Candida tropicalis as a Predominant Isolate from Clinical Specimens and its Antifungal Susceptibility Pattern in a Tertiary Care Hospital in Southern India

An Unusual Case of Severe Pneumonia Caused Due Candida Tropicalis With a Favorable Clinical Response to Antifungals in a Nonimmunocompromised Patient From the Community

Severe pneumonia due to Candida tropicalis infection mainly occurs in immunosuppressed patients or those currently receiving broad-spectrum antibiotics. Herein, we report a case of severe pneumonia caused due to C tropicalis in an elderly patient. A 72-year-old man with a previous history of hypertension, ischemic stroke, and facial paralysis sequelae treated with the botulinic toxin, was admitted to the hospital for dyspnea. Severe acute respiratory syndrome coronavirus 2 (SARS-COV-2) infection was negative. Computed tomography of the chest revealed bilateral consolidation with left predominance. A bronchoalveolar lavage sample was sent to molecular biology, but no microorganisms were detected using a FilmArray respiratory panel. However, mamanocandidas test for candida was 166 pg/mL (positive), and fungal structures were identified by the MALDI-TOF Biotyper mass spectrometry and attributed to C tropicalis. Antifungal therapy was started using caspofungin 75 mg as the initial dose followed by 50 mg daily. After 10 days of treatment, ventilatory weaning was achieved. By day 14, the patient was decannulated from the tracheostomy. Oral antifungal treatment with voriconazole was continued, and he was discharged from intensive care in good clinical condition. Severe pneumonia due to C tropicalis might occur in specific cases, especially in those patients with risk factors, and must thus be considered when approaching such cases.

A Study on Prevalence and Characterization of Candida Species in Immunocompromised Patients

Candida spp. is one among the major causes of nosocomial infection, with candidemia gaining increasing prevalence worldwide in parallel with mortality rates ranging from 10-49%. Epidemiology and predisposing factors of candidemia have changed since the number of patients receiving transplants and immunosuppressive therapy, the use of broadspectrum antimicrobials, and the number of AIDS patients have increased. Candidemia is more common among patients with subcutaneous and cutaneous candida infections, through percutaneous inoculation. Major predisposing factors for invasive candidiasis includes neutropenia, haematological malignancies, bone marrow transplantation, total parenteral nutrition, chemotherapy, invasive procedures, and immune-suppressive agents. This study analyses the risk factors of immunocompromised patients with candidemia and antibiogram of Candida spp. isolated from ICU patients. To evaluate the prevalence, distribution and antibiogram of Candida spp., associated risk factors, and outcome in candidemia patients. Blood samples received from patients with clinically suspected fungal infections were subjected to gram staining, culture, sugar assimilation & fermentation, Candida Chrome agar (CCA) & Corn meal agar for identification and speciation. Antifungal susceptibility tests were performed by disk-diffusion tests. Among a total of 337 samples received, 22 (6.5%) samples were positive for candida infections, of which Candida tropicalis 9 (41%) was the predominant isolate followed by C. albicans 5 (23%), Candida glabrata 4 (18%), Candida parapsilosis 2 (9%) and Candida krusei 2 (9%). Male patients had a higher prevalence of candidemia 15 (68.2%). Among the age group of 51-70 years, uncontrolled DM(Diabetes mellitus) and CKD (chronic kidney disease) were found to be the predominant co-morbidities with candidemia.

Candida Pathogenicity and Interplay with the Immune System

Candida species are opportunistic fungal pathogens that are part of the normal skin and mucosal microflora. Overgrowth of Candida can cause infections such as thrush or life-threatening invasive candidiasis in immunocompromised patients. Though Candida albicans is highly prevalent, several non-albicans species are also isolated from nosocomial infections. Candida sp. are over presented in the gut of people with Crohn's disease and certain types of neurological disorders, with hyphal form and biofilms being the most virulent states. In addition, Candida uses several secreted and cell surface molecules such as pH related antigen 1, High affinity glucose transporter, Phosphoglycerate mutase 1 and lipases to establish pathogenicity. A strong innate immune response is elicited against Candida via dendritic cells, neutrophils and macrophages. All three complement pathways are also activated. Production of proinflammatory cytokines IL-10 and IL-12 signal differentiation of CD4⁺ cells into Th1 and Th2 cells, whereas IL-6, IL-17 and IL-23 induce Th17 cells. Importance of T-lymphocytes is reflected in depleted T-cell count patients being more prone to Candidiasis. Anti- Candida antibodies also play a role against candidiasis using various mechanisms such as targeting virulent enzymes and exhibiting direct candidacidal activity. However, the significance of antibody response during infection remains controversial. Furthermore, some of the Candida strains have evolved molecular strategies to evade the sophisticated host attack by proteolysis of components of immune system and interfering with immune signalling pathways. Emergence of several non-albicans species that are resistant to current antifungal agents makes treatment more difficult. Therefore, deeper insight into interactions between Candida and the host immune system is required for discovery of novel therapeutic options.

An Association of an eBURST Group With Triazole Resistance of Candida tropicalis Blood Isolates

Candidemia, a bloodstream infection caused by genus Candida, has a high mortality rate. Candida albicans was previously reported to be the most common causative species among candidemia patients. However, during the past 10 years in Thailand, Candida tropicalis has been recovered from blood more frequently than C. albicans. The cause of this shift in the prevalence of Candida spp. remains unexplored. We conducted in vitro virulence studies and antifungal susceptibility profiles of 48 C. tropicalis blood isolates collected during 2015-2017. To compare to global isolates of C. tropicalis, multilocus sequence typing (MLST), a minimum spanning tree, and an eBURST analysis were also conducted. C. tropicalis and C. albicans were the most (47-48.7%) and second-most (21.5-33.9%) common species to be isolated from candidemia patients, respectively. Of the C. tropicalis blood isolates, 29.2, 0, 100, and 93.8% exhibited proteinase activity, phospholipase activity, hemolytic activity, and biofilm formation, respectively. Moreover, 20.8% (10/48) of the isolates were resistant to voriconazole and fluconazole, and also showed high minimum inhibitory concentrations (MICs) to posaconazole and itraconazole. In contrast, most of the isolates were susceptible to anidulafungin (97.9%), micafungin (97.9%), and caspofungin (97.9%), and showed low MICs to amphotericin B (100%) and 5-flucytosine (100%). The MLST identified 22 diploid sequence types. Based on the eBURST analysis and minimum spanning tree, 9 out of 13 members (69.2%) of an eBURST group 3 were resistant to voriconazole and fluconazole, and also showed high MICs to posaconazole and itraconazole. Association analysis revealed the eBURST group 3 was significantly associated with the four triazole resistance (p < 0.001). In conclusion, the eBURST group 3 was associated with the triazole resistance and resistance to many antifungal drugs might be collectively responsible for the prevalence shift.

Catheter-related candidemia and identification of causative Candida species in patients with cardiovascular disorder

Background and Purpose

Catheter-related blood circulation infection is the most dangerous and serious side-effects of vascular catheters, which leads to the enhancement of the costs, mortality, and hospital stay duration, especially in the Intensive Care Unit. Regarding this, the aim of the current study was to identify the prevalence of catheter-induced candidemia in the Tehran Heart Center, a heart hospital in Tehran, Iran.

Materials and Methods

This study was conducted on patients admitted to Tehran Heart Center for a minimum of 7 days during 18 months. To detect the fungal elements, blood culture and catheter culture were performed in the patients receiving central or peripheral venous catheter. Then, the polymerase chain reaction (PCR) was applied to determine the possible diagnosis.

Results

The investigation of 223 samples led to the identification of a total of 15 (6.7%) yeast isolates obtained from 9 (60%), 4 (26.6 %), and 2 (13.4%) catheter, blood, and skin (of the catheter insertion areas) cultures, respectively. Out of nine Candida isolates obtained from the catheter samples, 1 (11.1%), 1 (11.1%), 2 (22.2%), and 5 (55.6%) cases were identified as C. tropicalis, C. membranifaciens, C. glabrata, and C. albicans, respectively, using the internal transcribed spacer region sequencing. Furthermore, the four yeasts isolated from the blood culture included C. tropicalis, C. carpophila, C. membranifaciens, and Cryptococcus albidus. Additionally, one case of C. glabrata and one case of C. albicans were isolated from the skin culture of the catheter insertion areas in patients with positive catheter culture. We reported two cases of catheter-related candidemia caused by C. membranifaciens and C. tropicalis on the basis of the genetic similarity of the species isolated from the blood and catheter. These cases were treated successfully with intravenous fluconazole and catheter removal.

Conclusion

There is some evidence indicating the growing prevalence of non-albicans Candida infections. Many risk factors, including prior antibiotic therapy, use of a central venous catheter, surgery, and parenteral nutrition, are considered to be associated with candidemia in hospitalized heart failure patients. The identification of the route of infection in candidemia is difficult. In the current study, the positive blood and catheter cultures for Candida isolates and the similarity of the ITS region of ribosomal DNA sequence of Candida isolated from two patients confirmed the diagnosis of intravenous catheter-related candidemia.

Multilocus Sequence Typing Reveals a New Cluster of Closely Related Candida tropicalis Genotypes in Italian Patients With Neurological Disorders

Candida tropicalis is a pathogenic yeast that has emerged as an important cause of candidemia especially in elderly patients with hematological malignancies. Infections caused by this species are mainly reported from Latin America and Asian-Pacific countries although recent epidemiological data revealed that C. tropicalis accounts for 6-16.4% of the Candida bloodstream infections (BSIs) in Italy by representing a relevant issue especially for patients receiving long-term hospital care. The aim of this study was to describe the genetic diversity of C. tropicalis isolates contaminating the hands of healthcare workers (HCWs) and hospital environments and/or associated with BSIs occurring in patients with different neurological disorders and without hematological disease. A total of 28 C. tropicalis isolates were genotyped using multilocus sequence typing analysis of six housekeeping (ICL1, MDR1, SAPT2, SAPT4, XYR1, and ZWF1) genes and data revealed the presence of only eight diploid sequence types (DSTs) of which 6 (75%) were completely new. Four eBURST clonal complexes (CC2, CC10, CC11, and CC33) contained all DSTs found in this study and the CC33 resulted in an exclusive, well-defined, clonal cluster from Italy. In conclusion, C. tropicalis could represent an important cause of BSIs in long-term hospitalized patients with no underlying hematological disease. The findings of this study also suggest a potential horizontal transmission of a specific C. tropicalis clone through hands of HCWs and expand our understanding of the molecular epidemiology of this pathogen whose population structure is still far from being fully elucidated as its complexity increases as different categories of patients and geographic areas are examined.

Antifungal susceptibility testing of vulvovaginal Candida species among women attending antenatal clinic in tertiary care hospitals of Peshawar

Background

Vulvovaginal candidiasis (VVC) is considered as a pervasive gynecological problem among women worldwide. Owing to this fact, in the current study, we aimed at assessing the prevalence rate of Candida spp. causing VVC in symptomatic pregnant women and their antifungal susceptibility pattern.

Methods

This study was carried out in the tertiary care hospitals of Peshawar during the period of July 1, 2016 to December 31, 2016. The study group included 450 pregnant women in the age group of 17–44 years with symptoms of excessive vaginal discharge, pain and pruritis. In all, 108 pregnant women were culture positive for Candida. Antimicrobial susceptibility testing (AST) was conducted on specimens against various azoles and polyene F group of antifungals.

Results

Out of 108 Candida spp. isolated from vaginal swabs, there were 45 (41.7%) Candida albicans, 18 (16.7%) Candida tropicalis, 18 (16.7%) Candida krusei, 16 (14.8%) Candida glabrata and 11 (10.2%) Candida dubliniensis. According to age distribution, 27 years was the mean age. Pregnancy trimester distribution among patients was as follows: 21 (19.4%) patients were in their first trimester, 65 (60.2%) patients were in their second trimester and 22 (20.4%) patients were in the third trimester. Susceptibility of fluconazole was determined as follows: 33.3% of the Candida isolates were sensitive, 4.6% were susceptible dose dependent (SDD) and 62% were resistant. Susceptibility of Candida spp. with respect to nystatin in patients with VVC was as follows: 25% were sensitive, 16.7% were SDD and 58.3% were resistant. Susceptibility of clotrimazole was analyzed, and it was sensitive in 21.3% of patients, SDD in 19.4% of patients and resistant in 59.3% of patients. Voriconazole susceptibility was recorded to be sensitive in 85.2% of patients, SDD in 4.6% of patients and resistant in 10.2% of patients suffering from VVC. Susceptibility results for itraconazole in patients with VVC were as follows: 42.6% of patients were sensitive, 16.7% of patients were SDD, and 40.7% of patients were resistant.

Conclusion

In this study, frequency of VVC was noted to be high in the second trimester of pregnancy, with the highest frequency of C. albicans isolated, followed by C. tropicalis and C. krusei. Antifungal susceptibility testing revealed that fluconazole was exceedingly resistant against Candida species (62%), followed by clotrimazole (59.3%) and nystatin (58.3%). On the contrary, voriconazole had the highest antimicrobial activity against Candida species (85.2%).