Mechanism of Resistance to Macrolide-Lincosamide-Streptogramin Antibiotics in Streptococcus thermophilus
Bibliographic record
Abstract
Resistance to macrolide-lincosamide-streptogramin (MLS) group antibiotics in the dairy bacterium Streptococcus thermophilus (ST) is documented but the mechanism of resistance has not been elucidated. MIC values for erythromycin (Erm), azithromycin (Azm), tylosin (Tyl), spiramycin (Spm), pristinamycin (Prm) and virginiamycin S (Vir) were determined by the disk diffusion method. PCR products were obtained with primer pairs for the L4, L22 and 23S rDNA (domain V) genes. The sequencing results ruled out mutations in the L4 and L22 ribosomal proteins and the presence of rRNA methylase, efflux, and inactivating genes. However, sequencing of domain V in each of the six ribosomal alleles detected by EcoRI/I-CeuI digestion in ST mutants identified three types of mutations that led to MLS resistance. Type A mutants, induced by Erm, had high resistance to 14- and 15-membered ring macrolides (Erm, Azm) and streptogramin B antibiotics (Prm, Vir), moderate resistance to 16-membered ring macrolides (Tyl, Spm), but remained susceptible to lincomycin. In Type B mutants, also induced by Erm, resistance was high to Erm, Tyl and Spm, and moderate to lincomycin but sensitivity was retained to Prm. Type C mutants, induced by Prm, showed high resistance to 16-membered ring macrolides but remained sensitive to Erm, Azm and lincomycin. The three identifiable resistance patterns were apparently due to point mutations in domain V of the 23S rRNA gene, resulting in three phenotypes among resistant S. thermophilus isolates. Type A phenotype mutants had a C2611G mutation in five of the six ribosomal alleles, Type B phenotypes had a A2058G mutation in five alleles, and Type C variants had a A2062C mutation in all six alleles. Resistance to MLS antibiotics in S. thermophilus was inducible by 14- and 15-membered ring macrolides and streptogramin B type antibiotics but not by 16-membered ring macrolides or lincosamides.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".