Peptide-antibiotic conjugates as novel developments for increased antimicrobial transport and efficiency

The emergence of bacterial strains with resistance to most known antibiotics has raised an urgent need for the development of new antimicrobial agents in order to avoid a serious threat to public health and return to the pre-antibiotic era. The ‘Trojan Horse’ strategy is one of the approaches that has been explored to evade membrane – based resistance mechanisms by smuggling the antibiotic in through the bacterial cell membrane(s). The ‘Trojan Horse’ strategy involves conjugating a siderophore, sugar or an amino acid moiety to an antimicrobial agent to allow more effective antimicrobial transport. They can be conjugated through a non-biolabile or a biolabile linker; both types of the ‘Trojan Horse’ conjugates were prepared based on the antibiotic ciprofloxacin and alanine (Ala) and di-alanine (Ala-Ala). The conjugates were screened against wild type E. coli to compare the minimum inhibitory concentrations (MIC)/minimum bacterial concentrations with those of the free parent drug ciprofloxacin. The conjugate coupled through a non-biolabile linker, Ala-Ala-ciprofloxacin, was found to have a very significant reduced antimicrobial activity compared to the parent drug with no evidence of active transport by peptide transporters. A DNA gyrase assay revealed that the conjugate was no longer an effective DNA gyrase-inhibitor. The conjugates coupled through the biolabile disulfide linker, ciprofloxacin-disulfide-Ala and ciprofloxacin-disulfide-Ala-Ala, were found to have retained some antimicrobial activity although lower than that of the parent drug. The conjugates reached a peak OD650 of 3.0 at 0.1 μM whereas ciprofloxacin reached a peak OD650 of 1.0 at the same concentration. No evidence of transport by peptide transporters was observed. The retained antimicrobial activity suggested that intracellular cleavage of the disulfide linker occurred releasing free ciprofloxacin however the reduced antimicrobial activity could be due to inefficient cleavage of the disulfide bond or inefficient intracellular release of ciprofloxacin due to slow formation of the thiirane ring allowing re-formation of a disulfide bond

Expert opinion on diagnosing, treating and managing patients with cerebrotendinous xanthomatosis (CTX): a modified Delphi study

Background Cerebrotendinous xanthomatosis (CTX) is a rare, chronic, progressive, neurodegenerative disorder requiring life-long care. Patients with CTX often experience a diagnostic delay. Although early diagnosis and treatment initiation can improve symptoms and prognosis, a standardised approach to diagnosis, treatment and management of patients is not yet established. Aim To assess expert opinion on best care practices for patients with CTX using a modified Delphi method. Methods A multidisciplinary group of healthcare professionals with expertise in CTX responded to a 3-round online questionnaire (n = 10 in Rounds 1 and 2; n = 9 in Round 3), containing questions relating to the diagnosis, treatment, monitoring, multidisciplinary care and prognosis of patients with CTX. Determination of consensus achievement was based on a pre-defined statistical threshold of >= 70% Delphi panellists selecting 1-2 (disagreement) or 5-6 (agreement) for 6-point Likert scale questions, or >= 70% Delphi panellists choosing the same option for ranking and proportion questions. Results Of the Round 1 (n = 22), Round 2 (n = 32) and Round 3 (n = 26) questions for which consensus was assessed, 59.1%, 21.9% and 3.8% reached consensus, respectively. Consensus agreement that genetic analyses and/or determination of serum cholestanol levels should be used to diagnose CTX, and dried bloodspot testing should facilitate detection in newborns, was reached. Age at diagnosis and early treatment initiation (at birth, where possible) were considered to have the biggest impact on treatment outcomes. All panellists agreed that chenodeoxycholic acid (CDCA) is a lifetime replacement therapy which, if initiated early, can considerably improve prognosis as it may be capable of reversing the pathophysiological process in CTX. No consensus was reached on the value of cholic acid therapy alone. Monitoring patients through testing plasma cholestanol levels and neurologic examination was recommended, although further research regarding monitoring treatment and progression of the disease is required. Neurologists and paediatricians/metabolic specialists were highlighted as key clinicians that should be included in the multidisciplinary team involved in patients' care. Conclusions The results of this study provide a basis for standardisation of care and highlight key areas where further research is needed to inform best practices for the diagnosis, treatment and management of patients with CTX