All of the following statement are true about Staphylococci except :

“Methicillin resistance is expressed more when Staph. is incubated at 30 0 C than at 37 0 C.” Penicillin resistance in Staphylococcus is by following ways : 1. Production of β lactmase : Plasmid mediated inducible enzyme which is transmitted by transduction (more commonly) or conjugation. Now only <5% of strains of staph are sensitive to penicillin. Hospital strains mostly form type A penicillinase. Same plasmid carry genes for resistance to tetracycline, Erythromycin, Aminolgycoside too. 2.  Altered penicillin binding protein : Due to production of novel penicillin binding protein PBP2a. The protein is synthesized by mecAgene. Chromosomally mediated expressed more at 30 0 C than at 37 0 C. Responsible for resistance against penicillinase resistant penicillin such as methicilin, cloxacillin. Strains are called MRSA (Methicillin resistant Staph. aureus). 3. Tolerance to pencillin : Bacteria only inhibited not killed.