Prevalence and Etiological Agents for Chronic Suppurative Otitis Media among Patients Attending Otorhinolaryngology Department at Muhimbili National Hospital, Tanzania CURRENT STATUS:

Objective Chronic suppurative otitis media is among the commonest otological condition reported in otorhinolaryngology practice commonly attributing to preventable hearing loss. The aim of this study was thus to determine the prevalence and etiological agents for chronic suppurative otitis media in our department. Results A total of 5591 patients were recruited in this study where 79 (1.4%) were found to have chronic suppurative otitis media. Male preponderance (54.4%) was found in this study and the left ear (58.2%) was more affected than right ear. Central perforation was the commonest pattern reported in 53% of cases and none had attic perforation. Of the 81 processed ear swabs, microbial growth was seen in 80 (98.8%) whilst one sample showed no microbial growth whereas 52.5% had polymicrobial growth.


Introduction
Chronic suppurative otitis media (CSOM) is a disease condition associated with chronic inflammation of the middle ear cleft characterized by persistent perforation of tympanic membrane with recurrent or persistent mucopurulent otorrhoea. The duration of otorrhoea for classifying CSOM has been a subject of discussion among Otorhinolaryngologists with duration ranging from 3 weeks to 3 months.
In this study the period taken will be at least 2 weeks in accordance with WHO [1].
It is also one of the leading causes of preventable hearing loss worldwide and in most cases it is a sequela of improperly attended acute otitis media and it consequently impairs one's quality of life [1,2].
Hearing loss is common among patients with CSOM and exceed 30dB and with tendency to occur in about 50 to 60 percent of such patients [3,4]. Conductive hearing loss is typically moderate to severe in up to two-thirds of patients and being marked at low frequencies and with increased bone conduction threshold tendency [4-12. The site of the perforation corresponds to degree of hearing loss, with posterior perforations having greater decibel level loss probably as a result of loss of protection of the round window membrane from impinging sound pressure waves [7].
MRSA and MSSA have been found in pus swab culture of patients with CSOM and this pose a significant challenge in medical management due to its resistance to commonly antibiotics used [13,14].
On the other hand, there has been increased incidence of multi drug resistance which poses a significant challenge as they are related to increased complications associated with CSOM [13,14]. In Tanzania, most of the available studies were based on the prevalence of this condition and very few studies have been conducted to look on the bacteriological and sensitivity pattern to antibiotics of which its pertinent in management of such patients.

Methods
Study design, participants and sampling method.
This was a hospital based descriptive cross-sectional study conducted between September 2015 and February 2016 and included 1200 patients who attended Otorhinolaryngology (ORL) Department.
Convenient sampling technique was utilized.

Inclusion and exclusion criteria
All adult patients who consented to participate in the study and those under the age of 18 years whose parents/caretakers consented on their behalf. Patients on regular follow up were excluded.

Specimen Collection Procedures
Pus swab was collected from the external auditory canal and introduced into Amies transport medium bottle and sent for laboratory analysis.

Laboratory Procedures
From each specimen, a portion was subjected to primary gram stain for pus cells and possible organism while the remaining portions were inoculated into Blood agar (Oxoid, UK), and MacConkey agar (Oxoid, UK) and incubated aerobically at 370C for 24-48 Hours.

Identification of Bacterial Pathogens
Identification of pathogens was based on Microscopy (Gram stain, shape, cells arrangement) and colony characteristics (colony morphology, hemolysis on blood agar, changes in the physical appearance of the differential media). Organisms from discrete colonies were cultured into Nutrient Agar (Oxoid, UK) for subsequent. Biochemical tests. Gram positive isolates were tested for catalase and Coagulase tests while biochemical tests for gram negative isolated bacteria were tested for oxidase, Triple sugar Iron (TSI), Sulphur indole and motility (SIM), urease production and citrate utilization [15].

Antimicrobial Susceptibility Testing
Antibiotic susceptibility pattern of isolated bacteria pathogens was performed using modified Kirby Bauer disc diffusion method according to the guidelines of the clinical and Laboratory Standard Institute(CLSI) [16].
A colony suspension with concentration equivalent to 0.5 McFarland solution was prepared for each identified isolate and inoculated into Mueller Hinton-Agar (Oxoid, UK). Appropriate Selected Antibiotic discs were placed onto the media and incubated at 37°Celsius for 24 hours.

Data analysis
Data analysis was done using the Statistical Package for Social Sciences version 21. p-value of <0.05 was considered statistically significant.

Demographic Characteristics of Study Participants
A total of 5591 patients were recruited including both in patients and out patients. The age distribution ranged from 7 months to 82 years. The mean age of study participants was 12.9, (SD ± 7.9). Majority of patients were over 40 years old (28.1%) and the least were 16 -20 (4.9%) ( Table 1).

Distribution of Bacterial and Fungal Isolates
Of the 79 patients with CSOM whom pus specimen were collected for culture, 98.8% yielded positive culture. Most of culture growth yielded polymicrobial growth (52.5%), in which the most common was a mixture of Proteus mirabilis and Klebsiella pneumoniae (16.7%) ( Figure 1). As for single microbial growth, Escherichia coli and Staphylococcus aureus were equally prevalent (21.1%).

Susceptibility Pattern of Bacterial Isolates
Klebsiella pneumoniae was highly susceptible to Gentamicin (80.8%) and moderately susceptible to Ceftriaxone (73.1%) and Ciprofloxacin (61.5%), whereas none among these two isolates were susceptible to Ampicillin and Amoxicillin/clavulanic acid. (Table S1).

Discussion
CSOM is one of the public health concerns particularly in developing countries [1]. Early identification and proper management of these cases is of help in alleviating complications associated with this disease. In the present study, the proportion of patients with chronic suppurative otitis media was found to be 1.4%. This observation was slightly lower than the previous hospital based study in Tanzania [17] and other community based studies conducted in Dar es Salaam and Northern Tanzania [18,19]. Elsewhere hospital based studies in Sudan [20] and community based studies in India [21] and Solomon Islands [22] had reported higher prevalence than what has been found in our study. This low proportion observed could likely be due to differences in sample size and sampling techniques.
Subjects aged below five years had high proportion of the disease accounting for 26.6% of all cases of chronic suppurative otitis media. This may be explained by their relative immature immunity, leading to recurrent upper respiratory tract infections and their relatively short and horizontal eustachian tube making them prone to infection. This finding correlate to what has been found in other studies previous studies where majority of the cases were below five years of age [1]. In this study, we found males to be more affected than females with male to female ratio being 1.2:1 and this was statistically significant. Such finding shows resemblance to other studies done elsewhere [22] though differing with observed findings done elsewhere with female propensity [23] and equal gender predominance [10]. Since our study employed random selection of subjects, male predominance might be an incidental findings and still no known anatomical and genetic differences between male and females pertaining the ear exists.
Our study found left ear disease to account for the majority of the cases (58.2%) with bilateral involvement accounting for the least (2.5%) number of cases. This has resemblance with was found by Olowookere et al [23] though differing with findings established by Taipale et al and an Aboriginal study [3,24] with bilateral predominance. Predominance of the left ear may be due to random selection of the study cases but no any genetic or structural differences have been identified between the right and left ear.
This study found central perforation (tubotympanic type) to be predominant (53%) while none of patients had attic perforation. Such findings correlate closely with what was found elsewhere [22,25]. We also observed that gram negative bacteria accounted for the majority of the isolates with the least being fungi and most of the isolates were facultative anaerobes similar to other studies [17,27] while other authors observed gram positive Staphylococcus aureus as the predominant isolates [28,29].
Isolation of coliform bacteria Escherichia coli and Klebsiella pneumoniae which are known to be fecal bacteria and Pseudomonas aeruginosa which is associated with wet environmental conditions suggests people are at high-risk of infection due to poor hygienic environment. These findings were in line with observational study done in Nigeria by Bakari A. et al [27] which had Klebsiella pneumoniae as the commonest isolated bacteria. But most authors elsewhere have reported Pseudomonas aeruginosa as the commonest isolates [17,20,26,30,31] while Ferede et al [32] in their study found Proteus species followed by Staphylococcus aureus as their commonest isolates.
Antimicrobial susceptibility test was carried out for all the aerobic isolates (except for Coagulase negative staphylococcus). Ciprofloxacin was found to be the most effective drug resembling other studies [27,33]. This study has thus elucidated the prevalence and etiological profile for CSOM at MNH which is the largest country's tertiary hospital.

Conclusions
Prevalence of CSOM at MNH appears to be in line with what has been reported elsewhere. Male predominance was found and the left ear was more affected than the right ear. Prevalent Polymicrobial nature and antimicrobial resistance among isolates in CSOM cases warrants importance for culture and sensitivity of pus isolates. Ciprofloxacin, Gentamicin, Ceftriaxone and Amikacin are highly recommended as the first line management in patients with CSOM, with consideration of appropriate antifungals for possible fungal etiology as per our study findings.

Limitations
Due to lack of anaerobic culture facility we couldn't further explore the role of anaerobic bacteria in chronic suppurative otitis media. Contaminants were also identified and this is explained by the nature of swab which was employed.

Declarations
Ethics approval and consent to participate: Ethical clearance was obtained from the Senate Research and Publications Committee of Muhimbili University of Health and Allied Sciences. Permission to conduct the study was obtained from MNH authority as per hospital management protocols. A written informed consent was obtained from participants before recruiting them into our study. Consent for publication: Written informed consent was obtained from research participants Availability of data and materials: All relevant data pertinent to this research can be obtained from the corresponding author upon a reasonable request.
Competing interests: The authors declare that they have no competing interests