria is their multiresistant characteristic which confers great difficulty in treating infections. We carried out a 24 h time-kill study to assess the bactericidal effect of three β-lactams [imipenem (IPM), ticarcillin + clavulanic acid (TCC), piperacillin + tazobactam (PTB)] in combination with each other and with sulbactam (SUL) and amikacin (AKN) against 8 P. aeruginosa strains and 8 A. baumannii strains. The initial inoculum was 10⁶ cfu/ml. Antibiotics were tested at clinically achievable concentrations: TCC (112 mg/l), PTB (100 mg/l), IPM (25 mg/l) and AKN (15 mg/l). The results showed: IMP+TCC+AKN = PTB+SUL+AKN = PTB+TCC+ AKN >> IMP+SUL+AKN against P. aeruginosa; and PTB+SUL+AKN = PTB+TCC+AKN > IMP+SUL+AKN or IMP+TCC+AKN against A. baumannii. When infection due to these multiresistant strains was suspected, PTB+AKN combined with either TCC or SUL was bactericidal against both strains. These combinations appeared to be an alternative therapy in the treatment of undocumented nosocomial infections in intensive care units. These In Vitro results are being evaluated in patients and seem to give good results for the moment.     

In- Vitro Susceptibility of Clinical Isolates of Pseudomonas aeruginosa to β-Lactam and Aminoglycoside Antibiotics

Summary

The in-vitro susceptibilities of 198 isolates of Pseudomonas aeruginosa from clinical human specimens were determined by an agar dilution technique against (β-lactams and aminoglycosides. These isolates were susceptible to imipenem, aztreonam and ceftazidime with the minimum inhibitory concentration (MIC) for 90% of the strains tested being 8, 16 and 8 μg/ml, respectively. Aminoglycosides, except amikacin, had low activity (MIC90 > 128 μg/ml).     

In Vitro and In Vivo Efficacy of YTR-830H and Piperacillin Combinations Versus β-Lactamase-Producing Bacteria

Summary

YTR-830H, a β-lactamase inhibitor, is a non-amino penicillanic sulfone. In vitto synergistic activity with piperacillin was determined for 226 β-lactamase producing clinical cultures. Combination of piperacillin: YTR in ratios of 2:1, 4:1, and 8:1 were highly effective vs Escherichia coli, Proteus, Providencia, Morganella, Staphylococcus, and Bacteroides. Minimum inhibitory concentrations (MICs) of piperacillin were reduced from the resistant to susceptible range. The higher ratios were less effective vs Enterobacter, Serratia, and Citrobacter. YTR-830H was not antagonistic with piperacillin. Combinations of 2:1, 4:1, and 8:1 increased the therapeutic effectiveness of piperacillin 8 - to 36 - fold against acute lethal infections produced in mice with piperacillin-resistant Escherichia coli, Klebsiella pneumoniae, Morganella morganii, and Staphylococcus aureus.     

Kinetics of Antimicrobial Activity of Amoxicillin/Clavulanic Acid and Metronidazole against β-Lactamase-Producing Bacteroides fragilis Group

Summary

Bacteroides fragilis group are the most common anaerobic bacteria isolated in clinical specimens. The use of a beta-lactam with a β-lactamase inhibitor should result in a marked increase in the group's sensitivity to the β-lactams. Since the activity (MIC) shown by the amoxicillin + clavulanic acid combination against Bacteroides fragilis group is good, other parameters of in vitro activity have been studied. This study was also done with metronidazole. The minimum inhibitory concentration (MIC) was determined in 26 strains of Bacteroides fragilis group (14 B. fragilis; 5 B. thetaiotaomicron; 4 B. vulgatus; 3 B. distasonis). Likewise, the minimum bactericidal concentration (MBC), the killing curve, the sub-MIC and post-antibiotic effect were determined.

The MIC ranged between 0.5 and 32 mg/l. The MBC was two- to four-fold the MIC for amoxicillin/clavulanic acid, and one- to two-fold the MIC for metronidazole for most strains. The killing curve showed a continuous decrease, sloping most sharply between 0-2 hours and 6-8 hours. Amoxicillin + clavulanic acid showed a post-antibiotic effect between 2 and 4 hours. The inhibitory minimum antibiotic concentration was one-half the MIC for most strains.     

Update of the Activity of Cefditoren and Comparator Oral β-lactam Agents Tested Against Community-Acquired Streptococcus pneumoniae Isolates (USA, 2004-2006)

Abstract

Cefditoren and other orally administered cephalosporins are infrequently included in resistance surveillance studies. Here we evaluated 359 contemporary (2004-2006) strains of Streptococcus pneumoniae, including penicillin-intermediate (12.0%) and -resistant (22.8%) subsets from United States patients by reference broth microdilution methods. Cefditoren was the most potent cephalosporin tested (MIC₅₀, 0.015 mg/L), including against penicillin-intermediate strains (MIC₅₀, 0.12 mg/L), and was two-, fourand eight-fold more active than cefuroxime, cefdinir and cefprozil, respectively. Penicillin- resistant strains were largely resistant to all tested β-lactams. We confirm the continued spectrum and potency for cefditoren against S. pneumoniae that surpasses that of other orally administered cephalosporins.     

Comparative In Vitro Activity of Telithromycin and β-Lactam Antimicrobials Against Bacterial Pathogens from Community-Acquired Respiratory Tract Infections: Data from the First Year of PROTEKT (1999-2000)

Abstract

The In Vitro activity of telithromycin, a new ketolide, was compared with β-lactam antimicrobials against pathogens commonly associated with community-acquired respiratory tract infections. These pathogens were collected during 1999-2000 as part of the ongoing PROTEKT surveillance study. Globally, penicillin non-susceptibility among Streptococcus pneumoniae (n=3362) was 36.3%, ranging from 21.5% (Australasia) to 68.0% (Far East). Telithromycin showed higher potency (MIC₉₀ 0.12 mg/L) than β-lactams against S. pneumoniae; 99.9% of all and 99.6% of multi-resistant isolates were susceptible to telithromycin. Among Streptococcus pyogenes isolates (n=1485), 100% were susceptible to β-lactams, and the telithromycin MIC₅₀ and MIC₉₀ were both 0.015 mg/L. Among Haemophilus influenzae (n=2948), 16.6% produced β-lactamase, which reduced the activity of ampicillin, cefaclor and cefprozil. 99.9% of H. influenzae were susceptible to telithromycin and the MIC range for M. catarrhalis was 0.004-0.5 mg/L. The first year results of PROTEKT confirmed high potency for telithromycin against common respiratory tract pathogens, including β-lactam-resistant strains.     

Combination of microtubule associated protein-tau and β-tubulin III predicts chemosensitivity of paclitaxel in patients with advanced gastric cancer

AimTo investigate the role of microtubule associated protein-tau (MAP-tau) and β-tubulin III (TUBB3) in predicting the chemosensitivity of paclitaxel in patients with advanced gastric cancer (GC).MethodsMAP-tau and TUBB3 expressions were detected using immunohistochemistry in 244 advanced GC patients prior to chemotherapy. The associations of MAP-tau and TUBB3 expressions with paclitaxel sensitivity were assessed using in vitro and in vivo xenograft analysis.ResultsA total of 149 patients receiving paclitaxel plus capecitabine (cohort 1) and 95 patients receiving cisplatin plus capecitabine (cohort 2) were included in this study. In cohort 1, the clinical benefit rate (CBR), median progression-free survival (PFS) and overall survival (OS) were found to be significantly higher in patients with low levels of MAP-tau and TUBB3 expressions and were significantly higher than those in patients with high levels of MAP-tau and TUBB3 expressions (CBR: 72.2% versus 35.9%; PFS: 271 versus 102 days; OS: 394 versus 173 days; all P < 0.05). This was not observed in cohort 2. In in vitro studies, the sensitivity of paclitaxel in human gastric cancer cells was inversely correlated with the expression levels of MAP-tau and TUBB3, as in in vivo animal xenografts.ConclusionsThe combination of MAP-tau and TUBB3 was found to predict chemosensitivity to paclitaxel in gastric cancer in vitro and in vivo. This merits further study and may help guide individual therapy.     

Small Molecule Inhibitors of Wnt/β-Catenin/Lef-1 Signaling Induces Apoptosis in Chronic Lymphocytic Leukemia Cells In Vitro and In Vivo

Background

Lymphoid enhancer factor-1 (lef-1) is overexpressed in B-cell chronic lymphocytic leukemia (CLL) when compared with normal B cells and transcribes several genes implicated in the pathogenesis of CLL. We therefore hypothesize that antagonism of lef-1 might lead to killing of CLL cells. We used two small molecule inhibitors of Wnt/β-catenin/lef-1 signaling (CGP049090 and PKF115-584) to test our hypothesis.

Design and Methods

Enriched CLL cells and healthy B cells were used in this study. Small interfering RNA (siRNA)-mediated knockdown of lef-1 in primary CLL cells was done using nucleofection, and 50% lethal concentration (LC₅₀) of two small molecules was assessed using ATP-based cell viability assay. Apoptotic response was investigated in time course experiments with different apoptotic markers. Specificity of the small molecules was demonstrated by coimmunoprecipitation experiments for the lef-1/β-catenin interaction. In vivo studies were done in JVM-3 subcutaneous xenograft model.

Results

Inhibition of lef-1 by siRNA leads to increased apoptosis of CLL cells and inhibited proliferation of JVM-3 cell lines. The two small molecule inhibitors (CGP049090 and PKF115-584) efficiently kill CLL cells (LC₅₀<1 µM), whereas normal B cells were not significantly affected. Coimmunoprecipitation showed a selective disruption of β-catenin/lef-1 interaction. In vivo studies exhibited tumor inhibition of 69% with CGP049090 and 57% with PKF115-584 when compared with vehicle-treated controls, and the intervention was well tolerated.

Conclusions

We have demonstrated that targeting lef-1 is a new and selective therapeutic approach in CLL. CGP049090 or PKF115-584 may be attractive compounds for CLL and other malignancies that deserve further (pre)clinical evaluation.     

Combination of baseline total metabolic tumor volume measured on FDG-PET/CT and β2-microglobulin have a robust predictive value in patients with primary breast lymphoma

The aim was to build a prognostic model to stratify patients at diagnosis into different risk categories. We investigated the prognostic value of functional PET parameters and clinical features in 64 primary breast lymphoma (PBL) patients. With a median follow-up of 60 months, 5-year progression-free survival (PFS) and overall survival (OS) was 62.5% and 73.4%. In multivariate analysis, baseline total metabolic tumor volume (TMTV0) and β2-microglobulin remained more reliable predictors of survival than other prognostic factors. The optimal TMTV0 cut-off value was 90 cm³. Among 29 patients with high TMTV0, 5-year PFS and OS were 44.8% and 62.1%, respectively, while 5-year PFS and OS of 35 patients with low TMTV0 were 74.3% and 85.7%, respectively. TMTV0 combined with β2-microglobulin identified three groups with very different prognosis, including low-risk group with low TMTV0 and β2-microglobulin≤normal (n = 30), intermediate-risk group with high TMTV0 or β2-microglobulin>normal (n = 20), and high-risk group with high TMTV0 and β2-microglobulin>normal (n = 14). In the three groups, 5-year PFS rates were 80%, 55% and 28.6% (P = .003), and 5-year OS rates were 90%, 65%, and 50% (P = .023) respectively. We established a new prognostic model through TMTV0 and β2-microglobulin, and can divide PBL at diagnosis into different risk categories.