Full
Outline
To elucidate the differences in molecular epidemiological characteristics, antibiotic resistance and virulence properties of methicillin-resistant Staphylococcus aureus (MRSA) ST59 and ST398 in retail pork in the Hanzhong, and assess their potential public health risks.
Whole-genome sequencing was used to perform multilocus sequence typing (MLST), staphylococcal protein A gene (spa) typing, and staphylococcal cassette chromosome mec (SCCmec) typing for the isolates, and their resistance and virulence gene profiles were predicted. Antimicrobial susceptibility testing was conducted using the broth microdilution method; sheep red blood cell hemolysis test was used to evaluate hemolytic activity, and microplate crystal violet staining was employed to assess biofilm-forming ability.
Among the 43 MRSA isolates, ST59 (51.16%, 22/43) and ST398 (46.51%,20/43) were the dominant types. ST59 strains showed high homogeneity in molecular typing, mainly clustering in spa t437 (81.82%) and SCCmec IVa(2B) (90.91%); in contrast, ST398 strains exhibited high genetic diversity with various spa types and SCCmec types. The resistance rates of ST398 strains to gentamicin, tetracycline, levofloxacin,clindamycin and trimethoprim-sulfamethoxazole were significantly higher than those of ST59 strains (P<0.01).ST398 strains carried more abundant acquired resistance genes, including high carriage rates of tet(M) (95.00%),lnu(B) (75.00%), lsa(E) (90.00%) and dfrG (90.00%). Additionally, 3 strains carried the poxtA gene; while the resistance gene profile of ST59 strains was relatively simple. In terms of virulence characteristics, ST398 strains showed strong hemolytic activity; ST59 strains had stronger biofilm-forming ability and carried a more complex virulence gene profile, with significantly higher carriage rates of immune escape genes sak, scn, and enterotoxin genes seb, sek, seq compared to ST398 strains.
The main prevalent clones of MRSA in retail pork products in Hanzhong are ST59 and ST398. The different biological characteristics pose differential challenges to public health, requiring targeted monitoring and prevention measures.
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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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