<prompt> Which of the following is catalase positive? RepeatStaph epidermidisEnterococcusStreptococcusPneumococcus  <response>: Ans: A Staph epidermidis Ref: Ananthanarayan, Paniker CJ. Textbook of microbiology. 8th Edition. London: John Wiley Sons: 2009. Pg. 52, 159Explanation:Catalase test:When a bacterial colony is placed in hy drogen peroxide, if it produces catalase enzyme there will be prompt effervescence.Catalase positive organisms:Staphylococcus aureusCoagulase negative staphylococci such asS. epidermidisMicrococciPseudomonasCandidaColiformsdeg Citrobacter, Enterobacter. E.coli, Klebsiella which are all lactose deg Shigella. Yersinia, Proteus and Salmonella which are all lactose -deg Serratia a slow lactose fermenterAlthough Shigella dysenteriae type 1 is a coliform, it is catalase negative.Streptococcus, pneumococcus and enterococcus are catalase negative.In patients with chronic granulomatous disease, a familial condition with disorder of phagocytosis, recurrent infections due to catalase positive organisms are more common as the leucocytes are unable to kill catalase positive bacteria following phagocytosis. 