Two strains of bacteria, P. aeruginosa and S. aureus, were clinically isolated from CRS patients who had poor outcomes following functional endoscopic sinus surgery. The bacterial strains were grown into robust bacterial colonies and treated with a variety of commonly used therapies, including antibiotics and hypertonic saline. These existing therapies were compared to static and pressurized application of the new irrigating apparatus and irrigation solution developed by Medtronic.
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June 2007
Persistence of viable bacteria was assessed quantitatively by assessment of colony-forming units and semiquantitatively by confocal scanning laser microscopy. Treatment with static application of saline alone or topical antibiotic solutions at standard concentrations produced no reduction in bacterial counts. However, treatment with a new solution developed by Medtronic-citric acid/zwitterionic surfactant (CAZS)-accorded significant reductions in bacterial counts. When associated with hydrodynamic delivery, this produced the greatest reduction in bacteria. The researchers found that 99.98% of S. aureus and 99.999% of P. aeruginosa bacterial colonies were removed by the pressurized application of CAZS. When conventional treatments were applied without pressure, they had no, or only a moderate, effect. Even with a pressurized application, the conventional therapies had a lesser success in eliminating the biofilms (i.e., 99.4% for saline).
In summarizing the study, Dr. Desrosiers noted that the in vitro results confirm that conventional therapies are of little use against biofilm infections and support the idea that delivery of a soaplike surfactant with a calcium ion-sequestering agent combined with the use of hydrodynamic force can break down bacterial biofilms possibly associated with CRS.
Biofilms and RAOM
The RAOM study, presented by Giancarlo Zuliani, MD, of the Division of Pediatric Otolaryngology at Wayne State University in Detroit, also pointed out the wide variety of recalcitrant infections linked to biofilms.
Recurrent acute otitis media in the pediatric population is a poorly understood disease with a wide range of etiologic factors that often require many rounds of antibiotics or surgical interventions, Dr. Zuliani said.
Noting that biofilms were present in the nasopharyngeal samples that were collected by his team, he said the degree to which biofilms are present in relation to controls is striking and should not be ignored. Average mucosal biofilm density was 90.5% on adenoids removed from children with RAOM versus 1.4% on those from children with obstructive sleep apnea. In addition, the biofilms identified from otitis-prone children appeared to be multiorganismal and mature.
Dr. Zuliani noted that biofilms are complex microenvironments containing sessile organisms that intermittently shed metabolically active planktonic organisms. Intermittent shedding of planktonic middle ear pathogens from the nasopharynx may help explain the recalcitrance and recurrence of otitis media, he said, adding that the clinical benefit seen with adenoidectomy in RAOM may be due to mechanical debridement of these resistant nasopharyngeal biofilms.