Table 1.
Primer sequences used for molecular characterisation of bacterial isolates from dairy-cow quarter milk
| Gene | Forward primer | Reverse primer | Expected product length (bp) |
|---|---|---|---|
| 16S rRNA | AGGGAGCTTGCCTTGGATTC | GGATGCAGTTCCCAGGTTGA | 557 |
| dinB1 | CGCTGCACATCCGTGAAATC | TGCGCCAAATCGTATTGCTG | 382 |
| dinB2 | GATCGCTCAGGAGATCCGTC | CCAGCTCGGGGTAGAGTTTG | 452 |
| rpoB | TTGTTTCTGTTGCTGCGTCG | GATTTCCTCTGGGCCAAGCT | 572 |
Table 2.
Microorganisms identified during the individual stages of microbiological analysis of dairy-cow quarter-milk samples
| Month and year | Samples (n) | Cows (n) | Serratia sp. | CNS | CPS | MRSA | Streptococcus sp. | Enterococcus sp. | Enterobacterales other than Serratia | Micrococcus sp. | Bacillus sp. | Aerococcus viridans | Candida sp. | No growth | Contamination |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Feb 2024 | 34 | 34 | 1 | 3 | 0 | 0 | 13 | 2 | 0 | 0 | 0 | 0 | 2 | 8 | 7 |
| Mar 2024 | 35 | 35 | 0 | 1 | 0 | 0 | 13 | 0 | 0 | 0 | 0 | 0 | 1 | 9 | 9 |
| Apr 2024 | 56 | 55 | 1 | 2 | 0 | 0 | 4 | 1 | 0 | 1 | 0 | 0 | 0 | 6 | 1 |
| May 2024 | 45 | 44 | 1 | 5 | 0 | 0 | 19 | 1 | 1 | 1 | 0 | 0 | 0 | 10 | 6 |
| Oct 2024 | 54 | 52 | 1 | 7 | 0 | 0 | 3 | 0 | 0 | 0 | 1 | 0 | 0 | 9 | 3 |
| Nov 2024 | 47 | 46 | 1 | 2 | 1 | 0 | 17 | 1 | 2 | 0 | 0 | 0 | 1 | 10 | 6 |
| Feb 2025 | 35 | 24 | 0 | 1 | 1 | 0 | 9 | 1 | 3 | 2 | 0 | 0 | 0 | 8 | 9 |
| Mar 2025 | 53 | 52 | 2 | 7 | 1 | 1 | 8 | 2 | 5 | 1 | 0 | 0 | 2 | 19 | 7 |
| Apr 2025 | 44 | 37 | 2 | 4 | 0 | 0 | 9 | 2 | 10 | 0 | 1 | 0 | 1 | 8 | 4 |
| May 2025 | 44 | 40 | 0 | 12 | 0 | 0 | 9 | 2 | 5 | 0 | 0 | 1 | 0 | 9 | 6 |
| Jun 2025 | 34 | 32 | 1 | 3 | 0 | 0 | 8 | 2 | 5 | 1 | 0 | 0 | 0 | 12 | 2 |
Table 3.
Minimum inhibitory concentrations against Serratia marcescens isolates and antibiograms of those isolates from dairy-cow quarter-milk samples
| Antimicrobial agent | Isolate 1 (Feb 2024) | Isolate 2 (Apr 2024) | Isolate 3 (May 2024) | Isolate 4 (Oct 2024) | Isolate 5 (Nov 2024) | Isolate 6 (Mar 2025) | Isolate 7 (Mar 2025) | Isolate 8 (Apr 2025) | Isolate 9 (Apr 2025) | Isolate 10 (Jun 2025) |
|---|---|---|---|---|---|---|---|---|---|---|
| Amikacin | ≤2 S | ≤2 S | 8 S | 8 S | 8 S | 8 S | 8 S | 8 S | 4 S | 4 S |
| Amoxicillin/clavulanic acid | 16 R | 8 R | 16 R | 16 R | 16 R | 16 R | 16 R | 16 R | 16 R | 16 R |
| Cefepime | ≤0.12 S | ≤0.12 S | 2 I | 2 I | 2 I | 1 S | 1 S | 1 S | 1 S | 1 S |
| Cefotaxime | ≤0.25 S | ≤0.25 S | 8 R | 8 R | 8 R | 8 R | 4 R | 4 R | 4 R | 4 R |
| Ceftazidime | 0.25 S | 0.25 S | ≥64 R | ≥64 R | ≥64 R | ≥64 R | ≥64 R | 16 R | 32 R | 16 R |
| Cefuroxime | 32 R | 16 R | ≥64 R | ≥64 R | ≥64 R | ≥64 R | ≥64 R | 32 R | 32 R | 32 R |
| Ciprofloxacin | ≤0.25 S | ≤0.25 S | ≤0.25 S | ≤0.25 S | ≤0.25 S | ≤0.25 S | ≤0.25 S | ≤0.25 S | ≤0.25 S | ≤0.25 S |
| Colistin | ≤16 R | ≤16 R | ≤16 R | ≤16 R | ≤16 R | ≤16 R | ≤16 R | ≤16 R | ≤16 R | ≤16 R |
| Gentamicin | ≤1 S | ≤1 S | 2 S | 2 S | 2 S | 2 S | 2 S | ≤1 S | ≤1 S | ≤1 S |
| Meropenem | ≤0.25 S | ≤0.25 S | 4 I | 4 I | 4 I | 4 I | 4 I | 8 S | 4 I | 4 I |
| Piperacillin/tazobactam | ≤4 S | ≤4 S | 64 R | 64 R | ≤4 S | ≤4 S | ≤4 S | ≤4 S | ≤4 S | ≤4 S |
| Tigecycline | 1 R | 1 R | 2 R | 2 R | 1 R | 1 R | 1 R | 2 R | 2 R | 2 R |
| Tobramycin | 2 S | ≤1 S | 8 R | 8 R | 8 R | 8 R | 8 R | 4 R | 4 R | 4 R |
| Trimethoprim/sulfamethoxazole | ≤20 S | ≤20 S | ≤20 S | ≤20 S | ≤20 S | ≤20 S | ≤20 S | ≤20 S | ≤20 S | ≤20 S |
Table 4.
Basic local alignment search tool results for molecular identification of bacterial isolates from dairy-cow quarter-milk samples
| Sequence | Query coverage | Percent identit | Accession length | Taxon | Accession No. |
|---|---|---|---|---|---|
| rpoB | 95% | 97.59% | 5144137 | Serratia marcescens | CP090244.1 |
| dinB1 | 100% | 99.71% | 4962287 | Serratia marcescens | CP132290.1 |
| dinB2 | 96% | 98.74% | 4962287 | Serratia marcescens | CP132290.1 |
| 16S rRNA | 97% | 88.30% | 1220 | Serratia marcescens | MH001477.1 |