Unchanged antibiotic susceptibility in Escherichia coli and Pseudomonas aeruginosa after long-term in vitro exposure to antineoplastic drugs

Repurposing High-Throughput Screening Identifies Unconventional Drugs with Antibacterial and Antibiofilm Activities against Pseudomonas aeruginosa under Experimental Conditions Relevant to Cystic Fibrosis

Pseudomonas aeruginosa is the most common pathogen infecting cystic fibrosis (CF) lungs, causing acute and chronic infections. Intrinsic and acquired antibiotic resistance allow P. aeruginosa to colonize and persist despite antibiotic treatment, making new therapeutic approaches necessary. Combining high-throughput screening and drug repurposing is an effective way to develop new therapeutic uses for drugs. This study screened a drug library of 3,386 drugs, mostly FDA approved, to identify antimicrobials against P. aeruginosa under physicochemical conditions relevant to CF-infected lungs. Based on the antibacterial activity, assessed spectrophotometrically against the prototype RP73 strain and 10 other CF virulent strains, and the toxic potential evaluated toward CF IB3-1 bronchial epithelial cells, five potential hits were selected for further analysis: the anti-inflammatory and antioxidant ebselen, the anticancer drugs tirapazamine, carmofur, and 5-fluorouracil, and the antifungal tavaborole. A time-kill assay showed that ebselen has the potential to cause rapid and dose-dependent bactericidal activity. The antibiofilm activity was evaluated by viable cell count and crystal violet assays, revealing carmofur and 5-fluorouracil as the most active drugs in preventing biofilm formation regardless of the concentration. In contrast, tirapazamine and tavaborole were the only drugs actively dispersing preformed biofilms. Tavaborole was the most active drug against CF pathogens other than P. aeruginosa, especially against Burkholderia cepacia and Acinetobacter baumannii, while carmofur, ebselen, and tirapazamine were particularly active against Staphylococcus aureus and B. cepacia. Electron microscopy and propidium iodide uptake assay revealed that ebselen, carmofur, and tirapazamine significantly damage cell membranes, with leakage and cytoplasm loss, by increasing membrane permeability. IMPORTANCE Antibiotic resistance makes it urgent to design new strategies for treating pulmonary infections in CF patients. The repurposing approach accelerates drug discovery and development, as the drugs' general pharmacological, pharmacokinetic, and toxicological properties are already well known. In the present study, for the first time, a high-throughput compound library screening was performed under experimental conditions relevant to CF-infected lungs. Among 3,386 drugs screened, the clinically used drugs from outside infection treatment ebselen, tirapazamine, carmofur, 5-fluorouracil, and tavaborole showed, although to different extents, anti-P. aeruginosa activity against planktonic and biofilm cells and broad-spectrum activity against other CF pathogens at concentrations not toxic to bronchial epithelial cells. The mode-of-action studies revealed ebselen, carmofur, and tirapazamine targeted the cell membrane, increasing its permeability with subsequent cell lysis. These drugs are strong candidates for repurposing for treating CF lung P. aeruginosa infections.

Impact of extensive antibiotic treatment on faecal carriage of antibiotic-resistant enterobacteria in children in a low resistance prevalence setting

We prospectively studied the consequences of extensive antibiotic treatment on faecal carriage of antibiotic-resistant enterobacteria in a cohort of children with cystic fibrosis (CF) and a cohort of children with cancer compared to healthy children with no or low antibiotic exposure. The study was conducted in Norway in a low resistance prevalence setting. Sixty longitudinally collected faecal samples from children with CF (n = 32), 88 samples from children with cancer (n = 45) and 127 samples from healthy children (n = 70) were examined. A direct MIC-gradient strip method was used to detect resistant Enterobacteriaceae by applying Etest strips directly onto agar-plates swabbed with faecal samples. Whole genome sequencing (WGS) data were analysed to identify resistance mechanisms in 28 multidrug-resistant Escherichia coli isolates. The prevalence of resistance to third-generation cephalosporins, gentamicin and ciprofloxacin was low in all the study groups. At inclusion the prevalence of ampicillin-resistant E. coli and trimethoprim-sulfamethoxazole-resistant E. coli in the CF group compared to healthy controls was 58.6% vs. 28.4% (p = 0.005) and 48.3% vs. 14.9% (p = 0.001), respectively, with a similar prevalence at the end of the study. The prevalence of resistant enterobacteria was not significantly different in the children with cancer compared to the healthy children, not even at the end of the study when the children with cancer had been treated with repeated courses of broad-spectrum antibiotics. Children with cancer were mainly treated with intravenous antibiotics, while the CF group mainly received peroral treatment. Our observations indicate that the mode of administration of antibiotics and the general level of antimicrobial resistance in the community may have an impact on emergence of resistance in intestinal enterobacteria during antibiotic treatment. The WGS analyses detected acquired resistance genes and/or chromosomal mutations that explained the observed phenotypic resistance in all 28 multidrug-resistant E. coli isolates examined.

The weaned pig as a model for Doxorubicin-induced mucositis

BACKGROUND

Chemotherapy-induced mucositis (CIM) complicates cancer therapy and limits maximum tolerated doses and efficacy. Rodent models do not reproducibly mimic clinical CIM, so alternative models are needed.

METHODS

CIM severity was assessed after weaned pigs were treated with doxorubicin (5 and 3.75 mg/kg) using clinical observations, laboratory parameters and gastrointestinal structure and functions. Bovine colostrum was provided as an experimental intervention to the pigs treated receiving the 3.75 mg/kg dose.

RESULTS

Doxorubin at 3.75 mg/kg decreased food intake and weight gain (p < 0.05) and caused diarrhea and vomiting that coincided with damage to the small intestine mucosa based on histological scoring (p < 0.05). It resulted in higher serum TNF-α concentrations, increased chloride secretion and reduced brush border membrane disaccharidase activities and carrier-mediated glucose uptake (all p < 0.05). The gastrointestinal damage and dysfunction resemble the clinical and laboratory features of CIM in humans; these can be partially prevented by providing cow colostrum.

CONCLUSION

The weaned pig is a relevant large animal for studying CIM and evaluating existing and experimental interventions for mucositis.

Chiari malformation type III and results of surgery: a clinical study: report of eight surgically treated cases and review of the literature

BACKGROUND

The characteristics of Chiari malformation type III and its treatment are evaluated in this study. Radiological and surgical findings were correlated and the benefits of the therapy are discussed.

METHODS

Eight patients (6 males, 2 females) with Chiari malformation type III were studied. All patients underwent surgery to remove encephalocele along with neural tissue and to repair the dura and the skin. Associated pathologies such as hydrocephalus, tethered cord syndrome and syringomyelia were also surgically treated. Follow-up was based on the evaluation of postoperative motor and mental development, as well as on magnetic resonance imaging findings.

RESULTS

Ventriculoperitoneal shunt malfunction in 2 patients was the only surgical complication. One patient died 10 days after the operation, 7 patients survived, and the outcome of 2 patients was quite poor because of severe mental retardation and neurological deficits at the beginning. In the remaining patients, motor and mental development was normal, and the neurological outcome was satisfactory.

CONCLUSION

Surgery in the newborn period, initial severity of neurological deficits, the presence of intermittent apnoea, delayed treatment of hydrocephalus and the amount of neuronal tissue within the excised encephalocele were determined as unfavourable prognostic factors for the outcome. If the appropriate surgical procedure is done at the right time, the outcome of the Chiari malformation type III patient can be satisfactory with a low mortality rate.