All are true regarding resistance of penicillin in staphylococcus aureus, except ?
Correct Answer: Hospital strains mostly produce type D penicillinase
Description: Ans. is 'c' i.e., Hospital strains mostly produce type D penicillinase Resistance to antibiotics a Penicillin resistance is of three types? 1. Production of beta-lactamase (penicillinase) It inactivates penicillin by splitting 13-lactam ring Its production is controlled by plasmid. Plasmid is transmitted by transduction (mainly) or conjugation. Penicillinase is an inducible enzyme As a result of the widespread dissemination of plasmids containing penicillinase, less than 5% strains of staph. remain susceptible to penicillin. Staphylococci produce four type of penicillinases, A to D. Hospital strains usually forms type 'A' penicillinase. 2. Changes in bacterial surface receptors by lack or inaccessibility of ceain penicillin binding proteins (PBPs) in the organism. Methicillin resistant is mainly due to this mechanism and is independent of /3 - lactamase production. It is due to production of PBP 2a. This change ( in bacterial surface receptors) is normally chromosomal in nature. The resistance gene is mec A gene which is a pa of large mobile genetic element - staphylococcal cassette chromosome (SCCmec). This genetic material has been transferred to Staph. aureus from S. seiuri. 3. Development of tolerance to penicillin, by which the bacterium is only inhibited but not killed
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