|Year : 1983 | Volume
| Issue : 5 | Page : 575-576
Incompatibility of gentamycin and chloramphenicol invitro and invivo study
K Anandakannan, ET Selvam, K Thiruneelakandan, T Sundaravelu, S Mahadevan
Government Ophthalmic Hospital, Egmore, Madras, India
Government Ophthalmic Hospital, Egmore, Madras-600008
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Anandakannan K, Selvam E T, Thiruneelakandan K, Sundaravelu T, Mahadevan S. Incompatibility of gentamycin and chloramphenicol invitro and invivo study. Indian J Ophthalmol 1983;31:575-6
Gentamycin, a bactericidal antibiotic is being used extensively in combination with chloramphenicol-a bacterio static antibiotic in severe ocular diseases like corneal ulcers, postoperative ocular infections etc. This combination is prefered by many ophthalmologists since these two antibiotics have better penetration into the blood aqueous barrier and are more specific against Pseudomonas and Staphylococcal infections. The use of combination of these two antibiotics is a controversial subject. A study was undertaken to determine the efficacy of these commonly used antibiotics individually and in combination in vitro and in vivo. The results are analysed and presented.
| Materials and Methods|| |
Forty five cases of bacterial corneal ulcers and five cases of post operative infection were undertaken for the study. Smear and scrappings were taken from these cases for smear and culture. Earliest growth was seen in the culture after about 18 hours; pseudomonas was grown in 18 cases and staphylocci in 4 cases.
Isolation of the organisms was done on special media and they were identified as Pseudomons aeruginosa and coagulase positive Staphylococcus aureus. An antibiogram was done by incorporating
a) Chloramphenical 30 me gms/ml
b) Gentamycin 30 me gms/ml and
c) Combination of both antibiotics in Mullter Hinton Agar
The organisms were inoculated on to the media containing above antibiotics and the growth of the organisms was watched for 48 hrs. The experiments were repeated thrice and the average of the results are presented.
7 cultures of Pseudomonas and 3 of Staphylococci were sub cultured and antibiogram was done in 30 sub cultures of 3 groups.
I Group - Chloramphenicol 30 me gms/ml
II Group - Gentamycin 30 me gms/ml
III Group - Combination of both antibiotics
There was no growth in 7 tubes belonging to the I group showing that 70% of the organisms were sensitive to chloramphenical (four pseudomonas and 3 staphylocci). There was no growth in 5 tubes belonging to II group showing that 50% of organisms (all pseudomonas) were sensitive to Gentamycin.
Third group of sub cultures showed resistance to antibiotics in 70% of cases esp. the pseudomonas group of organisms. However, the Staphylocci did not grow in any of the tubes belonging to this group. This goes to prove the incompatability of these two drugs 'invitro,.
As the next part of the study corneal ulcer was produced in animals and the efficacy of these antibiotics was studied individually and in combination.
Six rabbits and six rats were taken for this study. They were divided into two groups of 3 rabbits and 3 rats in each from Animal Experimental Laboratory attached to this College.
The I group was infected with pseudomonas. The organisms were obtained from subcultures and they were inoculated into the eye by scrapping the cornea. All the six animals showed corneal ulceration of moderate to severe degree in less than 24 hrs. One rabbit died after 2 days for some unknown reason.
The II group was infected with staphylocci in the same manner. The rabbits showed corneal ulceration of mild to moderate intensity. The rats did not show any sign of eye infection and so they were removed from the study.
These animals were divided into 3 categories and the treatment schedule was started.
A Group: was given Gentamycin locally every 2 hrs. and systemically by IM at the dose of 3 mgms/kg/day
B Group: Chloramphenical locally every 2 hrs and systemically by IM 15 mgms/kg/day
C Group: Gentamycin locally every 2 hrs and chloramphenical systemically by IM
The animals were examined daily for 15 day and the results analysed.
Analysis: A Group: one rabbit died after 2 days; other rabbit showed good response whereas the rat went in for perforation of the cornea and poor response to the drug.
B Group: The two rabbits and the rat showed very good response and the ulcer healed well in two animals whereas it left behind an opacity in the cornea in one rabbit.
C Group: One rabbit responded well; the other rabbit and the rat lost their eyes due to perforation and non-healing of the ulcer.
| Discussion|| |
Chloramphenicol acts by inhibiting protein synthesis. The drug rapidly penetrates into the bacterial cells and binds to the ribosomal subunit preventing peptide formation so long as the drug remains bound to the ribosome.
Gentamycin binds to ribosomal subunit of RNA and causes.
(a) inhibition of the I step in protein synthesis at the ribosome.
(b) abnormal limitation complexes accumulate in the cell and
(c) include misreading of the genetic code of the RNA template and in-correct aminoacids are incorporated into the growing polypeptide chains.
When these two antibiotics are administered together by the same route or different routes, they become incompatible and loose their potency, this has been evidenced well in the sub cultures as 'invitro' study. Even though the number of animals used for 'invivo' study is limited it is again established that the combination of these two drugs has brought in adverse effect compared to their use individually.
| Conclusion|| |
Chloramphenicol proves to have better effect when used alone in infection caused by Staphylocci and equivocal results with gentamycin in pseudomonas infections. The combination of these two antibiotics has led to the loss of their efficacy.
| Acknowledgements|| |
Our sincere thanks to the Dean, Madras Medical College, Madras for the kind help rendered in collaborating the various departments of this College to conduct this study and his permission to present this paper.