<prompt> Most common organism responsible for pseudo membranous colitis is -Clostridium difficileClostridium botulismClostridium histolyticumClostridium butyricum  <response>: Ans. is a i.e., Clostridium difficile Pseudomembranous colitis is the advanced form of Clostridium difficile - associated disease CDAD.Remember:o CDAD is the most commonly diagnosed diarrheal iiiness acquired in the hospital.o C. diffiele is acquired exogenously not as an endogenous infection, most frequently in the hospital,o C. diffiele is the most common bacterial cause of nosocomial diarrhea,o Diarrhea is the most common symptom of CDAD.Risk factors for Clostridium difficile associated disease CDADo CDAD almost exclusively associated antibiotic used,o The most common antibiotics associated with CDAD are-ClindamycinAmpicillinCephalosporin mainly cefotaxim, ceftriaxone, cefuroxime and ceftazidimeo Piperacillintazobactiim and ticarc i llinclavlanate less commonly associated with CDAD.o The risk of Clostridium difficile infection is directly proportionate to the hospital stay,o Other risk factors-Old ageGreater severity of underlying illnessGasterointestinal surgeryUsed electrical thermometerCentral tube feedingAntacid useProton pump inhibitorsDiagnosis and Treatment of CDADo Diagnosis The diagnosis is based on a combination of clinical criteria :Diarrhea 3 unformed stools per 24 hrs for 2 days, with no other recognized cause.plusToxin A or B detected in the stool, toxin - producing C. difficile detected by stool culture, or pseudomembrane seen in the colon.o TreatmentMetronidazole is drug of choiceAlternatives -Vancomycin Fusidic acidTeicoplanin BacitracinRemembero Most sensitive test for diagnosis of CDAD-Stool culture for C. difficileo Most specific tests for diagnosis of CDAD-Cell culture cytotoxin test on stool and pseudomembrane seen on colonoscopy or sigmoidoscopy 