Antibiotic Treatment for Chronic Rhinosinusitis: Prescription Patterns and Associations With Patient Outcome and the Sinus Microbiota

Background

Chronic rhinosinusitis (CRS) is a common and debilitating inflammatory condition of the sinuses, afflicting 5% of the general population. Although antibiotics are frequently prescribed for the medical management of CRS, there is surprisingly little evidence to support their efficacy. In this study, we aimed to establish associations between medication usage, the sinus microbiota and patients’ clinical outcomes.

Methods

Antibiotic prescription patterns for the year before sample collection of 156 CRS patients, 45 disease control patients (mostly requiring septoplasty and inferior turbinate reduction) and 35 healthy control subjects were examined and analyzed together with previously published bacterial 16S rRNA gene amplicon data from our group.

Results

The highest antibiotic usage was observed among the two CRS patient categories. Despite heavy antibiotic usage, CRS patients’ clinical outcomes as indicated by patient questionnaires and radiologic scores were similar to those patients that did not receive any antibiotics. The sinus microbiota was dominated by members of the bacterial genera Corynebacterium and Staphylococcus in all three cohorts. Bacterial community dispersion as measured by principal coordinate analysis was significantly higher in CRS patients compared to healthy control subjects, but not disease control patients. Pairwise comparisons within cohorts revealed differences in the relative 16S rRNA gene sequence abundances of the genera Staphylococcus and Lawsonella between antibiotic users and non-users. However, overall antibiotic effects were minimal and unpredictable.

Conclusion

The unpredictable effects of antibiotic treatment on the sinus microbiota found in this study, together with the lack of differences in patients’ symptom scores between cohorts, do not support preoperative antibiotic treatment for CRS patients.

Low-dose and long-term azithromycin significantly decreases Staphylococcus aureus in the microbiome of refractory CRS patients

BACKGROUND

The sinonasal microbiome is believed to play an important role in the pathophysiology of refractory chronic rhinosinusitis (CRS). We evaluated changes in the microbiome following a 4-month course of low-dose azithromycin. Assessing microbiome alterations following such a treatment may help identify underlying mechanisms of this drug.

METHODS

A total of 48 adults with refractory CRS were enrolled in a double-blind, randomized, placebo-controlled trial. Patients were randomized to 250 mg of azithromycin or placebo 3 times weekly for 4 months. During this time, daily budesonide saline irrigations were continued. Sinonasal swabs were collected by endoscopically-assisted method prior to treatment initiation and at the end of it, and sent for 16S ribosomal RNA gene sequencing. High-resolution ANCHOR pipeline was used to infer and annotate putative species. The 2 patient groups were compared using DESeq2 differential abundance analysis.

RESULTS

From initiation to the end of azithromycin treatment, patients showed a significant difference in beta diversity analysis (p = 0.0004) along with a significant decrease in 71 different operational taxonomic units (OTUs) of Staphylococcus aureus (false discovery rate [FDR] < 0.05) obtained from the differential abundance analysis. This was not observed in placebo-treated patients. By the end of treatments, azithromycin-treated patients had a significant decrease in 29 different OTUs of S. aureus (FDR < 0.05) when compared to placebo.

CONCLUSION

A 4-month course of 250 mg of azithromycin 3 times weekly in patients with refractory CRS significantly decreases S. aureus abundance in the sinonasal microbiome. Considering the pathogenic role of S. aureus in the refractory CRS population, azithromycin may constitute an additional therapeutic option to help control this disease.

Diseases of the nasal cavity

Despite garnering minimal attention from the medical community overall, olfaction is indisputably critical in the manner in which we as humans interact with our surrounding environment. As the initial anatomical structure in the olfactory pathway, the nasal airway plays a crucial role in the transmission and perception of olfactory stimuli. The goal of this chapter is to provide a comprehensive overview of olfactory disturbances as it pertains to the sinonasal airway. This comprises an in-depth discussion of clinically relevant nasal olfactory anatomy and physiology, classification systems of olfactory disturbance, as well as the various etiologies and pathophysiologic mechanisms giving rise to this important disease entity. A systematic clinical approach to the diagnosis and clinical workup of olfactory disturbances is also provided in addition to an extensive review of the medical and surgical therapeutic modalities currently available.

The sinonasal microbiota, neural signaling, and depression in chronic rhinosinusitis

BACKGROUND

The complex relationships between the human microbiota, the immune system, and the brain play important roles in both health and disease, and have been of increasing interest in the study of chronic inflammatory mucosal conditions. We hypothesized that the sinonasal microbiota may act as a modifier of interkingdom neural signaling and, subsequently, mental health, in the upper respiratory inflammatory condition chronic rhinosinusitis (CRS). In this study we investigated associations between the sinonasal microbiota; local concentrations of the neurotransmitters serotonin, dopamine, and γ-aminobutyric acid (GABA); and depression severity in a cohort of 14 CRS patients and 12 healthy controls.

METHODS

Subject demographics, clinical severity scores, depression index scores, and sinonasal swab and mucus samples were collected at the time of surgery. Bacterial communities were characterized from swabs by 16S rRNA gene-targeted sequencing and quantified by quantitative polymerase chain reaction. Mucus concentrations of the neurotransmitters serotonin, dopamine, and GABA were quantified by enzyme-linked immunosorbent assay.

RESULTS

Several commonly "health-associated" sinonasal bacterial taxa were positively associated with higher neurotransmitter concentrations and negatively associated with depression severity. In contrast, several taxa commonly associated with an imbalanced sinonasal microbiota negatively associated with neurotransmitters and positively with depression severity. Few significant differences were identified when comparing between control and CRS subject groups, including neurotransmitter concentrations, depression scores, or sinonasal microbiota composition or abundance.

CONCLUSION

The findings obtained lend support to the potential for downstream effects of the sinonasal microbiota on neural signaling and, subsequently, brain function and behavior.

Chronic Rhinosinusitis and the Evolving Understanding of Microbial Ecology in Chronic Inflammatory Mucosal Disease

Chronic rhinosinusitis (CRS) encompasses a heterogeneous group of debilitating chronic inflammatory sinonasal diseases. Despite considerable research, the etiology of CRS remains poorly understood, and debate on potential roles of microbial communities is unresolved. Modern culture-independent (molecular) techniques have vastly improved our understanding of the microbiology of the human body. Recent studies that better capture the full complexity of the microbial communities associated with CRS reintroduce the possible importance of the microbiota either as a direct driver of disease or as being potentially involved in its exacerbation. This review presents a comprehensive discussion of the current understanding of bacterial, fungal, and viral associations with CRS, with a specific focus on the transition to the new perspective offered in recent years by modern technology in microbiological research. Clinical implications of this new perspective, including the role of antimicrobials, are discussed in depth. While principally framed within the context of CRS, this discussion also provides an analogue for reframing our understanding of many similarly complex and poorly understood chronic inflammatory diseases for which roles of microbes have been suggested but specific mechanisms of disease remain unclear. Finally, further technological advancements on the horizon, and current pressing questions for CRS microbiological research, are considered.

Intranasal Delivery of Topically-Acting Levofloxacin to Rats: a Proof-of-Concept Pharmacokinetic Study

PURPOSE

To evaluate the potential of levofloxacin intranasal administration as a promising alternative approach to treat local infections such as chronic rhinosinusitis, by delivering drug concentrations directly to the site of infection.

METHODS

Drug concentrations were measured in plasma, olfactory bulb and nasal mucosa of anterior (ANM) and posterior regions after intranasal (0.24 mg/kg) and intravenous (10 mg/kg) administration to rats, and pharmacokinetic parameters were compared between routes. For intranasal administration a thermoreversible in-situ gel was used.

RESULTS

Plasma and olfactory bulb exposure to levofloxacin was minimal following intranasal dose, preventing systemic and central nervous system adverse effects. Levofloxacin concentration-time profile in ANM revealed higher concentrations during the first 60 min of the study following intranasal administration than the corresponding ones obtained after intravenous administration. A rapid and continuous decay of levofloxacin concentration in this nasal region was observed after intranasal delivery, resulting in much lower values at the last sampling time-points.

CONCLUSION

The higher dose-normalized concentrations and pharmacokinetic exposure parameters of levofloxacin in ANM after intranasal administration, demonstrates that intranasal delivery of the formulated gel is, by itself, advantageous for delivering levofloxacin to biophase and thus an attractive approach in management of chronic rhinosinusitis.

Evidence of microbiota dysbiosis in chronic rhinosinusitis

BACKGROUND

Despite considerable research, the pathogenesis of chronic rhinosinusitis (CRS) remains poorly understood. Potential microbial roles in the etiology or progression of CRS have long been hypothesized, yet few specific associations have been identified. In this study we investigate associations between patterns in resident bacterial communities and clinical variants of CRS.

METHODS

Bacterial communities were assessed in 94 patients with extensive bilateral CRS undergoing endoscopic sinus surgery (ESS) and 29 controls undergoing ESS for indications other than CRS. Patients were grouped on the basis of phenotypic variants (with or without polyposis) and clinical parameters, including asthma and cystic fibrosis. Bacterial communities were characterized via 16S rRNA gene amplicon sequencing, and quantified by quantitative polymerase chain reaction.

RESULTS

Controls and idiopathic CRS subjects tended to be dominated by members of the genera Corynebacterium and Staphylococcus, together with lower abundances of several other genera, including Streptococcus, Moraxella, and Haemophilus. Aberrant (dysbiotic) bacterial assemblages (with changes in community membership and structure, reduced diversity, and increased bacterial load) and increased inter- and intrasubject variability were more common in subjects with comorbidities such as asthma and cystic fibrosis. Dysbiotic communities were variably dominated by members of the genera Staphylococcus, Streptococcus, Haemophilus, Pseudomonas, Moraxella, or Fusobacterium.

CONCLUSION

Bacterial community dysbiosis was more apparent than specific associations with examined phenotypes or endotypes, and may play a role in the pathogenesis or influence the severity of CRS. Reductions in several common core bacterial taxa, increased inter- and intrasubject variability, reduced bacterial diversity, and increased bacterial load characterized aberrant bacterial communities in CRS.

Intranasal delivery of ciprofloxacin to rats: A topical approach using a thermoreversible in situ gel

Intranasal administration of antibiotics is an alternative and attractive delivery approach in the treatment of local infections such as chronic rhinosinusitis. This topical route has the advantage of delivering high drug concentrations directly to the site of infection when trying to eradicate the highly resistant bacterial biofilms. The purpose of this study was to assess and compare the pharmacokinetic parameters of ciprofloxacin following intranasal and intravenous administrations to rats in plasma, olfactory bulb and nasal mucosa of two different nasal regions. For intranasal administration a thermoreversible in situ gel was used to increase drug residence time in nasal cavity. Ciprofloxacin concentration time-profile in nasal mucosa of the studied anterior region (at naso- and maxilloturbinates level) was markedly higher after intranasal administration (0.24mg/kg) than that following intravenous administration (10mg/kg), while in nasal mucosa of the more posterior region (at ethmoidal turbinates level) ciprofloxacin concentrations were found to be higher after intranasal administration when the different dose administered by both routes is taken into account. A plateau in ciprofloxacin concentration was observed in nasal mucosa of both studied regions after intranasal administration, suggesting a slow delivery of the drug over a period of time using the nasal gel formulation. In plasma and olfactory bulb, concentration of ciprofloxacin was residual after intranasal administration, which demonstrates this is a safe administration route by preventing systemic and particularly central nervous system adverse effects. Dose-normalized pharmacokinetic parameters of ciprofloxacin exposure to nasal mucosa revealed higher values after intranasal delivery not only in the anterior region but also in the posterior nasal region. In conclusion, topical intranasal administration appears to be advantageous for delivering ciprofloxacin to the biophase, with negligible systemic and brain exposure using a 41.7-fold lower dose than intravenous administration. Therefore, it may represent a promising approach in the drug management of chronic rhinosinusitis.