Background: A viral, bacterial, or fungal infection may cause tonsillitis, which is an inflammation of the palatine tonsils. The McIsaac modified Centor score, which differs from the original Centor score in that it only applied to patients who were at least 15 years old, is a tool for predicting tonsillitis brought on by group A -hemolytic Streptococcus. Because the McIssaac modified Centor score adjusts by age, it may be used on both children and adults. Objective:To identify whether patients with chronic tonsillitis are suitable candidates for the modified McIsaac Centor score when tonsil core bacteria are present.. Method:a cross sectional research that combines descriptive analysis with analysis. Patients with chronic tonsillitis after tonsillectomy participated in the trial from June 2020 to June 2021 at the ORL-HNS outpatient clinic of RSUDZA. Using the SPSS application, all data were entered, coded, and analyzed using Chi-square statistics and a kappa test with a 95% confidence level. Kappa value > 0,8 -1 is seen to indicate very high compliance, whereas kappa value 0,2 is thought to indicate very poor conformance. Results:The research covered 35 patients in total. There were more women overall (28.6%), those aged 15 to 44 made up the largest age group (41.3%), and T3 tonsils made up the majority (38%). The most prevalent germs were Staphylococcus aureus (59.4%). Levofloxacin, linezolid, gentamicin, and ciprofloxacin had the greatest antibiotic sensitivity tests results for gram positive bacteria, whereas levofloxacin, meropenem, ceftazidime, gentamicin, and amikacin had the highest results for gram negative bacteria. With 100% sensitivity, 79.41% specificity, 12.5% positive predictive value, 100% negative predictive value, and 80% accuracy value, a score of 4 was determined to be the best cut-off point. Based on a Kappa value of 0.181 [CI95% (-0.13) -0.492] and a p value of 0.062, the McIsaac modified Centor score was 18.1% congruent with the outcomes of the tonsillar core microorganism culture. Conclusion: In individuals with chronic tonsillitis, there was very little agreement between the McIsaac modified Centor score and the bacterium in the tonsil core culture.