Recurrent tonsillitis is a common inflammatory condition encountered in otorhinolaryngological practice, characterized by repeated episodes of sore throat, fever, odynophagia, dysphagia, and cervical lymphadenopathy.[1] It affects individuals across different age groups and contributes significantly to morbidity, repeated healthcare consultations, school and work absenteeism, and increased healthcare expenditure. Although tonsillitis may have viral or bacterial origins, bacterial pathogens are particularly important in recurrent cases because of their association with persistent infection and repeated inflammatory episodes. Patients experiencing frequent episodes despite adequate medical management may eventually require tonsillectomy [2].The bacteriological etiology of recurrent tonsillitis is diverse and involves both Gram-positive and Gram-negative microorganisms. Streptococcus pyogenes, particularly Group A beta-hemolytic Streptococcus, is a well-recognized pathogen associated with tonsillar infections. Other frequently isolated organisms include Staphylococcus aureus, Haemophilus influenzae, Streptococcus pneumoniae, Klebsiella pneumoniae, and Moraxella catarrhalis. The distribution of these microorganisms varies according to geographical location, patient characteristics, previous antibiotic exposure, and local epidemiological factors [3,4]. Furthermore, the presence of normal oropharyngeal flora and differences between tonsillar surface and core microbiota complicate the identification of clinically significant pathogens [5,6].The persistence of bacterial infections in recurrent tonsillitis may be attributed to several mechanisms, including polymicrobial colonization, intracellular bacterial survival, and biofilm formation. Biofilms provide a protective environment that enables microorganisms to evade host immune responses and exhibit reduced susceptibility to antimicrobial agents. Previous investigations have highlighted the role of Staphylococcus aureus in recurrent tonsillar infections, particularly its ability to persist within tonsillar tissues [7,8]. These mechanisms may contribute to repeated episodes despite apparently appropriate antibiotic treatment. Additionally, differences between superficial tonsillar swab cultures and deeper tonsillar tissue cultures suggest that the site of specimen collection may influence bacterial isolation and microbiological interpretation [9,10].Antibiotic therapy remains an important component of treatment for bacterial tonsillitis. However, empirical antibiotic prescribing, repeated antimicrobial exposure, and the emergence of resistant bacterial strains have complicated clinical management. Variations in susceptibility to commonly prescribed antimicrobial agents may contribute to inadequate bacterial eradication, persistent symptoms, and recurrent infections. The presence of beta-lactamase-producing organisms and other resistance mechanisms further emphasizes the importance of appropriate antimicrobial selection [11]. Bacterial culture and antibiotic susceptibility testing provide valuable information for identifying potential pathogens, determining their resistance patterns, and guiding targeted antimicrobial treatment [12,13]. Such investigations may also help minimize unnecessary antibiotic exposure and support rational antibiotic prescribing practices.Understanding the local bacteriological profile and antibiotic susceptibility patterns is essential for improving the management of recurrent tonsillitis. Regional variations in bacterial distribution and antimicrobial resistance limit the generalizability of findings from other populations, emphasizing the need for institution-specific microbiological surveillance. Identification of commonly isolated organisms and their susceptibility to routinely prescribed antibiotics may facilitate evidence-based therapeutic decisions and strengthen antimicrobial stewardship. Therefore, the present prospective observational study was designed to evaluate the bacteriological profile and antibiotic susceptibility patterns among patients with recurrent tonsillitis.

Study Design and Setting This prospective observational study was conducted over 12 months in the Department of Otorhinolaryngology at a tertiary care teaching hospital The study evaluated the bacteriological profile and antibiotic susceptibility patterns among patients with recurrent tonsillitis.A total of 140 patients diagnosed with recurrent tonsillitis were enrolled using consecutive sampling based on predefined eligibility criteria. Inclusion Criteria 1. Patients aged 5 years and above diagnosed with recurrent tonsillitis. 2. Patients with three or more episodes of tonsillitis during the preceding 12 months. 3. Patients presenting with clinical features suggestive of recurrent tonsillar infection. 4. Patients or guardians who provided written informed consent. Exclusion Criteria 1. Patients with peritonsillar abscess or deep neck space infections. 2. Patients who had received systemic antibiotics within seven days before sample collection. 3. Patients with previous tonsillectomy. 4. Patients with immunodeficiency or receiving immunosuppressive therapy. 5. Patients who declined consent. Data Collection and Clinical Assessment Demographic and clinical details, including age, sex, duration of illness, frequency of tonsillitis episodes, presenting symptoms, and previous antibiotic use, were recorded using a structured proforma. All patients underwent otorhinolaryngological examination to assess tonsillar size, congestion, exudates, crypts, and cervical lymphadenopathy. Sample Collection and Microbiological Examination Tonsillar swabs were collected aseptically from the tonsillar surface and crypts before antibiotic administration. Specimens were transported promptly to the microbiology laboratory and inoculated onto blood agar, chocolate agar, and MacConkey agar. Cultures were incubated at 35–37°C for 24–48 hours under appropriate atmospheric conditions. Bacterial isolates were identified based on colony morphology, Gram staining, and standard biochemical tests, including catalase, coagulase, oxidase, and organism-specific reactions. Antibiotic Susceptibility Testing Antibiotic susceptibility testing was performed using the Kirby–Bauer disc diffusion method on appropriate culture media. Antibiotics tested included penicillin, amoxicillin-clavulanic acid, erythromycin, azithromycin, clindamycin, cephalosporins, and ciprofloxacin, as applicable to the isolated organisms. Inhibition zones were measured and interpreted according to the Clinical and Laboratory Standards Institute (CLSI) guidelines applicable during the study period. Isolates were classified as susceptible, intermediate, or resistant using organism-specific criteria. Study Grouping and Classification Patients were categorized as culture-positive or culture-negative based on microbiological findings. Culture-positive specimens were further classified according to bacterial species and Gram-staining characteristics. Antibiotic susceptibility patterns were analyzed separately for each clinically relevant bacterial isolate. Outcome Measures Primary outcomes included the frequency and distribution of bacterial isolates and their antibiotic susceptibility patterns. Secondary outcomes included culture positivity, distribution of Gram-positive and Gram-negative organisms, antimicrobial resistance patterns, and associations with demographic and clinical characteristics. Statistical Analysis Data were analyzed using IBM SPSS Statistics version 25.0. Categorical variables were expressed as frequencies and percentages, while continuous variables were presented as mean ± standard deviation. The Chi-square test or Fisher's exact test was used for categorical comparisons, and the independent-samples t-test or appropriate nonparametric tests were applied for continuous variables. A p-value of less than 0.05 was considered statistically significant.

A total of 140 patients with recurrent tonsillitis were included in the study. The majority belonged to the 16–30 years age group (37.1%), followed by 5–15 years (27.1%) and 31–45 years (24.3%). Males constituted 54.3% and females 45.7%. Regarding the frequency of tonsillitis, 41.4% experienced 3–4 episodes annually, 35.0% had 5–6 episodes, and 23.6% reported ≥7 episodes. Sore throat was the most common clinical manifestation (94.3%), followed by tonsillar congestion (84.3%), fever (77.1%), dysphagia (68.6%), tonsillar exudates (51.4%), and cervical lymphadenopathy (45.7%) (Table 1 and Figure 1).Bacterial culture positivity was observed in 106 patients (75.7%), while 34 patients (24.3%) had negative cultures. Among culture-positive cases, Staphylococcus aureus was the predominant isolate (32.1%), followed by Streptococcus pyogenes (24.5%), Klebsiella pneumoniae (13.2%), Streptococcus pneumoniae (11.3%), Haemophilus influenzae (9.4%), Pseudomonas aeruginosa (5.7%), and Escherichia coli (3.8%). Gram-positive organisms accounted for 67.9% of isolates, whereas Gram-negative organisms constituted 32.1% (Table 2 and Figure 2).The association between demographic and clinical characteristics and bacterial culture positivity is presented in Table 3. Culture positivity showed no significant association with age (p=0.857) or sex (p=0.856). However, a significant association was observed with the frequency of tonsillitis episodes (p=0.018), with culture positivity increasing from 63.8% among patients experiencing 3–4 episodes annually to 87.9% among those with ≥7 episodes. Culture positivity was significantly higher among patients presenting with tonsillar exudates (86.1% vs 64.7%, p=0.003) and cervical lymphadenopathy (84.4% vs 68.4%, p=0.028).Antibiotic susceptibility testing of Gram-negative isolates demonstrated variable sensitivity patterns. K. pneumoniae showed the highest susceptibility to meropenem (92.9%), followed by piperacillin-tazobactam (78.6%) and ceftazidime (71.4%). H. influenzae demonstrated maximum susceptibility to ceftriaxone (90.0%), followed by amoxicillin-clavulanate (80.0%). Among P. aeruginosa isolates, susceptibility was highest for piperacillin-tazobactam and meropenem (83.3% each). E. coli showed 100.0% susceptibility to meropenem, followed by 75.0% susceptibility to ceftriaxone, ceftazidime, ciprofloxacin, and piperacillin-tazobactam (Table 5).Correlation analysis demonstrated a significant positive correlation between the frequency of tonsillitis episodes and bacterial culture positivity (r=0.231, p=0.006). Tonsillar exudates (r=0.246, p=0.003) and cervical lymphadenopathy (r=0.185, p=0.028) also showed significant positive correlations with culture positivity. However, age showed no significant correlation with the frequency of tonsillitis episodes (r=0.142, p=0.094) or bacterial culture positivity (r=−0.071, p=0.405) (Table 6 and Figure 3). Table 1. Distribution of demographic and clinical characteristics among patients with recurrent tonsillitis (N = 140) Characteristics Number (n) Percentage (%) Age group (years) 5–15 38 27.1 16–30 52 37.1 31–45 34 24.3 >45 16 11.4 Total 140 100.0 Sex Male 76 54.3 Female 64 45.7 Total 140 100.0 Frequency of tonsillitis (episodes/year) 3–4 58 41.4 5–6 49 35.0 ≥7 33 23.6 Total 140 100.0 Clinical manifestations Sore throat 132 94.3 Fever 108 77.1 Dysphagia 96 68.6 Tonsillar congestion 118 84.3 Tonsillar exudates 72 51.4 Cervical lymphadenopathy 64 45.7 Table 2. Distribution of bacterial culture findings and bacterial isolates among patients with recurrent tonsillitis (N = 140) Microbiological findings Number (n) Percentage (%) Culture findings (N = 140) Culture-positive 106 75.7 Culture-negative 34 24.3 Total 140 100.0 Bacterial isolates (n = 106) Staphylococcus aureus 34 32.1 Streptococcus pyogenes 26 24.5 Streptococcus pneumoniae 12 11.3 Klebsiella pneumoniae 14 13.2 Haemophilus influenzae 10 9.4 Pseudomonas aeruginosa 6 5.7 Escherichia coli 4 3.8 Total 106 100.0 Gram-staining classification (n = 106) Gram-positive 72 67.9 Gram-negative 34 32.1 Total 106 100.0 Table 3. Association of demographic and clinical characteristics with bacterial culture positivity (N = 140) Characteristics Culture-positive (n = 106) Culture-negative (n = 34) p-value Statistical Test Age group (years) 0.857 Chi-square test 5–15 30 (78.9%) 8 (21.1%) 16–30 40 (76.9%) 12 (23.1%) 31–45 25 (73.5%) 9 (26.5%) >45 11 (68.8%) 5 (31.3%) Sex 0.856 Male 58 (76.3%) 18 (23.7%) Female 48 (75.0%) 16 (25.0%) Frequency of tonsillitis (episodes/year) 0.018 3–4 37 (63.8%) 21 (36.2%) 5–6 40 (81.6%) 9 (18.4%) ≥7 29 (87.9%) 4 (12.1%) Tonsillar exudates 0.003 Present 62 (86.1%) 10 (13.9%) Absent 44 (64.7%) 24 (35.3%) Cervical lymphadenopathy 0.028 Present 54 (84.4%) 10 (15.6%) Absent 52 (68.4%) 24 (31.6%) Total 106 (75.7%) 34 (24.3%) Table 3. Association of demographic and clinical characteristics with bacterial culture positivity (N = 140) Characteristics Culture-positive (n = 106) Culture-negative (n = 34) p-value Statistical Test Age group (years) 0.857 Chi-square test 5–15 30 (28.3%) 8 (23.5%) 16–30 40 (37.7%) 12 (35.3%) 31–45 25 (23.6%) 9 (26.5%) >45 11 (10.4%) 5 (14.7%) Sex 0.856 Male 58 (54.7%) 18 (52.9%) Female 48 (45.3%) 16 (47.1%) Frequency of tonsillitis (episodes/year) 0.018 3–4 37 (34.9%) 21 (61.8%) 5–6 40 (37.7%) 9 (26.5%) ≥7 29 (27.4%) 4 (11.8%) Tonsillar exudates 0.003 Present 62 (58.5%) 10 (29.4%) Absent 44 (41.5%) 24 (70.6%) Cervical lymphadenopathy 0.028 Present 54 (50.9%) 10 (29.4%) Absent 52 (49.1%) 24 (70.6%) Total 106 (100.0%) 34 (100.0%) Table 5. Antibiotic susceptibility pattern of Gram-negative bacterial isolates (n = 34) Antibiotics K. pneumoniae (n = 14) H. influenzae (n = 10) P. aeruginosa (n = 6) E. coli (n = 4) Amoxicillin-clavulanate 8 (57.1%) 8 (80.0%) — 2 (50.0%) Ceftriaxone 9 (64.3%) 9 (90.0%) — 3 (75.0%) Ceftazidime 10 (71.4%) — 4 (66.7%) 3 (75.0%) Ciprofloxacin 9 (64.3%) — 4 (66.7%) 3 (75.0%) Piperacillin-tazobactam 11 (78.6%) — 5 (83.3%) 3 (75.0%) Meropenem 13 (92.9%) — 5 (83.3%) 4 (100.0%) Table 6. Correlation of clinical and microbiological parameters among patients with recurrent tonsillitis (N = 140) Correlation variables Correlation coefficient (r) p-value Statistical test Age vs frequency of tonsillitis episodes 0.142 0.094 Spearman's correlation Frequency of tonsillitis episodes vs bacterial culture positivity 0.231 0.006 Spearman's correlation Tonsillar exudates vs bacterial culture positivity 0.246 0.003 Phi coefficient Cervical lymphadenopathy vs bacterial culture positivity 0.185 0.028 Phi coefficient Age vs bacterial culture positivity −0.071 0.405 Spearman's correlation

In the present study of 140 patients, the majority belonged to the 16–30-year age group (37.1%), with a male predominance (54.3%). Most patients experienced 3–4 tonsillitis episodes annually (41.4%). Sore throat (94.3%), tonsillar congestion (84.3%), and fever (77.1%) were the common manifestations. Adam et al. [14] and Krause et al. [15] investigated microbial biofilms rather than patient demographics; therefore, direct clinical comparisons were not possible.Bacterial culture positivity was observed in 75.7% of patients, with Gram-positive organisms accounting for 67.9% of isolates. Staphylococcus aureus was predominant (32.1%), followed by Streptococcus pyogenes (24.5%) and Klebsiella pneumoniae (13.2%). Adam et al. [14] demonstrated interactions between Candida albicans and Staphylococcus epidermidis in mixed-species biofilms. Similarly, Krause et al. [15] reported enhanced S. aureus growth in the presence of C. albicans, supporting the potential role of microbial interactions in bacterial persistence.Culture positivity increased from 63.8% among patients experiencing 3–4 episodes annually to 87.9% among those experiencing seven or more episodes (p = 0.018). Tonsillar exudates (p = 0.003) and cervical lymphadenopathy (p = 0.028) were also associated with culture positivity. Krause et al. [15] demonstrated significantly increased S. aureus growth in mixed biofilms (p < 0.001), providing a possible mechanistic explanation for microbial persistence, although their findings were not obtained from tonsillitis patients.Among Gram-positive isolates, S. pyogenes showed 100.0% penicillin susceptibility, while S. aureus demonstrated 82.4% cefoxitin and 73.5% clindamycin susceptibility. Among Gram-negative isolates, K. pneumoniae showed 92.9% susceptibility to meropenem. Adam et al. [14] reported that mixed C. albicans–S. epidermidis biofilms influenced antimicrobial responses, including reduced vancomycin activity against certain bacterial cells. Krause et al. [15] demonstrated that fungal-derived prostaglandin E₂ promoted S. aureus biofilm formation, suggesting that microbial interactions may influence treatment responses. This analysis showed positive associations between recurrence frequency and culture positivity (ρ = 0.231, p = 0.006), tonsillar exudates and culture positivity (φ = 0.246, p = 0.003), and cervical lymphadenopathy and culture positivity (φ = 0.185, p = 0.028). Krause et al. [15] demonstrated increased S. aureus proliferation in mixed biofilms, supporting the biological plausibility of microbial persistence, although their experimental findings were not directly comparable with these clinical associations.The present study obtained tonsillar surface and crypt swabs, yielding 75.7% culture positivity. Klagisa et al. [16] described a punch biopsy needle incorporating a 125° angled blade holder for tissue sampling.

The findings demonstrated a high bacterial culture positivity rate (75.7%) among patients with recurrent tonsillitis, with Staphylococcus aureus (32.1%) being the predominant isolate. Higher recurrence frequency, tonsillar exudates, and cervical lymphadenopathy were significantly associated with culture positivity. Variations in antibiotic susceptibility patterns highlighted the importance of microbiological evaluation and culture-guided antimicrobial therapy. LIMITATIONS The study was limited by its single-centre observational design and relatively small sample size of 140 patients. Tonsillar core cultures, anaerobic bacterial isolation, molecular identification, and biofilm analysis were not performed.

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