161
7.5.2 Mechanical Removal by Ultrasonic Disruption
Mechanical removal of biofilms is proved to be most effective; the most basic example being brushing of tooth. However, the major limitation is that its effectiveness is
limited to only accessible surfaces. Ultrasonic treatment is most preferred for
removal of implant associated biofilms. Various medical devices like catheters, artificial cardiac valves, pacemakers, and prosthetic joints are more prone to infections
and biofilm formation. Sonication of such implants help in effective removal of
bacterial cells and dispersion which may further be subjected to multiplex polymerase chain reaction (PCR) for tracing microbial pathogen derived DNA in order
to identify the infectious pathogens like Propionibacterium acnes and
Corynebacterium species, Finegoldia magna, and Peptostreptococcus species
(Achermann et al. 2010). Biofilms of Staphylococcus aureus, Enterococcus faecalis, and P. acnes can be significantly dislodged from titanium and steel surfaces
using sonication at 30 kHz with a power output of 300 W at 37 °C for 5 min. This
ability of sonication mediated biofilm disruption is dependent upon equipment type,
the output power, oscillation frequency, reaction volume, fluid temperature, and
sonication time (Bjerkan et al. 2009). Electrophysiological cardiac devices are also
susceptible to biofilms which may lead to potentially life-threatening complications. Biofilm formation by P. acnes, S. aureus, Streptococcus mitis and coagulase
negative staphylococci may involve the generator pocket, the leads or both when
cardiac pacemakers are used in patients with atrioventricular conduction block, sick
sinus syndrome, and sinus bradycardia. Implantable cardioverter/ defibrillators
(ICDs) are used for patients with heart failure after myocardial infarction and ventricular arrhythmia (Rohacek et al. 2010). Similar process is also applicable for
spinal implants. Bacterial biofilms are closely associated with chronic rhinosinusitis. Remarkable improvement in chronic rhinosinusitis symptoms is reported due to
efficient biofilm disruption employing pulsed ultrasound therapy. High levels of
ultrasonic treatment effectively kill bacteria due to formation of cavity in/on bacterial cell surfaces with simultaneous generation of peroxides. Further, lower levels of
ultrasonic power reverts biofilm associated bacteria to planktonic state which are
highly susceptible to both antibiotics as well as innate and adaptive antibacterial
immunity. Thus, co-application of ultrasound and antibiotics (gentamicin) significantly kills live sessile Pseudomonas aeruginosa, which is referred to as bioacoustical effect (Fig. 7.2). Ultrasonic therapy co-administered with antibiotics may be
significant against various biofilm associated infections (Young et al. 2010).
7.5.3 Enzyme Mediated Disruption
Enzyme mediated biofilm disruption due to degradation of biofilm matrix is also
considered as a powerful strategy to cope up with the biofilm associated diseases.
Although the target of biofilm disrupting enzymes is primarily extracellular
7 Control of Bacterial Biofilms for Mitigating Antimicrobial Resistance
7.5.2 Mechanical Removal by Ultrasonic Disruption
Mechanical removal of biofilms is proved to be most effective; the most basic example being brushing of tooth. However, the major limitation is that its effectiveness is
limited to only accessible surfaces. Ultrasonic treatment is most preferred for
removal of implant associated biofilms. Various medical devices like catheters, artificial cardiac valves, pacemakers, and prosthetic joints are more prone to infections
and biofilm formation. Sonication of such implants help in effective removal of
bacterial cells and dispersion which may further be subjected to multiplex polymerase chain reaction (PCR) for tracing microbial pathogen derived DNA in order
to identify the infectious pathogens like Propionibacterium acnes and
Corynebacterium species, Finegoldia magna, and Peptostreptococcus species
(Achermann et al. 2010). Biofilms of Staphylococcus aureus, Enterococcus faecalis, and P. acnes can be significantly dislodged from titanium and steel surfaces
using sonication at 30 kHz with a power output of 300 W at 37 °C for 5 min. This
ability of sonication mediated biofilm disruption is dependent upon equipment type,
the output power, oscillation frequency, reaction volume, fluid temperature, and
sonication time (Bjerkan et al. 2009). Electrophysiological cardiac devices are also
susceptible to biofilms which may lead to potentially life-threatening complications. Biofilm formation by P. acnes, S. aureus, Streptococcus mitis and coagulase
negative staphylococci may involve the generator pocket, the leads or both when
cardiac pacemakers are used in patients with atrioventricular conduction block, sick
sinus syndrome, and sinus bradycardia. Implantable cardioverter/ defibrillators
(ICDs) are used for patients with heart failure after myocardial infarction and ventricular arrhythmia (Rohacek et al. 2010). Similar process is also applicable for
spinal implants. Bacterial biofilms are closely associated with chronic rhinosinusitis. Remarkable improvement in chronic rhinosinusitis symptoms is reported due to
efficient biofilm disruption employing pulsed ultrasound therapy. High levels of
ultrasonic treatment effectively kill bacteria due to formation of cavity in/on bacterial cell surfaces with simultaneous generation of peroxides. Further, lower levels of
ultrasonic power reverts biofilm associated bacteria to planktonic state which are
highly susceptible to both antibiotics as well as innate and adaptive antibacterial
immunity. Thus, co-application of ultrasound and antibiotics (gentamicin) significantly kills live sessile Pseudomonas aeruginosa, which is referred to as bioacoustical effect (Fig. 7.2). Ultrasonic therapy co-administered with antibiotics may be
significant against various biofilm associated infections (Young et al. 2010).
7.5.3 Enzyme Mediated Disruption
Enzyme mediated biofilm disruption due to degradation of biofilm matrix is also
considered as a powerful strategy to cope up with the biofilm associated diseases.
Although the target of biofilm disrupting enzymes is primarily extracellular
7 Control of Bacterial Biofilms for Mitigating Antimicrobial Resistance