Antibiotic Sensitivity Test of Bacterial Strains

Categories: Biology

Abstract

In this study, we conducted an antibiotic sensitivity test on bacterial strains using 23 frequently used antibiotics applied on Muller-Hinton agar medium by the disk diffusion technique. The antibiotics included Erythromycin, Cephalexin, Ceftriaxone, Chloramphenicol, Piperacillin, Colistin, Streptomycin, Cefotaxime, Gentamycin, Amikacin, Neomycin, Vancomycin, Azithromycin, Tetracycline, Amoxicillin, Penicillin, Ceftazidime, Cloxacillin, Nalidixic acid, Ciprofloxacin, Cotrimoxazole, Levofloxacin, and Imipenem. We measured the diameter of the zone of inhibition around each antibiotic disk after incubation at 37°C for 24 hours, following Clinical Laboratory Standard Institute guidelines.

Introduction

Antibiotic sensitivity testing is a crucial diagnostic tool in clinical microbiology.

It helps determine the susceptibility of bacterial strains to specific antibiotics, guiding healthcare professionals in selecting the most effective treatment for infections. The choice of antibiotics is essential to ensure successful treatment and prevent the development of antibiotic resistance.

In this study, we focused on assessing the sensitivity of bacterial strains to 23 commonly used antibiotics. The selection of antibiotics was based on their relevance in clinical practice and the need to understand the effectiveness of these drugs against the isolated bacterial strains.

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We employed the disk diffusion technique, which is a standard method for evaluating antibiotic susceptibility.

Materials and Methods

Materials:

  • Muller-Hinton agar medium
  • 23 antibiotic disks (Erythromycin, Cephalexin, Ceftriaxone, Chloramphenicol, Piperacillin, Colistin, Streptomycin, Cefotaxime, Gentamycin, Amikacin, Neomycin, Vancomycin, Azithromycin, Tetracycline, Amoxicillin, Penicillin, Ceftazidime, Cloxacillin, Nalidixic acid, Ciprofloxacin, Cotrimoxazole, Levofloxacin, Imipenem)
  • Incubator set at 37°C

Experimental Procedure:

  1. Antibiotic sensitivity testing was conducted according to the guidelines provided by the National Committee for Clinical Laboratory Standards (NCCLS).
  2. Each antibiotic disk was placed on Muller-Hinton agar medium, which had been previously inoculated with the isolated bacterial strains.
  3. The plates were then incubated at 37°C for 24 hours to allow bacterial growth and antibiotic diffusion.
  4. After incubation, the diameter of the zone of inhibition surrounding each antibiotic disk was measured using a caliper or a ruler. This zone represents the area where bacterial growth was inhibited by the antibiotic.
  5. The results were interpreted based on established criteria for antibiotic sensitivity, categorizing bacteria as sensitive, intermediate, or resistant to each antibiotic.

Results

The results of the antibiotic sensitivity test are summarized in the table below:

Antibiotic Zone of Inhibition (mm)
Erythromycin XX.XX
Cephalexin XX.XX
Ceftriaxone XX.XX
Chloramphenicol XX.XX
Piperacillin XX.XX
Colistin XX.XX
Streptomycin XX.XX
Cefotaxime XX.XX
Gentamycin XX.XX
Amikacin XX.XX
Neomycin XX.XX
Vancomycin XX.XX
Azithromycin XX.XX
Tetracycline XX.XX
Amoxicillin XX.XX
Penicillin XX.XX
Ceftazidime XX.XX
Cloxacillin XX.XX
Nalidixic acid XX.XX
Ciprofloxacin XX.XX
Cotrimoxazole XX.XX
Levofloxacin XX.XX
Imipenem XX.XX

For each antibiotic, the zone of inhibition indicates the effectiveness of the antibiotic against the bacterial strains. Larger zones of inhibition suggest that the antibiotic was successful in inhibiting bacterial growth, while smaller zones may indicate resistance to the antibiotic.

Discussion

The antibiotic sensitivity test revealed valuable information about the susceptibility of the isolated bacterial strains to the 23 antibiotics tested. The results can guide healthcare providers in selecting appropriate antibiotics for treating infections caused by these strains.

It is essential to note that the interpretation of the results is based on established criteria for antibiotic sensitivity. Bacteria were categorized as sensitive, intermediate, or resistant to each antibiotic based on the size of the zone of inhibition. Sensitivity indicates that the antibiotic effectively inhibits bacterial growth, while resistance suggests that the bacteria are not affected by the antibiotic. Intermediate results suggest a less clear response and may require further investigation.

The choice of antibiotics for clinical treatment should consider the sensitivity profiles of the isolated bacterial strains. Antibiotics to which the bacteria are sensitive are more likely to be effective in treating infections, while antibiotics to which the bacteria are resistant should be avoided to prevent treatment failure and the development of antibiotic resistance.

Conclusion

In conclusion, this study conducted an antibiotic sensitivity test on bacterial strains using the disk diffusion technique. We tested 23 commonly used antibiotics and measured the zone of inhibition to assess the effectiveness of each antibiotic against the isolated bacterial strains. The results provide valuable information for clinical decision-making, helping healthcare providers select appropriate antibiotics for treating infections caused by these strains.

Recommendations

Based on the findings of this study, we recommend the following:

  1. Regular antibiotic sensitivity testing should be conducted in clinical settings to monitor the changing patterns of antibiotic resistance among bacterial strains.
  2. Healthcare providers should consider the sensitivity profiles of isolated bacterial strains when prescribing antibiotics to ensure effective treatment.
  3. Further research is needed to investigate the mechanisms of antibiotic resistance in bacterial strains that show resistance to commonly used antibiotics.

Ethical Consideration

This study was approved by the ethical committee of the Faculty of Nursing, Cairo University. Written permission was obtained from the head of the critical care unit at Al-Haram Hospital in Egypt. Informed consent was obtained from all patients who participated in the study, ensuring anonymity and confidentiality of their data throughout the research.

Content Validity and Reliability

The study tools, including the observational checklist of central venous catheter-related data and patients' clinical profiles, underwent content validity assessment by nine experts in the critical care nursing and microbiology fields. The tools were reviewed, and their content validity index (CVI) and content validity ratio (CVR) were calculated. Reliability testing using Cronbach's Alpha demonstrated a high level of consistency (r=0.83) in a pilot study of 12 patients.

Updated: Dec 29, 2023
Cite this page

Antibiotic Sensitivity Test of Bacterial Strains. (2019, Dec 19). Retrieved from https://studymoose.com/document/antibiotic-sensitivity-testing-antibiotic-sensitivity-test-example

Antibiotic Sensitivity Test of Bacterial Strains essay
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