International Journal of Otolaryngology and Head & Neck Surgery, 2013, 2, 290-294
Published Online November 2013 (
Open Access IJOHNS
Clinical Application of a Microbiological Study on Chronic
Suppurative Otitis Media
Prayaga N. Srinivas Moorthy1, Jadi Li nga iah2, Sudhakar Katari2, Anil Nakirakanti2
1Department of E.N . T.-Head & Neck Surgery, Decca n College of Medical Sciences, Hyderabad, India
2Department of E.N.T.-Head & Neck Surgery, Chalmeda Anand Rao Institute of Medical Sciences, Karimnagar, India
Received March 18, 2013; revised April 19, 2013; accepted May 15, 2013
Copyright © 2013 Prayaga N. Srinivas Moorthy et al. This is an open access article distributed under the Creative Commons Attribu-
tion License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly
Our prospective study conducted over a period of 9 months includes 100 samples of ear discharge collected from 90
patients suffering from tubo-tympanic type of chronic suppurative otitis media (CSOM). The ear discharge which is
collected with sterile swabs is subjected to Gram’s staining and culture of the causative organism. Antibiotic sensitivity
test of cultured bacterial growth is u ndertaken to know the susceptibility of th e causative organism. Of the 100 samples,
62 were culture positive where Pseudomo nas aeruginosa was the most common pathogen followed by Staphylococcus
aureus. Most of the cultured organisms in our study were sensitive to drug Ciprofloxacin. The outcome of our study
enabled us to set an empirical medical treatment for an early resolution of ear discharge and inflammation in our pa-
tients with CSOM as we could understand the aetiological pathogens and their susceptibility pattern. Effective medical
treatment in obtaining a discharge free ear prior to surgical treatment led us to improve the surgical outcome in our pa-
tients with CSOM.
Keywords: Chronic Suppurative Otitis Media; Microbiology; Antib iotic Resistance; Ciprofloxacin
1. Introduction
Otitis media, an inflammation of the middle ear, is quite
common in the developing world [1]. Based on the dura-
tion of symptoms, like ear discharge or perforation of the
tympanic membrane, it is labeled as chronic otitis media
when the symptoms are present beyond 12 weeks.
Chronic suppurative otitis media (CSOM) is inflamma-
tion of the middle ear cleft and its contents which are
classically divided into 1) a tubo-ty mpanic type affecting
the middle ear mucoperiosteum and 2) an attico-antral
type which is an active squamous disease within a
growth of squamous epith elium into the middle ear cleft.
CSOM is the leading cause of preventable hearing loss in
the developing world [1]. Our institute, Chalmeda Anan -
drao Institute of Medical Scien ces (CAIMS), is located in
Karimnagar district of India and caters to the health
needs of rural population of adjoining four districts. Pa-
tients with a tubotympanic type of CSOM constitute a
major proportion of patients who belong to low socio-
economic status and have inadequate health education. In
effect, they present it to us late and are often with inade-
quate and improper treatment. The aetiology of a tubo-
tympanic type of CSOM involves ascending infection
from nasopharynx through the Eustachian tube or an in-
fection entering from external auditory canal through a
perforation in tympanic membrane. The aim of our study
on bacterial aetiology and their antibiotic susceptibility
pattern is to know whether an empirical treatment based
on the result of the study will effectively shorten the pe-
riod of infection associated with discharge in patients of
CSOM and thereby improve the surgical outcome.
2. Materials and Methods
The present study is a prospective study involving 90
patients examined at CAIMS and 100 samples of ear
discharge were collected from these patients. Out of 90
patients 10 patients h ad bilateral active ear discharg e and
swabs were collected from both the ears separately.
The inclusion criteria for the study are 1) a patient
with active ear discharge who has no t used any antib iotic
medication either topical or systemic for at least 7 days
immediately preceding to presentation to us, irrespective
of age and sex 2) only patients with tubo-tympanic type
of CSOM with a central perforation are included. A
thorough history with regard to duration of illness, asso-
ciated symptoms and usage of antibiotics has been taken
prior to inclusion in the study.
The clinical features of patients included in the study
were similar that all have chief complaint of active ear
discharge with a history of more than 3 months duration,
a central perforation most often in antero inferior quad-
rant of tympanic membrane and a conductive hearing
loss ranging from 30 dB SPL to 55 dB of SPL measured
by pure tone audiometry.
The exclusion criteria are 1) a patient with attico-antral
type of CSOM with attic or posterior marginal perfora-
tion, who may commonly have anaerobic bacterial patho-
gens, as our study did not use anaerobic culture media or
2) a patient who has been using an antibiotic within 7
days of clinical presentation.
Our institute has a policy of waiting for at least 4
weeks of discharge free interval before posting a patient
with tubo-tympanic type of CSOM for tympanoplasty to
avoid surgery in an inflamed middle ear environment. In
case of attico-antral CSOM we do not wait for the dis-
charge to subside before posting the patient to undergo
ear surgery as complications can occur even during
seemingly discharge free interval or the discharge may
never subside. For this reason we have not included pa-
tients with attico-antral type of CSOM in the study.
From each patient of active CSOM, two swabs of the
ear discharge are collected under aseptic precautions
without surface contamination and are transported to
Microbiology department. One swab was utilized for
Gram’s staining and the other was inoculated on Nutrient
agar, Blood agar and MacConkey agar for bacterial cul-
ture. After overnight incubation at 37˚C the culture plates
were observed for growth. Single colony was stained by
Gram’s Method from each culture plate. Hanging drop
was done if Gram negative bacilli were seen. The cul-
tured bacteria are subjected to various biochemical tests
depending on the organism like catalase test, oxidase test,
urea hydrolysis test, phenol red test etc., at CAIMS mi-
crobiology lab (Figure 1). The organism isolated was
tested for antibiotic sensitivity on Mueller-Hinton agar
by Kirby-Bauer disc diffusion method according to Na-
tional Committee for Clinical Laboratory Standards
(NCCLS) criteria [2].
3. Results
In our study out of 90 patients 52 were males and 38
were females with in age range of 2 to 70 years. Out of
total 100 samples collected from 90 patients suffering
from tubo-tympanic CSOM in our study, 62 samples
were culture positive. There was no statistically signifi-
cant sex or age predilection for a sample to become cul-
Figure 1. Fluorescin pigment (greenish yellow) produced by
Pseudomonas aeruginosa on nutrient agar.
ture positive in our study. Among the 10 patients who
had bilateral ear discharge 3 patients had same organism
infecting both ears and two had different bacteria affect-
ing each ear.
Among the 62 bacterial isolates, Pseudomonas aeru-
ginosa was the most common bacterium cultured in 33
(54%) samples, followed by Staphylococcus aureus in 7
(11.3%) as indicated in Table 1.
Among the 33 isolates of Pseudomonas aeruginosa it
was sensitive to Imipenem (94%), Ciprofloxacin (85%),
Ceftazidime (82%), and resistant to Cefepime (66%),
Piperacillin/Tazobactam (64%), Cefoperazone (64%),
Cefotaxime (60%), Amikacin (55%), and others (Table 2
and Chart 1).
Staphylococcus aureus (Table 3) was sensitive to Ci-
profloxacin (85%), Gentamicin (72%), Ofloxacin (72%),
Amoxicillin (57%), Linezolid (57%), and resistant to Co-
trimoxazole (85%), Amikacin (72%), Cefotaxime (72%),
and Erythromycin (57%).
Gram negative bacteria (Table 4) other than Pseudo-
monas aeruginosa were mostly sensitive to Ciproflox-
acin (93%) and resistant to Tetracycline (81%), Oflox-
acin (62.5%), and Cefotaxime (44%), Cefoperazone
Staphylococcus saprophyticus was mostly sensitive to
Ciprofloxacin (85%) and Beta hemolytic Streptococci
were sensitive to Bacitracin.
4. Discussion
Among 100 samples collected from 90 patients, 62 sam-
ples were bacterial culture positive with a culture positiv-
ity of 69%. In studies done by Vikas Khanna et al. [3], V.
K. Poorey et al. [4], Tanmoy Dev et al. [5], and S. Ni-
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Table 1. List of organisms isolated.
Name of bacteria Number of
isolates Percentage
Pseudomonas aeru gi n os a 33 54%
Proteus mirabilis 5 8.06%
Klebsiella pneumoniae 5 8.06%
Proteus vulgaris 4 6.45%
Escherichia coli 2 3.25%
Staphylococcus aureus 7 11.3%
Staphylococcus saprophyticus 5 8.06%
Beta haemolytic Streptococci 1 1.6%
Table 2. Antibiotic susceptibility pattern in Pseudomonas
Cefepime – 22 (66%)
Piperacillin/Tazobactam – 21(64%)
Cefoperazone – 21 (6 4 %)
Carbenicillin – 20 (60%)
Cefotaxime – 20 (60%)
Amikacin – 18 (55%)
Imipenem – 31 (94%)
Ciprofloxacin – 28 (85%)
Ceftazidime – 27 (82%)
Levofloxacin – 23 (70% )
Gentamicin – 17 (52%)
Imepena m
Pi per a cillin/Tazobac tam
Amikac in
Gentam icin
Sen s itive
Resi stance
Chart 1. Antibiotic susceptibility pattern in Pseudomonas
Table 3. Antibiotic susceptibility pattern in Staphylococcus
Ciprofloxacin – 6 (85 %)
Gentamicin – 5 (72%)
Ofloxacin – 5 (72%)
Amoxicillin – 4 (57%)
Linezolid – 4 (57%)
Cotrimoxazole – 6 (85%)
Amikacin – 5 (72%)
Cefotaxime – 5 (72%)
Erythromycin – 4 (57%)
Table 4. Antibiotic susceptibility pattern in gram negative
bacteria other than Pseudomonas aeruginosa.
Ciprofloxacin – 15 (93%)
Gentamicin – 13 (81%)
Amoxycillin + Clavulanic acid – 12 (75%)
Ceftazidime – 11 (68.75%)
Amikacin – 10 (62.5%)
Levofloxacin – 8 (50%)
Piperacillin/Tazobactam – 8 (50%)
Tetracycline – 13 (8 1%)
Ofloxacin – 10 (62.5% )
Cefotaxime – 7 (44%)
Cefoperazone (37.5 % ).
kakhlagh et al. [6] the culture positivity was 84%, 92%,
53% and 82% respectively. In our study all were mono-
bacterial cultures where as in studies done by Vikas
Khanna et al. [3], V. K. Poorey et al. [4] polymicrobial
or mixed cultures were obtained in 39% and 10% respec-
Out of 62 bacterial isolates in the present study Pseu-
domonas aeruginosa was the predominant bacterium in
33 (54%) followed by Staphylococcus aureus in 7
(11.3%) isolates. Kenna et al. [7] found that Pseudomo-
nas was the predominant organism (67%) in their study.
In study done by Vikas Khanna et al. [3] the most com-
mon bacterial isolate was Pseudomonas aeruginosa
(40.57%), followed by Staphyloco ccus aureus in 36.23%
of cases. S. Nikakhlagh et al. [6] studied that Staphylo-
coccus aureus is common isolate in 32.4% followed by
21.69% of Pseudomonas aeruginosa. V. K. Poorey et al.
[4] observed that Pseudomonas pyocyaneous was the
most common organism isolated in 35.2%, followed by
Klebsiella aerogenes in 25.4%. The observations made
from different studies indicate there can be variation in
causative or ganism based on ethnic, geographi c fac t ors.
In the present study Ciprofloxacin drug has emerged
as the most effective antibiotic useful for the patients in
our study which is sensitive against more than 85% of
Pseudomonas, Staphylococci and other pathogens. In
studies done by Sharma K. et al. [8] and V. K. Po orey et
al. [4] Amikacin was the most effective drug. In our
study the strains of Pseudomonas which were resistant to
Ciprofloxacin were sensitive to Imipenem which is a
similar finding observed by Jang et al. [9]. The mecha-
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nism of resistance is believed to be mediated by forma-
tion of biofilms by infecting organisms [10,11].
Out of 90 patients in our study more than 70 patients
have used antibiotics during some part of their long dura-
tion of CSOM before presenting to us. Their drug history
included most commonly Cefixime, Amoxicillin with
Clavulanic acid and topical Ofloxacin which were not
useful for them. After obtaining the culture sensitivity
report they were put on oral and topical Ciprofloxacin
and we have observed early response as most of the dis-
charging ears were dry by 2 weeks of treatment. Those
patients who were culture negative were successfully
treated of their ear discharge by regular dry mopping of
ear, a medical treatment with oral Ciprofloxacin and
Ornidazole combination along with topical antifungal
Clotrimazole ear drops. This observation is suggestive of
a role of anaerobes and fungal pathogens in CSOM
[12-14]. All the patients were offered tympanoplasty
surgery 4 weeks after obtaining dry ear.
After the present study we now initially treat our tubo-
tympanic CSOM patients with oral Ciprofloxacin em-
pirically. Only those patients who fail to respond even
after 2 weeks of ciprofloxacin treatment are subjected to
culture and sensitivity test of their ear discharge. This
approach of empirical treatment with initial ciprof loxacin
has enabled us to successfully shorten the course of ear
discharge and avoided the cost and time involved in
sending each patient’s ear discharge for microbiological
study. We are making efforts to communicate the results
of our study with otolaryngologists and physicians in our
area for better patient care in our locality.
5. Conclusion
Our study, in the light of other various studies, indicates
that there can be a variation in the organisms infecting
and their susceptibility pattern based on season, locality
and ethnicity of a patient with CSOM [15-17]. Hence it is
prudent for any health centre catering to a defined area of
population to conduct periodically the microbiological
study of CSOM in order to install effective treatment
protocol s fo r t he po p ul at ion.
6. Acknowledgements
We thank the faculty and staff of the department of Mi-
crobiology of CAIMS, Karimnagar, who helped us to
carry out our study.
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