Sinusitis after radiation is caused by resistant bacteria

Plain x-ray showing opacification of right maxillary sinus

Patients who undergo radiotherapy for nasopharyngeal carcinoma tend to suffer from sinusitis because irradiation causes damage to sinonasal tissue. There is very little information about the organisms causing sinusitis after radiation therapy. Two recent studies from China provided important information about the unique microbiology of sinusitis in these patients.

Huang et al (Am J Rhinol. 2007) endoscopically obtained specimens from 25 patients with acute sinusitis that developed sinusitis after irradiation therapy. Staphylococcus aureus comprised 42% and Gram-negative bacilli 36% of all aerobic isolates. The main anaerobic isolates were Peptostreptococcus and Veillonella spp. Polymicrobial infections and beta-lactamase-producing pathogens were highly prevalent.

A study by Deng and Tang ( Eur. Arch.Otolaryngolog, 2009) compared the bacteriology of chronic maxillary sinusitis that developed after radiation therapy to chronic sinusitis in non irradiated individuals. Thirty people with each condition were evaluated using cultures for aerobic bacteria.

The most common isolates in the post irradiation chronic sinusitis group was S. aureus while those in the other group were Haemophilus influenzae, and Pseudomonas aeruginosa. The isolation rate of gram-positive cocci in the post irradiation group was higher than in the non irradiated patients. (62.5% compared with 30%, respectively; P < 0.05). In contrast the isolation rate of gram-negative bacilli in the irradiated patients was lower than in non-irradiated patients (31% compared with 70%, respectively; P < 0.05).

The findings of both studies illustrate the high rate of recovery of S. aureus from sinus aspirates of individual who were irradiated for head and neck cancer. Because of the high prevalence of methicillin resistant S. aureus (MRSA) these individuals may need to be treated with antimicrobials effective against these organisms.

These studies underscore the need to obtain appropriate cultures from patients with chronic sinusitis who were irradiated so that proper antimicrobials can be administered to them.

Are Topical Antibiotic Effective in Treating Chronic Sinusitis?

Many different treatment options for chronic sinusitis (CS) exist but questions remain regarding the best options. While oral and intravenous antimicrobial therapies have traditionally been prescribed to manage CS, topical administration of these agents has gained increasing popularity over the past few years. Topical antimicrobials have the advantage of local delivery to the sinonasal mucosa and minimize the systemic effects seen with systemic agents. This is especially important in treatment of biofilms where higher concentrations of antibiotics are usually required.

Topical antibiotic delivery devices to date have included nasal sprays, irrigations, and nebulizers. Nasal spraying of topical antibiotics are not believed to be very effective. This is supported by studies that have shown that the majority of deposition occurs only in the anterior part of the nasal cavity. In addition, the nasal sprays rely on mucociliary clearance to transport the drug from the anterior to the posterior nasal cavity, and in patients with CS, their mucociliary clearance may be impaired. There are, however, other studies that found nebulization and irrigation to be effective.


Fungi can play a role in the pathogenesis of CS both in an allergic and inflammatory manner. Several recent studies that evaluated the efficacy of topical amphotericin B showed trends that were promising. However, most of the placebo-controlled studies showed no statistical difference between the treated patients and untreated controls.

Recent animal studies found that mupirocin was effective in reducing Staphylococcus biofilm mass by over 90%. Staphylococcus aureus-related acute exacerbations of chronic sinusitis in patients was also treated effectively with topical mupiricin. No success was, however, achieved with aminoglycosides in reducing Pseudomonas aeruginosa biofilm.

Since most of the initial clinical work done with topical antibiotics in CS was retrospective, prospective studies are warranted to further evaluate the utility of this approach. These should evaluate the efficacy of antimicrobials, antifungals and steroids alone and in combinations.

Smoking and sinusitis

Smoking is one of the most important causes of head and neck cancer. Another important untoward result of active and second hand smoke exposure is the increased risk of respiratory bacterial infecion.  These include acute and chronic sinusitis, ear infections, bronchitis and pneumonia. Recent studies we and others did show that smokers harbor more pathogenic bacteria that are also resistant to antibiotics, can be a source of spread of these bacteria to others (including their children), and when smokers get respiratory infections treating them may be more difficult than treating non-smokers.

In a recent study we evaluated the microbiology of sinus aspirates of smokers and nonsmokers with acute (244 patients, 87 smokers and 157 nonsmokers ) and chronic (214 patients, 84 smokers and 130 nonsmokers) maxillary sinusitis. We found that sinusitis in smokers is more often caused by antibiotic resistant bacteria including methicillin resistant Staphylococcus aureus (MRSA) than in non smokers.

Oropharyngeal ccolonization with potential bacterial pathogens is higher in smokers than non smokers. Cesation of smoking reverses the increased colonozation by pathogens.