ss -lactamase resistance of staphylococcus aureus is due to:
Ans: a (Transduction) Ref:Ananthanarayan,7th ed, p. 194"One of the causes for penicillin resistance in staphylococcus is ss lactamase production which is plasmid mediated.Plasmid mediated inducible enzyme is transmitted by transduction (more commonly) or conjugation"Penicillin resistance in staphylococcus is by following ways:1. Production of ss - lactamasea. Plasmid mediated inducible enzyme which is transmitted by transduction (more commonly) or conjugationb. Hospital strains mostly form Type A penicillinasec. Same plasmid carry genes for resistance to tetracycline, erythromycin, aminoglycoside too2. Altered penicillin binding protein:a. Chromosomally mediated and expressed more at 30deg C than at 37 degC. (A1IMS)b. Responsible for resistance against penicillinase resistant penicillin such as methicillin. cloxacillinc. Strains are called MRSA (methicillin resistant Staph, aureus)3. Tolerance to penicillin.Bacteria only inhibited not killedTransformation:The first example of genetic exchange in bacteria was described by Griffith.This is the transfer of genetic material through the agency of free DN A.This has been studied mainly in BPH:BacillusHemophilusPneumococcusTraasductionTransfer of a portion of DNA from one bacterium to the other by means of a bacteriophage. This has been proposed as a method of genetic engineering and in treatment of some inborn errors of metabolism.Conjugation:Transfer of genetic elements after actual physical contact between a male donor bacterium and female recipient e.g., transfer of episomes and plasmid such as those for resistance.Bacterial conjugation was first described by Lederberg and Tatum in a strain of E.coli called K-12Lysogenic conversion:In lysogenic conversion the phage DNA itself is the new genetic element as it becomes integrated with the bacterial host DNA with which it multiplies and is transferred to daughter cells. E.g.: Diphtheriae corynebacterium
Transduction
Conjugation
Mutation
Transformation
Staphylococci