Recurrent otorrhea in chronic suppurative otitis media: is biofilm the missing link?

Dispersal of bacteria from a biofilm in the middle ear, serving as a bacterial reservoir, could explain the recurrent and chronic nature of chronic suppurative otitis media (CSOM). The objective of this study is to investigate if the same strains of bacteria could be detected in repeated episodes of otorrhea in CSOM. In a prospective case series at a primary healthcare clinic in Nuuk, Greenland, patients with more than 14 days of otorrhea were included consecutively. Samples for culturing and biofilm analysis were taken at enrollment and at any subsequent episode with otorrhea. Participants were treated with daily saline irrigation and Ciprofloxacin eardrops for 7-14 days. Biofilm was identified in otorrhea in 81% (17/21) of participants at enrollment. Multispecies infections dominated with Non-typeable Haemophilus Influenzae (NTHI), Staphyloccocus aureus, and anaerobes being the most frequent pathogens. After the initial treatment, 19 (90%) had dry ears. Median observation period was 140 days (range 14-280) where 13 participants had one or more recurrences. Median time to first recurrence was 60 days (range 14-197). Among the 13 with recurrence, three individuals had the same genotype of bacteria at a subsequent episode. Another two had the same phenotype (NTHI). The remaining eight had new multispecies infections. We confirmed a high rate of biofilm in CSOM. However, the clinical implication might be of minor importance when treating with irrigation and antibiotic eardrops, as recurrent episodes of otorrhea were dominated by new pathogens in each episode.

Mucosal biofilm detection in chronic otitis media: a study of middle ear biopsies from Greenlandic patients.

The objectives of this study were to examine middle ear biopsies from Greenlandic patients with chronic otitis media (COM) for the presence of mucosal biofilms and the bacteria within the biofilms. Thirty-five middle ear biopsies were obtained from 32 Greenlandic COM patients admitted to ear surgery. All biopsies were examined by means of peptide nucleic acid-fluorescent in situ hybridization (PNA-FISH), and if possible culture and polymerase chain reaction (PCR) of the 16s rDNA and sequencing. Light microscopy and confocal laser scanning microscopy were used. Skin biopsies from 23 of the patients served as controls. PNA-FISH showed morphological signs of biofilms in 15 out of 35 (43 %) middle ear biopsies. In the control skin biopsies, there were signs of biofilms in eight out of 23 biopsies (30 %), probably representing skin flora. PCR and 16s sequencing detected bacteria in seven out of 20 (35 %) usable middle ear biopsies, and in two out of ten (20 %) usable control samples. There was no association between biofilm findings and PCR and 16s sequencing. Staphylococci were the most common bacteria in bacterial culture. We found evidence of bacterial biofilms in 43 % of middle ear biopsies from patients COM. The findings may indicate that biofilms are a part of the pathogenesis in recurrent episodes of ear discharge in COM, but further investigations are necessary.

Polymorphonuclear leukocytes restrict growth of Pseudomonas aeruginosa in the lungs of cystic fibrosis patients.

Cystic fibrosis (CF) patients have increased susceptibility to chronic lung infections by Pseudomonas aeruginosa, but the ecophysiology within the CF lung during infections is poorly understood. The aim of this study was to elucidate the in vivo growth physiology of P. aeruginosa within lungs of chronically infected CF patients. A novel, quantitative peptide nucleic acid (PNA) fluorescence in situ hybridization (PNA-FISH)-based method was used to estimate the in vivo growth rates of P. aeruginosa directly in lung tissue samples from CF patients and the growth rates of P. aeruginosa in infected lungs in a mouse model. The growth rate of P. aeruginosa within CF lungs did not correlate with the dimensions of bacterial aggregates but showed an inverse correlation to the concentration of polymorphonuclear leukocytes (PMNs) surrounding the bacteria. A growth-limiting effect on P. aeruginosa by PMNs was also observed in vitro, where this limitation was alleviated in the presence of the alternative electron acceptor nitrate. The finding that P. aeruginosa growth patterns correlate with the number of surrounding PMNs points to a bacteriostatic effect by PMNs via their strong O2 consumption, which slows the growth of P. aeruginosa in infected CF lungs. In support of this, the growth of P. aeruginosa was significantly higher in the respiratory airways than in the conducting airways of mice. These results indicate a complex host-pathogen interaction in chronic P. aeruginosa infection of the CF lung whereby PMNs slow the growth of the bacteria and render them less susceptible to antibiotic treatment while enabling them to persist by anaerobic respiration.