Antibiotics are widely used as adjunct to mechanical debridement in surgical and non surgical periodontal therapy. Many periodontal bacteria are now found to be resistant to some antibiotic or other. Which one is playing a larger role in the development of resistance, local administration in periodontal pockets, or systemic administration?
In general the topic use of antibiotics is less likely to induce antibiotic resistance if the dosing is adequate. Resistance development in bacteria under antibiotic treatment usually results from mutations in the target genes. A high dose of bactericidal antibiotics avoids the development of resistance if the mutant prevention concentration is exceeded.
Resistance mechanisms based on newly acquired genetic elements (e.g. MRSA, ESBL-producing Enterobacteriaceae) do not develop under therapy. Antibiotic treatment reduce the normal flora an facilitates the new colonization with resistant bacteria. However, for these organisms correct hygiene measurements are required to avoid spread in antibiotic treated patients.
I agree with Dr. Knobloch that In general the topic use of antibiotics is less likely to induce antibiotic resistance if the dosing is adequate, specifically local drug delivery in periodontal pockets less likely to result in antibiotic resistance than systemic administration of the same drug
Selection of local drugs is more wide than those used parenteral (systemic administration). Thus, it is better to select antimicrobial agent other than antibiotic (or other antimicrobial molecule) for using it locally.
The selection of antibiotic resistance does not depend on the way of administration, but on the concentrations reached in blood and tissues. The problem with topic use of antibiotics is that you does not control the concentrations reached, that are much more variable and less predictable than with oral or parenteral administration. Moreover, when you use topic antibiotic you have very high concentrations on the surface, but concentrations decline very fast inside the tissues, that is where you usually have the infection. As whole, if you use adequate dosage, the risk for selecting resistance is higher when you use topic antibiotic than with sistemic administration.
Local drug delivery requires same caution as used with systemic therapy. The ability to minimize the drug related adverse effects is the main benefit of local drug delivery as compared to the systemic administration. But local delivery does not preclude selection of resistant strains or overgrowth of intrinsically resistant organisms either at the site of administration or at other body sites. There is no data on the effect of local drug delivery on GI flora but there is a growing speculation and even possible increase risk of multidrug resistance transfer by indiscriminate use of local drug delivery systems as advocated by some manufacturers.
There is also only few studies on the increase in bacterial resistance in oral microbiota following tetracycline and minocycline local delivery. But it has been found to transient in nature for a period of 3-6 months when the resistant strains were restored to pre treatment levels.
It is important that in periodontology as well as in dentistry as a whole, antibiotics should be used very selectively and appropriately and not repeatedly as advocated by manufacturers. Juan Luis Munoz Bellido has rightly pointed out concentration reached systemically as an important variable factor for resistant strains.
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Dr. Akilesh. R
India
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