BACAMPICILLIN IS AN ESTER OF AMPICILLIN. IT DOES NOT MARKEDLY DISTURB INTESTINAL ECOLOGY. IT IS CHARACTERIZED BY ITS MORE COMPLETE AND MORE RAPID ABSORPTION FOR THE G.I. TRACT THAN AMPICILLIN, INHIBITS THE SYNTHESIS OF CELL WALL MUCOPEPTIDE. AMPICILLIN CLASS ANTIBIOTICS ARE INACTIVATED BY BETA-LACTAMASES PRODUCED BY CERTAIN STRAINS OF ENTEROBACTER, CITROBACTER, HAEMOPHILUS INFLUENZAE, AND ESCHERICHIA COLI, AND BY MOST STRAINS OF STAPHYLOCOCCI AND INDOLE-POSITIVE PROTEUS SPP. AMPICILLIN CLASS ANTIBIOTICS ARE NOT ACTIVE AGAINST PSEUDOMONAS, KLEBSIELLA, OR SERRATIA SPP.