Chronic suppurative otitis media (CSOM) is a persistent inflammation of the middle ear cleft (Eustachian tube, middle ear, and mastoid cavity) characterised by recurrent ear discharge or otorrhea through a tympanic perforation lasting two weeks or longer.[1] 

CSOM typically manifests within the initial six years of a child's life, peaking at approximately two years of age.[2 ]The World Health Organisation estimates that approximately 330 million individuals worldwide are affected by chronic suppurative otitis media (CSOM).According to WHO, a prevalence rate of 1–2% for CSOM is deemed low, while a rate of 3–6% is regarded as high. India has a prevalence rate exceeding 4%, necessitating urgent attention to address a significant public health issue.[1]

Chronic suppurative otitis media (CSOM) is characterised by a perforation of the tympanic membrane accompanied by continuous purulent discharge from the middle ear for a duration of at least two weeks.[1]It is a significant cause of acquired hearing loss of varying severity, predominantly in developing nations.[2]Chronic suppurative otitis media is prevalent among infants and children from lower socioeconomic backgrounds, resulting in hearing loss, impairing speech and language development, and adversely affecting academic performance and social interactions.[3]

Environmental factors have been identified as risk factors, with higher prevalence observed in lower socioeconomic groups. A cohort study involving 12,000 children identified significant factors associated with draining ears: general health scores, maternal smoking, and nursery attendance.[4 ]Other factors linked to CSOM include Eustachian tube dysfunction, which is more prevalent in patients with CSOM than in the general population.[5]Craniofacial abnormalities correlate with an elevated risk of chronic suppurative otitis media (CSOM). The prevalence of cleft palate among patients is approximately 20%, with 2% of these individuals exhibiting cholesteatoma.[6 ]The tensor veli palatini muscle is underdeveloped in children with cleft palate, potentially leading to Eustachian tube dysfunction.[7]

The global burden of illness from chronic suppurative otitis media (CSOM) is estimated to affect approximately 63-330 million individuals with otorrhea, 60% of whom (39-200 million) experience substantial hearing loss. It results in 28,000 fatalities and a disease burden exceeding 2 million Disability Adjusted Life Years (DALYs). More than 90% of the burden is shouldered by developing nations in Southeast Asia, the Western Pacific, and Africa.

Common pathogens enter the middle ear via insufflation of respiratory pathogens through the Eustachian tube from the nasopharynx and propagate from the external ear canal inward through a perforated tympanic membrane.[8,9] Research on microbiologic diagnoses of chronic suppurative otitis media (CSOM) varies based on patient age, geographic location, and the occurrence of complications like cholesteatoma, which likely contributes to the discrepancies in reported pathogens. A segment of the variability noted may be attributed to discrepancies in sampling and processing techniques.[8,10]

Aerobes, anaerobes, and fungi are all possible pathogens in chronic suppurative otitis media (CSOM). The understanding of the actual prevalence of polymicrobial infections, especially regarding anaerobic participation, is constrained by variations in collection and culture methodologies.In chronic suppurative otitis media (CSOM), bacteria may be aerobic (e.g., Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus, Streptococcus pyogenes, Proteus mirabilis, Klebsiella species) or anaerobic (e.g., Bacteroides, Peptostreptococcus, Propionibacterium).[11-13 ]These bacteria are rarely present on the skin of the external ear canal but may proliferate in conditions of trauma, inflammation, lacerations, or elevated humidity.

These bacteria may subsequently infiltrate the middle ear via a chronic perforation. [14,15]Pseudomonas is the most frequently isolated organism in chronic suppurative otitis media (CSOM). Numerous researchers in recent decades have identified Pseudomonas in 48 to 98% of patients with chronic suppurative otitis media (CSOM), although other studies indicate that Staphylococcus aureus is the predominant pathogen, particularly in the presence of cholesteatoma. [16,17,18] Fungi, specifically Aspergillus and Candida species, although infrequent, are documented as pathogens.[19].

The prospective study was conducted at a tertiary care hospital over a one-year period, during which clinically diagnosed cases of chronic suppurative otitis media (CSOM) were included.Pus specimens from both outpatient and inpatient departments were incorporated.A comprehensive history was collected from each patient in accordance with the case proforma.

Sample collection - Ear discharge is obtained from clinically diagnosed chronic suppurative otitis media (CSOM) patients using sterile cotton wool swabs under aseptic conditions, facilitated by an aural speculum, before the application of any topical medication. Swabs are subsequently conveyed to the laboratory. The urine specimen must be transported to the laboratory immediately for processing. In the event of a delay, samples must be stored in a refrigerator at 4°C.

Identification assessments

Specimen processing

The following procedures were conducted:

• Gramme staining
• Culture
• Identification of pathogenic organisms Screening Test
• Gramme Staining - The swab containing ear discharge was applied to a glass slide, covering an area of approximately 1 cm².The smear was subjected to Gramme staining.The presence of one or more bacteria per oil immersion field indicates a significant pathogen.[20]

CULTURE
Pus samples were inoculated onto blood agar (BA) and MacConkey agar (MA) using the direct streak method. The plates were incubated for twelve hours at 37˚C.The unadulterated proliferation of isolated colonies was regarded as significant pathogens.The growth of two potential organisms is deemed significant and has been processed.[21]

Pathogen identifications The subsequent tests were conducted in accordance with established protocols. 22

• Gramme staining
• Assessment of motility utilising the hanging drop preparation technique
• For Gram-negative bacilli - Catalase assay - Oxidase assay - Sugar fermentation assay (Utilising Triple Sugar Iron agar) - Citrate utilisation test - Urease production test - Indole test
• For Gram-positive cocci

Catalase Test

Positive: Staphylococcus species 

Negative: Streptococcus species

Further Tests for Differentiation: 

Positive Catalase (Staphylococcus): 

  Slide Coagulase Test

  Tube Coagulase Test

  Oxidation Fermentation Test

Negative Catalase (Streptococcus): 

  Bile Solubility Test

  Bacitracin Susceptibility Test

  Optochin Susceptibility Test

The pathogens were identified using standard microbiological techniques by examining their colony characteristics, morphology, and biochemical reactions.
Colony characteristics such as size, shape, elevation, margins, surface, opacity, consistency, alterations in the medium, and pigment production were examined.[23]

• 
  Morphology: A segment of the colony was emulsified in a small drop of saline on a glass slide.Upon drying the smear, it was fixed by passing the slide through the Bunsen burner flame 4-5 times.The fixed smear underwent Gramme staining.[24]The smear was coated with crystal violet and permitted to remain undried on the surface for one minute.After rinsing the slide with water, it was immersed in Gram's iodine for 20 seconds, followed by a rinse with water.The smear was decolorised with acetone until no violet hue was eluted.The smear is counterstained with safranin for 30 seconds, after which the slide is washed and gently blotted dry.Gramme reaction, size, shape, arrangement, and pleomorphism were documented.[24]

Biochemical reactions: Various biochemical reactions, including catalase, oxidase, coagulase, carbohydrate fermentation (lactose, glucose, mannitol, sucrose), indole, methyl red, citrate utilisation, urease production, and H2S production tests, were conducted according to standard procedures.Appropriate positive and negative controls were utilised for all biochemical tests.

Table 1 Gender Distribution of Patients

In the study of 61 patients, there were 35 males (57.38%) and 26 females (42.62%). This distribution indicates a slightly higher proportion of male patients compared to females in the sample, accounting for just over half of the total patient population.

Table 2: Culture Results with Significant and Insignificant/No Growth

Out of 61 total samples, 60 (98.36%) showed significant bacterial growth, while 1 sample (1.64%) showed either insignificant growth or no growth. This indicates a high rate of bacterial isolation from the samples, with only a small proportion yielding no growth.

Table 3: Microbial Isolates Based on Gram Staining

In the study involving 61 patients, microbial isolates were categorized based on Gram staining. The majority of isolates were Gram-negative bacteria, accounting for 48 (78.69%) of the total isolates. Gram-positive bacteria were less prevalent, with 13 (21.31%) isolates identified. This distribution highlights a predominance of Gram-negative bacteria in the sample population.

Table 4: Distribution of Sample Isolates (Morphotypes) Based on Singular or Multiple Growths

In the analysis of 61 samples, the majority demonstrated monomicrobial growth, with 57 samples (93.44%). Polymicrobial growth was observed in 3 samples (4.92%), while only 1 sample (1.64%) was sterile. This distribution indicates that monomicrobial growth is the predominant morphotype observed in the studied population.

Table 5: Distribution of Individual Clinical Isolates from Culture

In a study involving 61 patients, Klebsiella pneumonia was the most frequently isolated organism, identified in 15 cases (24.59%). Pseudomonas aeruginosa and Proteus mirabilis were equally prevalent, each appearing in 11 cases (18.03%). E. coli accounted for 10 cases (16.39%), followed by Staphylococcus aureus in 7 cases (11.48%). Less common isolates included Staphylococcus coagulase-negative spp. (5 cases, 8.20%), Acinetobacter spp. (2 cases, 3.28%), and both Enterococcus spp. and Proteus vulgaris in 1 case each (1.64%). This data underscores the diversity of microbial isolates in the patient population.

Table 6: OPD/IPD Distribution of Sample Isolates

In a study of 61 patients, significant bacterial growth was more commonly observed in samples from OPD patients, with 49 (85.25%) showing single microbial growth and 3 (83.33%) showing mixed microbial growth. In comparison, IPD samples accounted for 9 (14.75%) single growth and 1 (16.67%) mixed growth. Insignificant/no growth was observed only in OPD samples (1 case, 100%), while no such findings were recorded for IPD samples. This highlights that OPD samples had a higher rate of significant bacterial growth compared to IPD samples.

Table 7: Types and Pattern of Pus Discharge

In the study of 61 patients, 34 cases presented with continuous discharge, and 27 cases with recurrent discharge. Among continuous discharges, mucoid was the most common type (15 cases, 44.12%), followed by mucopurulent (13 cases, 38.24%), purulent (5 cases, 14.71%), and blood-stained (1 case, 2.94%). For recurrent discharges, purulent was the most frequent type (11 cases, 40.74%), followed by mucoid (10 cases, 37.04%) and mucopurulent (6 cases, 22.22%). No recurrent discharges were blood-stained.

Table 8: Location of Tympanic Membrane Perforation

In the study of 61 patients, tympanic membrane perforations were most commonly located centrally, with 28 cases (45.90%). Marginal perforations were observed in 14 cases (22.95%), while subtotal perforations accounted for 13 cases (21.31%). Attic perforations were less common, with 5 cases (8.20%), and only 1 case (1.64%) had a total perforation. This distribution highlights the central location as the predominant site of tympanic membrane perforation.

Table 9: Association Between Age & COM-Causing Microorganisms

In the study of 61 patients, Klebsiella pneumoniae was the most frequently isolated bacterium, with the highest prevalence observed in the age group 11-20 (4 cases). Pseudomonas aeruginosa was the second most common, predominantly isolated from the 11-20 and 31-40 age groups. Proteus mirabilis was also prevalent, with notable cases in the 11-20 age group. Other bacterial species such as E. coli, Staphylococcus aureus, and Staphylococcus coagulase-negative spp. were also represented in various age groups, with fewer cases in older age groups. This distribution emphasizes the diverse range of bacteria found across different age groups in clinically suspected cases of COM.

Table 10: Seasonal Variation Found in Isolates

The seasonal distribution of microbial isolates across 61 patients reveals variations in bacterial prevalence throughout the year. In March, Pseudomonas aeruginosa was the most common isolate, while in April, E. coli and Staphylococcus coagulase-negative spp. were more prominent. Klebsiella pneumoniae was most frequently isolated in August, and Proteus mirabilis peaked in July. In contrast, November and December saw fewer bacterial isolations, with only a few species detected, notably E. coli and Staphylococcus aureus. This suggests that certain bacterial species show seasonal fluctuations in their prevalence in patients with CSOM.

Out of 61 patients with clinical evidence of CSOM attending the ENT Clinic, the distribution of CSOM cases by age group was as follows: 14 patients (22.95%) were below 10 years of age, 17 patients (27.87%) were aged 11-20 years, 11 patients (18.03%) were aged 21-30 years, 9 patients (14.75%) were aged 31-40 years, and 11 patients (18.03%) were aged 40 years and above. This age distribution pattern is consistent with findings in studies conducted by other authors【25,26】.

This observation can be attributed to several factors, including the shorter, narrower, and more horizontal eustachian tube in children, as well as the higher incidence of upper respiratory tract infections in this age group.[4 ]Nevertheless, these results contrast with another study that indicated a higher prevalence of the disease in the 31-40 age group.

Out of 61 pus samples, significant growth was observed in 60 samples (98.36%), while 1 sample (1.64%) showed either insignificant or no growth . It is commonly observed that aerobic gram-negative rods outnumber gram-positive cocci in CSOM, as reported by some authors【27】. This trend is reflected in the present study, where gram-negative rods accounted for 47 samples (77.05%) and gram-positive cocci for 14 samples (22.95%).

Analysis of the 61 specimens collected revealed that pure culture growth was obtained in 57 specimens (93.44%), mixed culture growth was found in 3 specimens (4.92%), and no growth was observed in 1 specimen (1.64%) .Figures reported by other authors vary significantly, where pure cultures were isolated in more patients than mixed cultures【28】. The proportion of different organisms isolated also varies across studies. In this study, the most common bacteria isolated as the cause of CSOM were aerobic bacteria: Klebsiella pneumoniae (14 cases, 24.16%), Pseudomonas aeruginosa (11 cases, 17.50%), and Proteus mirabilis (10 cases, 17.50%).

A study conducted in rural Malawi in 1998 revealed that Proteus mirabilis was the predominant aerobic bacterium. [27]The results from the rural context were analogous to those observed in this study conducted in an urban setting of Malawi regarding microorganisms responsible for CSOM. A comparative study conducted in a rural region of Kenya revealed that Proteus mirabilis was the predominant isolate, a finding consistent with urban areas in Congo and Ethiopia. [29, 30] In contrast to this study, other research has identified Pseudomonas aeruginosa as the predominant pathogen responsible for chronic suppurative otitis media (CSOM).[31, 32, 33 ]This may be ascribed to the influence of climate and the variation of organisms across diverse communities, localities, and study sites, whether hospital-based or community-based. In this study, E. coli was isolated in 19 specimens (15.83%), while Klebsiella species were found in 29 specimens (24.16%), consistent with findings reported by various authors in the literature. The increased isolation of faecal bacteria such as E. coli and Klebsiella species suggests that individuals face a heightened risk of infection attributable to inadequate hygiene practices. Certain studies have indicated anaerobic isolation rates ranging from 20% to 50%.[34,35]

A substantial correlation existed between chronic suppurative otitis media (CSOM) and the presence of microorganisms, as well as the volume of pus drainage, onset pattern, otalgia, auditory impairment, site of tympanic membrane perforation, and mucosal appearance, in contrast to a study indicating that bacteriological findings had no significant impact on symptoms and signs. [36] In a study involving 61 patients, Klebsiella pneumonia was the most frequently isolated organism, identified in 15 cases (24.59%). Pseudomonas aeruginosa and Proteus mirabilis were equally prevalent, each appearing in 11 cases (18.03%). E. coli accounted for 10 cases (16.39%), followed by Staphylococcus aureus in 7 cases (11.48%). Less common isolates included Staphylococcus coagulase-negative spp. (5 cases, 8.20%), Acinetobacter spp. (2 cases, 3.28%), and both Enterococcus spp. and Proteus vulgaris in 1 case each (1.64%). This data underscores the diversity of microbial isolates in the patient population. The identification of Proteus mirabilis as the predominant isolate aligns with the results reported by Chirwa in 2014 in Malawi, where it constituted 28.6%, by Aduba et al. in 2010 in Garissa (Kenya), where it represented 32.7%, and by Muluye et al. in 2013 in Ethiopia, where it comprised 27.5%.Thirty These findings differ from those of other studies, which identified Pseudomonas aeruginosa as the most prevalent isolate. The variation in microbiological isolates may be attributed to differences in geographical conditions and population dynamics.[39]

The dominant microbiological isolate in this study was Klebsiella pneumoniae (14 cases, 24.16%), a gram-negative aerobe. This was followed by Proteus mirabilis (11 cases, 17.50%) and Pseudomonas aeruginosa (11 cases, 18.33%), both gram-negative aerobes. In terms of gender distribution, male patients (35, 56.66%) were more affected than females (26, 43.33%). The finding of Proteus mirabilis as the mostcommon isolate is similar to findings by Chirwa in 2014 in Malawi where Proteus mirabilis accounted for 28.6%,³⁷ Adubaet al in 2010inGarissa (Kenya) where Proteus mirabilis accounted for 32.7%,²⁹and Muluye et alin 2013 in Ethiopiawere Proteus mirabilis accounted for 27.5%.^[30]

These findingsare different from those of other studies where they found thatpseudomonas aeruginosa was the most common isolate.[^38]The difference in the pattern of microbiological isolates may be explained by differences in the geographical conditions and population dynamics.[³⁹]The bacteriological profile is to some extent dependent on the seasonal variations[table 13/graph 12]. 

A month wise data have been arranged according to the number of isolations. This projects that there is considerable aggregation of case in the months of July to September. 82.75% cases of klebsiella pneumoniae cases and 76.19% of cases belonging to Proteus mirabilis have occurred during monsoon and in post monsoon periods. This needs further study to delineate the relationship of humidity, temperature and effect of bacteriological load in the cases of chronic suppurative otitis media.The similer study was done by P.K Maji et al.[^40][P.K Maji T.K. Chatterjee S. Chatterjee J. Chakrabarty B.B. Mukhopadhyay Ab Indian J. Otolaryngol. Head Neck Surg. 128 (April-June 2007)[ ^42-46]

The variation in microbiological isolates may be attributed to geographical conditions and population dynamics. Proteus species are extensively found in environments with inadequate sanitation, including faeces, decaying meat, and sewage.[41]

This high frequency of Klebsiella pneumoniae could be attributed to the fact that the majority of patients (60.66%) in this study resided in peri-urban areas, which are often associated with poor sanitary conditions. Furthermore, most of the patients in this study were from the Hindu religion (66.39%), followed by Muslims ( 26.22%).

He findings of this study underscore the significance of bacterial pathogens, particularly Gram-negative organisms, in the etiology of CSOM. The high rates of significant growth, predominantly from Klebsiella pneumoniae and Pseudomonas aeruginosa, emphasize the critical role of bacterial infections in the chronicity and severity of the disease. Early and appropriate microbiological diagnosis, coupled with targeted treatment, is essential for reducing the burden of CSOM and preventing complications such as hearing loss, which can have a profound impact on the quality of life, especially in children.

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