Ngo Thi, H. | Search bioRxiv

bioRxiv2025

In Vitro Evidence to Support Amphotericin B and Flucytosine Combination Therapy for Talaromycosis

BackgroundTalaromyces marneffei causes talaromycosis, a life-threatening fungal disease with limited treatment options. The standard treatment of amphotericin B (AmB) induction followed by itraconazole consolidation still results in 15% to 30% mortality. This study aimed to investigate the potential of AmB and flucytosine (5FC) combination therapy to enhance antifungal activity. MethodsThe in vitro antifungal activity of AmB and 5FC alone and in combination against 60 T. marneffei clinical isolates was evaluated using a validated colorimetric antifungal susceptibility assay and the checkerboard method. The minimum inhibitory concentration (MIC) was defined as the lowest drug concentration inhibiting [≥] 95% fungal growth (MIC95) for both AmB and 5FC. The combination effect between AmB and 5FC against T. marneffei was determined using fractional inhibitory concentration index. Combination effects were further tested using a time-kill assay. ResultsThe MIC95 was 0.25 - 2 g/mL (geometric mean [GM] 0.68 g/mL) for AmB, and 0.03 - 0.5 g/mL (GM 0.28 g/mL) for 5FC. Full synergy was observed in 4 isolates (7%), and indifference was observed in the remaining 56 isolates (93%). The time-kill experiments revealed a concentration-dependent fungicidal activity of AmB, and concentration-independent fungistatic effect of 5FC. Synergy between AmB and 5FC was confirmed, showing greater than 2-log10 reduction in colony forming units when used in combination. No antagonism was observed. ConclusionsOur study demonstrated in vitro evidence of synergistic activity between AmB and 5FC against T. marneffei, providing the evidence to support in vivo and clinical trial testing of AmB and 5FC combination therapy, and dosing reduction strategies of 5FC. Lay SummaryThis study demonstrated in vitro synergy between amphotericin B and flucytosine against Talaromyces marneffei, providing the proof of concept to test this antifungal combination in a clinical trial of talaromycosis.

pharmacology and toxicology↗

bioRxiv2017

Global Phylogenetic Analysis Of Escherichia coli And Plasmids Carrying The mcr-1 Gene Indicates Bacterial Diversity But Plasmid Restriction

To understand the dynamics behind the worldwide spread of the mcr-1 gene, we determined the population structure of Escherichia coli and of mobile genetic elements (MGEs) carrying the mcr-1 gene. After a systematic review of the literature we included 65 E. coli whole genome sequences (WGS), adding 6 recently sequenced travel related isolates, and 312 MLST profiles. We included 219 MGEs described in 7 Enterobacteriaceae species isolated from human, animal and environmental samples. Despite a high overall diversity, 2 lineages were observed in the E. coli population that may function as reservoirs of the mcr-1 gene, the largest of which was linked to ST10, a sequence type known for its ubiquity in human faecal samples and in food samples. No genotypic clustering by geographical origin or isolation source was observed. Amongst a total of 13 plasmid incompatibility types, the Incl2, lncX4 and IncHI2 plasmids accounted for more than 90% of MGEs carrying the mcr-1 gene. We observed significant geographical clustering with regional spread of lncHI2 plasmids in Europe and Incl2 in Asia. These findings point towards promiscuous spread of the mcr-1 gene by efficient horizontal gene transfer dominated by a limited number of plasmid incompatibility types.

microbiology↗