How To Assess The Bacterial Burden Of DFUs

Guy Pupp, DPM, FACFAS, and Robert Koivunen, DPM

Emerging Insights On The Development Of Biofilms

There is much controversy concerning the treatment of biofilm infections although there have been great strides recently as we gain a better understanding of biofilms. According to the Center for Biofilm Engineering at Montana State University, bacteria initially adhere to a surface utilizing weak bonds called van der Waals forces. If these bonds are not separated, the bacteria utilize cell adhesion molecules to bind other cells.24 They begin to build the matrix that holds the biofilm together. If there are species that are unable to attach to a surface on their own, they often attach to the matrix or the earlier cells.

   During this time, pathogens inside the biofilm can communicate thanks to a phenomenon called quorum sensing. Bacteria must reach a certain concentration before quorum sensing allows bacteria to sense its concentration and release enzymes and/or toxins into the wound environment.25 This can occur within a single bacterial species as well as between diverse species.

   The development of a biofilm allows for its cells to become more resistant to antibiotics administered in a standard fashion. Biofilm bacteria can be up to 1,000 times more resistant to antibiotics than free floating or planktonic bacteria of the same species found in an acute wound.21

   Biofilms grow slowly and are often slow to produce overt symptoms. Biofilm bacteria can move in numerous ways that allow them to infect new tissues easily.26 Research on the molecular and genetic basis of biofilm development has made it clear that when cells switch from planktonic to community mode, they also undergo a shift in behavior that involves alterations in the activity of numerous genes.27 A study by Cho and colleagues states: “When bacteria are under stress, they team up and form this collective called a biofilm. If you look at naturally occurring biofilms, they have a very complicated architecture. They are like cities with channels for nutrients to go in and waste to go out.”28

Keys To Judicious Antibiotic Treatment

The clinician must have an understanding of biofilm physiology in order to render adequate treatment. The application of topical antimicrobials may aid in the treatment of biofilm buildup when one uses the topicals in the appropriate manner. Iodine, especially iodine-impregnated dressings, is effective against biofilms. According to Hill and colleagues, iodine is more effective against biofilms than silver products.21 In fact, most silver dressings contain a low concentration of silver, which is ineffective in treating bacterial biofilm. For the best results, one should combine sharp excisional debridement with topical antimicrobial therapy for treating biofilms. Debridement allows prevention of biofilm formation, interference of the quorum sensing and facilitates better penetration of topical antimicrobial agents.13

   Traditional administration of antibiotics is often ineffective when biofilms are present in the wound. Patients with biofilm infections frequently hear from mainstream doctors that they have an untreatable infection and that biofilms in the lower extremity can often lead to an amputation. Unfortunately, when one administers an antibiotic in high doses, the antibiotic may temporarily weaken the biofilm but is incapable of destroying it as certain cells inevitably persist and allow the biofilm to regenerate.

   To be effective, physicians must administer antibiotics in a specific manner. The Marshall Protocol states that biofilm pathogens succumb to specific bacteriostatic antibiotics given in very low, pulsed doses.29,30 With traditional high-dose antibiotic regimens, the first onslaught of antibiotics does not eliminate some cells called “persisters,” which form the biofilm again. Persister cells form with particular ease in immunocompromised patients.31

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