Purpose: The genus Aspergillus is one of the most prevalent in several highly contaminated occupational environments, such as the waste sorting industry. The identification and quantification of Aspergillus sections present on filters from the air-conditioning systems in fork lifters were performed, including the screening of azole-resistance. In addition, toxigenic strains from Aspergillus spp. were detected.
Methods: Filter pieces from fork lifters (n=17) and personal vehicles (n=28) were extracted and streaked onto MEA and DG18. After incubation at 27 ºC for 5 to 7 days, Aspergillus spp. densities (CFU/m2) were calculated, and Aspergillus sections were identified through macro and microscopic characteristics. The prevalence of azole-resistance was determined in screening agar plates containing Saboraud media supplemented with 4 mg/ml itraconazole, 1 mg/ml voriconazole, and 0.5 mg/ml posaconazole, according to the EUCAST guidelines, incubated at 27 °C for 5 days. The molecular detection of the Aspergillus sections Circumdati, Fumigati and Flavi (only the toxigenic strains) was performed by Real Time PCR (RT-PCR).
Results: Fungal contamination ranged from 5x102 to 71x103 CFU/m2 in MEA. Aspergillus sp. was the most prevalent (59.5%). Aspergillus sections Nigri (28.2%), Fumigati (26.6%) and Circumdati (26.2%) were the most frequent. In the DG18 the range was from 5x102 to 75x103 CFU/m2 and Aspergillus sp.was also the most prevalent (47.5%). Aspergillus sections Circumdati (51.7%) and Nigri (22.8%) were the most frequent. Regarding personal vehicles fungal contamination ranged from 0 to 82x103 CFU/m2 with MEA and Aspergillus genus presented a prevalence of 1%. Among Aspergillus genus sections Candidi (and Nigri (50%)were the only ones found. Fungal contamination ranged from 0 to 28x103 CFU/m2 with DG18. Aspergillus sp. was the second most prevalent (15.6%) being species from section Versicolores the only ones found.
Aspergillus section Nigri was the most prevalent among azole-resistant species. Overall, the prevalence of azole-resistant Aspergillus section Nigri was 76% in 4 mg/mL itraconazole, 43% in 1 mg/mL voriconazole, and 0.33% in 0.05 mg/mL posaconazole. Azole-resistance was also detected in personal vehicles. Azole-resistant Aspergillus section Candidi was approximately 71-fold higher in filters from personal vehicles than in fork lifters, with 40% being resistant to 4 mg/mL itraconazole.
By qPCR analysis we detected Aspergillus section Fumigati in 47% of the fork filters. Aspergillus section Versicolores was detected in 11.8% of the filters, suggesting that molecular detection was more sensitive than culture based- methods in the detection of these two fungi. By contrast, no Aspergillus sections Flavi and Circumdati were amplified by qPCR in any of the filters, despite the fact that they were identified by culture based-methods in some of the assessed filters. No amplification was detected in any of the control vehicles analysed.
Conclusions: The fungal assessment of the filters from the air-conditioning systems should be suggested as an approach to be followed in future for forklifts drivers working in waste sorting industry. This study corroborates the complementarity of using culture based-methods (with selective and supplemented media) with molecular tools. Moreover, it reinforces the need to cover the azole-resistance surveillance also in this occupational environment.
Full conference title:
- AAA 8th (2018)