Caspofungin at sub-inhibitory concentration promotes the formation of Candida albicans persister cells.

AIMS: Low caspofungin exposure is frequently encountered in patients with invasive candidiasis caused by Candida albicans. This study aimed to investigate the effects of caspofungin on C. albicans at sub-inhibitory concentrations. METHODS AND RESULTS: First, a comparative transcriptomics analysis was performed on C. albicans receiving caspofungin at sub-minimum inhibitory concentrations (sub-MICs). The results showed that caspofungin significantly changed the mRNA expression profile in DAY185, with DE-mRNAs enriched in the functions of cell wall biosynthesis, metabolism, etc. Subsequently, cellular fitness, cell aggregation, energy metabolism activity and the proportion of persister cells of C. albicans were quantitatively and/or qualitatively assessed after sub-MIC caspofungin exposure. No significant changes in cell fitness and aggregation formation were observed during treatment of C. albicans with sub-MIC caspofungin. In C. albicans aggregation treated with sub-MIC caspofungin, we observed a decrease in respiratory metabolism and an increase in persister cells; this effect was more pronounced in als1ΔΔ than in DAY185. CONCLUSIONS: Pre-exposure to sub-MIC caspofungin suppresses C. albicans respiratory metabolism and promotes persister cell development. SIGNIFICANCE AND IMPACT OF THE STUDY: Caspofungin should be used with caution in patients with C. albicans infections, as anti-infection therapy may fail due to persister cells.

Acquisition of Tigecycline Resistance by Carbapenem-Resistant Klebsiella pneumoniae Confers Collateral Hypersensitivity to Aminoglycosides.

Tigecycline is a last-resort antibiotic for infections caused by carbapenem-resistant Klebsiella pneumoniae (CRKP). This study aimed to broaden our understanding of the acquisition of collateral hypersensitivity by CRKP, as an evolutionary trade-off of developing resistance to tigecycline. Experimental induction of tigecycline resistance was conducted with tigecycline-sensitive CRKP clinical isolates. Antimicrobial susceptibility testing, microbial fitness assessment, genotypic analysis and full-genome sequencing were carried out for these clinical isolates and their resistance-induced descendants. We found that tigecycline resistance was successfully induced after exposing CRKP clinical isolates to tigecycline at gradually increased concentrations, at a minor fitness cost of bacterial cells. Quantitative reverse transcription-polymerase chain reaction (RT-PCR) found higher expression of the efflux pump gene acrB (5.3-64.5-fold) and its regulatory gene ramA (7.4-65.8-fold) in resistance-induced strains compared to that in the tigecycline-sensitive clinical isolates. Stable hypersensitivities to aminoglycosides and other antibiotics were noticed in resistance-induced strains, showing significantly lowered MICs (X 4 - >500 times). Full genome sequencing and plasmid analysis suggested the induced collateral hypersensitivity might be multifaceted, with the loss of an antimicrobial resistance (AMR) plasmid being a possible major player. This study rationalized the sequential combination of tigecycline with aminoglycosides for the treatment of CRKP infections.

[Spermatozoal immobilization ability and virulence genes of Staphylococcus aureus isolated from the semen of infertile men].

OBJECTIVE: To investigate the impact of Staphylococcus aureus from infertile men on sperm motility and the relationship between virulence genes and the activity of spermatozoal immobilization. METHODS: We collected 60 strains of non-repeated Staphylococcus aureus from the semen of 589 infertile males and analyzed the influence of Staphylococcus aureus on sperm motility using the computer-aided sperm analysis system. We selected the strains that apparently decreased sperm motility and detected their virulence genes by PCR. RESULTS: Sperm motility was significantly decreased in 17 of the 60 strains of Staphylococcus aureus (P < 0.05). The main virulence genes in these strains were hlg (33.3%), scn (23.3%), cna (20%), hlb (20%), and clfA (18.3%), others including icaA, fnbA, tst, seb, hld, eta and sea. The scn gene carriers accounted for 47.1% in the spermatozal immobilization positive group, significantly higher than 14% in the negative group (P < 0.05). No statistically significant differences were found in the percentages of the carriers of the other virulence genes between the two groups (P > 0.05). CONCLUSION: Infections of Staphylococcus aureus in male reproductive system can lead to the decrease of sperm motility, which may be associated with the Staphylococcus complement inhibitor encoding gene scn.