Introduction
Aspergillosis is a severe fungal infection caused by various Aspergillus species found in soil, rotting organic matter, and confined spaces. Aspergillus fumigatus is a frequently observed species that causes approximately 70–80% of human aspergillosis cases. Infections with other species, such as Aspergillus niger, Aspergillus flavus, and Aspergillus terreus, are also becoming more common, particularly in immunocompromised hosts [Reference Yang, Chen, Liang, Tan, Liu, Sun, Wang, Xu, Li and Zhou1]. It can affect several organs and manifest in various clinical forms, such as pulmonary, otoaspergillosis, endophthalmitis, systemic, and cutaneous aspergillosis. Pulmonary aspergillosis occurs in various clinical forms, such as invasive pulmonary aspergillosis (IPA), chronic pulmonary aspergillosis (CPA), bronchial colonisation, allergic bronchopulmonary aspergillosis, and severe asthma [Reference Vuong, Hollingshead and Waymack2]. The global burden of aspergillosis is rising, posing a threat to healthcare systems worldwide. The prevalence of aspergillosis in China is, however, poorly documented, with only a few studies conducted in specific areas [Reference Zhou, Jiang, Li, Huang, Yip, Denning and Zhu3]. A study in 2017 reported global estimates of 3,000,000 cases of chronic pulmonary aspergillosis, and ~ 250,000 cases of invasive aspergillosis [Reference Bongomin, Gago, Oladele and Denning4]. The immunocompromised hosts, such as those with haematological malignancies, solid organ transplants, and chronic lung diseases, and those exposed to environmental triggers such as dust and mould, are disproportionately affected by aspergillosis [Reference Otu, Kosmidis, Mathioudakis, Ibe and Denning5].
Aspergillosis is typically treated with triazole antifungal drugs such as voriconazole, itraconazole, isavuconazole, and posaconazole. Amphotericin B and caspofungin are significant antifungal agents against azole-resistant isolates. Caspofungin is typically not used alone but is given as a part of a multidrug antifungal regimen along with azoles [Reference Verweij, Chowdhary, Melchers and Meis6]. However, the selection of a specific drug is determined by various factors, including the type of aspergillosis, infection severity, and the susceptibility profile of the concerned Aspergillus isolates [Reference Romero, Messina, Marin, Arechavala, Depardo, Walker, Negroni and Santiso7]. Antifungal susceptibility testing is essential for selecting appropriate antifungal therapy because it identifies wild-type and non-wild types Aspergillus isolates against particular antifungal agents [Reference Otto, Arendrup and Fisher8].
Antifungal susceptibility of Aspergillus isolates varies based on species types, geographical region, and local antifungal consumption patterns [Reference Badali, Cañete-Gibas, McCarthy, Patterson, Sanders, David, Mele, Fan and Wiederhold9]. Recently, there has been an increase in antifungal non-wild-type Aspergillus isolates, especially for azole drugs, which are the primary therapy for aspergillosis [Reference Burks, Darby, Gómez Londoño, Momany and Brewer10]. Surveillance studies based on antifungal susceptibility patterns in Aspergillus species are critical in identifying emerging non-wild types isolates, directing the appropriate selection of an antifungal agent, and significantly impacting aspergillosis management and outcome [Reference Zakaria, Osman, Dabboussi, Rafei, Mallat, Papon, Bouchara and Hamze11].
This retrospective study aimed to analyse the epidemiology, risk factors, and antifungal susceptibilities of aspergillosis in a tertiary care hospital in the eastern Guangdong region of South China. The findings of this study will help healthcare officials manage aspergillosis and may have implications for the selection of appropriate antifungal agents and treatment strategies in the region.
Methods
Study design and setting
The current retrospective study was performed at a tertiary care hospital named Meizhou People’s Hospital in Meizhou, South China [Reference Bilal, Zhang, Shafiq, Khan, chen, Khan, Wang, Cai, Islam, Hu and Zeng12]. The study included all aspergillosis cases reported from January 2017 to December 2022. The ethical review committee of the hospital approved the study following the standards of the Helsinki Declaration (Reference number: 2021-C-106).
Definitions
The aspergillosis cases reported in the current study were classified as CPA, IPA, otoaspergillosis, and cutaneous aspergillosis. Chronic and invasive pulmonary aspergilloses were diagnosed and classified based on the European Organization for Research and Treatment of Cancer (EORTC) and the Mycoses Study Group Education and Research Consortium (MSG/ERC) guidelines [Reference Bassetti, Azoulay, Kullberg, Ruhnke, Shoham, Vazquez, Giacobbe and Calandra13, Reference Denning, Cadranel, Beigelman-Aubry, Ader, Chakrabarti, Blot, Ullmann, Dimopoulos and Lange14]. Chronic pulmonary aspergillosis is a slowly progressing infection that affects immunocompromised patients or those with underlying lung illnesses. It is distinguished by cavities or lung fibrosis, positive Aspergillus serology, and symptoms lasting more than 3 months. Invasive pulmonary aspergillosis is a quickly progressing infection that primarily affects people who have significant immunosuppression or are critically unwell. It is distinguished by blood vessel invasion and spread to other organs, positive biomarkers such as galactomannan or PCR for Aspergillus, and symptoms lasting fewer than 3 months. Otoaspergillosis is an Aspergillus infection that affects the ear, frequently resulting in otitis externa or otomycosis. Cutaneous aspergillosis is a type of Aspergillus infection that affects the skin, resulting in skin lesions or ulcers [Reference Cadena, Thompson III and Patterson15].
Data collection
The demographic and clinical data of all aspergillosis patients were collected from the hospital’s electronic medical record using a Microsoft Excel sheet (2021). The data included patients’ characteristics such as gender, age, seasonal infection period, patient type, reported department, sample source, infection type, and underlying patient status. Moreover, the laboratory record of Aspergillus species type and their antifungal susceptibility testing were also collected. Data analysis was confined to only the first positive culture for patients with repeated positive cultures for Aspergillus species.
In routine laboratory protocol, Aspergillus species are identified by combining colony morphology and matrix-assisted laser desorption/ionisation–time of flight mass spectrometry (MALDI-TOF MS) analysis (Bruker Daltonik, Bremen, Germany) [Reference Oviaño and Rodríguez-Sánchez16]. The identification was carried out with the use of the Bruker library application Spectra (version 4.0.0.1, which contained 5627 entries) that came preinstalled on the Bruker Biotyper (version 3.1; Bruker.1). All the cases included in the current study were confirmed by the clinical characteristics and routine laboratory protocols such as microscopy, culture, serological test (Aspergillus-specific IgG antibodies and galactomannan (GM) test), and radiography (if needed). The current study only included Aspergillus infection patients; cases of colonisation were excluded. The sputum samples in the current study were expectorated sputum, in which the aforementioned methods confirmed the infection. Furthermore, the antifungal susceptibilities testing (AST) was performed against five drugs: amphotericin B, caspofungin, itraconazole, voriconazole, and posaconazole (Sigma Aldrich, St. Louis, MO, USA). The AST was performed following the standard protocol of broth microdilution methods. The Candida krusei ATCC 6258 and Candida parapsilosis ATCC 22019 were quality control strains. The AST results were interpreted according to the Clinical and Laboratory Standards Institute (CLSI M38-A3) guidelines [Reference Wayne17]. The Minimum Inhibitory Concentration (MIC) for itraconazole, voriconazole, posaconazole, and amphotericin B was determined after 48 h as the lowest concentration preventing observable growth. The Minimum Effective Concentration (MEC) for caspofungin was determined as the lowest concentration that caused the growth of small, rounded, compact hyphal forms compared to the hyphal growth found in the growth control well at 24 h [Reference Alexander and Procop18–Reference Procop, Dufresne, Berkow, Castanheira, Fuller, Hanson, Holliday, Pincus, Schuetz and Verweij20].
Data analysis
Two researchers independently cross-checked all the information collected via Microsoft Excel to minimise possible errors. The quantitative findings were expressed as medians and interquartile ranges, while qualitative information was presented as absolute numbers and relative percentages. The characteristics of aspergillosis caused by various Aspergillus species (A. fumigatus, A. niger, A. flavus, and A. terreus) were analysed using the chi-square test for categorical variables and ANOVA for continuous variables. For AST data, the ranges of MICs, MECs, geometric mean (GM), and absolute numbers and percentages of MIC50/MEC50, MIC90/MEC90, wild-type (WT), and non-wild-type (NWT) isolates were quantified for each of the Aspergillus species types. Furthermore, the number of WT isolates against different antifungal agents recovered from inpatients and outpatients was statistically analysed using the chi-square test. The p-values less than 0.05 were considered statistically significant. GraphPad Prism v.8.0.2 was used for statistical analysis and visualisation of the data.
Results
Incidence of aspergillosis
In the current study, a total of 474 cases of aspergillosis were reported, in which a high number of cases were caused by Aspergillus section Fumigati n = 357,), followed by Aspergillus section Nigri n = 47), Aspergillus section Flavi n = 42), and Aspergillus section Terrei n = 28). The high number of cases were reported in the year 2018 (n = 140,), followed by 2019 (n = 118,), while only 18 cases were reported in 2017. The fluctuation in number of cases each year was reported; however, a 5.94-fold increase in aspergillosis was observed from 2017 to 2021. The complete depiction of different Aspergillus species reported each year is presented in (Figure 1).
Figure 1. The incidence of Aspergillus species reported yearly from 2017 to 2021.
Among various departments of the hospital, a high number of cases were reported from the intensive care unit (ICU) (n = 250, 52.74%), followed by the surgical department, from where a total of 13 (2.74%) cases were reported. A high number of cases from each department were caused by A. fumigatus, except otolaryngology, in which 50.75% (n = 34) cases were A. niger among the 67 reported cases. The percentages of aspergillosis cases from various departments of the hospital and different Aspergillus species from each department are presented in (Figure 2).
Figure 2. Aspergillosis cases reported from different departments of the hospital. Each pie chart in the surrounding shows the incidence of Aspergillus species from each department. In the department, others represent 7 cases each from cardiology and urology, 4 cases each from gastroenterology and Chinese medicine, 2 cases each from neurology, immunology, endocrinology, and haematology, and 1 case each from the dermatology and orthopaedics department.
Among the sample types, sputum had the highest frequency of Aspergillus isolates (n = 294, 62.03%), followed by bronchoalveolar lavage fluid (BALF) with 101 (21.31%) total cases. From both the samples, A. fumigatus was frequently isolated. Ear secretion and pus samples had lower frequencies, with 41 (8.65%) and 29 (6.12%) samples, respectively. The A. niger was the most frequently isolated species in both sample types, with 19 (46.34%) and 16 (55.17%) samples, respectively. The distribution of Aspergillus species isolated from different sample types is shown in Figure 3.
Figure 3. Aspergillus species isolated from different sample types. Each pie chart shows the incidence of Aspergillus species from each sample type. In the sample types, Others represent two samples each for wound and pleural effusion and one for catheter, nail, tissue, peritoneal fluid, and renal drainage.
Characteristics of aspergillosis
The demographic and clinical characteristics of aspergillosis caused by various Aspergillus species are presented in Table 1. Based on gender, a higher number of cases were reported in the male population (n = 315, 66.46%), while only 159 (33.36%) cases were reported among females. The same trend occurred for all species except A. niger, in which most cases (n = 29, 61.7%) were reported from the female population. Most cases were reported in senior adults with a median age of 65 years and an interquartile range of 52–76. Comparatively, the A. niger cases were reported in younger ages with a median age of 44 years (IQR; 35–56), followed by A. terreus (57 years, 1QR; 37–76).
Table 1. Baseline characteristics of Aspergillus species
Abbreviations: X2 = chi-square, df = degree of freedom, p-value = probability value, IQR = Inter quartile range, COPD = Chronic Obstructive Pulmonary Disease, ABPA = Allergic Bronchopulmonary Aspergillosis, UTI = Urinary tract Infection.
The distribution of Aspergillus species among various age groups revealed statistically significant differences (p < 0.05). A. niger was more common in younger age groups (under 50 years), whereas A. fumigatus was more common in older age groups (over 50 years). Only five cases were reported in the age group 2–17 years, and all were A. niger. A. flavus was highly prevented in age groups older than 50, and thirteen (30.96%) cases were reported in age groups 51 to 60. These findings suggest that age may influence the prevalence of different Aspergillus species, emphasising the importance of considering age as a factor in understanding the epidemiology of aspergillosis.
Seasonally, the distribution of Aspergillus species varies significantly. During winter, A. fumigatus was the most prevalent species, whereas there was no significant difference in species distribution during spring and summer. However, A. niger was the most common species in autumn, with a statistically significant difference from other species (p = 0.0038). This suggests that seasonal environmental factors may influence the prevalence of Aspergillus species.
Most cases were reported among hospitalised patients (n = 380, 80.17%), while only 94 (19.84%) cases were reported from outpatients. The distribution of Aspergillus species based on patient type (inpatients vs. outpatients) was statistically significantly correlated (p < 0.0001). A. fumigatus (88.8%) was more frequently detected in hospitalised patients, whereas A. niger (57.45%) was more prevalent in outpatients.
The clinical and laboratory data about invasive and chronic aspergillosis are presented in Table S1 (supplementary file). Among the clinical manifestation, cough was the most commonly reported, with 85.07% in CPA patients and 72.79% in IPA patients. Among the others, fever was reported in high proportion in IPA (67.57%), while hemoptysis in CPA (54.4%) patients. Among the imaging manifestation, consolidation was reported in a high proportion in IPA patients (62.16%), while cavitation was reported more in CPA patients (64%). In the cases of CPA, most Aspergillus species were isolated from sputum culture (77.33%), while in IPA, most species were isolated from BALF culture (81.08%). The serum GM was detected in 11.2% of CPA patients and 59.46% of IPA patients, while BALF GM was found in 16.8% of CPA patients and 35.13% of IPA patients. The Aspergillus-specific antibodies were reported in 35.13% of IPA patients and 39.46% of CPA patients.
Antifungal susceptibilities profiles
The antifungal susceptibilities profiles of Aspergillus species are summarised in Table 2. Amphotericin B had relatively high MIC values against all species ranging from 0.125 to 1 for MIC50 and 0.25 to 4 for MIC90. A. niger had the highest percentage of amphotericin B NWT isolates (4/47, 8.52%), followed by A. terreus (2/28, 7.15%), A. flavus (2/42, 4.77%), and A. fumigatus (3/357, 0.85%). Caspofungin had lower MEC values and a 100% WT percentage against A. fumigatus and A. terreus. In contrast, the percentages of NWT isolates in A. niger and A. flavus were 2/47 (4.26%) and 4/42 (9.53%), respectively. Among the tested azoles, posaconazole and voriconazole have lower MIC than itraconazole. A. niger, A. flavus, and A. terreus all showed 100% susceptibility to voriconazole. Similarly, A. flavus and A. terreus were 100% wild types for posaconazole. For itraconazole, a high number of NWT isolates were reported in the case of A. terreus (2/28, 7.15%), followed by A. niger (2/47, 4.26%), A. fumigatus (10/357, 2.81%), and A. flavus (1/42, 2.39%). Among the examined isolates, 5 A. fumigatus, 2 A. niger, and 1 A. flavus were NWT for more than one antifungal agent.
Table 2. Antifungal susceptibilities profiles of Aspergillus species detected in the current study
Abbreviations: MIC = Minimum inhibitory concentration, MEC = Minimum effective concentration, GM = Geometric mean, ECV = Epidemiological cutoff values, WT = Wild types, NWT = non-wild types.
a For all drugs, MIC was determined except caspofungin, for which MEC was found.
Furthermore, we compared the WT isolates reported from inpatients and outpatients to determine the relative difference in susceptibilities between the two groups. Interestingly, we noted that the percentages of WT isolates in the case of amphotericin B and caspofungin were comparatively lower for inpatients than outpatients. On the other hand, for azole drugs, the percentages of WT isolates were comparatively higher for inpatients than outpatients. However, the difference was only statistically significant (p < 0.05) in the case of itraconazole and posaconazole against A. fumigatus, while all others were statistically insignificant. The complete depiction of the comparative analysis of WT isolates in inpatients and outpatients is presented in Figure 4.
Figure 4. Comparatively analysis of wild-type isolates recovered from outpatients and inpatients. On the top of the bars are p-values derived by the chi-square test. NA; not applicable, AMP; amphotericin B, CAS; caspofungin, ITR; itraconazole, POS; posaconazole, VRC; voriconazole.
Discussion
The current retrospective study analyses the incidence of Aspergillus species, as well as the demographic and clinical characteristics associated with them, in a tertiary care hospital in South China. A 5.94-fold increase in aspergillosis was reported during the study duration. The increasing trend is inconsistent with previous reports from China [Reference Yang, Chen, Liang, Tan, Liu, Sun, Wang, Xu, Li and Zhou1, Reference Zhong, Ji, Qin and Cheng21]. Several factors, such as improving diagnostic capabilities, awareness in healthcare professionals, and changes in patients’ population and risk factors, contributed to the increase in aspergillosis [Reference Benedict, Richardson, Vallabhaneni, Jackson and Chiller22, Reference Hou, Zhang, Kou, Lv, Lu and Li23]. Furthermore, a significant increase in aspergillosis incidence, particularly for A. fumigatus, was reported between 2017 and 2018. In 2017, the international guidelines for diagnosing aspergillosis were less practical as those were recently published at that time (2016) [Reference Denning, Cadranel, Beigelman-Aubry, Ader, Chakrabarti, Blot, Ullmann, Dimopoulos and Lange14]. Histopathology and tissue cultures were considered gold-standard techniques for diagnosing aspergillosis at earlier times [Reference McCarthy, Aguilar-Zapata, Petraitis and Walsh24]. However, health professionals were later aware of international guidelines, which might be the reason for reporting the high number of A. fumigatus in 2018 and onward. The A. fumigatus were reported in high proportion, comprising 75.32% of the total isolates. The A. fumigatus is a worldwide highly reported Aspergillus species, previously reported in high proportion from China, USA, Europe, Africa, and Australia. The most frequent reporting of A. fumigatus might be due to its opportunistic pathogenicity, ubiquity, fast growth, and competitive advantage [Reference Ortiz, Pennington, Thomson and Bertuzzi25]. The A. niger was the second most commonly isolated species in the current study, just like previously reported from Korea [Reference Heo, Shin, Choi, Park, Lee, Koo, Lee, Kim, M-G and Suh26]. However, some other studies from Brazil and Australia reported a high proportion of A. flavus and A. terreus [Reference Lackner, Coassin, Haun, Binder, Kronenberg, Haas, Jank, Maurer, Meis and Hagen27, Reference Negri, Gonçalves, Xafranski, Bergamasco, Aquino, Castro and Colombo28]. Different trends in the prevalence of Aspergillus species indicate that it might be due to geographically oriented variation [Reference Yang, Chen, Liang, Tan, Liu, Sun, Wang, Xu, Li and Zhou1]. The A. flavus were not reported in the years 2017 to 2019, while in 2020 and 2021, a total of 25 and 17 cases were reported, respectively. A. flavus is a prevalent infectious species in Asia; nevertheless, its occurrence is comparatively smaller and more geographically limited when compared to A. fumigatus [Reference van Rhijn and Bromley29]. The non-detection of A. flavus in our investigation from 2017 to 2019 may indicate geographical or temporal disparities in the occurrence of this species, potentially driven by environmental variables such as temperature, humidity, and agricultural practices [Reference Majumdar, Kandel, Cary and Rajasekaran30]. However, the absence noticed of A. flavus within a given time period may be a chance occurrence. It is suggested that further investigation should be conducted to explore the underlying factors contributing to the temporal fluctuations of A. flavus in the specified area. This can be achieved by using a more extensive sampling approach over an extended timeframe, in order to enhance our comprehension of the species’ ecological dynamics. Among the hospital’s various departments, more than half of the total cases (52.74%) were reported from the ICU department in the present study. Several factors favour the development of aspergillosis in ICU patients, in which critical underlying status, prolonged corticosteroid treatment, and systemic diseases requiring immunosuppressive therapy are prominent [Reference Kluge, Strauß, Kochanek, Weigand, Rohde and Lahmer31]. Early diagnosis, swift antifungal treatment, strict infection control, optimisation of the immune status, and ongoing education and surveillance are needed to overcome ICU aspergillosis [Reference Ward, Aghaeepour, Bhattacharyya, Clish, Gaudillière, Hacohen, Mansour, Mudd, Pasupneti and Presti32].
Regarding the sample sources, sputum was the most commonly reported specimen, followed by BAL fluids having A. fumigatus isolated in high proportion from both specimens. The current study’s finding is similar to the previously reported 20-year retrospective study from China, indicating the endemic nature of A. fumigatus as a respiratory tract pathogen in the region [Reference Yang, Chen, Liang, Tan, Liu, Sun, Wang, Xu, Li and Zhou1]. The A. niger was isolated in high proportion from pus and ear secretion specimens. The association between A. niger and ear infection has been well documented in previous studies, which reported that almost half of otomycosis is caused by A. niger. This might be due to A. niger preference for the external auditory canal and its ability to produce a large number of conidia [Reference Nandyal, Choudhari and Sajjan33].
The distribution of Aspergillus species based on gender is always controversial. In the current study, A. fumigatus, A. flavus, and A. terreus were found in large proportions in males, while A. niger was found in high percentages in females. Smoking habits and occupational exposure to these species are frequently reported as likely causes of pulmonary aspergillosis among the male population [Reference Hammond, McDonald, Vestbo and Denning34]. While A. niger was primarily reported in association with otomycosis, the high incidence of this fungus in the female population and younger age group might be attributed to their propensity for using cosmetics [Reference Aso, Hammuel, Ade, Briska and Hyelnaya35]. The precise mechanism linking cosmetic usage to A. niger infections was not investigated in our study or other reported studies; nonetheless, we hypothesised that cosmetics, particularly those used in the ear region, could transfer fungal spores or establish an environment favourable to fungal growth. The use of infected or expired cosmetic items, poor hygiene, or excessive moisture in the ear due to cosmetic use may all lead to a rise in A. niger infections. Furthermore, there is currently no robust, large-scale investigation that can conclusively determine the impact of gender on the development of aspergillosis. Therefore, further research is needed to better understand the role of gender in aspergillosis risk factors.
Regarding age, most cases were reported in the senior adult age group, with a median age of 65 years (IQR; 52–76). The present investigation found that A. fumigatus, A. flavus, and A. terreus exhibit a high prevalence among individuals aged 50 and above. Additionally, it was observed that these species are predominantly linked to cases of pulmonary aspergillosis, particularly among patients in the ICU who have significant underlying pulmonary and systemic disorders. The greater vulnerability of older people to aspergillosis may be attributed to their impaired immune system and the presence of significant underlying co-morbidities. [Reference Dogar, Ahad, Ahmad, Nosheen, Malik, Inam, Ali, Fatima and Hafeez36]. Unlike the other species in the current study, A. niger was reported comparatively high in the younger age group (< 50 years). Occupational dust exposure and poor hygiene, such as using non-sterile ear-cleaning instruments, can cause A. niger growth in the external auditory canal and high morbidity rates in this age group [Reference Nemati, Hassanzadeh, Khajeh Jahromi and Delkhosh Nasrollah Abadi37]. Additionally, in the paediatric population (age group 2 to 17 years), only five cases were reported, all attributed to A. niger. We speculate that the high incidence of A. niger in females may also serve as a potential explanation for these infections in children. It is imaginable that the close attachment between children and their mothers could be a contributing factor [Reference Jameel and Al-Ezzy38]. Further investigation is warranted to explore the potential link between maternal exposure and A. niger infections in paediatric patients. No prominent differences in Aspergillus incidence based on season were reported in the current study. Similar to our findings, previously published studies from Serbia and Spain reported no association of specific seasons with aspergillosis [Reference García-Agudo, Aznar-Marín, Galán-Sánchez, García-Martos, Marín-Casanova and Rodríguez-Iglesias39, Reference Tasić-Otašević, Golubović, Đenić, Ignjatović, Stalević, Momčilović, Bojanović and Arsić-Arsenijević40]. However, the prevalence was a little higher in winter (34.18%) than in spring (23.21%), summer (19.63%), and autumn (23%). This might be due to the increased indoor activities and cold and damp winter environments [Reference Guo, Qian, Ye, Sun, Zhuge, Wang, Liu, Cao and Zheng41]. More cases were reported in inpatients (80.17%) than outpatients (19.84%). The opportunistic nature of the Aspergillus species, immunocompromised status, underlying health issues, exposure to invasive medical procedures, and antifungal use increased the risk of aspergillosis in inpatients [Reference Latgé and Chamilos42]. Among the patients’ underlying issues were a higher proportion of immunosuppressant drugs used (8.02%), followed by gastrointestinal disorder (5.7%), haematological malignancy (4.22%), and cardiovascular disorders (4.22%). These risk factors are worldwide reported in association with aspergillosis [Reference Akram, Ejaz, Mallhi, Syed Sulaiman and Khan43–Reference Montrucchio, Lupia, Lombardo, Stroffolini, Corcione, De Rosa and Brazzi45]. However, none of the underlying statuses was statistically significant to Aspergillus species except hypertension, which occurs in a high proportion (10.71%) in A. terreus infection (p < 0.0001). There is currently no documented study that links A. terreus to hypertension. Hypertension is a complicated medical condition influenced by various factors, including age, family history, excessive alcohol consumption, physical inactivity, obesity, smoking, poor diet, diabetes, kidney disease, and immune system dysfunction [Reference Mills, Stefanescu and He46]. However, the association between hypertension and A. terreus remains unknown and will need to be investigated in future studies.
Regarding the antifungal susceptibility testing, we found that in the case of A. fumigatus, the proportion of WT isolates against amphotericin (99.1%) was higher than triazoles (97–98%). Similar results were reported in previously published literature from various regions of China and Europe. The high proportion of WT isolates against amphotericin B might be because of its fungicidal and limited use due to its nephrotoxicity [Reference Bilal, Shafiq, Hou, Islam, Khan, Khan and Zeng47]. Contrarily, triazoles are first-line therapy against aspergillosis, leading to the emergence of azole non-wild types isolates [Reference Perlin, Rautemaa-Richardson and Alastruey-Izquierdo48, Reference Wiederhold49]. Conversely, in non-fumigatus Aspergillus species, the triazole (95–100%) WT proportion was higher than amphotericin B (91–95%). These findings are in line with previous research [Reference Yang, Chen, Liang, Tan, Liu, Sun, Wang, Xu, Li and Zhou1, Reference Gomez-Lopez, Garcia-Effron, Mellado, Monzon, Rodriguez-Tudela and Cuenca-Estrella50]. However, based on these findings, it is hard to classify triazoles as effective antimicrobials against non-fumigatus species theoretically. One factor to consider is the small number of non-fumigatus strains included in the current study compared to A. fumigatus isolates. Additional large-scale molecular studies focusing on triazole susceptibility in non-fumigatus isolates are required to confirm this hypothesis. Among the triazoles, the proportion of NWT isolates against itraconazole was high compared to posaconazole and voriconazole. It might be linked to its wide use as a first-line and alternative therapy for chronic pulmonary aspergillosis and allergic bronchopulmonary aspergillosis, respectively. Furthermore, by comparative analysis of AST profiles for inpatients and outpatients, it was noted that triazole susceptibilities were comparatively lower for outpatients than inpatients. The triazoles non-wild types isolates in outpatients might be attributed to the high use of triazoles as an agricultural antifungal agent [Reference Chen, Dong, Zhao, Fan, Qin, Li, Verweij, Zheng and Han51]. A study reported that agriculture’s entire quantity of azoles accounted for over one-third of all antifungal agents used in China [Reference Zhang, Jiang and Ou52]. This high use of azoles causes the emergence of azole-non-wild-type environmental Aspergillus species, which can infect humans and other animals [Reference Fisher, Alastruey-Izquierdo, Berman, Bicanic, Bignell, Bowyer, Bromley, Brüggemann, Garber and Cornely53]. Continuous surveillance studies under the One-Health approach are required to monitor the emergence of non-wild types Aspergillus species.
The limitation of the current study is its retrospective nature, so some data might not be available for analysis; for example, all the species were not accessible for molecular identification, which have a higher level of specificity in identifying fungal species. This study is based on a single centre in South China with a limited sample size, especially for non-fumigatus isolates. Therefore, the results might not be generalisable for other regions in China. Furthermore, we did not have access to data on antifungal therapy prior to the isolation of the Aspergillus species for the patients included in our study. As a result, we could not investigate the effect of prior antifungal medication on resistance development. However, the current study’s findings might help health officials manage aspergillosis in the regions.
Future prospective studies based on molecular epidemiology and antifungal resistance mechanisms from multi-centres are required. The researchers need to specifically target the mutation determinant of the CYP51A gene and its linkage with azole NWT isolates. Moreover, it is necessary to determine the correlation between prior antifungal therapy and the development of resistance in fungal isolates.
Conclusion
The present study reported 474 aspergillosis cases, with a high proportion of cases caused by A. fumigatus. Among the non-fumigatus cases, A. niger was reported in high proportion, followed by A. flavus. A high number of cases were reported from the ICU, indicating the immunocompromised status of the patients. Chronic pulmonary aspergillosis was reported in high proportion, showing that Aspergillus species are mainly involved in respiratory tract pathogenicity. Amphotericin B appears to be the most active antifungal agent against A. fumigatus, while for non-fumigatus isolates, the triazole’s MICs were lower than amphotericin B, which warrants further large-scale research confirmation. The Aspergillus species reported from outpatients have lower MIC/MEC to amphotericin B and caspofungin than triazoles, indicating that the agricultural use of triazole led to this emergence of non-wild types isolates. Further extensive molecular-based surveillance studies under the umbrella of One-Health approaches are required for the continuous monitoring of Aspergillus species, which will help manage aspergillosis.
Supplementary material
The supplementary material for this article can be found at http://doi.org/10.1017/S095026882300167X.
Data availability statement
All the data are presented in the manuscript; any raw data can be available by request to the first author (email; [email protected]).
Acknowledgements
All the authors thank the second affiliated hospital of Shantou University Medical College, Shantou, China for supporting this work.
Author contribution
Conceptualisation, H.B. and D.Z.; methodology, H.B.; software, H.B.; validation, M.S., M.N.K. and C.C.; formal analysis, S.K. and Q.W.; investigation, L.C.; resources, Y.Z.; data curation, H.H.; writing—original draft preparation, H.B.; writing—review and editing, R.K.; visualisation, M.S.; supervision, Y.Z.; project administration, D.Z.; funding acquisition, Y.Z. All authors have read and agreed to the published version of the manuscript.
Financial support
This research received no external funding.
Competing interest
The authors declare no conflict of interest.
Institutional review board statement
The study was conducted in accordance with the Declaration of Helsinki, and approved by the Institutional Review Board (or Ethics Committee) of Meizhou People’s Hospital (protocol code; 2021-C-106 and date of approval; 25-12-2021).
Patient consent form
Patient consent was waived due to the retrospective nature of study, and information was collected from the hospital record as secondary data; no personal image or figure of patients is included in this study.
Open access
