Interactions métaboliques des antifongiques azolés

[Antimicrobial peptides: A new alternative for the treatment of aspergillosis]

Aspergillus fumigatus is the predominant fungal species causing pulmonary aspergillosis. The present-day anti-aspergillosis arsenal is limited, with a number of molecules occasioning severe side effects (amphotericin B) or provoking significant drug interactions (azole derivatives). Moreover, the recent emergence of azole-resistant A. fumigatus strains is a cause for concern. In this context, antimicrobial peptides (AMPs) are emerging as a promising therapeutic approach and alternative or complement to conventional antifungals.

Invasive aspergillosis in liver transplant recipients

BACKGROUND

Liver transplantation is increasing worldwide with underlying pathologies dominated by metabolic and alcoholic diseases in developed countries.

METHODS

We provide a narrative review of invasive aspergillosis (IA) in liver transplant (LT) recipients. We searched PubMed and Google Scholar for references without language and time restrictions.

RESULTS

The incidence of IA in LT recipients is low (1.8%), while mortality is high (∼50%). It occurs mainly early (<3 months) after LT. Some risk factors have been identified before (corticosteroid, renal, and liver failure), during (massive transfusion and duration of surgical procedure), and after transplantation (intensive care unit stay, re-transplantation, re-operation). Diagnosis can be difficult and therefore requires full radiological and clinicobiological collaboration. Accurate identification of Aspergillus species is recommended due to the cryptic species, and susceptibility testing is crucial given the increasing resistance of Aspergillus fumigatus to azoles. It is recommended to reduce the dose of tacrolimus (50%) and to closely monitor the trough level when introducing voriconazole, isavuconazole, and posaconazole. Surgery should be discussed on a case-by-case basis. Antifungal prophylaxis is recommended in high-risk patients. Environmental preventative measures should be implemented to prevent outbreaks of nosocomial aspergillosis in LT recipient units.

CONCLUSION

IA remains a very serious disease in LT patients and should be promptly sought and, if possible, prevented by clinicians when risk factors are identified.

Influence of Experimental Cryptococcal Meningitis in Wistar Rats on Voriconazole Brain Penetration Assessed by Microdialysis

To make advances in the treatment of cryptococcal meningitis, it is crucial to know a given drug's free fraction that reaches the biophase. In the present study, we applied microdialysis (μD) as a tool to determine the free levels reached by voriconazole (VRC) in the brains of healthy and Cryptococcus neoformans-infected rats. The infection was induced by the intravenous (i.v.) administration of 1 × 105 CFU of yeast. The dose administered was 5 mg/kg (of body weight) of VRC, given i.v. Plasma and microdialysate samples were analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and LC-UV methods. The free brain/free plasma ratio (fT) and population pharmacokinetic (popPK) analyses were performed to evaluate the impact of infection on PK parameters of the drug. The brain penetration ratio showed an increase on brain exposure in infected animals (fThealthy = 0.85 versus fTinfected = 1.86). The structural PK model with two compartments and Michaelis-Menten (MM) elimination describes the VRC concentration-time profile in plasma and tissue simultaneously. The covariate infection was included in volume of distribution in the peripheral compartment in healthy animals (V2) and maximum rate of metabolism (VM ). The levels reached in infected tissues were higher than the values described for MIC of VRC for Cryptococccus neoformans (0.03 to 0.5 μg ml-1), indicating its great potential to treat meningitis associated with C. neoformans.

Antimicrobial activity of saquayamycins produced by Streptomyces spp. PAL114 isolated from a Saharan soil

A new strain of actinomycete designated PAL114, producing antimicrobial compounds, was isolated from a Saharan soil in Ghardaïa, Algeria. Morphological and chemical studies showed that this strain belonged to the genus Streptomyces. Two bioactive compounds, named P41A and P41B, were extracted by dichloromethane from the cell-free supernatant broth of strain PAL114 and were purified by HPLC. Minimum inhibitory concentrations of the pure antibiotics were determined against yeasts, filamentous fungi and bacteria, most of which are pathogenic or toxigenic for human and multiresistant to antibiotics. The strongest activities were observed against Candida albicans M3 and Bacillus subtilis ATCC 6633. The chemical structures of the compounds were determined by spectroscopic analysis of UV-visible and 1H and 13C NMR spectra and spectrometric analysis of mass spectrum. The compounds P41A and P41B were identified as saquayamycins A and C, respectively. These compounds belong to the aquayamycin-group antibiotics, which are known in the literature for their anticancer and antibacterial activities.

[Auditory hallucinations due to voriconazole: Illustration by plasma monitoring]

Voriconazole is a second-generation azole antifungal that is widely indicated in the treatment of invasive aspergillosis. It is generally well tolerated. It has nevertheless numerous side effects like hepatotoxicity, photosensitivity, skin rashes, and visual disturbances. Hallucinations were also reported as side effects to voriconazole but auditory hallucinations were rarely reported and seem to be related to toxic voriconazole blood levels. We report, herein, a case of auditory hallucination with monitoring of voriconazole plasma concentration during hallucination and after its disappearance. A 38-year-old man was treated with intravenously voriconazole for a pulmonary aspergillosis. Seven days after the initiation of voriconazole, the patient presented a sudden history of auditory hallucination associated to incoherence and temporo-spatial disorientation. Therapeutic drug monitoring of voriconazole showed a plasmatic residual concentration (C0) of 7.5μg/mL (therapeutic interval: 1.4-1.8μg/mL) and a pic concentration (Cmax) of 9.83μg/mL (therapeutic interval: 2.1-4.8μg/ml). Voriconazole was then stopped and, two days later, symptomatology completely disappeared and at the same time levels of voriconazole decreased (C0=0.11μg/mL and Cmax=2.17μg/mL). We concluded in our case that the patient's auditory hallucinations were caused by voriconazole treatment. In fact, the sudden onset of hallucinations was concomitant with high plasmatic voriconazole levels, and since the medication was stopped, an important decrease of voriconazole levels was observed which was associated with a sudden disappearance of the auditory hallucinations.

Effects of voriconazole on tacrolimus metabolism in a kidney transplant recipient

Infection occurs frequently in the organ transplant recipients during the post-transplant period because of immunosuppression. Therefore, prophylactic antimicrobial agents are often used. The azole antifungals, widely prescribed prophylactically, are known to have many drug-drug interactions. This report presents a case of drug-drug interaction between voriconazole and tacrolimus in a kidney transplant recipient. Voriconazole treatment led to a dramatic increase in tacrolimus concentration that required its discontinuation in spite of the manufacturer's guidelines that recommend a reduction of tacrolimus dosage by one-third. The present drug-drug interaction can be attributed to a strong inhibitory effect on cytochrome P450-3A4 activity by voriconazole. When voriconazole and tacrolimus are coadministered, close monitoring of tacrolimus blood levels is recommended as the rule-of-thumb reduction of tacrolimus dose by one-third may not be satisfactory.