Egyptian Journal of Ear, Nose, Throat and Allied Sciences (2013) 14, 191–194

Egyptian Society of Ear, Nose, Throat and Allied Sciences

Egyptian Journal of Ear, Nose, Throat and Allied

Sciences

www.ejentas.com

ORIGINAL ARTICLE

Antibiotics in chronic suppurative otitis media:

A bacteriologic study

Shamweel Ahmad *

Department of Clinical Laboratory Sciences, College of Medical Sciences, Salman Bin AbdulAziz University, Saudi Arabia

Received 20 May 2013; accepted 14 June 2013

Available online 12 July 2013

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KEYWORDS

Chronic suppurative otitis

media;

Antibiotic sensitivity;

Topical antibiotics;

Ear discharge

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Abstract Objective: This study sought to determine causative microorganisms of chronic suppu-

rative otitis media (CSOM) and to estimate their susceptibility to antibiotic agents.

Materials and methods: One hundred sixty-four (164) patients with unilateral or bilateral active

chronic suppurative otitis media were prospectively studied. They had chronic ear discharge and

had not received any antibiotics for the previous 5 days. Swabs were taken from all patients, and

sent to the Microbiology Department for processing. The specimens were cultured and the isolates

were identified using standard microbiological techniques. The antibiotic susceptibilities of the iso-

lates were determined with standard antibiotic discs using the Kirby–bauer disc diffusion method.

Results: This study analyzes the causal organisms and their sensitivity to various antibiotics. The

major organisms isolated were Methicillin sensitive Staphylococcus aureus [MSSA] (45.1%) followed

byPseudomonas aeruginosa (19.5%). The sensitivity of S. aureus (MSSA) was 79.7% to ciprofloxacin,

69% to cotrimoxazole, and 82.5% to gentamicin whereas the sensitivity ofP. aeruginosawas 100% to

ceftazidime, 84.4% to ciprofloxacin, 90.6% to gentamicin, and 78.1% to Piperacillin. Majority of the

isolates of P. aeruginosa were completely resistant to polymixin B (71.9%) whereas 50% of S. aureus

(MSSA) showed resistance to Ampicillin. All Methicillin resistant S. aureus (MRSA) isolates showed

100% resistance to Ampicillin, Augmentin and cephalothin. Among the available topical antibiotic

preparations for use in the ear, we found gentamicin and ciprofloxacin as the best choices.

Conclusion: The study ofmicrobial pattern and their antibiotic sensitivity determines the prevalent

bacterial organisms causingCSOM in the local area to start empirical treatment of otitis media and its

complications for a successful outcome, and thus to prevent the emergence of resistant strains.ª 2013 Production and hosting by Elsevier B.V. on behalf of Egyptian Society of Ear, Nose, Throat and

Allied Sciences.

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1. Introduction

Chronic suppurative otitis media (CSOM) is defined as achronic inflammation of the middle ear and mastoid cavity,which presents with recurrent ear discharges or otorrhoea

through a tympanic membrane perforation. The diseaseusually begins in childhood1,2 as a tympanic membrane

gyptian Society of Ear, Nose, Throat and Allied Sciences.

Table 1 Age distribution of the patients.

Age group (in years) 0–12 13–20 21–30 31–40 41–50 >50 Total

Number of patients 05 41 52 09 35 22 164

192 S. Ahmad

perforation due to an acute infection of the middle ear, knownas acute otitis media (AOM), or as a sequel of less severe formsof otitis media (e.g. secretary OM).3–5 The infection may occur

during the first 6 years of a child’s life, with a peak around2 years.6 The point in time when AOM becomes CSOM is stillcontroversial. Generally, patients with tympanic perforations

which continue to discharge mucoid material for periods from6 weeks7 to 3 months, despite medical treatment, are recog-nized as CSOM cases. Chronic suppurative otitis media

(CSOM) is a commonly encountered infection of the middleear all over the world. In 1990, about 28,000 deaths all overthe world and largely among developing countries were dueto otitis media.8,9 Mortality and disabilities due to otitis media

are primarily related to the complications of CSOM,10 partic-ularly brain abscess.11 Population-based estimates in develop-ing countries range from 0.24% in Thailand to 1.8% in Africa.

In South Korea, 10.4% of CSOM had complications.12

Chronic suppurative otitis media (CSOM) has assumed world-wide importance. For instance, the United States government

spends over 2 billion dollars yearly to treat acute and chronic earinfections.13 In the developing countries, it has continued to consti-tute a heavy disease burden, with the prevalence of chronic ear

infections being up to 72 cases per 1000 inhabitants.14

So untreated cases of CSOM can result in a broad range ofcomplications. These may be related to the spread of bacteriato structures adjacent to the ear or to local damage in the mid-

dle ear itself. Such complications range from persistent otor-rhoea, mastoiditis, labyrinthitis, facial nerve paralysis tomore serious intracranial abscesses or thromboses.15–17 So

the knowledge of the local pattern of infection is essential toenable efficacious treatment of this disorder. The goal of themanagement is to achieve a safe, dry ear, eradicate disease

and improve hearing.The main aim of this study was to determine the microbial

profile (aerobic and anaerobic) and the antibiograms of active

CSOM patients among Saudi population. CSOM is a verycommon problem in Saudi Arabia and is seen mostly in pop-ulations from far flung areas.

2. Methods

This study was conducted on Outpatient basis in the Depart-ment of Ear, Nose and Throat (ENT) over a period of one

and a half (11/2) years = from September, 2011 to February,2013. In this prospective study, a total of one hundred sixty-four (164) patients were involved. All our patients had perfo-

rated tympanic membranes with active purulent discharge. De-tailed clinical history regarding age, sex, duration of dischargeand antibiotic treatment was taken. Only patients who had not

received antibiotic therapy (topical or systemic) for the previ-ous 5 days were included in the study. Single use Mini-tip Cul-ture swabs were used to harvest the middle ear microflorathrough the tympanic membrane perforation. Much care was

taken to avoid surface contamination and the swabs weretransported to the microbiology department of the hospitalfor culture and sensitivity testing. A total of 164 swabs were

taken from 164 patients, processed aerobically and anaerobi-cally for the isolation of aerobic and anaerobic bacteria, usingstandard microbiological procedures. All organisms isolated

were identified according to standard microbiologicalmethods.

Antibiotic susceptibility testing was carried out using theKirby–Bauer disc diffusion technique on Muller–Hinton agarand commercial antibiotic discs (Oxoid, United Kingdom)

were used for antimicrobial testing.18 The antibiotic discs usedwere: Penicillin G (10U), Ampicillin (10 lg), Augmentin(30 lg), Trimethoprim-Sulphamethoxazole (1.25/23.75 lg),Cephalothin (30 lg), Polymixin B (300 U), Ceftazidime(30 lg), Piperacillin (100 lg), Chloramphenicol (30 lg), Cipro-floxacin (5 lg), Amikacin (30 lg), Gentamicin (10 lg), Neomy-

cin (30 lg) and Bacitracin (10 U).Apart from the standard antibiotics, testing was also done

specifically for Gentamicin, Neomycin, Chloramphenicol andBacitracin which are available locally as topical antibiotic ear-

drops. The antibiotic disc impregnated culture plates wereincubated at 37 �C overnight. The diameter of the zone of inhi-bition was measured and recorded as resistant or susceptible

according to the National Committee for Clinical LaboratoryStandards (NCCLS) interpretative criteria.19

3. Results

The mean age of patients was 25 years, with the range beingbetween 20–47 years (Table 1). From the 164 patients enrolled

in the study, there were 148 (90.2%) isolates. Ninety-four (94)patients (63.5%) had a single organism isolated from the mid-dle ear culture, while the remaining 54 patients had two or

more organisms isolated. There were only sixteen patients(9.8%) who had a sterile culture with no bacteria isolated (Ta-ble 2). The most common causal organisms isolated wereMethicillin sensitive Staphylococcus aureus [MSSA] (45.1%),

followed by Pseudomonas aeruginosa (19.5%), MethicillinResistant S. aureus (MRSA), Coagulase negative Staphylococ-cus, Proteus mirabilis and Escherichia coli (Table 2). The anti-

microbial sensitivities of the organisms were tested and theresults for the six most common organisms are shown (Ta-ble 3). Of the four antibiotics that are available commonly as

topical eardrops, gentamicin has the highest susceptibility rate(88.3%) for all the isolates tested, followed by chlorampheni-col (72.4%). Neomycin showed 74.3% sensitivity against

Gram negative bacteria while isolates of MSSA, MRSA andCoagulase negative Staphylococcus showed 78.8% susceptibil-ity to Bacitracin.

4. Discussion

Chronic suppurative otitis media and its complications areamong the most common conditions seen by otologists and

general practitioners. Chronic suppurative otitis media is apersistent inflammation of the middle ear or mastoid cavity,and is characterized by recurrent or persistent ear discharge

through a perforation of the tympanic membrane.20 Due tothe perforated tympanic membrane, bacteria can gain entryinto the middle ear via the external ear canal. Infection of

the middle ear mucosa subsequently results in ear discharge.Chronic suppurative otitis media is a common and potentially

Table 2 Microorganisms isolated in positive cultures.

Organism Number Percentage (%)

Gram Positive

Staph. aureus (MSSA) 74 45.1

Staph. aureus (MRSA) 19 11.6

Coagulase �ve Staph. 9 5.5

Gram Negative

Pseudomonas aeruginosa 32 19.5

Proteus miribilis 6 3.7

E. coli 4 2.4

Citrobacter Spp. 3 1.8

Anaerobe

Bacteroids spp. 01 0.6

No growth 16 9.8

Total 164 100

Antibiotics in chronic suppurative otitis media: A bacteriologic study 193

dangerous clinical condition that is difficult to treat becausethe most common infecting organisms are often resistant tomany antibiotics.21 Untreated cases of CSOM can result in a

broad range of complications. These may be related to thespread of bacteria to structures adjacent to the ear or to localdamage in the middle ear itself. Such complications range frompersistent otorrhoea, mastoiditis, labyrinthitis, facial nerve

paralysis to more serious intracranial abscesses or thrombo-ses.15,16 While the incidence of such complications is low, theyneed to be borne in mind when faced by a patient with active

CSOM.Treatment hence needs to be instituted early and effectively

to avoid such complications. The treatment of this condition

can be medical; with therapy directed at eradicating patho-genic aerobic and anaerobic organisms.22 Those cases thatare resistant to medical treatment might need surgical

intervention.The mainstay of treatment for uncomplicated CSOM is

twofold: meticulous aural toilet (with suction/mopping up ofear debris and discharge) and instillation of a topical and sys-

temic antimicrobial agent. The therapeutic use of antibiotics isusually started empirically prior to results of microbiologicalculture. Selection of any antibiotic is influenced by its efficacy,

resistance of bacteria, safety, risk of toxicity and cost. Knowl-edge of the local microorganism pattern and their antibiotic

Table 3 Antimicrobial susceptibility pattern of major organisms ca

Percent of resistant isolates against

Organism P AMP COT AMC CTN P

Gram positive bacteria

S. aureus (MSSA) 52.7 50.0 31.0 35.1 50.0 N

S. aureus (MRSA) 100 100 31.6 100 100 N

Coag. �ve Staph. 55.5 44.4 55.5 44.4 55.5 N

Gram negative bacteria

Pseudomonas aeruginosa NT NT NT NT NT 7

Proteus mirabilis NT 33.3 33.3 16.6 NT 5

Escherichia coli NT 25.0 25.0 25.0 100 5

P = Penicillin, AMP= Ampicillin, COT= Cotrimoxazole, AMC=Au

dime, PIP = Piperacillin, C = Chloramphenicol, CIP = Ciprofloxa

BAC= Bacitracin, NT =Not tested.

sensitivity is then essential to allow for effective and cost-sav-ing treatment. Microbiology cultures yield many, frequentlymultiple, organisms and these vary depending on climate, pa-

tient population and whether antibiotics have or have not beenrecently used. Several studies have reported different organ-isms in different proportions.17 Our study showed that active

CSOM infection in the Saudi population is mainly due to S.aureus, P. aeruginosa followed by P. mirabilis. Similar findingshave been reported by Gehanno.21 S. aureus (MSSA) was the

commonest organism isolated, although various such studiesin different countries have shown P. aeruginosa to be morecommon.16 Our study showed the predominance of S. aureusfollowed by P. aeruginosa which is in agreement with oth-

ers.21,23 This finding is in agreement with the pattern of CSOMinfection within the tropical region. The antibiotic susceptibil-ity pattern of MSSA showed that 82% were sensitive to genta-

micin, �80% were sensitive to ciprofloxacin and 79.7% toBacitracin. Antimicrobial sensitivity of P. aeruginosa in ourstudy revealed that ceftazidime was sensitive in 100%, Genta-

micin was sensitive in �91%, Ciprofloxacin was sensitive in�85% and 78% were sensitive to Piperacillin. Previouslyamoxicillin/ampicillin was used frequently than quinolones

for acute and chronic middle ear infections in our set up.But the present study has clearly shown a changing behaviourof microorganisms, showing more sensitivity to quinolones,cephalosporins and gentamicin. Also the clinicians used to

avoid the use of quinolones due to their adverse effects on car-tilage in growing children after their prolonged usage, howeverit has been documented that quinolones can be used if required

in children without any apprehensions.24,25 So the use of cipro-floxacin has been found superior both empirically and topi-cally. Among the most commonly available topical antibiotic

solutions gentamicin has shown promising results after cipro-floxacin. Added advantage of ciprofloxacin ear drops over gen-tamicin is not being ototoxic.26 There remains, however a

controversy over the question of ototoxicity with the topicalusage of aminoglycoside (gentamicin) while the systemic usageof aminoglycoside has been known to have a deleterious effecton the inner ear. The fact that the disease process in CSOM it-

self causes a sensorineural hearing loss26 has led many to con-clude the benefits derived from the usage of topicalaminoglycosides in the treatment of CSOM and the

prevention of attendant complication far outweigh the

using CSOM.

B CAZ PIP C CIP AK GM NEO BAC

T NT NT 20.3 20.3 21.6 17.5 NT 20.3

T NT NT 31.6 36.8 21.0 15.8 NT 21.0

T NT NT 33.3 22.2 22.2 11.1 NT 22.2

1.9 0 21.9 21.9 15.6 21.9 9.4 18.7 NT

0.0 33.3 16.6 33.3 16.6 33.3 16.6 33.3 NT

0.0 25.5 25.0 25.0 0 25.0 0 25.0 NT

gmentin, CTN= Cephalothin, PB = Polymixin B, CAZ= Ceftazi-

cin, AK = Amikacin, GM= Gentamicin, NEO=Neomycin,

194 S. Ahmad

ototoxic side-effects which may potentially occur. Keeping inview the high prevalence of S. aureus and P. aeruginosa inour set up and their high susceptibility to quinolones (cipro-

floxacin) and cephalosporins (ceftazidime), ciprofloxacin eardrops or systemic therapy of ciprofloxacin, piperacillin or ceft-azidime can be used safely in all age groups. However injudi-

cious use of such drugs can lead to emergence of drugresistant isolates especially in Staph. aureus and P. aerugin-osa,27 as has previously been experienced, there should there-

fore be judicious usage of this class of antibiotics in all typesof otitis media.

The study of microbial pattern and their antibiotic sensitiv-ity determines the prevalent bacterial organisms causing

CSOM in the local area to start empirical treatment of otitismedia and its complications for successful outcome, and thusto prevent the emergence of resistant strains.

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