Back to the Future: Penicillin-Susceptible Staphylococcus aureus
Bibliographic record
Abstract
Background. Penicillin was first used to treat septicemia in 1942. Subsequent widespread usage resulted in the emergence of resistance in Staphylococcus aureus. However, new data suggests that penicillin susceptibility may be in a period of renaissance. The objective of our study was to explore the resistance patterns in methicillin-susceptible Staphylococcus aureus (MSSA) bacteremias. Methods. We retrospectively reviewed all adult MSSA bacteremia from April 2010 to April 2015 at the McGill University Health Centre (Montreal, Canada). Susceptibility to penicillin, macrolides, clindamycin and trimethoprim-sulfamethoxazole (TMP-SMX) were determined in accordance with the Clinical and Laboratory Standards Institute guidelines. Only the first positive culture per patient was included. Results. There were 324 unique episodes of MSSA bacteremia. Ninety (28%) isolates were susceptible to penicillin, 229 (71%) to macrolides, 239 (74%) to clindamycin and 317 (98%) to TMP-SMX. Isolates that were penicillin resistant were more likely to also be resistant to macrolides (76 of 234 versus 19 of 90, p = 0.04) but not clindamycin (68 of 234 versus 17 of 90, p = 0.06) or trimethoprim-sulfamethoxazole (6 of 234 versus 1 of 90, p = 0.42). The median age of patients was 67.5 years (IQR 52–78) and overall in-hospital 30-day mortality was 16.3% (53 deaths). Patients 75 and older were more likely to die (28 of 99, 28.3%) than those 65–74 (14 of 82, 17.1%) or below (11 of 143, 7.7%) (p < 0.001). After adjustment for patient age, there was no association between penicillin resistance and either ICU admission or death. Conclusion. More than one quarter of patients with MSSA bacteremia could be treated with parenteral penicillin. When susceptible, penicillin has prolonged time over minimal inhibitory concentration compared with other β-lactams: providing a theoretical advantage in achieving cure while minimizing spectrum of activity. Our results may support a return to penicillin testing among invasive SA isolates in centers that have stopped. Disclosures. All authors: No reported disclosures.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| 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) | 0.002 | 0.007 |
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; both teacher heads agree on what is shown here.
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".