Production and Extraction of Penicillin

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The antibiotic properties of Penicillin are a major advancement in the studies of pathogenic diseases and have revolutionised antibiotic treatments. However, certain bacterial species have adapted and developed resistance to its antibacterial effects . Extraction and evaluation of the secondary metabolite Penicillium chrysogenum, enabled the compounding of research to determine the bacterial species which are resistant to its antibiotic properties. Antibiotic diffusion assay of extracted penicillin G displayed susceptibility of both tested bacterial species, namely Escherichia coli and Staphylococcus aureus.

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Experimental findings demonstrated that both the hydrophobic penicillin G and extracted penicillin G had an antibiotic effect on E. coli; as observed by the significant halo formations. The obtained result deviated from the expected observation as the gram-negative tends to exhibit resistance to hydrophobic antibiotics. Resistance either occurs due to chromosomal modifications such as the modification of two or more genes or the introduction of extra-chromosomal factors, or high production and secretion of penicillinase, most likely to β-lactamase (Burman, et al., 1968). However, the action of penicillinases contributes more significantly to drug resistance .

Based on the unexpected result obtained, it is assumed that possible horizontal gene transfer (HGT) of mutated resistance gene occurred. Studies have recorded paragenetic mutation reversion of E. coli plasmids by complete or partial deletion of resistance gene caused by RNA polymerase or ribosome enzymes. Modulation of reduced resistant gene expression level in E. coli strains, without disruption of resistance genes and possible requisition of resistance, has also been previously observed. (Allen, et al., 2017)

Antibiotic sensitivity testing against S. aureus showed susceptibility to extracted penicillin G. Experimental findings concurred with expected results as S. aureus is gram-positive which is susceptible to penicillin G activity (Lobanovska & Pilla, 2017). However, as related from the results which displayed resistance of S. aureus to penicillin G, it has been found that certain strains display resistance to penicillin G due to the presence of penicillinase activity or high concentrations of penicillin because of a paradoxical action known as the “Eagle effect” (Percival, et al., 1963) (Yourassowsky, et al., 1975).

The “Eagle effect” is principled on the phenomena that high dosages of penicillin decrease its efficacy against bacterial species (Yourassowsky, et al., 1975). It is assumed that the experimental strain of S. aureus utilised in the following experiment was resistant to penicillin G due to its dosage and not because of the presence of penicillinase since it displayed sensitivity to the extracted penicillin. 

Experimental shortcomings such as the possible contamination of penicillin or bacterial species samples should be accounted for. In order to increase the accuracy and reliability of the experimental data observed, the experiment should be repeated with better experimental techniques to avoid contamination.

Despite these limitations on the experiment, it is concluded that the aim of the experiment was achieved as penicillin G was adequately extracted and its presence was observed through antibiotic sensitivity assays tested with different bacterial species. However, the assumption of expected results with regards to the sensitivity of bacterial species was incorrect since E. coli displayed sensitivity to both penicillin treatments and S. aureus displayed resistance to penicillin G.


  1. Allen, R. C. et al., 2017. Reversing resistance: different routes and common themes across pathogens. Proceedings of the Royal Society B: Biological Sciences, 284(1863), pp. 1-10.
  2. Burman, L. G., Nordstrom, K. & Boman, H. G., 1968. Resistance of Escherichia coli to Penicillins: V. Physiological Comparison of Two Isogenic Strains, One with Chromosomally and One with Episomally Mediated Ampicillin Resistance. JOURNAL OF BACTERIOLOGY., 96(2), pp. 438-446.
  3. Gaynes, R., 2017. The Discovery of Penicillin—New Insights After More Than 75 Years of Clinical Use. Emerg Infect Dis. , 23(5), p. 849–853.
  4. Lehtinen, J. & Lilius, E., 2007. Promethazine renders Escherichia coli susceptible to penicillin G: real-time measurement of bacterial susceptibility by fluoro-luminometry. Int J Antimicrob Agents., 30(1), pp. 44-51.
  5. Lobanovska, M. & Pilla, G., 2017. Penicillin’s Discovery and Antibiotic Resistance: Lessons for the Future?. Yale J Biol Med. , 90(1), p. 135–145.
  6. Percival, A., Brumfitt, W. & Louvois, J. D., 1963. The Role of Penicillinase in Determining Natural and Acquired Resistance of Gram -Negative Bacteria to Penicillins. J. gen. Microbiob., Volume 32, pp. 77-89.
  7. Yourassowsky, E., Vanderlinden, M. P., Lismont, M. J. & Schoutens, E., 1975. Paradoxical Action of Penicillin G on Staphylococcus aureus: a Time Study of the Effect of a Zonal Antibiotic Concentration Gradient on Bacterial Growth. Antimicrob Agents Chemother. , 8(3), p. 262–265.

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