The Bacteriology of Chronic Rhinosinusitis With and Without Nasal Polyps

Objective  To compare the bacteriologic findings in ethmoidal biopsy specimens and nasal lavage samples from healthy control patients and from patients with chronic rhinosinusitis (CRS) with nasal polyps (CRSNP+) and without nasal polyps (CRSNP−).

Design  Comparative microbiologic investigation.

Setting  University hospital.

Patients  The study included 31 CRSNP+ patients, 13 CRSNP− patients, and 21 control patients.

Intervention  Aerobe and anaerobe bacterial culture of nasal lavage samples and biopsy specimens of anterior ethmoidal mucosa.

Main Outcome Measure  Analysis of biopsy specimens from 65 patients and nasal lavage samples from 63 patients.

Results  Mixed cultures of aerobe and anaerobe bacteria were mainly detected in the biopsy specimens. The most common aerobe bacteria found in the biopsy specimens were coagulase-negative staphylococci, Corynebacterium species, Staphylococcus aureus, and α-hemolytic streptococci. Propionibacterium and Peptostreptococcus species were the most common anaerobes. Pathogenic bacteria such as S aureus, Enterobacteriaceae, and Haemophilus influenzae were detected in biopsy specimens from 16 of 31 CRSNP+ patients (52%), 4 of 13 CRSNP− patients (31%), and 10 of 21 control patients (48%). There were no significant differences in the bacterial cultures of the biopsy specimens between the 3 patient groups (P >.30). The majority of bacteria detected in the biopsy specimens were also detected in the corresponding lavage samples; however, in 35% of patients, pathogenic bacteria were found only in nasal lavage samples and not in corresponding biopsy specimens.

Conclusions  There are no significant differences in the bacteriologic features of ethmoidal biopsy specimens between CRSNP+, CRSNP−, and control patients. Therefore, a bacteriologic pathogenesis of the polyps in CRSNP+ patients seems unlikely. The general use of antibiotics in patients with CRS appears questionable. Investigation of nasal lavage samples is not suitable for predicting the bacteriologic features of inflamed sinuses of patients with CRS.

Chronic rhinosinusitis (CRS) is a widespread health problem that affects approximately 15% of the human population.¹ Inflammation of the nasal and paranasal sinus mucosa that lasts for more than 12 weeks leads to an impairment of the quality of life of affected people and causes a high financial burden to society.² Chronic rhinosinusitis is divided into 2 subgroups: CRS with nasal polyps (CRSNP+) and CRS without nasal polyps (CRSNP−). These disease entities differ in their immunologic pattern. In CRSNP+, there is a T_H2-shifted immune response, which includes a predominance of eosinophils and interleukin-5 as the dominant cytokine, whereas CRSNP− is a T_H1-dominated disease that demonstrates predominance of mononuclear cells and interferon gamma in the nasal tissue.¹

The predilection, which is dependent on genetic factors that are not yet fully understood, may be influenced by specific bacteria. It has been suggested that Staphylococcus aureus, gram-negative bacilli, or anaerobes play a role in the pathogenesis of CRS.^1,3,4 Also, S aureus exotoxins may be involved in the T_H2 shift in CRSNP+ patients.⁵ However, published data on the bacteriologic characteristics of CRS vary considerably, which may be explained in part by differences in the sampling techniques.

Our goal was to determine a possible role of specific bacterial species in the pathogenesis of CRSNP+ in comparison to CRSNP−. Therefore, we investigated a clearly defined study population of CRSNP+ and CRSNP− patients and compared them with control patients without inflamed mucosa. Biopsy specimens from the anterior ethmoid were used as sample material because this region is part of the ostiomeatal complex, which represents a functional unit of the maxillary sinus ostia, anterior ethmoid cells and their ostia, ethmoid infundibulum, hiatus semilunaris, and middle meatus.¹ The ostiomeatal complex is also the site from which polyps originate. Furthermore, noninvasive nasal lavage samples were examined to determine whether the bacteriologic features of these samples allow conclusions about the bacteriologic composition of tissue biopsy specimens, as nasal lavage samples are representative of almost all areas of the nose.⁶ The investigation included aerobe and anaerobe cultures as well as selective cultures for the detection of S aureus small-colony variants (SASCVs), which may play a role in the pathogenesis of CRS.^7,8

Patients treated in the Department of Otorhinolaryngology, University Hospital of Ulm, Ulm, Germany, between May 2006 and May 2007 were consecutively screened. Those who complied with the CRS definition of the European Academy of Allergy and Clinical Immunology¹ and who were aged 18 to 70 years were eligible. A modified Lund and Mackay computed tomographic score⁹ of at least 15 was required for inclusion. Patients with CRS, bilateral nasal polyps, and a Malm score¹⁰ of at least 3 were categorized as CRSNP+, whereas CRSNP− patients needed to have a bilateral Malm score of 0, ie, no polyps visible on nasal endoscopy. Patients with CRS and Malm scores of 1 and 2 were not eligible so that patients in whom the CRS subtype could not be clearly defined could be excluded. Further reasons for exclusion were treatment with antibiotics or steroids within the previous 4 weeks, acute CRS exacerbations, current immunotherapy or aspirin desensitization, and cystic fibrosis or unilateral sinus disease. Pregnant or lactating women were also excluded. Various additional parameters were recorded, including atopy, which was defined as a skin prick test that was positive for common inhalant allergens; self-reported or clinically diagnosed acetylsalicylic acid intolerance; and bronchial asthma. Patients admitted for surgical treatment of nasal structural abnormalities were eligible as controls if their history did not suggest sinus abnormalities and if they showed no signs of mucosal inflammation on nasal endoscopy. The study was approved by the institutional review board of the University of Ulm (No. 243/2005).

Before surgery, nasal lavage samples were obtained as described elsewhere.¹¹ Briefly, each nostril was flushed with 5 mL of isotonic saline solution. After 10 seconds, the patient blew the solution into a sterile plastic tube, which was immediately transferred for microbiologic examination. During surgery, biopsy specimens measuring approximately 5 mm in diameter from both sides of the anterior ethmoid region were obtained from patients with CRS; they were obtained from the inferior turbinate, close to the middle meatus, from control patients after thorough disinfection of the nasal vestibules with octenidine dihydrochloride–2-phenoxyethanole (Octenisept; Schuelke & Mayr, Vienna, Austria).

Within 4 hours after sampling, the specimens were processed. Biopsy specimens were aseptically minced and suspended in approximately 0.5 mL of sterile 0.9% saline solution. One drop (approximately 30 μL) of the tissue suspension was plated semiquantitatively on Columbia sheep blood agar, Schaedler agar (in duplicate), Schaedler agar with kanamycin (0.1 g/L) and vancomycin (7.5 mg/L, Schaedler-KV agar), chocolate agar with bacitracin (50 U/mL), and MacConkey agar (all commercially available from Heipha, Heidelberg, Germany) as well as S aureus ID agar (BioMérieux, Nürtingen, Germany). The plates were incubated for 5 days at 36°C as follows: S aureus ID agar and MacConkey agar at room air; Columbia, chocolate agar, and 1 plate of Schaedler agar under room air with 5% carbon dioxide; and 1 plate of Schaedler agar and Schaedler-KV agar in an anaerobe jar. Ten microliters of the native nasal lavage sample and a 1:100 dilution of the nasal lavage sample in 0.9% sterile saline solution were plated on the same agar panel as the biopsy specimens. The plates were examined every day.

All cultured bacteria were identified on the basis of standard microbiologic procedures, including morphological and Gram stain characteristics and oxidase reactions, as well as detection of katalase, coagulase, and clumping factor for determination of S aureus.

Of 148 patients screened for this study, 95 were eligible. Reasons for noninclusion were nasal steroid use within the last 4 weeks (n = 19), a computed tomographic score that was too low (n = 16), a polyp score of 1 or 2 (n = 10), or other reasons (n = 8). Among the 95 eligible patients, insufficient tissue was obtained in 24 cases, 5 tissue samples were used for other studies, and 1 tissue sample was contaminated. Of the remaining 65 patients, 31 were CRSNP+, 13 were CRSNP−, and 21 (control patients) had undergone surgery for nasal structural abnormalities without rhinosinusitis (Table 1). The prevalence of atopy (P = .80), bronchial asthma (P = .06), and acetylsalicylic acid intolerance P = .20) did not differ significantly between the 3 groups (Table 1).

Aerobe and anaerobe bacterial cultures of the biopsy specimens were obtained in all 65 patients. Biopsy specimens from the left and right ethmoid region were cultured separately. Culture of the biopsy specimens showed bacterial growth in one or both biopsy specimens in 63 of the 65 specimens examined (97%); no bacterial growth was observed in the cultures of specimens from 2 CRSNP+ patients (Table 2). The most common aerobe species detected in the 3 patient groups were coagulase-negative staphylococci (SCN) and Corynebacterium species; S aureus was detected more often in CRSNP+ patients (7 of 31 [23%]) and control patients (6 of 21 [29%]) than in CRSNP− patients (1 of 13 [8%]), while Haemophilus influenzae was detected more often in CRSNP− patients (4 of 13 [31%]) than in the other 2 patient groups (CRSNP+, 4 of 31 [13%]; controls, 1 of 21 [5%]; P = .93). The differences, however, were not significant. Staphyloccus aureus small-colony variants were not detected in the biopsy specimens.

Anaerobes were cultured in 74% of the biopsy specimens from CRSNP+ patients, 100% of the specimens from CRSNP− patients, and 90% of the specimens from control patients. The most frequent anaerobe detected in the biopsy specimens among all 3 patient groups was Propionibacterium species. The pathogenic species S aureus, Enterobacteriaceae, and H influenzae were detected in 16 biopsy specimens from CRSNP+ patients (52%), 4 biopsy specimens from CRSNP− patients (31%), and 10 biopsy specimens of control patients (48%). This difference between the 3 patient groups, however, was not significant (P = .24).

The bacteriologic features of the biopsy specimens consisted mostly of mixed infections, with a median of 3 different species (Table 3). There were no significant differences in the number of different species found in biopsy specimens among the 3 patient groups. Pathogenic bacteria were found in conjunction with species of the physiologic flora in 15 CRSNP+ patients (48%), 4 CRSNP− patients (31%), and 10 control patients (48%). They were found in pure culture of a biopsy specimen from only 1 CRSNP+ patient (3%).

Nasal lavage samples were available in 63 of 65 cases; however, anaerobe culture of lavage samples was performed in only 35 of the 63 cases. The majority of the bacteria that were detected in the biopsy specimens were also detected in the corresponding lavage samples (Table 4). All cases that were positive for S aureus in the biopsy specimen were also positive in the lavage sample. In contrast, H influenzae and Enterobacteriaceae organisms were found in the corresponding lavage samples from 25% to 75% of the patients with CRS and from 25% to 100% of the control patients (Table 4). In 35% of the cases, the pathogenic bacteria S aureus, Escherichia coli, Klebsiella species, Citrobacter species, and H influenzae were found only in the lavage samples and not in corresponding biopsy specimens. The predictive value of a positive lavage sample regarding a positive biopsy culture was only 67% for S aureus, E coli, and Citrobacter species; 50% for Klebsiella species; and 45% for H influenzae (Table 4). Anaerobe bacteria were cultured less often from lavage samples than from biopsy specimens.

To determine whether pathogenic bacteria differ in their numbers in lavage samples with respect to their occurrence in the corresponding biopsy specimens, lavage samples were cultured quantitatively. Staphylococcus aureus, H influenzae, and Enterobacteriaceae were cultured in concentrations of 10² to 10⁴ colony-forming units (CFU)/mL in CRSNP+ patients, 10² CFU/mL in CRSNP− patients, and 10² to 10⁴ CFU/mL in controls (Table 5). Concentrations of bacteria in lavage samples with and without a positive culture result in the corresponding biopsy specimen did not differ appreciably.

Despite the high prevalence of CRS, its pathogenesis and the causes for development of nasal polyps in some of the patients are still unclear. Therefore, in this study, we investigated the bacteriologic composition of ethmoid mucosal specimens in a well-defined study population of patients with CRS with (CRSNP+) and without (CRSNP−) polyps and in controls. The results of bacteriologic studies are largely influenced by preanalytic and analytic factors, including collection and type of specimen, sampling site, transportation, and processing in the microbiologic laboratory.¹² Therefore, we ensured rapid transport and plating of specimens and used culture media and conditions that facilitated detection of facultative and strict anaerobes as well as SASCVs. The anterior ethmoid sinus was chosen as the sampling site for the biopsy specimens as it is part of the ostiomeatal complex and is assumed to play an important role in CRS.^1,13 We preferred biopsy specimens instead of swab specimens to minimize contaminations from nasal secretions and to facilitate detection of anaerobes and intracellular bacteria such as SASCVs. Because mucosal biopsy specimens near the ostiomeatal unit can be obtained during septorhinoplasty without clinically relevant additional trauma, patients with nasal structural abnormalities but without CRS served as controls. Patients with Malm 1 and 2 polyps were excluded. The exclusion of patients with a Malm score of 1 or 2 served to create 2 definitely distinct groups and to exclude patients in whom the polyp state might be questionable.

Like Doyle and Woodham,⁴ who also investigated ethmoid sinus biopsy specimens in patients with CRS, we did not find a significant difference in the detection frequency of various microorganisms between patients with CRS and controls. In contrast to the study of Doyle and Woodham, our patients were divided into 2 groups: those with CRSNP and those without CRSNP. However, there was no significant difference in the bacteriologic findings between these different disease entities (see “Results” section).

In the ethmoid biopsy specimens, we mainly detected a mixed growth of aerobe and anaerobe bacteria, with a predominance of aerobe and facultative anaerobe isolates. These findings differ from those of Brook,³ who detected a predominance of anaerobe bacteria in his studies of different sinuses. These differences could be explained by the different sampling locations. In inflamed sinuses with blocked ostia, the growth conditions are favorable for anaerobe bacteria because of lower oxygen tension,³ while the region of the anterior ethmoid sinus is assumed to be better aerated than a blocked sinus. In contrast to the findings of Brook as well as to our data, Doyle and Woodham⁴ and Busaba et al¹⁴ found anaerobes in none or a minority (11 of 179) of biopsy specimens of ethmoid mucosa only. The absence and low prevalence of anaerobes in those studies may be attributable to delays in the plating of cultures or to insufficient culture conditions, as the majority of specimens were incubated anaerobically for only 2 days. In our study, the majority of the anaerobes grew only after 3 days of incubation. Also, Doyle and Woodham assumed that presurgical treatment that increases the drainage of purulent material leads to oxygenation of the ethmoid sinus. This assumption appears reasonable in cases involving patients with CRS who suffer from purulent secretions, but we also detected anaerobes, including Peptostreptococcus species, Propionibacterium species, and Prevotella intermedia, in 90% of control patients, without blockage of the sinus or signs of sinus inflammation. Therefore, we assume that gram-positive anaerobes belong to the physiologic flora of the ethmoid sinus. Propionibacterium and Peptostreptococcus species, the most frequent anaerobes in our study, were also detected frequently by Brook.^15,16 Although both genera belong to the physiologic flora of the nasopharynx, Propionibacterium species was detected in nasal lavage samples and biopsy specimens, whereas Peptostreptococcus species was detected only in large numbers in the biopsy specimens, possibly indicating that Peptostreptococcus species is more sensitive to aerobe conditions in the nasal cavity than Propionibacterium species.

Regarding aerobe bacteria, SCN and corynebacteria were found in the majority of ethmoid biopsy specimens from patients and controls. The pathogenic significance of SCN and Corynebacterium species therefore appears questionable. The predominance of SCN was also described by Nigro et al¹⁷ and Doyle and Woodham.⁴ Because these bacteria also occurred in most lavage samples, contamination of the biopsy specimens during surgery cannot fully be excluded. Pathogenic bacteria such as S aureus, Enterobacteriaceae, and H influenzae were also frequently found in our study. In their examinations of ethmoid biopsy specimens, Doyle and Woodham⁴ described a predominance of S aureus and Enterobacteriaceae organisms in patients with CRS and concluded that these bacteria played a possible role in the pathogenesis of CRS. However, they did not examine control patients in their study. Because these pathogenic organisms occurred in almost the same numbers of CRSNP+ (52%) and control (48%) patients in our study, their pathogenetic role in CRS is questionable. Our data agree with those of Busaba et al.¹⁴ Because we did not detect SASCVs and there were no significant differences between the 3 patients group in the detection rate of S aureus in the biopsy specimens, the theory that these bacteria are the pathogenetic reason for nasal polyp formation in CRSNP+ patients is unlikely.

In addition to the invasively obtained biopsy specimens, we examined nasal lavage samples to determine whether this easy-to-sample material allows conclusions about the bacterial composition of the ethmoid mucosa. As expected, nasal lavage samples contained more bacteria of the physiologic respiratory flora than the biopsy specimens. Pathogenic organisms that were cultured from biopsy specimens were found in 73% of the corresponding lavage samples, but S aureus was the only pathogenic species that was detected in 100% of the nasal lavage samples in relation to culture-positive biopsy samples. On the other hand, in 35% of our patients, pathogenic bacteria such as S aureus, E coli, Klebsiella species, Citrobacter species, and H influenzae were found exclusively in the lavage samples. Therefore, the findings of analysis of nasal lavage samples seem not to be sensitive and specific enough to predict the bacteriologic composition of the ethmoid sinus regarding Enterobacteriaceae, Haemophilus species, β-hemolytic streptococci, and gram-positive anaerobes (Table 4). The sensitivity of the lavage sample was 100% for S aureus compared with the invasive biopsy specimen; however, the predictive value of a positive lavage culture compared with a positive biopsy culture was only 67%. The predictive value of a positive lavage culture was even lower for the other pathogenic species. The concentration of pathogenic species in the lavage samples does not predict the occurrence of the species in the ethmoid biopsy specimens either.

In conclusion, regarding the restrictions of a small study population, our results of aerobe and anaerobe bacterial culture do not show any significant differences in the bacteriologic composition of ethmoid biopsy specimens in CRSNP+ and CRSNP− patients compared with controls. Therefore, a bacteriologic pathogenesis of the polyps in CRSNP+ patients appears unlikely. From a microbiologic point of view, the general use of antibiotics in patients with CRS appears questionable. However, long-term therapy with low doses of macrolides has been proposed for the treatment of patients with CRS because of their immune-modulating properties.¹⁸ Although the immune-modulating effect of macrolides may alter the course of CRS, the exact mechanisms of this therapy and possible different effects in CRSNP+ and CRSNP− patients are not yet understood. Long-term antibiotic therapy also poses the risk of macrolide-resistent bacteria. In cases involving pneumococci, the prevalence of erythromycin resistance in the United States has already reached 30% and is increasingly associated with multiple resistance mechanisms and multidrug resistance.¹⁹

Correspondence: Nele Wellinghausen, MD, Institute of Medical Microbiology and Hygiene, University Hospital of Ulm, Robert-Koch Strasse 8, 89081 Ulm, Germany (nele.wellinghausen@web.de).

Submitted for Publication: March 12, 2008; final revision received May 26, 2008; accepted July 6, 2008.

Author Contributions: All authors had full access to all the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis. Study concept and design: Niederfuhr, Riechelmann, and Wellinghausen. Acquisition of data: Wellinghausen. Analysis and interpretation of data: Niederfuhr, Kirsche, Riechelmann, and Wellinghausen. Drafting of the manuscript: Niederfuhr and Wellinghausen. Critical revision of the manuscript for important intellectual content: Kirsche, Riechelmann, and Wellinghausen. Statistical analysis: Riechelmann. Administrative, technical, and material support: Niederfuhr, Kirsche, and Wellinghausen. Study supervision: Riechelmann and Wellinghausen.

Financial Disclosure: None reported.