<prompt> All of the following cephalosporins are active against Pseudomonas except:CeftazidineCefotaximeCefoperazoneCefaclor  <response>: Third Generation CephalosporinsThese are active against gram negative organisms resistant to other beta lactam antibiotics.These can also penetrate the blood brain barrier except cefoperazone and cefixime.Ceftazidime maximum, ceftolozane and cefoperazone are active against pseudomonas.Ceftazidime is drug of choice for meliodiosis caused by Burkholderia pseudomallei.Ceftizoxime has maximum activityy against Bacteroides.Ceftriaxone is the first choice drug for gonorrhoea, salmonellosis including typhoid, E. coli sepsis, Proteus, Serratia, Haemophilus and empirical therapy for bacterial meningitis.Long term use of 2gd of ceftriaxone is associated with biliary sludging syndrome and cholelithiasis due to precipitation in bile.Most of these drugs are reserved for serious infections.Ceftriaxone has long plasma half life.Cefotaxime is metabolized to an active metabolite desacetyl-cefotaxime.Note: Cefaclor is a 2nd generation cephalosporin and is ineffective against pseudomonas and MRSA. 