Captive lizards (Squamata: Sauria) as reservoirs of medically important and antifungal-resistant yeasts

Abstract

Zoological collections represent unique environments in which captivity-related alterations of host microbiota may increase susceptibility to infectious diseases. While reptiles are recognized reservoirs of microorganisms, data on quantitative yeast colonization and antifungal susceptibility in captive lizards remain limited. This study assessed 28 lizards belonging to nine species housed in a zoological park in southern Italy. Skin and cloacal swabs (n = 56) revealed yeast growth in 75% of animals and 57.1% of samples, with positivity rates of 60.7% and 53.6% for skin and cloacal samples, respectively. MALDI-TOF MS and ITS region sequencing identified 113 isolates belonging to 17 distinct fungal species, including Arthrographis spp., Meyerozyma spp., Candida spp., Pichia spp., Trichosporon spp., and others. Arthrographis kalrae was the predominant species (i.e., 36.3%), followed by Meyerozyma guilliermondii (i.e., 16.8%). Mean colonization loads were 4.25 CFU/swab for skin and 10.50 CFU/swab for cloacal samples. Eight species were considered clinically relevant, including the Candida parapsilosis complex, Pichia kudriavzevii, and Trichosporon asahii. Antifungal susceptibility testing performed according to Clinical and Laboratory Standards Institute (CLSI, 2022) guidelines revealed marked phenotypic heterogeneity and frequent elevation of minimum inhibitory concentration (MIC). Above-threshold MICs differed significantly according to yeast species, antifungal compound, and sampling site. Non-wild-type phenotypes and elevated MICs were observed across multiple antifungal classes, with amphotericin B >64 µg/ml and fluconazole >256 µg/ml in several isolates (i.e., 92.3% and 75.0%, respectively). Reduced susceptibility or resistance was evident in Clavispora lusitaniae, M. guilliermondii, and Wickerhamomyces anomalus. These findings support the hypothesis that captive lizards may represent asymptomatic reservoirs of opportunistic and potentially antifungal-resistant yeasts, emphasizing the importance of hygiene measures and microbiological surveillance in zoological settings.