Objective:To establish a real-time fluorescence-based PCR method for the rapid identification of mycobacteria in skin biopsies.Methods:Primers and probes targeting the genus Mycobacterium and 14 common Mycobacterium species were self-designed, and a real-time fluorescence-based PCR detection system/method was established. Twelve standard strains of Mycobacterium were used for in vitro validation. Tissue samples were collected from 119 patients clinically diagnosed with cutaneous mycobacterial infections at the Department of Dermatology and Venereology, Peking University First Hospital from 2019 to 2021, and were tested with the established real-time fluorescence-based PCR method. Results:In vitro testing demonstrated that the method had good sensitivity and specificity for all the 12 standard strains of Mycobacterium. Among the 119 skin biopsy samples from patients clinically diagnosed with cutaneous mycobacterial infections, the culture positivity rate was only 21.0% (25/119) ; the real-time fluorescence-based PCR yielded a positivity rate of 76.5% (91/119) for the detection of mycobacteria, and 44.5% (53/119) were identified to the species level with Mycobacterium marinum as the predominant species; 31.9% (38/119) were identified only to the genus level. Conclusion:A real-time fluorescence-based PCR method has been established for the efficient detection of mycobacteria in skin tissue samples; however, there remains a possibility of missed diagnoses, other molecular diagnostic techniques are required to be combined to improve the sensitivity and specificity.

Objective:To investigate the clinical and mycological characteristics, treatment and prognosis of invasive candidiasis(IC)in the elderly.Methods:This retrospective study included aged patients(≥65 years)admitted to the Peking University First Hospital between January, 2010 and December, 2019, who were diagnosed with IC based on positive culture results.The infecting strains were re-identified and their antifungal drug resistance was tested.The clinical and mycological characteristics, treatment and prognosis information of the elderly patients were collected and compared with those of non-elderly adults.Results:A total of 99 aged patients were included, with a median age of 78(70-83)years and a male-to-female ratio of 2.1∶1.0.The elderly accounted for 62.7%(99/158)of the adult IC patients.Compared with their younger counterparts, elderly patients were more likely to need medium-to long-term hospitalization and intensive care unit(ICU)stay, and to show concurrent heart failure, respiratory failure or renal failure, to require mechanical ventilation, and to show deep-seated bacterial infections and multifocal Candida colonization, especially for those with previous fluconazole exposure( P<0.05). Bloodstream was the most common Candida transmission route(71/99, 71.7%)and Candida albicans was the most prevalent species(47/99, 47.5%). Antifungal resistance was highest for fluconazole(17/117, 14.5%)and voriconazole(15/117, 12.8%). No significant difference was found between elderly patients and non-elderly patients in terms of infected sites, Candida species, and antifungal resistance( P>0.05). A total of 86 patients(86.9%)received systemic antifungal treatment and fluconazole was the most commonly used drug(35/86, 40.7%). The thirty-day all-cause mortality in aged IC patients was 32.6%(29/89), significantly higher than in younger patients( P=0.022). Logistic regression analysis revealed that advanced age( OR=1.12, 95% CI: 1.06-1.20, P<0.001), renal failure( OR=4.81; 95% CI: 1.65-14.03; P=0.004), and a high Candida score( OR=1.81, 95% CI: 1.06-3.11, P=0.031)significantly increased the risk of death. Conclusions:Elderly patients were the main affected population of IC, and the mortality of IC steadily increases with age.Treatment for aged IC patients should be proactive and cautious.