Fusarium species isolated from post-hatchling loggerhead sea turtles (Caretta caretta) in South Africa.

Species in the Fusarium solani species complex are fast growing, environmental saprophytic fungi. Members of this genus are filamentous fungi with a wide geographical distribution. Fusarium keratoplasticum and F. falciforme have previously been isolated from sea turtle nests and have been associated with high egg mortality rates. Skin lesions were observed in a number of stranded, post-hatchling loggerhead sea turtles (Caretta caretta) in a rehabilitation facility in South Africa. Fungal hyphae were observed in epidermal scrapes of affected turtles and were isolated. The aim of this study was to characterise the Fusarium species that were isolated from these post-hatchling loggerhead sea turtles (Caretta caretta) that washed up on beaches along the South African coastline. Three gene regions were amplified and sequenced, namely the internal transcribed spacer region (ITS), a part of the nuclear large subunit (LSU), and part of the translation elongation factor 1 α (tef1) gene region. Molecular characteristics of strains isolated during this study showed high similarity with Fusarium isolates, which have previously been associated with high egg mortality rates in loggerhead sea turtles. This is the first record of F. keratoplasticum, F. falciforme and F. crassum isolated from stranded post-hatchling loggerhead sea turtles in South Africa.

Reduced amplification efficiency of the RNA-dependent-RNA-polymerase target enables tracking of the Delta SARS-CoV-2 variant using routine diagnostic tests.

Routine SARS-CoV-2 surveillance in the Western Cape region of South Africa (January-August 2021) found a reduced RT-PCR amplification efficiency of the RdRp-gene target of the Seegene, Allplex 2019-nCoV diagnostic assay from June 2021 when detecting the Delta variant. We investigated whether the reduced amplification efficiency denoted by an increased RT-PCR cycle threshold value (RΔE) can be used as an indirect measure of SARS-CoV-2 Delta variant prevalence. We found a significant increase in the median RΔE for patient samples tested from June 2021, which coincided with the emergence of the SARS-CoV-2 Delta variant within our sample set. Whole genome sequencing on a subset of patient samples identified a highly conserved G15451A, non-synonymous mutation exclusively within the RdRp gene of Delta variants, which may cause reduced RT-PCR amplification efficiency. While whole genome sequencing plays an important in identifying novel SARS-CoV-2 variants, monitoring RΔE value can serve as a useful surrogate for rapid tracking of Delta variant prevalence.

First Record of the Water Mold Achlya bisexualis (Saprolegniaceae) Isolated from Ornamental Fish in South Africa.

The order Saprolegniales (Class Oomycota) is a group of fungus-like eukaryotic microorganisms that have been associated with infections in fish and fish eggs. Infections with microorganisms from this order are clearly evident because they have a cotton wool-like appearance. The aim of this study was to characterize and identify an oomycete that was isolated from the eye of an Orange Blotched Peacock Cichlid Aulonacara sp. A sample of cotton wool-like mycelia was isolated and single-spore isolations were conducted. Molecular characterization and phylogenetic analysis of the ITS1-5.8-ITS2 rDNA region for all isolates were used for species identification. Following molecular identification, one isolate was used to culture and characterize the reproductive structures. Physiological characterization entailed incubating the isolate on potato dextrose agar (PDA) at five different temperatures, ranging from 5°C to 25°C, to monitor growth rates. A multiple sequence alignment showed 100% similarity between all of the single-spore isolates and alignment with other Achlya bisexualis strains. Long, coarse hyphae with zoosporangia and gemmae typical of the order Saprolegniales were observed with an optimal growth rate at 25°C. The oomycete that was isolated from an Orange Blotched Peacock Cichlid was identified as A. bisexualis, the first record of this species in South Africa.

Mycotoxin production by three different toxigenic fungi genera on formulated abalone feed and the effect of an aquatic environment on fumonisins.

Mycotoxins are toxic secondary metabolites produced by various filamentous fungi, of which Fusarium, Aspergillus and Penicillium are the three main genera. Fusarium verticillioides is one of the most dominant toxigenic fungal species, associated with fumonisin contamination in grain-based feeds, such as compound abalone feed. Mycotoxin production is influenced by temperature and available nutrients. In this study the aims were: to determine if abalone feed as growth substrate favours mycotoxin production for toxigenic fungi; to determine the most effective temperature for fumonisin production by F. verticillioides on abalone feed; and to assess the effect of the aquatic environment on fumonisin-contaminated abalone feed. A total of 93 fungal isolates were inoculated onto abalone feed, including species belonging to the genera Fusarium, Aspergillus and Penicillium. Feed inoculated with F. verticillioides were incubated at two different temperatures and fumonisin-contaminated feed was submerged into seawater for 24 h. Results showed that mycotoxins were produced when abalone feed was inoculated with toxigenic fungi, and that F. verticillioides produced higher concentrations of fumonisins at a lower temperature. Submerging fumonisin-contaminated feed in seawater showed that this toxin leached into the seawater, lowering the risk of fumonisins to be consumed by abalone.