Otitis media (OM), an infection or inflammation of the middle ear, represents a significant public health concern globally, particularly in developing nations [1,2]. It is among the most frequent pediatric illnesses, contributing substantially to healthcare utilization, caregiver burden, and direct treatment costs. Although OM can affect individuals of all ages, its highest prevalence and clinical impact are observed in children. The condition is a leading cause of medical visits and antibiotic prescriptions among pediatric populations, resulting in numerous follow-up appointments and, in severe cases, surgical interventions [3-6]. The clinical spectrum of otitis media encompasses several subtypes, including acute otitis media (AOM), otitis media with effusion (OME), chronic otitis media (COM), and recurrent acute otitis media (RAOM). Otitis media with effusion, characterized by middle ear effusion (MEE) in the absence of acute symptoms, is particularly concerning as it occurs in approximately 10% of children following     AOM     and   can    lead  to  long-term   hearing impairment, delays in speech and language development, and social integration difficulties [7-10]. Inadequate treatment of OM—whether due to misdiagnosis, insufficient access to diagnostic tools such as otoscopy, or inappropriate antibiotic use—can result in persistent effusion, tympanic membrane perforation, chronic infection, or serious complications such as intracranial abscess and sepsis [11-16]. External otitis (otitis externa), though affecting a different anatomical site, also poses a risk, particularly in patients with comorbidities such as eczema or diabetes mellitus. Differentiating between otitis media and externa is essential to avoid mismanagement and associated morbidity [17,18,19]. A major challenge in the management of OM lies in the variability of its etiology. The disease is typically multifactorial, often following an upper respiratory tract infection. Viruses and bacteria both play significant roles, with viral agents present in the middle ear fluid in 5% to 25% of AOM cases and bacterial pathogens identified in 40% to 70% of cases. Common bacterial agents, including Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis, often colonize the nasopharynx before ascending to the middle ear via the Eustachian tube. The overlapping clinical manifestations of viral and bacterial OM complicate diagnosis and treatment, and the increasing resistance to commonly prescribed antibiotics further exacerbates this challenge [20-25]. In developing settings, such as Iraq, the burden of OM is magnified by resource constraints. Many healthcare facilities lack basic diagnostic tools, and empirical antibiotic use is common due to the absence of culture-based guidance. This situation contributes to inappropriate treatment regimens, antimicrobial resistance, and poor clinical outcomes. Moreover, there is limited regional data on the microbiological profiles of OM and their antibiotic susceptibility patterns, making it difficult to establish effective treatment protocols tailored to local epidemiology [26-30]. Therefore, the current study was undertaken to isolate and identify the predominant bacterial pathogens responsible for OM in patients presenting to healthcare facilities in the Kirkuk Governorate, Iraq. Additionally, the study aimed to evaluate the antimicrobial susceptibility of these isolates to commonly prescribed antibiotics, providing critical insights to improve clinical management and antimicrobial stewardship in the region.

This descriptive cross-sectional study was conducted in Kirkuk city, Iraq, from February 1, 2024, to the end of November 2024. The study involved 90 patients clinically diagnosed with otitis media (OM) at outpatient clinics affiliated with the Kirkuk Health Directorate. Diagnosis was made by ear, nose, and throat (ENT) specialists based on patient history, clinical examination, and otoscopic evaluation.

Inclusion criteria were:

• Patients of either gender aged 14 to 50 years

• Clinical diagnosis of OM with otorrhea (ear discharge)

• No history of antibiotic usage within 7 days prior to sample collection

Patients who had received recent antibiotics or had other concurrent otologic pathologies were excluded.

Clinical and Laboratory Evaluation: A structured form was used to document each patient’s clinical features including ear pain, ear discharge, hearing loss, fever, tinnitus, and dizziness. Patients were also evaluated for disease laterality (unilateral or bilateral) and duration, classifying OM as acute (<3 weeks), subacute (3–12 weeks), or chronic (>12 weeks).

Sample Collection and Microbiological Analysis: Ear discharge was collected under aseptic conditions. The external auditory canal was first cleansed using sterile saline. A sterile cotton swab was then used to collect samples from the infected site. Swabs were immediately inoculated onto the following media:

• Blood agar and MacConkey agar (for aerobic bacteria)

• Mannitol salt agar (for Gram-positive cocci)

All plates were incubated at 37°C for 24–48 hours. Bacterial colonies were initially assessed by colony morphology, hemolysis, and pigmentation.

Bacterial Identification

Presumptive identification was based on standard microbiological techniques including: Gram staining, Catalase, oxidase, indole, and urease tests. Triple sugar iron (TSI) reactions and Motility and hemolysis patterns.

Further confirmation was performed for selected isolates using the VITEK 2 Compact system (bioMérieux, France), which provides automated identification based on biochemical profiles.

Antimicrobial susceptibility of bacterial isolates was determined using the Kirby-Bauer disc diffusion method. For most isolates, Mueller-Hinton agar was used, while blood agar was employed for Streptococcus pneumoniae. The procedure followed Clinical and Laboratory Standards Institute (CLSI) and European Committee on Antimicrobial Susceptibility Testing (EUCAST) guidelines.

The following antibiotic discs (Oxoid, UK) were tested, Levofloxacin (5 µg), Ceftriaxone (30 µg), Amoxicillin-Clavulanic Acid (30 µg), Ciprofloxacin (5 µg), Gentamicin (10 µg), and Cefotaxime (30 µg). After incubation at 37°C for 18–24 hours, the zones of inhibition around each disc were measured in millimeters and interpreted as sensitive, intermediate, or resistant according to CLSI and EUCAST breakpoints [31].

Biochemical Analysis

Venous blood samples were collected and analyzed to evaluate systemic inflammation and infection. The following parameters were measured using automated analyzers [32,33]:

• White blood cell (WBC) count

• C-reactive protein (CRP)

• Erythrocyte sedimentation rate (ESR)

• Body temperature

• Hemoglobin concentration

• Serum glucose

• Neutrophil and lymphocyte differentials

Statistical Analysis

Data collected from patient records, clinical evaluations, and laboratory tests were entered into Microsoft Excel and analyzed using SPSS version 26.0 (Statistical Package for the Social Sciences, IBM Corp., Armonk, NY, USA). Descriptive statistics were used to summarize demographic variables, clinical symptoms, bacterial isolates, and antibiotic susceptibility patterns. Categorical variables, such as age groups, presence of symptoms, and bacterial species, were presented as frequencies and percentages. Continuous variables, including white blood cell count, C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), and body temperature, were expressed as mean±standard deviation (SD). Associations between bacterial isolates and clinical variables (e.g., symptom presentation, chronicity, and type of OM) were assessed using the Chi-square (χ²) test. A p-value < 0.05 was considered statistically significant.

Antibiotic susceptibility patterns were interpreted using zone of inhibition measurements according to CLSI and EUCAST standards, and results were tabulated to determine resistance and sensitivity frequencies [34,35].

A total of 90 patients diagnosed with otitis media (OM) at outpatient clinics in Kirkuk city were included in this study. Patients' ages ranged from 14 to 50 years. The largest age group was 14–22 years, comprising 30 patients (33.3%). The 22–26 years group included 18 patients (20%), followed by 26–30 years with 15 patients (16.7%), 30–35 years with 12 patients (13.3%), 35–40 years with 10 patients (11.1%), and the least represented was 40–50 years, with 5 patients (5.6%). Table 1.

Table 1. Age distribution of study population

Among the 90 samples, Streptococcus pneumoniae was the most frequently isolated pathogen, accounting for 25 cases (27.78%), followed by Pseudomonas aeruginosa with 20 isolates (22.22%), indicating their significant role in OM pathogenesis. Klebsiella pneumoniae (13.33%) and Staphylococcus aureus (11.11%) were also notable contributors. Meanwhile, Escherichia coli and Haemophilus influenzae comprised 10% and 8.89% of isolates, respectively, highlighting their involvement in a subset of infections. Staphylococcus epidermidis was the least commonly identified organism (6.67%), yet still relevant as a potential opportunistic pathogen. Table 2.

Table 2: Bacterial isolates from patients with OM

Streptococcus pneumoniae showed the highest sensitivity across all tested antibiotics, particularly to ceftriaxone (26.67%), levofloxacin (25.56%), and ciprofloxacin (24.44%), indicating that fluoroquinolones and third-generation cephalosporins may remain effective options. In contrast, Pseudomonas aeruginosa exhibited lower sensitivity overall, with gentamicin (16.67%) and ciprofloxacin (11.11%) being the most effective, while it showed complete resistance to amoxicillin-clavulanic acid. Klebsiella pneumoniae displayed moderate sensitivity to ciprofloxacin (12.22%) and levofloxacin (12.22%), but was less responsive to  beta-lactams. Staphylococcus aureus had relatively uniform but low sensitivity, with ceftriaxone and gentamicin (10.00%) being the most effective. Escherichia coli showed the highest sensitivity to ciprofloxacin (8.89%) and levofloxacin (10.00%), while Haemophilus influenzae had its best response to levofloxacin and ciprofloxacin (each 8.89%). Staphylococcus epidermidis demonstrated  poor sensitivity  across  all  agents   tested, with the highest being only 4.44% for ciprofloxacin. Table 3. 

Table 3: antibiotics sensitivity rate of bacteria isolated from otitis media

This table highlights the prevalence of key clinical manifestations among patients diagnosed with otitis media. The most common symptom was ear pain, affecting 75.6% of patients, followed by ear discharge in 57.8% and hearing loss in 48.9%, reflecting typical presentations of middle ear infection. Systemic symptoms such as fever were also notable, reported in 40.0% of cases, indicating an active inflammatory or infectious process. Less frequent but clinically relevant complaints included tinnitus (22.2%) and dizziness (11.1%), suggesting possible inner ear involvement or complications in a subset of patients (Table 4).

Table 4: Clinical Features Observed in OM Patients

The biochemical data reveal notable deviations from normal reference ranges, particularly in inflammatory markers. Elevated white blood cell count (11.2×10³/μL), C-reactive protein (18.5 mg/L), and erythrocyte sedimentation rate (24.3 mm/hr) indicate a significant inflammatory response in OM patients. The mean body temperature (37.8°C), slightly above the normal range, supports the clinical evidence of infection. Additional parameters, including normal serum glucose and hemoglobin levels, suggest the absence of metabolic stress or anemia in most cases. However, the high neutrophil percentage (68.3%) alongside moderate lymphocyte levels (24.5%) further supports a bacterial etiology in the majority of cases. These laboratory findings complement the clinical symptoms and provide supportive evidence for active bacterial otitis media (Table 5).

Table 5: Biochemical Parameters in OM Patients

Table 6 presents the distribution of patients based on the duration and laterality of otitis media. Acute OM was the most prevalent type, seen in 46.7% of patients, followed by subacute and chronic cases. In terms of presentation, unilateral OM was more frequent than bilateral OM, accounting for over two-thirds of cases. These findings suggest that most cases present early, although a significant proportion progress to chronicity, emphasizing the need for timely intervention.

Table 6. Duration and Type of Otitis Media

Otitis media (OM) remains a leading cause of outpatient visits worldwide and is particularly problematic in resource-constrained settings due to limited access to diagnostics, empirical antibiotic use, and inadequate follow-up. This study, conducted in Kirkuk city, provides updated insight into the epidemiology, microbial profile, clinical features, and biochemical responses among 90 patients diagnosed with OM, offering valuable comparisons to regional and global patterns. The predominance of younger individuals (14–22 years, 33.3%) among affected patients is consistent with earlier reports emphasizing the vulnerability of children and adolescents to OM. This susceptibility is attributed to anatomical and functional immaturity of the Eustachian tube, increased exposure to upper respiratory tract infections (URTIs), and underdeveloped immunity [36,37,38]. Although most literature centers on children under five, our findings indicate that OM continues to affect older pediatric and adolescent groups, particularly in settings where early childhood infections may be inadequately managed. Studies in Bangladesh and Nigeria similarly reported high rates of OM in patients up to 20 years, emphasizing that delayed healthcare access may prolong the disease burden into adolescence [39-46]. In this study, Streptococcus pneumoniae emerged as the predominant pathogen isolated from patients with otitis media (OM), accounting for 25 cases (27.78%). This finding is in strong agreement with prior research. Levy et al. [5] demonstrated that S. pneumoniae remains the leading bacterial cause of OM, even in the era of widespread pneumococcal conjugate vaccination. Similarly, Ngo et al. [12], in a systematic review, confirmed S. pneumoniae as a consistent leading pathogen in middle ear infections globally, underscoring its continued relevance in pediatric OM cases. Pseudomonas aeruginosa, the second most frequently isolated bacterium in this study (22.22%), is commonly associated with chronic suppurative otitis media (CSOM) and has been identified as a dominant pathogen in similar regional and global studies. For instance, Wasihun and Zemene [15] reported a high prevalence of P. aeruginosa in Ethiopian children with OM . A study by Chirwa et al. [17] also highlighted its frequent isolation in chronic cases in Malawi. Klebsiella pneumoniae was isolated in 13.33% of the cases, aligning with findings from Tadesse and Alem [28], who noted its involvement in OM infections in African hospital-based studies. Although not a classic otopathogen, K. pneumoniae is increasingly reported in nosocomial and recurrent OM infections, often associated with antibiotic resistance [40]. Staphylococcus aureus accounted for 11.11% of isolates in the present study [41]. This is consistent with findings by Agha and Al-Delaimi  [29] in Duhok, Iraq, who also documented a significant prevalence of S. aureus in OM cases. Brook and Frazier [43] highlighted the role of S. aureus particularly in chronic and recurrent OM, where biofilm formation plays a crucial role. Escherichia coli (10.00%) and Haemophilus influenzae (8.89%) were also notable [42]. Although E. coli is not typically considered a primary otopathogen, its presence has been reported in some studies, particularly in neonates and immunocompromised individuals. Hailegiyorgis et al. [1] found similar proportions of H. influenzae and E. coli in pediatric OM, emphasizing their opportunistic roles. Staphylococcus epidermidis was the least frequently isolated pathogen (6.67%), consistent with its status as a skin commensal and occasional contaminant [44]. However, its role as an opportunistic pathogen, particularly in immunocompromised patients or those with indwelling devices, cannot be overlooked. A study by Al-Ani [35] also documented the presence of S. epidermidis in OM cases, suggesting its potential clinical relevance in specific contexts [45]. The bacterial profile observed in this study mirrors trends documented in multiple geographical settings, reinforcing the polymicrobial and multifactorial nature of OM. As emphasized by Schilder et al. [3] and Kong and Coates [4], the diversity of bacterial agents in OM is shaped by multiple host and environmental factors, including age, vaccination status, immune response, and prior antibiotic exposure. [46] Streptococcus pneumoniae showed the highest sensitivity across all tested antibiotics, particularly to ceftriaxone (26.67%), levofloxacin (25.56%), and ciprofloxacin (24.44%), indicating that fluoroquinolones and third-generation cephalosporins may remain effective options [47]. This aligns with previous findings by Zielnik-Jurkiewicz and Bielicka [48], who reported relatively high susceptibility of S. pneumoniae to fluoroquinolones and cephalosporins, even in cases of treatment failure. Similarly, Sih et al. [49] documented good activity of ceftriaxone and levofloxacin against S. pneumoniae in Brazilian pediatric patients [50]. In contrast, Pseudomonas aeruginosa exhibited lower sensitivity overall, with gentamicin (16.67%) and ciprofloxacin (11.11%) being the most effective, while it showed complete resistance to amoxicillin-clavulanic acid [51]. This finding is consistent with studies by Wasihun and Zemene [15] and Chirwa et al. [17], both of which observed significant resistance of P. aeruginosa to beta-lactams and noted aminoglycosides and fluoroquinolones as remaining treatment options [52]. Klebsiella pneumoniae displayed moderate sensitivity to ciprofloxacin and levofloxacin (each 12.22%) but was less responsive to beta-lactams, which is in agreement with findings by Agha and Al-Delaimi [29] and Tesfa et al. [53], who reported increasing resistance of K. pneumoniae to cephalosporins due to extended-spectrum beta-lactamase (ESBL) production. Staphylococcus aureus showed relatively uniform but low sensitivity, with ceftriaxone and gentamicin (10.00%) being the most effective. [54] Similar patterns have been reported in Nigerian and Iraqi studies (29, 46), where S. aureus isolates exhibited varying resistance profiles, including emerging methicillin-resistant strains (MRSA), contributing to the diminished efficacy of standard agents. Escherichia coli showed the highest sensitivity to ciprofloxacin (8.89%) and levofloxacin (10.00%), consistent with global observations of increasing resistance to beta-lactams and moderate responsiveness to fluoroquinolones [15, 53]. Haemophilus influenzae had its best response to levofloxacin and ciprofloxacin (each 8.89%), supporting data from Ngo et al. [12], who noted similar antimicrobial activity against H. influenzae strains. Finally, Staphylococcus epidermidis demonstrated poor sensitivity across all agents tested, with the highest being only 4.44% for ciprofloxacin. This is aligned with reports that coagulase-negative staphylococci often exhibit multidrug resistance, especially in hospital settings and immunocompromised hosts [35, 43]. Clinically, ear pain (75.6%), discharge (57.8%), and hearing loss (48.9%) were the most common symptoms, consistent with classical OM manifestations [1-3,6]. Notably, 40% of patients also presented with fever, supporting the systemic nature of the infection in many cases. A smaller proportion experienced tinnitus (22.2%) and dizziness (11.1%), symptoms which may suggest inner ear involvement or early complications, necessitating more extensive evaluation, such as audiometry or imaging, in selected cases [25]. Biochemically, elevated WBC count, CRP, and ESR levels further confirmed the active inflammatory nature of OM. The neutrophil predominance (68.3%) supports the bacterial etiology, while stable glucose and hemoglobin values suggest the absence of systemic decompensation or metabolic stress. These findings are comparable to reports from pediatric OM cohorts in Ethiopia and Egypt, which similarly noted neutrophilic responses and raised CRP as predictors of bacterial infection [15,28,30]. Furthermore, temperature elevation (mean 37.8°C) in more than half the patients underscores the systemic impact of OM, which is often underestimated in clinical management. The distribution of disease duration showed that 46.7% had acute OM, while 24.4% had progressed to chronic OM. The bilateral involvement in 32.2% of cases indicates a moderate burden of more advanced disease, potentially due to delayed diagnosis or inadequate initial treatment. These findings suggest that although OM frequently presents acutely, a significant portion of patients may evolve into chronicity, especially in low-resource settings. This pattern supports the need for strengthened follow-up protocols and better health education to encourage early presentation. The rise in antibiotic resistance in OM pathogens, particularly in outpatient settings, represents a critical challenge for public health. As confirmed in this study and others [42,55,56], inappropriate use of antibiotics is the primary driver of this trend. The universal effectiveness of amoxicillin-clavulanate in this study must be cautiously interpreted; widespread empirical use without stewardship may erode its efficacy over time [57]. Continued education of physicians, improved patient compliance, and structured stewardship programs are essential to curb this trajectory [58,59].

This study highlights the bacterial spectrum and resistance trends in OM patients, underscoring the importance of local microbiological surveillance and targeted antibiotic therapy to improve patient outcomes and guide antimicrobial stewardship efforts in Iraq Finally, this study underscores the importance of integrating microbiological analysis into routine ENT practices. While otoscopy and symptom assessment remain the mainstay of diagnosis, laboratory-guided treatment is vital for cases that do not resolve with empirical therapy or that show signs of progression. Cost-effective diagnostic pathways incorporating basic microbiological tests can significantly improve patient outcomes and reduce chronic sequelae.

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