1

Introduction

The microbiology of chronic rhinosinusitis and the position of bacterial agents in the pathogenesis of this disease have been topics of debate . Knowledge of the bacterial flora of normal sinuses is mandatory to understand the pathogenicity of species isolated in diseased sinuses . Nevertheless, the bacteriology of the normal frontal sinuses does not necessarily have a bearing on what is found in chronic disease. However, the literature about the bacterial flora of normal sinuses in adults is heterogeneous. A number of studies assumed that the milieu of the un-diseased, un-operated sinus should be sterile as a consequence of native defense mechanisms avoiding bacterial colonization . Nonetheless, other papers have discovered bacteria in un-diseased sinuses . Sampling and culture methods are different in these papers and, most notably, the normal sinus cavities have diverse descriptions.

Studies published so far have been concentrated on the bacteriology of normal maxillary and ethmoid sinuses , but no attempt was made to study the bacterial flora of normal frontal sinuses. This is why the aim of this cross-sectional study is to determine the bacterial flora in the healthy adult frontal sinus cavities using sinus irrigation and quantitative techniques.

2

Material and methods

This prospective cross-sectional study (approved by the Institutional Review Board of the University of Medicine and Pharmacy Cluj-Napoca, in accordance with the Guidelines for Protection of Human Subjects) was conducted at the Department of Neurosurgery Cluj-Napoca between June 1, 2010, and October 1, 2011. Participants were all informed and consented to participate in the study. All consecutive patients undergoing surgery of the anterior cranial fossa were enrolled. The study included only patients admitted to the hospital on the day of surgery, in order to avoid sinus colonization by nosocomial flora. According to the previously published criteria , excluded from the study were patients with tumors of the sinuses, presenting a cold in the past 8 weeks, having signs or symptoms suggestive of sinus disease (nasal obstruction, rhinorrhea, postnasal drip, hyposmia), history suggestive of allergic rhinitis and/or asthma, having undergone hospitalization or an outpatient clinic visit within the past 12 months, patients with a known systemic disease (cystic fibrosis, ciliary dyskinesia, diabetes mellitus, human immunodeficiency, virus infection or other immunodeficiency condition), previous sinus or nose surgery, history of trauma of the sino-nasal region, use of systemic antibiotics, steroids, or nasal spray in the past 8 weeks.

A single ENT surgeon (SA) administered a questionnaire on major and minor sinus symptoms and treatments taken by the patients. Only strictly asymptomatic patients were included in the study. All patients had a CT scan of the sinuses the week before the operation. Each CT scan was scored according to the radiologic grading system proposed by Lund and McKay . As it relates to the frontal sinuses, patients with a Lund–Mackay score of > 0, absence or hypoplasia of the sinuses were classified as having abnormal radiological findings and were excluded from the study.

After the induction of general anesthesia and topical nasal decongestion, a nasal rigid endoscopy with a 45° endoscope was performed by the ENT surgeon. According to the criteria set forth for the maxillary sinuses, frontal sinuses were considered endoscopically normal if they fulfilled the following criteria: lack of middle meatal secretions, normal middle meatus mucosa without swelling, patent frontal recess, and lack of nasal septal deviation blocking the middle meatus .

Lavage specimens were obtained through trephination of the frontal sinus. The selection of this technique of sampling was founded on the most suitable method of sampling the sinus content . After the induction of anesthesia, the bicoronal scalp incision was performed, the pericranial flap was prepared and the anterior wall of the frontal sinuses and the orbital rim exposed. Ahead of the craniotomy and before the patient received the prophylactic antibiotic dose, the same ENT surgeon (SA) performed the frontal sinus trephination and lavages in a standardized fashion. Each patient had both frontal sinuses studied.

At that moment, the CT scan was reviewed to establish the presence and size of the frontal sinus. The extent of superior pneumatization of the frontal sinus needed to be assessed on the CT scan before the sinus trephination. During the sinus trephination and sampling, patients were positioned in the Trendelenburg position. After dissection of the periosteum, a 6 mm hole is drilled in the anterior wall of the frontal sinus near the midline, through which the trocar and an endoscope were inserted. Using the 30° endoscope, the mucosa and the frontal sinus ostium patency were reassessed, the presence of secretions or mucosal edema was recorded.

Two to three milliliters of sterile saline solution was gently instilled into the frontal sinus and reaspirated completely after 10 s. The same procedure was repeated for the second frontal sinus. Each aspirate was transported in a different air free carefully plugged syringe to the bacteriology laboratory. The time between the puncture and the inoculation of the specimen never exceeded 15 min. The lavage samples were processed to detect aerobic and anaerobic bacteria by the hospital laboratory according to generally accepted guidelines. Quantitative cultures were performed.

Each specimen was inoculated on three agar plates: Sabouraud plate and enriched chocolate agar for aerobes, nalidixic acid and colistin enriched sheep blood agar for anaerobes. Aerobic cultures were incubated at 37 °C in an atmosphere containing 5% CO ₂ . The plates were examined after 24 h and 48 h. The anaerobic cultures were incubated in an atmosphere of 4%–10% CO ₂ , the GasPak, (Becton Dickinson Microbiology Systems, Cockeysville, MD, USA) and examined after 48 h with renewal of GasPak. Both aerobic and anaerobic plates were cultured 5 more days and examined at day 7 in case of negative growth after 48 h. Bacterial identification was performed according to standardized techniques.

2

Material and methods

This prospective cross-sectional study (approved by the Institutional Review Board of the University of Medicine and Pharmacy Cluj-Napoca, in accordance with the Guidelines for Protection of Human Subjects) was conducted at the Department of Neurosurgery Cluj-Napoca between June 1, 2010, and October 1, 2011. Participants were all informed and consented to participate in the study. All consecutive patients undergoing surgery of the anterior cranial fossa were enrolled. The study included only patients admitted to the hospital on the day of surgery, in order to avoid sinus colonization by nosocomial flora. According to the previously published criteria , excluded from the study were patients with tumors of the sinuses, presenting a cold in the past 8 weeks, having signs or symptoms suggestive of sinus disease (nasal obstruction, rhinorrhea, postnasal drip, hyposmia), history suggestive of allergic rhinitis and/or asthma, having undergone hospitalization or an outpatient clinic visit within the past 12 months, patients with a known systemic disease (cystic fibrosis, ciliary dyskinesia, diabetes mellitus, human immunodeficiency, virus infection or other immunodeficiency condition), previous sinus or nose surgery, history of trauma of the sino-nasal region, use of systemic antibiotics, steroids, or nasal spray in the past 8 weeks.

A single ENT surgeon (SA) administered a questionnaire on major and minor sinus symptoms and treatments taken by the patients. Only strictly asymptomatic patients were included in the study. All patients had a CT scan of the sinuses the week before the operation. Each CT scan was scored according to the radiologic grading system proposed by Lund and McKay . As it relates to the frontal sinuses, patients with a Lund–Mackay score of > 0, absence or hypoplasia of the sinuses were classified as having abnormal radiological findings and were excluded from the study.

After the induction of general anesthesia and topical nasal decongestion, a nasal rigid endoscopy with a 45° endoscope was performed by the ENT surgeon. According to the criteria set forth for the maxillary sinuses, frontal sinuses were considered endoscopically normal if they fulfilled the following criteria: lack of middle meatal secretions, normal middle meatus mucosa without swelling, patent frontal recess, and lack of nasal septal deviation blocking the middle meatus .

Lavage specimens were obtained through trephination of the frontal sinus. The selection of this technique of sampling was founded on the most suitable method of sampling the sinus content . After the induction of anesthesia, the bicoronal scalp incision was performed, the pericranial flap was prepared and the anterior wall of the frontal sinuses and the orbital rim exposed. Ahead of the craniotomy and before the patient received the prophylactic antibiotic dose, the same ENT surgeon (SA) performed the frontal sinus trephination and lavages in a standardized fashion. Each patient had both frontal sinuses studied.

At that moment, the CT scan was reviewed to establish the presence and size of the frontal sinus. The extent of superior pneumatization of the frontal sinus needed to be assessed on the CT scan before the sinus trephination. During the sinus trephination and sampling, patients were positioned in the Trendelenburg position. After dissection of the periosteum, a 6 mm hole is drilled in the anterior wall of the frontal sinus near the midline, through which the trocar and an endoscope were inserted. Using the 30° endoscope, the mucosa and the frontal sinus ostium patency were reassessed, the presence of secretions or mucosal edema was recorded.

Two to three milliliters of sterile saline solution was gently instilled into the frontal sinus and reaspirated completely after 10 s. The same procedure was repeated for the second frontal sinus. Each aspirate was transported in a different air free carefully plugged syringe to the bacteriology laboratory. The time between the puncture and the inoculation of the specimen never exceeded 15 min. The lavage samples were processed to detect aerobic and anaerobic bacteria by the hospital laboratory according to generally accepted guidelines. Quantitative cultures were performed.

Each specimen was inoculated on three agar plates: Sabouraud plate and enriched chocolate agar for aerobes, nalidixic acid and colistin enriched sheep blood agar for anaerobes. Aerobic cultures were incubated at 37 °C in an atmosphere containing 5% CO ₂ . The plates were examined after 24 h and 48 h. The anaerobic cultures were incubated in an atmosphere of 4%–10% CO ₂ , the GasPak, (Becton Dickinson Microbiology Systems, Cockeysville, MD, USA) and examined after 48 h with renewal of GasPak. Both aerobic and anaerobic plates were cultured 5 more days and examined at day 7 in case of negative growth after 48 h. Bacterial identification was performed according to standardized techniques.