Full
Outline
To conduct a comprehensive biological characterization of an oxacillin-susceptible mecA-positive Staphylococcus aureus (OS-MRSA) strain isolated from a retail chicken sample, assess its virulence potential and molecular typing characteristics.
Staphylococcus aureus strain SAC10 was isolated from supermarket frozen whole-chicken samples. Identification was performed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), and antibiotic resistance profiles and the mecA gene were detected by antibiotic susceptibility testing and polymerase chain reaction (PCR). Whole-genome sequencing analyzed resistance genes, virulence genes and molecular typing. Virulence phenotypes were assessed via hemolysis assays, biofilm formation assays, and Galleria mellonella infection models. Sequence alignment elucidated the regulatory mechanism of the mecA gene.
SAC10 was identified as ST59-t437-IVa(2B) OS-MRSA. It carried mecA but exhibited phenotypic susceptibility, with its resistance gene profile consistent with the antimicrobial susceptibility pattern. The genome harbored multiple virulence factors (hlgABC, seb, sek, seq, aur, sak, scn),demonstrating strong hemolytic activity and biofilm-forming capability. Galleria mellonella assays revealed moderate virulence (16.67% survival at 72 h). Insertion of ISSau3 into the upstream promoter region of mecA suppressed its expression, resulting in the susceptible phenotype.
As a foodborne OS-MRSA, SAC10 combines virulence with concealed resistance genes, posing potential health risks via the food chain. The insertion mutation in mecA causing genotype-phenotype discordance highlights the need to combine conventional susceptibility testing with molecular detection to prevent underdiagnosis. These findings provide a scientific basis for improved monitoring and risk assessment of foodborne OS-MRSA.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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