45-year-old male known case of ischemic heart disease, congestive heart failure and chronic kidney disease presenting with fever, cough and worsening shortness of breath. On physical examination, blood pressure is 120/70 mmHg, pulse is 80 bpm, respiratory rate is 24 bpm and oxygen saturation on room air is 88% improved to 94% on 3 liters of oxygen. Local chest examination and chest x-ray findings confirmed presence of right sided pleural effusion. Diagnostic pleural aspiration was performed. Which of the following favors diagnosis of empyema?