Biomedical Engineering Reference
In-Depth Information
TABLE 25.2
Penicillins
O
CH
3
S
N
R
1
CH
NH
C
C
CH
3
COOY
N
C
H
O
R
2
R
1
R
2
Y
H
H
H
Ampicillin
OH
H
H
Amoxicillin
H
CH
2
OCOC(CH
3
)
3
H
Picampicillin
CH
OCOOC
2
H
5
H
H
Bacampicillin
CH
3
HC
O
H
H
Talampicillin
C
O
HN
N
CO
H
H
Azlocillin
O
C
2
H
5
N
N
CO
H
H
Piperacillin
O
O
has improved resistance, against b-lactamase. It is quite active against enterococci, but not against
Pseudomonas
.
Mecillinam is not an
N
-acyl derivative of 6-APA but is a semisynthetic 6-amidinopenicillanic
acid (Table 25.3). It is very active against some Gram-negative bacteria like
E. coli, Klebsiella
, and
Serratia
but not against
Pseudomonas, Proteus
, and
Haemophilus
. For oral administration, the
prodrugs pivmecillinam and bacmecillinam can be used.
25.2.1.3 Cephalosporins
In 1948, Brotzu at the University of Cagliari in Sardinia discovered antibacterial activity in the cul-
ture medium of a microorganism,
Cephalosporium acremonium
, collected at the sewage outlet of the
town in the sea. This strain was sent to the laboratory of Professor Florey in Oxford. from its culture
medium, Abraham et al. isolated in 1951, cephalosporin P, a steroid antibiotic related to fusidic acid,
and in 1954 cephalosporin N, later called penicillin N, which is a penicillin with d-a-aminoadipic
acid as side chain. When this penicillin was inactivated by acid, still another antibiotic, called cepha-
losporin C was isolated (Abraham and Newton, 1955). They were able to determine its structure in
1961 and they found that it also had a d-a-aminoadipic acid side chain but a b-lactam-hydrothiazine
ring system. The fact that this product was acid stable and resistant to penicillinase indicated that
it could be the starting point of a new group of important antibiotics. The side chain, however, was
