**4. Drug resistance and biofilm**

In a biofilm, rendering biofilm becomes ten to thousand times less prone to several antimicrobial agents than the same planktonic culture grown bacterium. As an example, it has been seen that there is an increase of 600-fold concentration in sodium hypochlorite (an oxidizing biocide that is counted in most effective

### *Bacterial Biofilms*

antibacterial drugs) for killing biofilm cells of *Staphylococcus aureus* as compared with its planktonic form [9]. Moreover, as compared to planktonic form, bacteria in biofilms shows a discrete physiology like reduced metabolic rate and enhanced cell to cell communication which helps in developing resistance to antibiotics or reduce their effects [10]. In the attempt to describe the resistance of biofilms to antibiotics, three assumptions have been made:


Presence of neutralizing enzymes also contributes to the antibiotic resistance in the biofilm. These proteinaceous enzymes degrade or inactivate antibiotics by mechanisms like hydrolysis and modification of antimicrobials by different biochemical reactions [7].

Although, intensive and insistent treatment of antibiotic is effective in reducing the biofilm and controlling the exacerbations of chronic biofilm infections but are not able to eliminate biofilm infections it is possibly because the minimal concentration of antibiotic (required to eliminate a mature biofilm) is challenging to reach *in vivo*. Hence, if a bacterial biofilm infection is established, it becomes much difficult to eradicate [12].

Experimental studies suggested that in most of the cases antibiotic treatment alone is not sufficient to eliminate infections of biofilm [12]. In a study, a nanoparticle called ciprofloxacin-loaded poly (lactic-co-glycolic acid), that were functionalized with DNase I, were prepared to observe their antibiofilm activity against *P. aeruginosa* biofilms. It has been found that they release ciprofloxacin in a controlled manner, as well as they effectively target and disassemble the biofilm by degrading the extracellular DNA that stabilizes the EPS [10]. Biofilm combination therapy is usually recommended for treating biofilm infections as this is found to be substantially better than antibiotic monotherapy [12].
