Full
Outline
This study aims to analyze the phenotypic and genotypic resistance to antibiotics and disinfectants in Salmonella isolated from fresh pork sold in Chengdu in 2021, and to investigate their regional distribution and phylogenetic relationships based on whole-genome sequencing (WGS). The findings provide scientific evidence for clinical treatment guidance, disinfectant selection in fresh markets, and foodborne disease prevention and control, while also supporting traceability investigations for Salmonella-related public health emergencies.
The antibacterial susceptibility of Salmonella isolated from fresh pork markets across Chengdu districts was tested against 14 antibiotics and 8 disinfectants using the broth microdilution method. WGS and bioinformatics analysis were performed on 114 strains for MLST typing, antibiotic resistance gene (ARG) profiling, and disinfectant resistance gene (DRG) distribution. Crystal violet staining was used to assess biofilm eradication.
Resistance rates were highest for tetracycline(TET, 87.72%) and trimethoprim-sulfamethoxazole(SXT, 67.54%). Significant regional variations were observed for resistance to ampicillin (AMP), ampicillin-sulbactam (AMS),cefazolin (CFZ), gentamicin (GM), ciprofloxacin (CIP), azithromycin (AZM), and SXT. High-tech Zone exhibited the highest resistance (55.95%), followed by Chenghua District (42.86%). All isolates tolerated 25% glutaraldehyde (GD), whereas the isolates were relatively susceptible to cetylpyridinium chloride monohydrate (CCM), and CCM could effectively disrupt Salmonella biofilms. A total of 38 ARGs spanning 10 classes were detected, with all strains carrying aac(6’)-Iaa (not phenotypically correlated), followed by tet(A) (84.21%). Significant phenotype-genotype correlations were identified for BlaTEM-1B, tet(A), floR,cmlA1, sul3, and dfrA12. The disinfectant resistance gene (DRGs) qacE was detected in 29.82% of isolates, with 83.33%concentrated in High-tech Zone. 94.12% of DRG-positive strains were multidrug-resistant (MDR). ST469 was the dominant sequence type (ST), widely distributed across Chengdu.
Salmonella from pork in Chengdu exhibits widespread and high antibiotic resistance, with increasing MDR trends. In retail fresh pork markets, CCM is recommended over GD (aldehyde-based disinfectants). ST469 was the predominant sequence type, indicating a substantial risk of cross-regional transmission.
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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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