Cross-Sectional Study of Candidemia from Isfahan, Iran: Etiologic Agents, Predisposing Factors, and Antifungal Susceptibility Testing
Maryam Ranjbar-Mobarake1, Jamileh Nowroozi1, Parisa Badiee2, Sayed Nassereddin Mostafavi3, Rasoul Mohammadi4
1 Department of Microbiology, North branch Islamic Azad University, Tehran, Iran
2 Clinical Microbiology Research Center, Shiraz University of Medical Sciences, Shiraz, Iran
3 Infectious Diseases and Tropical Medicine Research Center, Isfahan University of Medical Sciences, Isfahan, Iran
4 Infectious Diseases and Tropical Medicine Research Center; Department of Medical Parasitology and Mycology, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran
|Date of Submission||05-Apr-2021|
|Date of Decision||07-Jun-2021|
|Date of Acceptance||25-Jun-2021|
|Date of Web Publication||29-Nov-2021|
Dr. Rasoul Mohammadi
Department of Medical Parasitology and Mycology, Infectious Diseases and Tropical Medicine Research Center, School of Medicine, Isfahan University of Medical Sciences, Isfahan
Source of Support: None, Conflict of Interest: None
Background: Candidemia is a fatal invasive fungal infection that involves thousands of patients annually and is associated with high mortality rate and economic burden. The incidence of candidemia is increasing due to the use of invasive medical instruments and immunosuppressive drugs. The treatment of infection is problematic because of the increased resistance of clinical strains to antifungal drugs. The aim of the present study was to identify Candida species isolated from candidemia and determination of antifungal susceptibility patterns of clinical isolates. Materials and Methods: Three thousand eight hundred BACTEC bottles suspected to candidemia were evaluated from April 2019 to June 2020. For primary identification, a positive blood culture was subcultured onto the sabouraud glucose agar and CHROMagar™ Candida. For molecular identification, ITS1-5.8SrDNA-ITS2 region was amplified by ITS1 and ITS4 primers and MspI restriction enzyme was applied to digest polymerase chain reaction amplicons. Minimum inhibitory concentration of seven antifungals was determined against clinical isolates by broth microdilution method in accordance with the Clinical and Laboratory Standards Institute M27-A3 and M27-S4 documents. Results: Forty-six out of 3800 suspected specimens were positive for candidemia (1.2%). The age range of the patients was between 11 days and 89 years, with a median age of 34.8 years. Candida albicans was found to be the most Candida species (58.7%), followed by C. parapsilosis complex (19.6%), C. glabrata complex (8.7%), C. krusei (6.5%), C. famata (4.3%), and C. tropicalis (2.2%). Resistance to amphotericin B, fluconazole, itraconazole, and voriconazole was detected in 13.6%, 11.3%, 6.8%, and 4.5% of clinical isolates, respectively. Conclusion: The incidence of non-albicans Candida species is increasing that must be highlighted. Since resistant Candida strains are found repeatedly, consecutive tracing of the species distribution and in vitro antifungal susceptibility of clinical isolates is recommended for better management of infections.
Keywords: Antifungal susceptibility testing, candidemia, identification
|How to cite this article:|
Ranjbar-Mobarake M, Nowroozi J, Badiee P, Mostafavi SN, Mohammadi R. Cross-Sectional Study of Candidemia from Isfahan, Iran: Etiologic Agents, Predisposing Factors, and Antifungal Susceptibility Testing. J Res Med Sci 2021;26:107
|How to cite this URL:|
Ranjbar-Mobarake M, Nowroozi J, Badiee P, Mostafavi SN, Mohammadi R. Cross-Sectional Study of Candidemia from Isfahan, Iran: Etiologic Agents, Predisposing Factors, and Antifungal Susceptibility Testing. J Res Med Sci [serial online] 2021 [cited 2022 May 19];26:107. Available from: https://www.jmsjournal.net/text.asp?2021/26/1/107/331353
| Introduction|| |
Candidemia is the most prevalent invasive fungal infection (IFI) among hospitalized patients, with an incidence of 0.4–1.5/1000 admissions and a mortality rate of 10%–50%, even with the antifungal therapy., The incidence of IFI was shown to be increasing worldwide because of the use of invasive medical instruments such as urinary and venous catheters, antimicrobial therapy, parenteral nutrition, intensive care unit admission, surgery, and immunosuppressive therapies., Epidemiological surveys have revealed that causative agents of infection have changed from C. albicans to the non-albicans species, such as C. parapsilosis complex, C. glabrata complex, C. krusei and C. tropicalis. For example, in the North America ARTEMIS study, C. glabrata complex was the leading cause of non-albicans species isolated from candidemia and accounted for about 21.1% of cases, while in the countries of Latin America, C. tropicalis was the main cause of infection (13.2%). Treatment of candidemia is problematic due to the increased resistance to antifungal drugs. Antifungal susceptibility profiles differ among Candida species and may affect the clinical outcomes for critically ill patients. Non-selective treatment of candidemia without in vitro antifungal susceptibility assay, can lead to the development of drug-resistant Candida species by more intrinsically resistant species such as C. glabrata complex, C. famata, and C. krusei. The aim of the present study was to assess species distribution and antifungal susceptibility patterns of Candida species isolated from candidemia in Isfahan, the third-largest city of Iran.
| Materials and Methods|| |
From April 2019 to June 2020, 3800 BACTEC bottles suspected to candidemia were tested. The specimens were collected from three university hospitals (Al-Zahra, Seyed Al-Shohada, and Imam Hossein) in Isfahan, Iran.
Patients with persistent fever despite adequate antibacterial therapy and patients with severe immunodeficiency disorders were included in the study.
Patients who have taken antifungal drugs for the past week were excluded from the study.
A positive blood culture was subcultured onto the sabouraud glucose agar (Difco, Detroit, MI, USA) and CHROMagar™ Candida (Paris, France) for primary screening. This research was approved by the National Committee for Ethics in Biomedical Research (No. IR.IAU.SRB.REC.1397.171), and written informed consent was obtained from each patient.
Molecular methods for identification of Candida species
Genomic DNA of clinical isolates was extracted using boiling method. Briefly, a loopful of fresh colonies were suspended in 100 μL of double distilled water (DDW) and boiled for 15–20 min and then centrifuged for 5 min at 8000 rpm; finally, the supernatant was kept at −20°C.
Polymerase chain reaction
The ITS1-5.8SrDNA-ITS2 region was amplified by a polymerase chain reaction (PCR) mixture containing 5 μL of 10× reaction buffer, 0.4 mM dNTPs, 1.5 mM MgCl2, 30 pmol of ITS1 primer (5'-TCC GTA GGT GAA CCT GCG G-3'), 30 pmol of ITS4 primer (5'-TCC TCC GCT TAT TGA TAT GC-3'), 2.5 U of Taq polymerase, and 2 μL of extracted DNA in a final volume of 50 μL. The PCR cycling conditions were as follows: an initial denaturation phase at 94°C for 5 min, followed by 32 cycles of denaturation at 94°C for 30 s, annealing at 55°C for 45 s, and extension at 72°C for 1 min, with a final extension step at 72°C for 7 min.
Restriction fragment length polymorphism
At the next step, ITS amplicons were digested in a final volume of 15 μL containing 3 μL DDW, 1U of MspI restriction enzyme (Fermentas, Vilnius, Lithuania), 1.5 μL buffer, and 10 μL PCR product at 37°C for 2 h.
Aliquots of 5 μL of PCR and 12 μL of RFLP products were fractionated by electrophoresis on 1.5% and 2% agarose gel, respectively, and stained with SYBR Safe DNA gel stain (1:10,000 dilution in TBE) [Figure 1].
|Figure 1: (a) Agarose gel electrophoresis of ITS-polymerase chain reaction amplicons of Candida species, lanes 1–3: Candida albicans, lanes 4, 5: Candida parapsilosis complex, lane C: Negative control, and lane M is 100 bp DNA size marker. (b) Agarose gel electrophoresis of ITS-polymerase chain reaction amplicons after digestion with MspI. Lanes 1–3: Candida albicans, lanes 4, 5: Candida parapsilosis complex, and lane M is 100 bp DNA size marker|
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Antifungal susceptibility testing
Minimum inhibitory concentration (MIC) was assessed by the Clinical and Laboratory Standards Institute (CLSI) M27-A3 and M27-S4 documents., Fluconazole (FLC) (Pfizer Central Research, Sandwich, United Kingdom), amphotericin B (AMB) (Bristol-Myers-Squibb, Woerden, The Netherlands), itraconazole (ITR) (Janssen Research Foundation, Beerse, Belgium), posaconazole (POS) (Schering-Plough, Kenilworth, USA), caspofungin (CAS) (Merck Sharp and Dohme, Haarlem, The Netherlands), voriconazole (VOR) (Pfizer Central Research, UK), and luliconazole (LLCZ) (Sigma Chemical Co., St. Louis, MO, USA) were applied for preparation of the CLSI microdilution trays. The antifungal agents were diluted in the RPMI-1640 medium (Sigma Chemical Co., St. Louis, MO, USA) buffered to pH 7.0 with 0.165 M morpholinepropanesulfonic acid (Sigma Chemical Co., St. Louis, MO, USA) with L-glutamine and without bicarbonate. Final concentrations of antifungals were prepared as follows: 0.064–64 μg/ml for FLC, 0.016–64 μg/ml for POS, 0.016–16 μg/ml for ITR, CAS, AMB, VOR, and LLCZ. All identified Candida spp. were cultured on malt extract agar (MEA, Difco) and incubated at 35°C. The optical density (OD) was measured by a spectrophotometer, at a wavelength of 530 nm, and transmission of 75%–77%. Final inoculum sizes ranged from 2.5 × 103 to 5 × 103 CFU/ml. MIC results for all agents were determined visually following 24 h of incubation at 35°C, as we considered 100% growth inhibition for amphotericin B, and >50% growth inhibition for other antifungals. C. parapsilosis (ATCC 22019) and C. krusei (ATCC 6258) strains were used for quality controls.
The MIC range, MIC50, and MIC90 were determined. The MIC50 and MIC90 values were considered as the minimum concentrations of antifungal agents being able to inhibit 50% and 90% of the growth of clinical Candida strains, respectively. Data were analyzed using the SPSS software version 23 (IBM, Chicago, USA). Correlation between antifungal susceptibility and species distribution was adjusted using Fisher's exact test and Mann–Whitney U-test. p < 0.05 was considered statistically significant.
| Results|| |
Forty-six out of 3800 suspected specimens were positive for candidemia (1.2%). The age range of the patients was between 11 days and 89 years, with a median age of 34.8 years. The male-to-female ratio of the patients was 26/20. The predisposing factors were recorded as antibiotic consumption (n = 39, 84.8%), cancer (n = 18, 39%), hemodialysis (n = 4, 8.7%), preterm birth (n = 3, 6.5%), surgery (n = 2, 4.3%), the use of permanent central venous catheter system (port-a-cath) (n = 1, 2.2%), thalassemia (n = 1, 2.2%), peritoneal dialysis (n = 1, 2.2%), and systemic lupus erythematosus (n = 1, 2.2%). Three patients (6.5%) had coinfection with coronavirus disease 2019, and one of them passed away due to the acute respiratory distress syndrome. Candida albicans was found to be the most Candida species (n = 27, 58.7%), followed by C. parapsilosis complex (n = 9, 19.6%), C. glabrata complex (n = 4, 8.7%), C. krusei (n = 3, 6.5%), C. famata (n = 2, 4.3%), and C. tropicalis (n = 1, 2.2%). The MIC ranges of antifungal agents were as follows: C. albicans: AMB – 0.032–1 μg/mL, CAS – 0.008–16 μg/mL, VOR – 0.032–1 μg/mL, FLC – 0.125–4 μg/mL, POS – 0.032–0.5 μg/mL, ITR – 0.032–0.25 μg/mL, and LLCZ – 0.004–2 μg/mL; C. parapsilosis: AMB – 0.032–6 μg/mL, CAS – 0.25–4 μg/mL, VOR – 0.032–8 μg/mL, FLC – 0.25–64 μg/mL, POS – 0.032–8 μg/mL, ITR – 0.032–8 μg/mL, and LLCZ – 0.032–8 μg/mL; C. glabrata: AMB – 0.125–1 μg/mL, CAS – 0.032–0.125 μg/mL, VOR – 0.032 μg/mL, FLC – 1–32 μg/mL, POS – 0.25 μg/mL, ITR – 0.125–0.25 μg/mL, and LLCZ – 0.016–0.032 μg/mL; C. krusei: AMB – 0.125–1 μg/mL, CAS – 0.064–4 μg/mL, VOR – 0.008–0.125 μg/mL, FLC – 0.5–64 μg/mL, POS – 0.064–0.5 μg/mL, ITR – 0.125–0.5 μg/mL, and LLCZ – 0.004–0.25 μg/mL; C. famata: AMB – 0.064–0.125 μg/mL, CAS – 0.032–0.25 μg/mL, VOR – 0.064–0.125 μg/mL, FLC – 32–64 μg/mL, POS – 0.025–0.5 μg/mL, ITR – 0.25 μg/mL, and LLCZ – 0.5–1 μg/mL; and C. tropicalis: AMB – 0.064 μg/mL, CAS – 0.032 μg/mL, VOR – 0.25 μg/mL, FLC – 8 μg/mL, POS – 1 μg/mL, ITR – 1 μg/mL, and LLCZ – 1 μg/mL. [Table 1] indicates interpretive guidelines for in vitro susceptibility testing of Candida species according to M27-S4, M60 documents, and Borman et al.,,, and [Table 2], [Table 3], [Table 4] show the in vitro susceptibility patterns of Candida isolates, MIC of antifungal agents in details, and MIC50, MIC90, and geometric mean, respectively.
|Table 1: Interpretive guidelines for in vitro susceptibility testing of Candida species|
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|Table 2: In vitro susceptibility patterns of Candida species isolates from candidemia|
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|Table 3: The minimum inhibitory concentration of antifungal agents among Candida species isolated from candidemia|
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|Table 4: Minimum inhibitory concentration range, minimum inhibitory concentration 50, minimum inhibitory concentration 90, and geometric mean of the antifungal agents used in the present study|
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Fisher's exact test showed that the association between the MIC and Candida species was not statistically significant (p = 0.82).
| Discussion|| |
Bloodstream infections with the genus of Candida are a consequential concern that involves thousands of individuals annually and is associated with economic burden. Although C. albicans is the most common species, changing in the frequency of etiologic agents of candidemia has revealed a remarkable increase in the incidence of NAC species with intrinsic resistance to azoles such as FLC. NAC species affect mortality rate among patients, which is higher for C. krusei and C. tropicalis and lower for C. parapsilosis complex. There are geographical discrepancies for etiologic agents of candidemia; for instance, in Europe and North America, C. glabrata complex is a more prevalent species of candidemia than in other areas, while in Latin America, Candida bloodstream infections are more generally caused by C. tropicalis and C. parapsilosis complex with low incidence of C. glabrata complex. In the past, 68%–91% of clinical Candida species were C. albicans, and 5% included C. tropicalis, C. parapsilosis complex, and C. glabrata complex. Regrettably, the majority of the drug-resistant clinical Candida strains are reported from developing countries, where many patients with bloodstream fungal infections are treated with azoles, such as FLC, as the first treatment choice. The lack of precise identification of fungi in these countries by the novel and appropriate methods such as matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS), can be further worsen and lead to unselective use of antifungal agents. A multicenter survey from Brazil targeting the vulnerable population of candidemia showed that catheterization, chronic renal failure, and parenteral nutrition are the main risk factors for candidemia; whereas, we revealed antibiotic consumption (84.8%), malignancies (39%), and hemodialysis (8.7%) as leading predisposing factors in our investigation. Similar to our results, Hii et al. in Taiwan reported that more than 40% of patients had different underlying diseases containing malignancy and diabetes mellitus. In another research performed in Turkey, CVP catheterization, the length of hospitalization, parenteral nutrition, and chronic renal failure were also considered to be independent predisposing factors. In this regard, they showed that being female gender is another risk factor for candidemia, while bloodstream Candida infection was similar in males and females in the present survey. In agreement with our findings, Yapar et al. demonstrated that the use of antibacterial agents can remarkably increase the risk of candidemia among patients, and almost all patients had taken antibiotics prior to Candida infection. Although former studies revealed a mortality rate of 50% for candidemia,, the mortality rate was 19.6% in the present report. Similar to our study, Mirhendi et al. reported C. albicans and C. parapsilosis as the most common etiologic agent and NAC species of candidemia in Tehran, Iran, respectively. Contrary to the results of our study, they presented a uniform activity of AMB against all Candida isolates with no MICs equal or above the breakpoint of 1 mg/L; whereas, 13.6% of Candida species were resistant to AMB in the present investigation. Furthermore, they showed that VOR and FLC had 100% activity against nearly all Candida species, but we found 4.5% and 11.3% of resistant isolates to VOR and FLC, respectively. In this regard, 100% of C. famata isolates were resistant to FLC. In agreement with Ghahri et al., all Candida species but one of C. albicans (MIC = 16 μg/mL) were susceptible to CAS. They revealed that VOR was the most potent antifungal agent against isolated Candida species; nevertheless, our findings indicated that 4.5% of Candida species were resistant to VOR. Three out of 46 strains (6.5%) were resistant to ITR in the present study (MIC ≥1), close to the outcomes that Xiao et al. reported (7.8%). In the case of LLCZ, breakpoints or epidemiological cutoff values (ECVs) have not been described for Candida species; however, 19.6% of isolates had MIC ≥1 for LLCZ.
| Conclusion|| |
The incidence of NAC species is increasing that must be considered significant. C. parapsilosis was the most common Candida species causing non-albicans candidemia in our survey, and some C. parapsilosis were resistant to FLC, VOR, AMB, and ITR among the clinically NAC species. This can represent a regional phenomenon and points to the value of careful selection of empiric therapy. Consecutive tracing of the species distribution and in vitro antifungal susceptibility of clinical isolates is essential for better management of infection.
The authors would like to thank the laboratory personnel of Al-Zahra, Seyed Al-Shohada, and Imam Hossein Childrens' hospitals for helping to collect clinical specimens.
Financial support and sponsorship
This research was approved by the National Committee for Ethics in Biomedical Research (No.IR.IAU.SRB.REC.1397.171) and supported by the North Branch Islamic Azad University, Tehran, Iran, and Isfahan University of Medical Sciences, Isfahan, Iran.
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4]