Ans. (B) Cefaclor(Ref: KK Sharma 2/e p727)Cefaclor is a second generation cephalosporin and is not active against MRSA. Resistance in MRSA occurs due to altered PBPs (transpeptidase). As the binding site is altered, therefore, no beta lactam can bind and thus all beta-lactams (penicillins, cephalosporins, carbapenems and monobactams) are ineffective against MRSA. However, recently fifth generation cephalosporins like ceftaroline and ceftobiprol have been formed, which are effective against MRSA.