Resistance profile and minimum inhibitory concentration versus minimum biofilm inhibitory concentration of biofilm positive Staphylococci
Bibliographic record
Abstract
Background: Staphylococcal spp. are recognized as one of the most frequent causes of biofilm associated infections. In routine microbiology laboratories, standard method for testing antibiotic susceptibility is Kirby-Bauer disc diffusion method and minimum inhibitory concentration (MIC) which determine the antibiotic susceptibilities in planktonic phase. However, isolates capable of producing biofilm exist in biofilm state. Thus,antibiotics prescribed based on routine methods fail to eradicate biofilms thereby causing persistent infection and possible treatment failure. Thus, this work was designed to study prevalence of biofilm producing staphylococci, its resistance profile and to perform MIC versus MBIC (Minimum biofilm inhibitory concentration) in representative biofilm positive isolates. Methods and materials: 335 clinical isolates of staphylococci included in the study were screened for biofilm formation phenotypically by Congo red agar (CRA) and Tissue culture plate method (TCPM) followed by detection of biofilm genes (icaAD,aap,atlE) by PCR. Antibiotic susceptibility testing was done for biofilm positive isolates. MIC versus MBIC testing was performed for representative biofilm positive isolates for cefoxitin and vancomycin. MIC was done by broth microdilution and MBIC testing was performed using Calgary Biofilm Device. Results were interpreted according to CLSI guidelines,2015. Results: 77/335 (30%) staphylococcal isolates were biofilm positive of which S.haemolyticus (n = 35, 45.5%) was predominant followed by S. aureus (n = 27, 35.1%) and S.epidermidis (n = 15, 19.5%). By CRA, 22 (28.6%) isolates produced black colonies after 24 hours. By TCPM, 4 (5.2%), 1 (1.3%) & 49 (63.6%) isolates showed strong, moderate and weak biofilm production respectively. Overall, 77 isolates harboured biofilm genes (47aap,15atlE,15aap+atlE,5icaAD+aap+atlE).43/77 (55.8%)isolates were methicillin resistant. Highest resistance was found towards ciprofloxacin (74%) followed by erythromycin (70.1%),cotrimoxazole (65%) and pristinamycin (65%) respectively. MIC and MBIC were compared for 25 representative biofilm positive isolates. Cefoxitin MIC and MBIC ranged between 2–1024 μg/mL and 8–2048 μg/mL respectively. Vancomycin MIC and MBIC ranged between 0.5–8 μg/mL and 2–512 μg/mL respectively. Both cefoxitin and vancomycin MBIC values were 2–64 folds higher than their respective MIC. Conclusion: The present study documents biofilm producing capability in 30% of isolates. The antibiotic sensitivities of organisms in planktonic phase tested by MIC were significantly higher than for the same organism in their biofilm state as tested by MBIC. The results of the study questions the use of vancomycin as last resort antibiotic for biofilm-associated staphylococcal infections.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 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) | 0.001 | 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".