BACTERIOLOGICAL PROFILE AND ANTIBIOTIC SUSCEPTIBILITY IN COMMUNITY ACQUIRED AND HOSPITAL ACQUIRED CHRONIC SUPPURATIVE OTITIS MEDIA (CSOM) PATIENTS: A CROSS-SECTIONAL STUDY AT A TERTIARY CARE CENTRE

A persistent inflammatory disease of the middle ear and mastoid cavity, chronic suppurative otitis media (CSOM) is characterised by persistent otorrhea through a tympanic membrane that is not intact.^[1]In underdeveloped nations the prevalence of CSOM is much higher because of poor cleanliness, congestion and restricted access to healthcare^[1,2]. The WHO reports that the prevalence of CSOM in India is 7.8%, with rural areas being disproportionately impacted^[3].Significant morbidity, such as delayed speech development, intracranial problems, and conductive and mixed hearing loss, is linked to CSOM^[4,5]. Pseudomonas aeruginosa, Staphylococcus aureus, Proteus species, Klebsiella species, and Escherichia coli are among the bacteria linked to CSOM, albeit their regional distribution varies^[6]. Treatment problems are posed by the rise of multidrug-resistant pathogens, including MRSA and resistant Pseudomonas^[7].Resistance trends have advanced due to the abuse of antibiotics and the absence of culture-based therapy. Therefore, optimising empirical treatment and avoiding consequences need ongoing local surveillance of microbial aetiology and antibiotic susceptibility^[8,9].This study aims to determine the bacteriological profile and antimicrobial susceptibility pattern of isolates from chronic suppurative otitis media (CSOM) patientsand to compare the culture positivity rates between Communityacquired and Hospitalacquired CSOM cases to evaluate the statistical significance of this association.

A cross-sectional study was conducted in the Department of Microbiology, Central Laboratory, School of Medical Sciences and Research, Sharda Hospital, Greater Noida, India, over a period of 12 months. A total of 115 ear discharge samples were collected from clinically diagnosed chronic suppurative otitis media (CSOM) patients attending inpatient and outpatient departments.Ear discharge samples were collected aseptically using sterile swabs. Two swabs were obtained from each patient: one for direct Gram staining and one for culture and antimicrobial susceptibility testing. Samples were inoculated onto 5% Sheep Blood Agar, MacConkey Agar, and Nutrient Agar and incubated aerobically at 37°C for 18 to 24 hours. Bacterial isolates were identified based on colony morphology, Gram staining, motility testing, and standard biochemical tests.Isolates that could not be conclusively identified using conventional methods were further identified using the automated identification system (VITEK® 2Compact). Antimicrobial susceptibility testing was performed using the Kirby–Bauer disc diffusion method on Mueller–Hinton agar, and results were interpreted according to Clinical and Laboratory Standards Institute (CLSI) 2024 guidelines. As all data were obtained from the hospital Laboratory Information System (LIS) ,individual patient consent was not required for this study.

Statistical Analysis and Calculation of p-value

Data were entered into Microsoft Excel and analysed using SPSS version 23.0. Categorical variables were expressed as frequencies and percentages. To assess the association between patient setting and culture positivity, CSOM cases were categorized as community acquired (OPD) and hospital acquired (IPD). A 2×2 contingency table was constructed comparing positive and negative culture results in both groups. The chi-square (χ²) test was applied to evaluate statistical significance. The calculated chi-square value was 17.23 with 1 degree of freedom, yielding a p-value <0.001. A p-value <0.05 was considered statistically significant.

(B)

Chronic suppurative otitis media (CSOM) continues to represent a major public health challenge in developing countries, including India, where delayed healthcare access, poor hygiene, and irrational antibiotic use contribute to persistent infection and escalating antimicrobial resistance. In the present study, bacterial growth was detected in 60.9% of samples, a finding comparable to earlier Indian reports by Prakash et al. and Borah et al., reaffirming the chronic infectious nature of CSOM[3,8].This study also identified a slight male predominance in both the overall study population and culture-positive cases, along with a high rate of culture positivity. Males showed a greater proportion of positive cultures than females, which may be influenced by increased exposure risks or behavioral and occupational factors. Age-wise analysis revealed that the highest number of cases and isolates occurred in the 19–45-year age group, indicating increased vulnerability among young and middle-aged adults.

A key and clinically relevant observation in this study was the significant difference in culture positivity between community-acquired (OPD) and hospital-acquired (IPD) CSOM cases. Culture positivity was markedly higher among OPD patients (74.7%) than IPD patients (35.0%), and this association was statistically highly significant (χ² = 17.23, p < 0.001). This suggests that patients presenting from the community are more likely to harbour active, untreated infections, whereas hospitalized patients may have received prior antimicrobial therapy, leading to reduced bacterial recovery. The strong statistical significance confirms that this difference is unlikely to be incidental and highlights the importance of early microbiological evaluation and culture-guided therapy, particularly in outpatient settings. Of the 70 culture-positive isolates, 14 (20.0%) were from IPD and 56 (80.0%) from OPD patients. Pseudomonas aeruginosa was the predominant isolate in both groups, highlighting its central role in CSOM regardless of clinical setting. Its prevalence is likely due to its ability to thrive in moist environments, form biofilms, and exhibit intrinsic multidrug resistance, facilitating persistence despite prior therapy.

Hwang et al. reported Staphylococcus aureus as the predominant pathogen in discharging ears, with community-acquired MRSA accounting for 25.0% of S. aureus isolates and an overall prevalence of 12.2%, particularly in chronic otitis media.[12] In contrast, the present study identified Pseudomonas aeruginosa as the most common isolate in both OPD and IPD CSOM cases, irrespective of patient setting. Of the 70 culture-positive isolates, 80.0% were from OPD patients and 20.0% from IPD patients, with P. aeruginosa predominance likely related to its biofilm-forming ability, survival in moist environments, and intrinsic antimicrobial resistance. The observed differences may reflect regional variation, patient characteristics, and antibiotic exposure patterns, emphasizing the need for local microbiological surveillance to guide empirical therapy.

 Pseudomonas aeruginosa emerged as the most frequently isolated pathogen, consistent with findings from Borah et al., Prakash et al., and by Khairkaret al.[2,3,8]

An alarming finding was the very high prevalence of methicillin-resistant Staphylococcus aureus (MRSA), accounting for 70.83% of Gram-positive isolates. Inappropriate antibiotic use, incomplete treatment courses, recurrent infections, and limited access to culturebased diagnostics likely contribute to this rising burden. Adamu Abubakar et al. reported an overall MRSA prevalence of 6.5% in CSOM, with MRSA constituting 17.1% of Staphylococcus aureusisolates[13]. In contrast, the present study observed a substantially higher MRSA burden, accounting for 70.83% of Gram-positive isolates. This disparity likely reflects regional differences, recurrent disease, and patterns of antibiotic misuse, underscoring the need for routine culture-guided management of CSOM.  The presence of additional pathogens such as Klebsiella pneumoniae, Escherichia coli, Proteus spp., Citrobacterkoseri, Providencia rettgeri, and Acinetobacter spp., though less frequent, further underscores the polymicrobial nature of CSOM.

Considering the emergence of bacterial resistance and the availability of wide spectrum of newer antimicrobial agents, it is important to know the pattern of infections and the antimicrobial sensitivity of the isolates[9-11].

Antimicrobial susceptibility patterns in this study highlight the growing challenge of multidrug resistance. P. aeruginosaretained good susceptibility to carbapenems, cefepime, aztreonam, piperacillintazobactam, and amikacin, while showing increasing resistance to fluoroquinolones. This trend mirrors national reports indicating declining quinolone efficacy due to widespread misuse[14,15]. MRSA isolates demonstrated universal sensitivity to linezolid but complete resistance to penicillin and ciprofloxacin, with high resistance to macrolides, suggesting limited empirical treatment options for Gram-positive infections. These findings emphasize the diminishing effectiveness of commonly prescribed antibiotics and reinforce the necessity of routine culture-guided therapy.

Overall, the results of this study indicate that while the microbial profile of CSOM remains largely predictable, the resistance landscape has evolved considerably. The statistically significant OPD and IPD difference in culture positivity, coupled with the high prevalence of multidrug-resistant organisms, underscores the urgent need for regular microbiological surveillance, rational antibiotic prescribing, and robust antibiotic stewardship programs. Strengthening early diagnosis and ensuring access to evidence-based treatment strategies are essential to reduce CSOM-related morbidity and prevent serious complications.

This cross-sectional study provides a comprehensive overview of the bacteriological profile and antimicrobial susceptibility patterns of chronic suppurative otitis media (CSOM) among patients attending a tertiary care teaching hospital in Western Uttar Pradesh. The findings confirm that CSOM remains a significant public health concern, predominantly affecting males and individuals aged 19–45 years due to increased occupational exposure, higher levels of outdoor activity, and greater interaction with potential sources of infection. The lower number of isolates observed in older age groups could be due to limited sample representation, reduced exposure, or the early initiation of empirical therapy prior to microbiological investigation.

More than half of the clinical samples (60.9%) yielded bacterial growth, with Gram-negative bacilli predominating over Gram-positive cocci. Pseudomonas aeruginosa emerged as the principal pathogen, reaffirming its central role in the pathogenesis of CSOM. The notably high proportion of methicillin-resistant Staphylococcus aureus (MRSA) among Gram-positive isolates represents a concerning shift in resistance trends and indicates a substantial increase in community circulation of resistant staphylococcal strains.

A major strength of this study is the demonstration of a highly significant association between patient setting and culture positivity, with community-acquired CSOM cases showing a significantly higher culture yield than hospital-acquired cases (p < 0.001). This finding highlights the likelihood of delayed presentation and untreated infection at the community level and underscores the importance of early diagnosis and microbiological evaluation, particularly in outpatient settings.

The antimicrobial susceptibility patterns observed reveal a diminishing effectiveness of commonly prescribed antibiotics, especially fluoroquinolones and cephalosporins. In contrast, higher-generation agents such as meropenem, piperacillin–tazobactam, cefepime, aztreonam, and linezolid continue to demonstrate good activity against major pathogens. However, reliance on these agents must be carefully regulated, as indiscriminate use could accelerate resistance to last-line therapies.

In conclusion, although the overall microbial etiology of CSOM remains relatively predictable, the antimicrobial resistance landscape has evolved considerably, posing serious challenges to empirical treatment. Overall, the findings of this study have direct implications for both empirical therapy and antimicrobial stewardship in CSOM. The predominance of Pseudomonas aeruginosa and the high burden of MRSA indicate that empirical treatment should be guided by local resistance patterns rather than routine broad-spectrum prescribing. Early culture sampling, particularly in outpatient cases, and timely modification of therapy based on susceptibility results are essential to optimize clinical outcomes. Furthermore, judicious use of higher-generation antibiotics and avoidance of unnecessary fluoroquinolone exposure are critical to limiting the further emergence of resistance. These measures underscore the need for sustained microbiological surveillance and structured antimicrobial stewardship programs in the management of CSOM.

Limitations of this study

The study did not investigate the underlying factors or molecular mechanisms contributing to antimicrobial resistance among the isolates.

Anaerobic bacteria and fungal pathogens were not evaluated, potentially underestimating the complete microbial spectrum involved in chronic suppurative otitis media.

DECLARATIONS

Conflicts of interest: There is no any conflict of interest associated with this study

Consent to participate: There is consent to participate.

Consent for publication: There is consent for the publication of this paper.

Authors' contributions: Author equally contributed the work.

1.     Acuin J. Global burden of disease due to chronic suppurative otitis media: Disease, deafness, deaths and DALYs.In: Chronic Suppurative Otitis Media – Burden of Illness and Management Options. Geneva: World Health Organization; 2004. p. 9–23. Available from: http://www.who.int/pbd/deafness/activities/hearing_care/otitis_media.pdf

2.     Khairkar M, Deshmukh P, Maity H, Deotale V. Chronic suppurative otitis media: a comprehensive review of epidemiology, pathogenesis, microbiology, and complications. Cureus. 2023;15:e43729. doi:10.7759/cureus.43729

3.     Prakash R, Juyal D, Negi V Pal S, Adekhandi S, Sharma M, Sharma N. Microbiology of chronic suppurative otitis media in a tertiary care centre setup of Uttarakhand state, India. North Am J Med Sci. 2013;5(4):282–287. doi:10.4103/1947-2714.110436

4.     Berman S. Otitis media in developing countries. Pediatrics. 1995;96:126–131.

5.     Wiwanitkit S, Wiwanitkit V. Pyogenic brain abscess in Thailand. North Am J Med Sci. 2012;4:245–247.

6.     ⁠Sena RB, Gandham P. Antibiotic susceptibility pattern among chronic suppurative otitis media patients attending AIMSR. Natl J Integr Res Med. 2016;7:108–111.

7.     Hassan O, Adeyemi A. A study of bacterial isolates in cases of otitis media in patients attending OAUTHC, Ile-Ife. Afr J Exp Microbiol. 2007;8:130–136.

8.     Borah S, Borgohain R, Sangma R, et al. The pattern of bacterial infections among chronic suppurative otitis media cases at a tertiary care centre in North-East India. Cureus. 2024;16(5):e60371. doi:10.7759/cureus.60371

9.     Kaur P, Sood AS, Sharma S, Awal G. Microbiological profile and antimicrobial susceptibility pattern of chronic suppurative otitis media in a tertiary care centre. Trop J Path Micro. 2018;4(1):3–13. doi:10.17511/jopm.2018.i1.02

10.   https://www.ncbi.nlm.nih.gov/medgen/64530#:~:text=An%20infection%20would%20be%20classified,from%20MeSH%5D

11.   Tobin EH, Zahra F. Nosocomial Infections. [Updated 2025 Aug 2]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK559312/

12.   Hwang JH, Tsai HY, Liu TC. Community-acquired methicillin-resistant Staphylococcus aureus infections in discharging ears. Acta Otolaryngol. 2002 Dec;122(8):827-30. doi: 10.1080/0036554021000028076. PMID: 12542200.

13.   Mohammed Y. Methicillin-Resistant Staphylococcus Aureus (MRSA) Infection in Chronic Suppurative Otitis Media.

14.   Mehel DM, Turgut NF, Çeviker SA, Özdemir D, Özgür A. Effectiveness of ciprofloxacin in the treatment of Acute Otitis Media. Journal of Experimental and Clinical Medicine. 2022;39(2):365-8.

15.   Rao PS. Recent Trends in the Microbiology of Chronic Suppurative Otitis Media in a Tertiary Care Hospital, India.