Which of the following is catalase positive? (Repeat)
Staph epidermidis
Enterococcus
Streptococcus
Pneumococcus
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 fermenter)Although 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.
Staphylococci