Bacterial agents of the discharging middle ear among children seen at the University of Nigeria Teaching Hospital, Enugu

Introduction Discharging middle ear continues to be one of the commonest problems seen in the developing world. There is an ever growing need to carry out studies periodically to determine the common bacterial agents responsible for discharging otitis media and their antibiotic sensitivity especially in set-ups characterized with minimal laboratory services. The study sought to determine the common bacterial agents causing discharging middle ear among children presenting at the University of Nigeria Teaching Hospital, Enugu and their sensitivity to the commonly available antibiotics. Methods Middle ear swabs were collected from 100 children aged 1 month to 17 years at the Children Out-Patient and Otorhinolaryngology Clinics of the University of Nigeria Teaching Hospital, Enugu, Nigeria. The specimens were cultured for aerobic bacterial organisms and their sensitivity determined. Results Among those with acute discharge, Staphylococcal aureus was isolated in 31.3% and Proteus species in 25.0%. In chronically discharging ears, Proteus Species dominated (39.1%), followed by Staphylococcal aureus (28.3%). Conclusion Staphylococcal aureus and Proteus species were the commonest bacterial agents in acute and chronic otitis media respectively. Most isolates showed high sensitivity to the fluoroquinolone antibiotics.


Introduction
Otitis media is one of the most common infectious diseases of childhood worldwide [1]. It is the inflammation of the mucous membrane of the middle ear cleft which includes the middle ear cavity, mastoid antrum, the mastoid air cells and the Eustachian tube [2]. When the inflammation is associated with a discharge from the ear through a perforation in the tympanic membrane or via a ventilatinig tube, suppurative (or discharging) otitis media results.
Otitis media may be acute (less than 6 weeks) or chronic (at least 6 weeks) [1]. Discharging ear or otorrhea is drainage exiting the ear which may be serous, serosanguineous, or purulent [3].  [4], local studies done in Nigeria suggest that Moraxella catarrhalis is not a predominant organism in acutely discharging otitis media in Nigerian children [5]. Pseudomonas aeruginosa is commonly implicated in chronic discharging otitis media in Nigerian children [5,6]. Complications of discharging otitis media are numerous and include hearing impairment, mastoiditis, facial nerve paralysis, cholesteatoma, tympanosclerosis, bacterial meningitis and brain abscess, to mention a few. Treatment of otitis media is usually based on empiric knowledge of aetiologic organisms and their sensitivity pattern. There is emerging evidence of multi-drug resistance of bacterial isolates with reduction in antibiotic efficacy [7,8] and 70% alcohol solution and allowed to dry for 1-2 minutes. After this, an ear swab from the discharging ear was taken with the aid of sterile cotton-tipped applicators taking care not to touch the skin of the external auditory meatus to limit contamination of the specimen.
In patients with bilateral discharging otitis media, samples were collected from only one ear which was preferred by the patient or mother. The swabs were then quickly transported to the microbiology laboratory of the Eastern Nigeria Medical Center Enugu, a nearby specialist center located very close to the University of Nigeria Teaching Hospital Enugu.
Sample processing and analysis: Samples of the ear discharge were promptly plated onto freshly prepared chocolate, blood and cystine-lactose-electrolyte-deficient (CLED) agar. The blood and cystine-lactose-electrolyte-deficient (CLED) agar plates were Page number not for citation purposes 3 incubated aerobically at 37 o C for 24 hours while the chocolate agar plates were incubated microaerobically using the candle jar extinction technique [9]. After the 24 hour incubation period, the plates were examined for growth and individual colonies were further analysed for their physical characteristics such as morphology, colour (pigmentation), odour and in case of blood agar, haemolysis. No anaerobic cultures were carried out and mycobacteria were not searched for because of unavailability of the required laboratory materials. A Gram stain was carried out on all cultured isolates. Thereafter, characterization to species level was carried out using standard bacteriological methods [10]. Antibiotic susceptibility tests with multi-discs were carried out for various drugs using the disc diffusion method [10]. Choice of the antibiotics to be tested for was based primarily on knowledge of commonly available antibiotic discs. Zones of inhibition for each antibiotic, if formed were then measured to the nearest millimeter and documented. Interpretation of these results in terms of resistance or susceptibility was according to accepted protocol [10].
Ethical approval: Ethical Clearance for this study was obtained from the ethical committee of the University of Nigeria Teaching Hospital Enugu before the study was commenced. Informed written consent was obtained from parents and guardian of the participants and assent was obtained from children where appropriate.
Data analysis: Data were entered into a computer database and were analyzed using SPSS version 11.0. Chi-square tests (χ 2 ) were used to test for significance; and probability value (p-value) of less than 0.05 was taken as being statistically significant.

Results
The subject were aged 1 month to 17years (median 3 years).  [18]. Resistant strains are however emerging [19]. Systemic use of this group of antibiotics has been limited in children because of the observation that these antibiotics, when administered systemically, may have an adverse effect on the development of weight-bearing joints in juvenile animals [18,19].
Ohyama and co-workers [20] in Japan demonstrated that 0.3% ofloxacin otic solution was efficacious without ototoxic effects in discharging otitis media of the chronic variety. Again, Dohar and fellow workers [18] showed that otic formulation of 0.

Conclusion
Staphylococcal aureus and Proteus species were the most common bacterial agents in acute and chronic otitis media respectively.
Fluoroquinolones were found to be effective in their treatment.
What is known about this topic  Bacterial agents are known causes of both acute and chronic otitis media. Antibiotic therapy is key in the management of otitis media. In resource poor countries like Nigeria, empirical therapy is not uncommon, hence the need for implicating agents and susceptible antibiotics.

What this study adds
 This study shows that the leading organisms in both acutely and chronically discharging otitis media among Nigerian children were Staphylococcal aureus and Proteus species, these organisms were more sensitive to fluoroquinolones group of antibiotics and should now be the first-line antibiotic management of otitis media among Nigerian children.

Competing interests
The authors declare no competing interests.

Acknowledgments
We are thankful to the children and their families who participated in this study. Our gratitude also goes to the Medical Laboratory Scientist, Mr Chris Ireoba.