Isolation and antimicrobial drug susceptibility pattern of bacterial pathogens from pediatric patients with otitis media in selected health institutions, Addis Ababa, Ethiopia: a prospective cross-sectional study

Otitis media is an inflammation of the middle ear and the tympanic membrane, mostly after an acute upper respiratory tract infection [1]. Otitis media is the most common episode of infection in children and the second most important cause of hearing loss affecting 1.23 billion people, thus ranked fifth global burden of disease [2, 3]. It is one of the major chronic disease in low and middle-income countries and the most common reason for which children receive antibiotics [2‐4]. Otitis media have 2–8 fold higher incidence in Sub-Saharan Africa and South Asia than developed world [4, 5] and the associated complications lead to the death of around 20,000 people annually, the highest mortality rate being in < 5 children [5]. Hearing loss, reduced learning ability, and low scholastic achievement have been indicated due to the chronic and recurrent form of the disease [6]. The major pathogens being bacteria like non typeable H. influenzae, S. pneumoniae, S. aureus, S. pyogenes, P. aeruginosa, P. mirabilis, E. coli and M. catarrhalis [7‐11], otitis media can also be caused by virus and fungi [10, 12]. Viral upper respiratory tract infections (URTI) predispose children to acute otitis media (AOM) by disrupting the mucociliary system, impairing the host’s primary mechanical defense from bacterial invasion, and viruses alone can cause AOM [8, 11]. An episode of otitis media is directly associated to the bacterial colonization rate of the nasopharynx [8]. In Ethiopia, few studies have indicated that there is a high level of antimicrobial resistance isolates from otitis media [13, 14]. The true picture of otitis media in under five-year-old children is not known in Addis Ababa and many general practitioners and pediatricians base their treatment on empirical evidence of the etiologic agent and susceptibility to commonly used antibacterial drugs. Knowing the local antibiogram is important for cost-effective and appropriate treatment of otitis media and help prevent its complications that may arise due to the luck of treatment or improper treatment. Thus, the aim of this study was to acquire data on bacterial pathogens responsible for otitis media and their antibacterial susceptibility pattern among under five children who come to visit public health institutions in Addis Ababa.

Among children, peak prevalence of otitis media was observed in the age group of under five years with previous studies conducted in Ethiopia [17] and Nigeria [18‐20], and the present study concentrates in this age group. This is due to the fact that younger children are more prone to otitis media related to the immaturity of their immune status, the shorter and horizontal nature of Eustachian tubes, frequent exposure to upper respiratory tract infections and malnutrition [11, 21, 22].

The overall culture positivity rate of bacterial isolates from children with otitis media in the present study was 48.5%; which is lower than other studies conducted in Nigeria 91% [23], 80.7% in Pakistan [24] and previous studies conducted in Ethiopia such as in Dessie 81.25% [7] and Gondar 87.93% [25]. This lower isolation rate could be due to high antimicrobial usage history in the area which is 66.8% which will increase the difficulty of isolating fastidious organisms like H. influenzae, M. catarrhalis and S. pneumoniae. In addition, anaerobic isolates and fungal isolates were not cultured due to lack appropriate laboratory facility.

Isolate ratio for gram positive to gram-negative bacteria in the present study was 1.27:1, which is agreement with studies from Yemen, Poland and Ethiopia, [26‐28] and in contrast to previous studies that have been conducted in Ethiopia [7, 17] and Nigeria [20, 23, 29] indicating more gram-negative isolates. In the present study, 90 (93.75%) of samples were with single bacterial isolate which is similar to the other studies conducted in Finland, Ethiopia, and Nigeria [19, 27, 30, 31].

The predominant bacterial isolates in the present study were S. aureus (15.8%) followed by P. aeruginosa (10.9%), which is similar to previous studies [23‐26, 30]. Viridians streptococcus (9.9%), S. pneumoniae (8.9%), Acenitobacter species (7.9%), P. mirabilias (7.9%) and S. pyogenes (7.9%) include other isolated pathogens in contrast with studies [14, 29, 30, 32, 33] which isolated Enterobacteriaceae, while Jido et al. [20] indicated P. aeruginosa as a major isolate. The probable explanation for this variation in dominant isolates could be the climatic and geographical difference. Unlike other study which indicates H. influenzae prevalence to be 3.9% [34], 40% [31], 16.03% [28], 11.1% [35] and 9.7% [36] there was no H. influenzae isolate in this study.

Demographic factors like gender have no significant association with otitis media which agrees to some studies [31, 37], and argues to some other studies [18, 25], but some studies [38] reported that females were more affected by ear infections. This variation could be due to the cultural differences in different communities, or bias from the smaller sample size.

There have been statistically significant differences of culture positivity in those who have experienced previous upper respiratory tract and ear infection; compared to those who have no previous infection history (p-value = 0.035, AOR = 2.011). This could be due to that fact that previous upper respiratory tract infection will disrupt the muco-ciliary mechanical defense of Eustachian tube [8, 11]. As well, there has been a significant difference of culture positivity in between children from the urban and rural area (p-value = 0.003, AOR = 4.837). This difference could be due to the difference in personal hygiene and ear cleaning habit since bacteria responsible to ear infection are environmental organisms which can be transmitted though water and soil [39]. However, caregiver’s knowledge and habit about child care and health may have an effect since it is not assessed in the current study.

In the present study, S. aureus revealed > 60% level of resistance to Amoxicillin, Chloramphenicol, and Erythromycin which is in agreement with a report from Nigeria [18, 40]. But a study by Khalil et al., 2013 [24] has shown the higher sensitivity of S. aureus to erythromycin. Ciprofloxacin sensitivity for S. aureus was 50% in our study, but some other studies have shown higher sensitivity (> 80%) [32, 41, 42]. S. aureus isolates were resistant to gentamycin in the current study in contrast to other studies which have observed > 80% sensitivity [26, 27, 42]. P. aeruginosa isolates were relatively susceptible (63%) to Ciprofloxacin, > 80% susceptible to Amoxicillin -Clavulanic acid, Tobramycin, Ceftazidime and Cefuroxime comparable with another study [20, 43]. However, a study in Ethiopia by Wasihun and Zemene, 2015 [35] and Pakistan by Khalil et al. [24] have shown high resistance of P. aeruginosa to Amoxicillin -Clavulanic acid. But P. aeruginosa isolates were less susceptible to Gentamycin (18%), Chloramphenicol (36.4%), Cotrimoxazole (18%) and Erythromycin (18%) which is in consistent with other studies [19, 27, 35, 36]. This result is in contrast to studies conducted in Nigeria [20], Yemen [26] and Ethiopia [27] Sensitivity to Ciprofloxacin is in concordance with reports by Nia et al., Agrawal et al., and Suhail et al.

Generally, the majority of the isolates were susceptible to Amoxicillin- Clavulanic acid, Cefuroxime, Tobramycin, Cefotaxime, and Ceftazidime have been found to be active antibiotics on the majority of isolates. The high sensitivity to those drugs has also been reported by some other authors [44]. A study conducted by Suhail et al. [42] showed the higher activity of cotrimoxazole for isolates. High level of resistance to Amoxicillin, Erythromycin, cotrimoxazole, and Chloramphenicol were observed which is comparable with results from Ethiopia [35], Nigeria [23] and Iraq [36]. However high sensitivity to Gentamicin was reported from findings in Gondar, Ethiopia [27, 45], Brazil [46] and Pakistan [47]; unlike in the present study which was 19.8%. This declined trend of sensitivity for these drugs could be due to a number of factors including inappropriate dose, sales without prescription, injudicious use [48] and developing enzymatic resistance.

This report showed that monomicrobial infection especially by Enterobacteriaceae, Streptococcus species, S. aureus and P. aeruginosa are responsible for otitis media in < 5 children. Majority of the isolates showed antimicrobial drug resistance to commonly prescribed agents.