Virulence Factors and Antifungal Susceptibility Profile of C. tropicalis Isolated from Various Clinical Specimens in Alexandria, Egypt

Abstract

Background: The incidence of candidiasis caused by non-albicans Candida (NAC) species is increasing. Candida tropicalis has emerged as one of the most important NAC species. This study aims to examine the antifungal susceptibility profile and some virulence factors of C. tropicalis isolated from various clinical specimens. Methods: A total of 71 C. tropicalis isolates from various clinical specimens (69.01%, 18.31%, 9.86%, and 2.82% of isolates were collected from urine, respiratory samples, blood, and skin and soft tissue infections, respectively) from ICU patients in Alexandria, Egypt. The isolates were identified at species level by CHROMagar Candida and VITEK 2 compact system. Furthermore, the antifungal susceptibility was determined using the VITEK 2 system AST-YS07 card containing different antifungals. Hemolysin, phospholipase, and proteinase activity and biofilm formation were also tested as virulence factors. Results: Only 30 isolates (42.25%) were non-susceptible (MIC ≥ 4 µg/mL) to fluconazole, of which 28 isolates showed non-susceptibility (MIC ≥ 0.25 µg/mL) to voriconazole. All isolates showed both hemolysin and proteinase activities, while only 9 isolates (12.68%) showed phospholipase production and 70 isolates (98.59%) demonstrated biofilm formation. Strong biofilm production was observed among the blood culture isolates (85.71%), followed by the respiratory and urinary isolates (61.54% and 46.94%, respectively). Conclusions: This study sought to provide useful data on the antifungal susceptibility of C. tropicalis isolates from ICU patients suffering from invasive infections with an increased trend towards elevated MICs levels of both fluconazole and voriconazole. Due to the high incidence of systemic candidiasis and antifungal resistance, C. tropicalis is emerging as a serious root of infections. Therefore, early and accurate identification of Candida species along with susceptibility testing is of utmost importance.

Multilocus sequence typing (MLST) analysis reveals many novel genotypes and a high level of genetic diversity in Candida tropicalis isolates from Italy and Africa

“…In parallel, a worrying increase in the isolation of NAC species has been observed in many geographical regions 39–41 and C. tropicalis appears to be the most frequently isolated species in Latin America and Asian Pacific region 39,41–43 . However, several studies documented the emergence of azole non‐susceptible C. tropicalis isolates in many other geographical areas such as Spain, 19 Italy, 44,45 Turkey, 23 Cameroon, 46 Tanzania, 47 Egypt, 48 Tunisia, 24,49 Lebanon 50 and Algeria, 16 supporting several recent Asian reports that raise awareness of the growing problem of fluconazole resistance detected in this species 31,43,51,52 . Similarly, in this study, we confirm the occurrence of a high level of fluconazole resistance also in Egyptian and Cameroonian isolates, a phenomenon that is in line with the global increasing trend in resistance seen over the last years 39 .…”

Species characterization and antifungal susceptibility profile of yeast isolates from blood cultures of fungemic patients in Thammasat University Hospital, Thailand

“…17 On the contrary, C. albicans isolates (46%) were reported as the most common cause of invasive fungal infection in a study in Srinagarind University Hospital, the Northeast Thailand between 2006 and 2011 and other countries in Asia-Pacific region including Australia, Japan, Korea, Hong Kong (China), Taiwan, Malaysia, Saudi Arabia and Singapore. [17][18] A predominance of C. tropicalis may cause from its pathogenic mechanism reported as a very strong biofilm producer, [19][20] the owner of various virulence factors such as hemolysin, proteinase activity and the ability to survive to high salt concentration. 19,21 Besides, geographic variance especially in tropical countries including Thailand.…”

“…[17][18] A predominance of C. tropicalis may cause from its pathogenic mechanism reported as a very strong biofilm producer, [19][20] the owner of various virulence factors such as hemolysin, proteinase activity and the ability to survive to high salt concentration. 19,21 Besides, geographic variance especially in tropical countries including Thailand. [16][17]22 Although no statistically significant difference between species of Candida and age group was seen, C. glabrata seem to be the most frequent detection among aged patients (mean age = 64±23 years) and C. parapsilosis seem to be more frequently isolated from younger patients (mean age = 42+32 years).…”

Isolamento e perfil de resistência de Candida spp. de animais domésticos e selvagens

“…não segue o mesmo padrão, pois no presente estudo a espécie mais frequentemente isolada foi C. rugosa, seguida de C. parapsilosis. Podese também concluir que existe um envolvimento cada vez maior de espécies não-albicans nas infecções; isso, por sua vez, sugere sua patogenicidade crescente devido a formação de biofilmes e aumento da resistência aos antifúngicos, expandindo a capacidade de infectar e permanecer no hospedeiro (El-Kholy et al, 2021).…”