Chronic Otitis Media – Bacteria – Antibiotics – Sensitivity – Antananarivo.


Chronic otitis media is a frequent and serious bacterial infection. Despite appropriate therapy, acute otitis media can progress to chronic suppurative otitis media associated with ear drum perforation and purulent discharge. Ear infections are common in poor countries and one of the most common reasons for health consultations and prescriptions for antibiotics. Chronic suppurative otitis media are a common disease with approximately 5% global incidence [1].The precise diagnosis of chronic otitis media is based on the bacteriological examination of the auricular secretions which impose rigorous conditions of collection, conservation and realization.In Madagascar, chronic middle ear infections are under diagnosed due to the inadequacy or inaccessibility of the means of diagnosis and poses therapeutic problems.The investigation of chronic otitis media by bacteriological examinations has not yet been incorporated into the practice of physicians in the presence of clinical signs of ear infections.Thus, the management is not yet codified errors of precise bacteriological data. In front of an otitis media, the physicians prescribe some treatments antibiotic probabilistic source of bacterial resistances. The choice of antibiotics should be based on bacterial epidemiological data which should be periodically updated. The emergence of bacterial resistances is directly linked to this important consumption, it is imperative that all actors of health are sensitized to this problematic and contribute to the good use of the antibiotics. Antibiotic resistance is a real challenge and a major stake of public health [2]. Very few studies of chronic otitis media were performed in Malagasy people. The aim of the present study was to identify the bacteria responsible for chronic otitis media in order to assess the susceptibility of bacteria to antibiotics.

Materials And Methods

This is a prospective, multicentric, descriptive and analytical study of unilateral atrial flow from patients with otitis media seen in external consultation in 3 sanitary formations in Antananarivo including 2 university hospitals centers, the University Hospital Manarapenitra Andohatapenaka, University Health and Public Health Center Analakely (EUSSPA) and a private hospital, Lutheran Hospital Ambohibao. The bacteriological examinations of the samples were carried out within the Microbiology Unit of the Laboratory of Training and Research in Medical Biology (LBM) Faravohitra Antananarivo.

The study was carried out over a period of 3 months running from November 2016 to January 2017.Patients with otorrhea in favor of chronic otitis media were included. Patients with an otorrhea other than middle ear inflammation were excluded.In the case of a spontaneous otorrhea (after rupture of the tympanic membrane), the sampling was done after disinfection of the external auditory canal.For the pus of paracentesis, the sample will be done by the otorhinolaryngologist, after cleaning of the external auditory duct then incision of the eardrum, with the help of a cathlon gone up on syringe or thin swabs gone up on metallic stem. The samples were taken using two swabs, one for extemporaneous spreading on a blade and one for cultivation. The samples are brought directly to the laboratory with the data collection sheet.Regarding the bacteriological examination of samples, for the first day, to avoid any contamination, culture was performed on agar media to blood and chocolate with Polyvitex (PVX) and agar Mac Conckey a dial seeding, incubated at 37°C under CO2 for 18 to 24 hours. Followed by direct examination after Gram staining by notifying the presence of leukocytes and bacteria. Identification of the bacteria was carried out using biochemical and enzymatic tests such reduced gallery or API 20 E for Enterobacteriaceae or testing of catalase and coagulase for cocci Gram positive and oxidase tests or tests to optochin. The antibiograms were launched on Mueller Hinton or Mueller Hinton blood agar, according to the method of Kirby Bauer, that is to say the diffusion method on agar with antibiogram discs at 6 millimeters in diameter. Reading susceptibility testing was performed according to the recommendations of the Committee of the antibiogram of the French Society of Microbiology (CA-SFM) [3]. The antibiotics tested were: amoxicillin, amoxicillin + clavulanic acid, oxacillin, cefoxitin, ceftriaxone, ciprofloxacin, gentamicin, tetracycline, and imipenem. We have selected as patients with chronic otitis media those who have monomorphic pathogenic bacteria. Polymorphic flora will be considered as contaminated specimens, and requires another control sample, unless a pathogenic flora is associated with it. The variables studied were the antibiotic treatments possibly undertaken, the bacteria responsible for infection and their sensitivity to antibiotics. The data were processed and analyzed by Epi-info 7.1.3


During the study period, 750 patients were seen in external consultation. Otorrhoea was suspected in 320 patients (42.6%), but only 200 patients are under chronic otitis media. Chronic otitis media was encountered especially among the female gender with a sex ratio of male / female 0.54. We found cases of otitis media in patients under than 15 years in 30% of cases, followed by the age group 15 to 30 years in 25% of cases, then, cases of otitis decrease with patient age. This result is significant with p = 0.0001.During our study, 41.5% of the patients had already received antibiotic treatment before sampling.

Table 1 : Distribution of types of antibiotic therapy received by patients prior to collection.

Antibiotics n %
Third generation cephalosporins 28 33,7
Fluoroquinolones 37 44,6
Amoxicillin + clavulanic acid 18 21,7

Fluoroquinolones and third generation cephalosporins were the most used classes of antibiotics in probabilistic treatment before sampling with 44.6% and 33.7% respectively (Table I).

Table 2 : correlation between bacteriological examination and probabilistic antibiotic therapy.

Probabilistic antibiotic therapy Result of the bacteriological exams
Négatif Positif
n % n %
Non 5 7,0 66 93,0
Oui 26 31,3 57 68,7

Bacteriological examination was negative in 31.3% (n = 26) of the case when antibiotic therapy was started before taking the sample (Table II). This result was significant with p = 0.0001.

After the samples were cultured, germs were found in 73.5% (n = 143) of the samples. Staphylococcus aureus in 28.6% of cases and Coagulase-negative Staphylococci (CoNS) in 26.5% of cases were the main germs responsible for chronic otitis media found in our study followed by Proteus mirabilis (15.6%) and Pseudomonas aeruginosa (10.9%). The remaining isolated bacteria were Escherichia coli, Klebsiella spp and Streptococcus pneumoniae with 4.8%, 4.1% and 2.7%, respectively. We also found Candida spp in 6.8% of cases.

Table 3 : Antibiotic susceptibility of strains of S. aureus, CoNS, Proteus mirabilis and Pseudomonas aeruginosa.

S. aureus CoNS P. mirabilis P. aeruginosa
S (%) R (%) S (%) R (%) S (%) R (%) S (%) R (%)
AMX 23,8 76,2 25,6 74,4 13,0 87,0 0 100
AMC 33,3 66,7 38,5 61,5 17,4 82,6 0 100
FOX 59,5 40,5 38,5 61,5
CRO 47,8 52,2 50,0 50,0
CIP 85,7 14,3 82,1 17,9 78,3 21,7 56,3 43,7
GEN 88,1 11,9 61,5 38,5 65,2 34,8 87,5 12,5
OX 59,5 40,5 38,5 61,5
TET 50,0 50,0 59,0 41,0 39,1 60,9 18,7 81,3
IMP 100 0 93,7 6,3

AMX: amoxicillin, AMC: amoxicilline + clavulanique acid, FOX: cefoxitin, CRO: ceftriaxone, CIP: ciprofloxacin, GEN: gentamicin, OX: oxacillin, TET: tetracycline, IMP: imipenem. p>0,05

In most cases, strains of S. aureus were resistant to amoxicillin (76.2%) and amoxicillin with clavulanic acid (66.7%). In 40.5% of cases, S. aureus were resistant to methicillin. Molecules that remain sensitive in almost 85% of cases were gentamicin and ciprofloxacin (Table III).

The CoNS strains were resistant to amoxicillin in 74.4% of the cases and amoxicillin + clavulanic acid in 61.5% of the cases. The molecules that remained sensitive to CoNS were gentamicin and ciprofloxacin with 61.5% and 82.1% of the cases, respectively (Table III).

Proteus mirabilis strains were almost all resistant to amoxicillin and amoxicillin + clavulanic acid. Molecules that remained sensitive in most cases were ciprofloxacin, gentamicin and imipenem with respectively 78.3%, 65.2% and 100% (Table III).

The strains of Pseudomonas aeruginosa were all resistant to the combination of amoxicillin + clavulanic acid. Molecules that remained sensitive to Pseudomonas aeruginosa in the majority of cases were ciprofloxacin, gentamicin and imipenem with respectively 56.3%, 87.5% and 93.7% (Table III).

Two strains of which E. coli and Pseudomonas aeruginosa were producing extended spectrum beta-lactamase (ESBL).


Our study consists to identify the bacteria responsible for chronic otitis media and their sensitivity to antibiotics. It evokes the usefulness of carrying out a bacteriological examination of atrial levy to avoid antibiotic resistance problem.

Two hundred cases of purulent otorrhea were collected. Of these patients, 41.5% had already received antibiotic treatment prior to collection. The classes of antibiotic prescribed or taken by self-medication of the patient were fluoroquinolones (44.6%) followed by Third generation cephalosporins (33.7%) and amoxicillin + clavulanic acid (21.7%) (Table I). This antibiotic use without bacteriological evidence is linked to the probabilistic antibiotic prescription of doctors in cities and also related to self-medication by the patient who is the main source of bacterial resistance. Self-medication is mainly promoted by the free sale of these drugs in grocery stores and their more affordable cost compared to other classes of antibiotics. Cultures were negative in 31.3% of patients who had previously had antibiotic treatment and this was significant with p = 0.0001. This rate of negativity is higher compared to other studies carried out by other authors in Mali, who have found 5.3% [4]. The use of antibiotic treatment before sampling, the presence of bacteria that require special conditions for its thrust, also some yeasts that do not grow until after several days, as well as the viral etiology could lead to the negativity of bacteriological cultures.

This, therefore, implies that sole reliance on empirical antibiotic therapy is not appropriate for effective treatment of chronic suppurative otitis media. As a policy, bacteriological study and antibiotic sensitivity should be obtained for every chronic suppurative otitis media patient so that specific antibiotic therapy will be tailored to the individual cases. In our study, 26.5% of the cultures did not yield any microbial growths which is compatible with the findings in other reports in which negative cultures were also documented [5, 6, 7]. Such negative cultures may have been as a result of the modification of the bacterial flora in the affected ears by prior empirical antibiotic therapy [1]. For rational antibiotic use and successful of treatment of chronic suppurative otitis media, an appropriate knowledge of antibacterial susceptibility of causative microorganisms is imperative.

The study of the bacteriological profile of purulent otorrhea presents difficulties in terms of the sampling technique used and the presence of a commensal bacterial flora in the external auditory canal.

Of these 200 cases of purulent otorrhea, 143 (73.5%) cultures were positive, characterized by 93.7% bacterial strains and 6.2% yeasts (Table III).

In our study, the most commonly encountered bacteria in a chronic otitis media episode were Staphylococcus aureus, CoNS, Proteus mirabilis, and Pseudomonas aeruginosa, with respectively 28.6%, 26.5%, 15.6%, and 10.9%. These findings are consistent with chronic otitis media reported by other authors in India, Burkina Faso, Mali, and Nigeria [4, 8, 9, 10]. Staphylococcus aureus is the first isolated bacterium in our study in 28.6% of cases. Contamination from the external auditory canal is not to be excluded because it is a saprophytic bacterium of this place. It confirms the chronic infection and late diagnosis of otitis after a certain period of evolution in an often inadequate treatment in these patients, since the acute phase of the evolution of otitis media and it is virtually at the stage of chronicity that they are addressed to otolaryngologist specialists.

Coagulase-negative Staphylococci (CoNS) are commensal bacteria of the external auditory canal [11]. Their relatively high frequency (26.5%), should not rule out the strong possibility of contamination during sampling, even if genuine otitis media to CoNS have been reported. Their responsibility according to certain authors should be retained only if the same species is isolated in a rich and monomorphic culture on several samples, in the absence of other pathogenic bacteria and in the presence of favorable factors. Their isolation must incite the biologist to increase the number of samples.

Proteus mirabilis is the germ of usual superinfections of chronic otitis found in 15.6% of the cases in our study [11]

The presence of P. aeruginosa in 10.9% of the cases confirms the chronic nature of the infections and the late recourse of specialized care after therapeutic failures or recurrences. Opportunistic pathogen par excellence and present in the patient’s environment (water, food, medical equipment), this explains why contamination by this bacterium is very widespread in nature. Thus, its known presence in the commensal flora of the external auditory canal does not exclude the possibility of contamination during sampling.

Streptococcus pneumoniae is usually isolated from acute otitis media, particularly in children [11]. It accounts for only 2.7% of our isolates, which is in agreement with other studies including the one conducted in India which showed a rate of 1.7% [8].

There may be a difference between the bacteria responsible for chronic otitis media. The difference could be due to ecosystem from one country to another, the differences in the patient population studied and geographical variation [12]. Then, there is the technique of of the withdrawals of the pus. In Europe, almost all pus samples are taken after paracentesis. Rarely the stage of spontaneously opened otorrhea is reached. On the other hand, in Africa, all studies report specimens taken from spontaneously opened otorrhea. This may justify encountering superinfection germs from the surrounding environment such as Pseudomonas and Enterobacteria in greater numbers. And then, there is also the technique of manipulation. The time between sampling and culture can in some cases be detrimental to fragile germs such as Streptococcus pneumoniae and Haemophilus influenzae. The use of transport environment for the bacteria or rapid culture of the bacteriological laboratory sample may have improved crop yields for fragile bacteria.

Finally, there is self-medication. It is also possible that primitive bacterial otitis do not arrive early in the hospital. Patients simply be bought ear drops in pharmacies or from traditional treatment and it is only in case of failure, therefore in situation of superinfection, they are seen in consultation. Bacterial resistance to antimicrobial agents is a growing problem in medical practice [13, 14]. Dissemination of resistant bacteria is responsible for a considerable increase in mortality, morbidity and cost of treatment [15, 16].

In most cases, strains of S. aureus were resistant to amoxicillin (76.2%) and amoxicillin + clavulanic acid (66.7%) (Table III). The misuse linked to easy access to these molecules, in specialties, generics or counterfeit products (“street medicine”) in our country, would favor the selection of resistant strains. We found a very high frequency of methicillin-resistant Staphylococcus aureus (MRSA) with a rate of 40.5%. This prevalence of MRSA on chronic otitis media is very high compared to a study performed on MRSA on other secretions in Antananarivo (13.83%) and the nasal carriage rate of MRSA in children is 13.49. % in all of Madagascar [17, 18]. MRSA has long been the prototype of the exclusively nosocomial pathogen, maintaining betalactamins as the primary presumptive treatment for serious community infections, where MRSA was not to be taken into account. The situation changed dramatically in a few years with the almost simultaneous emergence of several distinct clones of community-acquired MRSA in Australia, Europe and then North America [19]. Strains of Staphylococcus aureus have good sensitivity to gentamicin (88.1%) and Ciprofloxacin (85.7%) (Table III), which is similar to a study conducted in Nigeria [10].

Among the betalactams, the imipenem of the carbapenem family, long recognized as the most potent anti-Pseudomonas, had a sensitivity of 93.7% in our study, but the study done in Algeria in 2008 found that imipenem has progressively lost its efficacy in the case of the mutation of the pyocyanic by its capacity of imipenemase production [20]. After imipenem, the aminoglycoside whose gentamicin retains a good sensitivity (87.5%) against Pseudomonas aeruginosa. Ciprofloxacin has a sensitivity of 56.3% against Pseudomonas aeruginosa and varies between 25 and 40% in Europe [21, 22, 23, 24]. It is around 16% in the United States and 25% in Tunisian hospitals [25, 26].

Proteus mirabilis strains were almost all resistant to amoxicillin and amoxicillin + clavulanic acid. Tetracycline resistance was 60.9%, and 52.2% of cases for C3G (Table III). Self-medication and the lack of guidelines for the management of infections also contribute to increased levels of resistance to these antibiotics. The molecules that remain sensitive in most cases to P. mirabilis were ciprofloxacin, gentamicin and imipenem with 78.3%, 65.2% and 100%, respectively (Table III). A study conducted in India in 2011 demonstrated 100% sensitivity of P. mirabilis to amoxicillin + clavulanic acid, ciprofloxacin and gentamicin [8]. Another study carried out in the same year showed a sensitivity of 100% Proteus mirabilis to ciprofloxacin and 72% to gentamicin [27]. The study conducted in Turkey in 2006 demonstrated 100% sensitivity to ciprofloxacin and 70% to gentamicin and imipenem [28].

Among the germs responsible for bacterial infections, enterobacteria are the most redoubtable because they produce betalactamases and possess other mechanisms of resistance to many antibiotics [29, 30]. Two strains of which an E. coli and a Pseudomonas aeruginosa were producing extended-spectrum beta-lactamase (ESBL) in our study. The significant concentration of these germs in the digestive tract promotes the exchange and dissemination of resistance genes [31, 32]. Pseudomonas aeruginosa is naturally resistant to many antibiotics. It also has the ability to rapidly acquire other resistances by enzymatic mechanism (proteases, extended spectrum beta-lactamase (ESBL), cephalosporinase, imipenemase).

In total, the imipenem had good activity on enterobacterial strains. However, its low tissue diffusion, the absence of oral and local presentation, the very high cost limit the use of this molecule to treat otitis media.

Regardless of the bacteria involved in chronic otitis media, gentamicin and ciprofloxacin have shown a high sensitivity which is confirmed in several of the works cited above. The ototoxicity of gentamicin should prompt us to take our therapeutic choice on another antibiotic such as ciprofloxacin. Quinolones do not carry a potential side effect of cochleotoxicity and vestibulotoxicity, which are attributed to aminoglycosides. A randomized controlled trial demonstrated that ciprofloxacin is more effective compared with aminoglycoside for the treatment of chronic suppurative otitis media [12]. Chronic otorrhea in the middle ear is difficult to treat, probably due to the low penetration of antibacterial agents and the presence of hard-to-treat bacteria such as P. aeruginosa, S. aureus, and Proteus mirabilis. Fluoroquinolones diffuse well at this level and the concentrations obtained are often superior to the MIC / MBC needed to eradicate the causative pathogens [33]. This leads us to propose ciprofloxacin as a first-line treatment in chronic otitis media, given its tolerance and good tissue diffusion. However, attention must be paid to the under-dosage of ciprofloxacin because it exposes the risk of emergence of resistant mutants, recognizing two essential mechanisms, namely target modification (DNA gyrase), which requires MIC controls, and a mechanism non-enzymatic (impermeability) which imposes high doses [33].

The results of this study may be influenced by contamination by commensal ear bacteria, the presence of bacteria that require specific conditions for its push, and the samples are not representative of all cases of chronic otitis media we could meet in all Madagascar.


The bacteriological profile of chronic otitis media in our study showed the prevalence of Staphylococcus aureus, coagulase negative staphylococci, Proteus mirabilis, and Pseudomonas aeruginosa. Depending on the bacteria found and their antibiotic sensitivity profiles, ciprofloxacin and gentamicin are the most sensitive antibiotics, but ciprofloxacin is best indicated by its spectrum of activity adapted to bacterial ecology, its good tolerance and high tissue concentrations.