1

Introduction

The draining ear is a frequently encountered complaint in an otolaryngologic practice. Aural drainage may be due to a variety of causes including otitis externa, myringitis, otitis media with perforation, infected cholesteatoma, otorrhea following tympanoplasty tube placement, and mastoiditis. Ototopical agents and oral antibiotics are the cornerstone of treatment of the draining ear. These treatments are generally based on empirical decisions regarding the most common bacteria for a given diagnosis. Previous studies have shown relatively low rates of resistant bacteria. Hence, cultures are not often obtained from draining ears. There is a paucity of literature describing the role for “culturing” in the management of the draining ear. Based on a significant rise in recent years of resistant bacteria in the outpatient setting, the role of culture in the treatment of the draining ear requires reevaluation.

Perhaps the most worrisome of these trends is the growing incidence of methicillin-resistant Staphylococcus aureus (MRSA) in both nosocomial and community-acquired infections over the past decade. In 2003, approximately 60% of staphylococcus isolates were shown to be MRSA . Community-acquired MRSA infections have been rising as well . The otologic incidence of MRSA has been reviewed by a few authors, with reported rates between 6% and 12% . Other bacterial genii, such as Pseudomonas and Corynebacterium , have also demonstrated resistance patterns that are often refractory to traditional therapy . In addition to identifying resistant strains of bacteria, obtaining a culture may help identify cases of otomycosis which commonly present as a painful, draining ear and can be a great imitator of “resistant otorrhea” . Approximately 10% of otitis externa is of fungal origin and is less likely to respond to standard antibacterial treatment . The incidence of fungal infections as a cause for post–tympanostomy tube otorrhea has risen in the period since the advent of fluoroquinolone drops, with Candida and Aspergillus being the most commonly isolated species .

The purpose of this study is to examine trends in culture data from chronically draining ears over the past 3 years and, in particular, look for correlations between the specific diagnosis at the time of culture, the organism(s) cultured, and the resistance patterns of the bacteria isolated.

2

Methods

The clinic charts and culture results of 170 patients with draining ears that were cultured and with various underlying diagnoses were retrospectively reviewed. These diagnoses included otitis externa, myringitis, otitis media with perforation, infected cholesteatoma, otorrhea following tympanostomy tube placement, and mastoiditis. It is our practice to obtain a culture in ears that do not respond to empirical therapy, show signs of impending complications, have a history of resistant organisms, have evidence of granulation tissue, or show signs suspicious of otomycosis. Cultures obtained in chronic mastoiditis were taken from open mastoid cavities. Although cultures were not obtained from all patients with aural drainage, cultures were obtained from the vast majority of such cases. All culture specimens were obtained in the outpatient setting of an academic otology practice from October 1, 2003, to September 30, 2006. Funding for this study was interdepartmental. Information obtained from the clinical chart included the primary and secondary diagnoses, suspicion of fungus at the time of the initial examination, and culture results. Antibiotic sensitivity and resistance patterns were assigned according to National Committee for Clinical and Laboratory Standards–approved procedures for antibiotic sensitivity testing and reporting. In this way, the antibiotic spectra tested reflect appropriate antibiotics for the specific bacterial type. Culture specific data included the organism, the presence of resistance, and the sensitivity spectrum. Because of complexity of analyzing multiple bacteria and sensitivities for each infection cultured, the sensitivity of each culture isolate was graded on a Likert scale as follows: 0 = sensitive to all appropriate antibiotics; 1 = resistant to some appropriate oral or topical antibiotics; and 2 = resistant to all oral antibiotics, only sensitive to intravenous antibiotics. Bacteria given a score of 1 or 2 were deemed to be “resistant.” Cultures that showed intermediate resistance (Minimium Inhibitory Concentration [MIC] = 8) to a particular antibiotic were considered sensitive to that antibiotic for the purposes of this study. It should be noted that sensitivity to linezolid was not included in the culture data.

The patient charts were also reviewed for clinical findings suggestive of a fungal infection (fungal mats or spores). Patients with persistent or recurrent infections within 3 months were considered a single infection event rather than separate infections. Culture results were, therefore, considered to be from separate events if 3 months had elapsed between cultures. Bacterial resistances, correlation with previous treatment, and diagnosis were analyzed statistically using a Fisher exact t test. The level of statistical significance was set at P ≥ .05.

2

Methods

The clinic charts and culture results of 170 patients with draining ears that were cultured and with various underlying diagnoses were retrospectively reviewed. These diagnoses included otitis externa, myringitis, otitis media with perforation, infected cholesteatoma, otorrhea following tympanostomy tube placement, and mastoiditis. It is our practice to obtain a culture in ears that do not respond to empirical therapy, show signs of impending complications, have a history of resistant organisms, have evidence of granulation tissue, or show signs suspicious of otomycosis. Cultures obtained in chronic mastoiditis were taken from open mastoid cavities. Although cultures were not obtained from all patients with aural drainage, cultures were obtained from the vast majority of such cases. All culture specimens were obtained in the outpatient setting of an academic otology practice from October 1, 2003, to September 30, 2006. Funding for this study was interdepartmental. Information obtained from the clinical chart included the primary and secondary diagnoses, suspicion of fungus at the time of the initial examination, and culture results. Antibiotic sensitivity and resistance patterns were assigned according to National Committee for Clinical and Laboratory Standards–approved procedures for antibiotic sensitivity testing and reporting. In this way, the antibiotic spectra tested reflect appropriate antibiotics for the specific bacterial type. Culture specific data included the organism, the presence of resistance, and the sensitivity spectrum. Because of complexity of analyzing multiple bacteria and sensitivities for each infection cultured, the sensitivity of each culture isolate was graded on a Likert scale as follows: 0 = sensitive to all appropriate antibiotics; 1 = resistant to some appropriate oral or topical antibiotics; and 2 = resistant to all oral antibiotics, only sensitive to intravenous antibiotics. Bacteria given a score of 1 or 2 were deemed to be “resistant.” Cultures that showed intermediate resistance (Minimium Inhibitory Concentration [MIC] = 8) to a particular antibiotic were considered sensitive to that antibiotic for the purposes of this study. It should be noted that sensitivity to linezolid was not included in the culture data.

The patient charts were also reviewed for clinical findings suggestive of a fungal infection (fungal mats or spores). Patients with persistent or recurrent infections within 3 months were considered a single infection event rather than separate infections. Culture results were, therefore, considered to be from separate events if 3 months had elapsed between cultures. Bacterial resistances, correlation with previous treatment, and diagnosis were analyzed statistically using a Fisher exact t test. The level of statistical significance was set at P ≥ .05.

3

Results

Clinical information from 170 patients was reviewed, comprising 243 infection events from 188 ears and 286 different cultures. The distribution was predominantly male (101:79), and the patient ages ranged from 3 months to 90 years, with a mean age of 34.6 years. The number of patients, the number of infection events, and the total number of bacterial isolates for each diagnosis category are listed in Table 1 . Despite the tertiary clinical setting, many of these patients (54%) had not been previously treated. The distributions of specific bacterial isolates for each diagnosis category are demonstrated in Table 2 . Staphylococcus aureus , Corynebacterium sp, and Pseudomonas aeruginosa were the most commonly isolated bacteria. Polymicrobial cultures were seen in 49.7% (142/286) of instances. Cultures containing both bacteria and fungus were seen in 20.2% (58/286) cultures. Fungus alone grew in 4.9% (14/286) of cultures, and 16.4% of the cultures showed no growth.

Table 2

Specific bacteria by diagnosis

Bacteria	Otitis externa	Myringitis	Otitis media w/ perforation	Cholesteatoma	Posttube otorrhea	Mastoiditis
Achromobacter xylosoxidans		1 (1.82%)				1(2.00%)
Acinetobacter baumannii	1 (1.75%)			1 (4.76%)
Alcaligenes xylosoxidans					2 (1.92%)
Bacteroides			2 (2.15%)	2 (9.52%)	4 (3.85%)	1 (2.00%)
Corynebacterium sp	8 (14.04%)	7 (12.73%)	9 (9.68%)	3 (14.29%)	16 (15.38%)	10 (20.00%)
Diphtheroids	1 (1.75%)		1 (1.08%)		2 (1.92%)	2 (4.00%)
Enterobacter cloacae			1 (1.08%)			2 (4.00%)
Escherichia coli			1 (1.08%)		1 (0.96%)
Fusobacterium nucleatum					1 (0.96%)	1 (2.00%)
Gram-neg rod	2 (3.51%)				1 (0.96%)
Haemophilus influenzae			5 (5.38%)		4 (3.85%)	2 (4.00%)
Klebsiella pneumoniae	1 (1.75%)		1 (1.08%)
Morganella morganii		2 (3.64%)		1 (4.76%)		1 (2.00%)
Moraxella catarrhalis			1 (1.08%)		1 (0.96%)
MRSA	3 (5.26%)	7 (12.73%)	5 (5.38%)	1 (4.76%)	2 (1.92%)	1 (2.00%)
Peptostreptococcus sp				2 (9.52%)	1 (0.96%)
Propionibacterium acnes					2 (1.92%)
Proteus mirabilis	1 (1.75%)	1 (1.82%)		1 (4.76%)
P aeruginosa	13 (22.81%)	11 (20.00%)	7 (7.53%)	1 (4.76%)	12 (11.54%)	3 (6.00%)
P fluorescens			2 (2.15%)
Serratia	1 (1.75%)		1 (1.08%)
S aureus ⁎	12 (21.05%)	2 (3.64%)	13 (13.98%)	1 (4.76%)	16 (15.38%)	8 (16.00%)
S auricularis			1 (1.08%)	1 (4.76%)
S epidermidis		1 (1.82%)	2 (2.15%)	2 (9.52%)	2 (1.92%)	2 (4.00%)
Staphylococcus , coag neg	4 (7.02%)	8 (4.55%)	12 (12.90%)	1 (4.76%)	10 (9.62%)	2 (4.00%)
Staphylococcus sp		1 (1.82%)	2 (2.15%)	1 (4.76%)		2 (4.00%)
Stenotrophomonas maltophilia		1 (1.82%)	1 (1.08%)	1 (4.76%)
Streptococcus α -hem	1 (1.75%)		2 (2.15%)		2 (1.92%)
Streptococcus group A		1 (1.82%)			1 (0.96%)
Streptococcus pneumoniae			3 (3.23%)		7 (6.73%)
S viridans			1 (1.08%)		1 (0.96%)
Other	1 (1.75%)	2 (3.64%)	1 (1.08%)	1 (4.76%)	5 (4.81%)	3 (6.00%)

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