INTRODUCTION

Fungi are eukaryotic, heterotrophic, unicellular, or pluricellular organisms, widely distributed in nature, found in atmospheric air, soil, water, vegetables, debris in general, food, humans, and other animals^1,2,3,4. The spread of these microorganisms can occur in various forms. When this propagation occurs through the air, the agents are called anemophilous fungi or allergenic fungi, whose spores are aeroallergens, responsible for respiratory manifestations, which may cause opportunistic infection in immunocompromised or high exposure hosts^1,4.

The concentration of anemophilous fungi in the environment depends on several factors; among them stand out indoor air conditioning, the intensity of human activity, and other environmental aspects, such as air current, rainfall, barometric pressure, cloudiness, temperature, relative humidity, and incidence of solar rays^2,5. In libraries, the environment becomes conducive to the spread of microorganisms, especially anemophilous fungi, due to ventilation/air conditioning conditions, humidity, and temperature^3,6.

Studies on anemophilous mycobiota from libraries show a wide variety of fungi, including potentially pathogenic ones, whose presence represents an occupational risk and can trigger allergic manifestations in its regulars^3,4,6. It is known that individuals confined indoors, with artificial ventilation and air conditioning, such as classrooms, libraries, theaters, cinemas, and others, may present persistent symptoms, including headaches, itching, irritation and edema of the ocular and mucous membranes, discomfort in the oropharynx and general malaise⁴, compromising their quality of life.

Due to these facts, good cleaning and environmental hygiene practices are implemented in many libraries through simple measures such as using brushes, cloth (dry), or even vacuum cleaner³. The air quality of these indoor environments, especially when considering the characteristics of anemophilous fungi, is more affected and may present a greater number of colony-forming units (CFU) when compared to surfaces and books⁶. However, despite the existence of environmental hygiene standards, there are few studies and initiatives to care for the air quality of these places^4,7.

In this context, there is a need to consolidate information on anemophilous fungi, increase studies on microorganisms with allergenic potential, and search for environmental indicators, such as fungi. Especially in libraries, the interest arises from the implications for the conservation of books and the health condition of workers and regulars, considering that the health problems most reported by workers of this service are related to allergic mechanisms^8,9. Therefore, this study aimed to evaluate the occurrence of anemophilous fungi in libraries of primary and higher education institutions in the city of Maceió, Alagoas State, Brazil.

MATERIALS AND METHODS

RESULTS

At the time of the dishes' exposure, thermal records of 24.6 °C, 28.1 °C, and 21.6 °C and humidity of 68%, 69%, and 59% were observed in collections A, B, and C, respectively, totalizing 55 samples (Table 1).

Of the 55 samples analyzed, 351 CFU were obtained, of which 331 CFU (94.3%) were filamentous fungi and 20 CFU (5.7%) yeast-like fungi. The overall colony count in bibliographic collections A, B, and C resulted in 212 (60.4%), 123 (35.0%), and 16 (4.6%) CFU, respectively, according to table 2.

Library A showed a higher CFU count of both filamentous and yeast-like fungi. Regarding the identification of fungi, a higher occurrence of Penicillium sp. (115 CFU) was observed, followed by Cladosporium sp. (79 CFU), Alternaria sp. (20 CFU), Aspergillus sp. (20 CFU), and Curvularia sp. (18 CFU). The greatest fungal diversity was verified in library A, registering 15 genera and Cladosporium sp. (69 CFU) was the predominant fungus, followed by Penicillium sp. (32 CFU) and Curvularia sp. (16 CFU). In library B, where there was no air conditioning, the genus with the highest occurrence was Penicillium sp. (80 CFU), while in library C, the genus Aspergillus sp. (6 CFU) predominated. Due to the absence of reproductive structures, 13.9% (49 CFU) of fungi were not identified (Table 3).

Several fungal cultures were obtained after sample collection by spontaneous sedimentation in the three libraries studied. Figure 1 shows the macroscopic and microscopic aspects of the six most prevalent fungi that exhibited more than 10 CFU in the evaluated environments, represented by Alternaria sp., Aspergillus sp., Cladosporium sp., Curvularia sp., Fusarium sp., and Penicillium sp.

Figure 1 - Macroscopic and microscopic aspects of fungi that showed higher prevalence in the libraries A, B and C, cultivated in Petri dishes containing potato agar dextrose at 28 ºC, in the city of Maceió, Alagoas State, Brazil 

This study's limitations are related to the number of spaces studied and the lack of structure to perform the molecular identification of these fungi.

DISCUSSION

The results obtained in this study are similar to those reported by Menezes et al.¹⁷, regarding fungal diversity found, since they obtained 220 CFU from 50 exhibitions in an air-conditioned library of a public higher education institution in northeastern Brazil. Air-conditioned enclosed environments tend to accumulate fungal cells dispersed in the air, as evidenced by Ribeiro and Lubisco⁶ when comparing the concentration of CFU from indoor and outdoor environments of a library, where the former presented approximately twice the concentration of CFU as the second.

Libraries are spaces that provide ideal conditions for the growth of microorganisms, since they concentrate a large amount of organic matter, including paper, starch glue, leather, and fabrics¹⁸. Therefore, evidence indicates that, even in controlled conditions, there is contamination by fungi on surfaces and in the air¹⁹.

In space C, a smaller number of CFU and filamentous fungal species was observed compared to library A, which is also acclimatized. This fact may be related to the cleaning systematization at this site and the lower temperature and humidity verified at the time of collection. Library C adopted regular cleaning and hygiene practices; in addition, the environment presented better refrigeration, mainly because it had a lower flow of people on-site, an observation made during the study period when compared to library A, which offered 88 face-to-face courses, and library C, with 13 courses and consisted of a smaller area. Thus, the higher frequency of fungi in space A may be related to greater visitation in this space by students and employees, since this library serves as a reference for other educational and research institutions in the state. Moreover, it is important to consider that the air conditioning equipment is frequently switched off at night and at weekends in this library, which causes temperature variability, mainly due to the thermal amplitudes experienced in the Northeast Region.

Second in CFU number and fungal diversity, space B did not possess air conditioning equipment and had the highest temperature during collection. Besides that, low rates of indoor air circulation can lead to an increase in the concentration of biological air pollutants²⁰. Pantoja et al.²¹ clarify that fungal growth occurs faster when the relative humidity of the air is above 65%, which was evidenced in environments A and B. According to Pereira and Lemos²², temperature plays a primary function in the growth, germination, sporulation, and metabolism of fungi.

Factors such as hygiene, temperature, and luminosity are directly related to greater fungal diversity²⁰. Inadequate cleaning, using methods that facilitate the aerial dispersion of microorganisms, can contribute to this fact, as occurs with brooms. It is important to consider that the fungal diversity reported in this study may be related to inefficient hygiene and air conditioning conditions, which vary in each space studied²¹, with a higher prevalence of fungi in the libraries of public institutions.

In order to avoid or decrease the proliferation of fungi and other microorganisms in libraries, it is recommended to practice regular cleaning, providing the conservation of the collection, maintaining air quality, and, consequently, preserving the health of its regulars. Hygiene corresponds mainly to the removal of particulate matter (dust, pollen, human skin scales, hair, among others) from documents and surfaces of the environment and should be performed periodically, with the use of appropriate techniques⁶. The physical space of the libraries must be sufficiently airy, illuminated, and have an adequate temperature (20 to 23 ºC) and humidity (55 to 65%) values for the preservation of books and documents²¹. In addition, it is essential to clean the air conditioner filter monthly, to decrease the growth of microorganisms, since the accumulation of moisture and organic material can make it a powerful dispersing source of pathogens^23,24.

Regarding the variability of fungal species, published studies corroborate the results obtained in this research because the collections carried out over the years in internal spaces of libraries showed that, among the fungi that contaminate these spaces, species of the genus Aspergillus and Penicillium predominate^8,17,20. In the present study, the most frequent filamentous fungi species were Penicillium sp. and Cladosporium sp.; however, Alternaria sp., Aspergillus sp. and Curvularia sp. also presented higher frequency than other identified species.

In the last 20 years, environmental studies with air from library environments have shown that species of Cladosporium, Aspergillus, and Penicillium are almost ubiquitous and can produce numerous conidia that are easily dispersed by air²⁵. According to Martins²⁶, the diversity of fungi present indoors results from the spread caused by the air currents, among other biotic factors of the external environment, and is especially related to the appearance of genera characteristic of the local microbiota of a given region.

In this sense, species belonging to the genera Aspergillus, Penicillium, and Verticillium present cellulolytic activity and can deteriorate materials rich in cellulose, such as wood, books, and paintings²⁷. Moreover, the genera of fungi most frequently found in the air are Aspergillus sp., Penicillium sp., Fusarium sp., Cladosporium sp., Curvularia sp., Neurospora sp. and Alternaria sp.; and Aspergillus and Penicillium are considered the primary colonizers of surfaces and interiors²⁸.

Regarding the filamentous fungi identified in this study, most of these microorganisms are commonly associated with pathological processes. Anemophilous fungi, when inhaled, can trigger diseases ranging from respiratory allergic manifestations, such as asthma and rhinitis, to severe infections in immunocompromised individuals²⁰.

Among these species, fungi of the genus Aspergillus cause great concern, because it can cause from allergic reactions to aspergillosis, a disease characterized by a bronchopulmonary clinical picture that can spread, compromising several organs²⁰. Invasive aspergillosis is related to a diversity of clinical scenarios, which commonly vary concerning manifestations, presenting a very high mortality rate²⁹.

Although Penicillium species are saprophytic, ubiquitous in the soil, survive on biodegradable organic substances, and prefer cold to moderate climates, their colonization is related to the ability to grow at a variety of temperatures, ability to survive in different ranges of water activity, and physicochemical conditions, which are found in libraries, making this environment conducive to their dispersion³⁰.

In addition, Cladosporium has been the most common fungal genus in several studies of climatized indoor environments, being considered a universal dominant fungus^{31,32,33,34,35,36}. Many Cladosporium species are recognized as emerging pathogens, responsible for pulmonary, cutaneous infections, and respiratory system-related problems, often associated with asthmatic complaints^37,38.

Less frequently, the presence of yeast-like fungi was observed in the study environments. Although the isolation of these fungi has been reported, little attention is paid to them when compared to filamentous fungi responsible for triggering allergic processes imminently, such as Aspergillus. In contrast, yeast-like fungi do not immediately produce allergic or respiratory reactions, although they may be harmful to immunocompromised individuals⁸. It is essential to highlight that they may be related to superficial and systemic infections, especially in impaired immune system³⁹.

Trichosporon sp. presented a higher frequency among the isolated yeast-like species, with 9 CFU (2.6%). Trichosporon is a fungus that can be part of the normal microbiota of the human skin and gastrointestinal tract, and 17 species of this genus are clinically relevant^40,41,42 because they cause white piedra, hypersensitivity pneumonitis, and various types of invasive infections, mainly in immunocompromised individuals⁴¹, and are therefore considered opportunistic.

Another yeast-like identified was Rhodotorula sp., considered commensal, found in the human airway, gastrointestinal and genital microbiota, and disseminated in the environment. It can cause opportunistic infections in immunocompromised patients, ranging from endocarditis, meningitis, ventriculitis, and peritonitis to cases of potentially fatal fungemia^43,44,45.

This study demonstrates the need to improve environmental disinfection measures to maintain the collection of the libraries and prevent diseases caused by fungi.

CONCLUSION

The results of this study show the importance of environmental disinfection routines in enclosed spaces, such as libraries, for the prevention of diseases in their participants and the conservation of the collection, since the health risk depends on the environmental control measures adopted, the cleaning frequency of the collection and environment in general, the monitoring of temperature, and relative humidity.