They are not active against cefotetan, cefoxitin and cephamycins
but are susceptible to clavulanic acid.
coli collected during a period of 6 months from urine samples for putative Amp C production based on reduced susceptibility to oxyimino-cephalosporins (ceftriaxone, ceftazidime) and cephamycins
These enzymes confer resistance to penicillins, cephalosporins, and monobactams, but not to cephamycins
or carbapenems, and are inhibited by [beta]-lactam inhibitors (6).
They can be differentiated from other ESBLs by their ability to hydrolyze cephamycins
as well as other extended spectrum cephalosporins.
Extended-spectrum [beta]-lactamases (ESBLs), which mediate resistance to oxyimino-cephalosporins but not to cephamycins
, are observed in Enterobacteriaceae worldwide (8).
classification of resistance 1 ESBL Class A Penicillins, Clavulanic Cephalosporins, acid, Monobactams Tazobactam, Sulbactam 2 Amp C Class C Penicillins, Cloxacillin, Cephalosporins, Boronic acid Cephamycins
, Monobactams 3 Carbapenemases- Class B Penicillins, EDTA and Metallo- Cephalosporins, other metal [beta]-lactamases Cephamycins
, chelators (MBL) Carbapenems Table 2: Results of various tests S.
AmpC beta (b)-lactamases are clinically substantial enzymes and are associated with the resistance to a large variety of b-lactam drugs except carbapenems and cefepime.1 AmpC b-lactamases are clinically significant as they can hydrolyse penicillins, cephalosporins and cephamycins
. They resist to a wide variety of b-lactamase inhibitor including a-methoxy-b-lactam such as cefoxitin.
ESBLs are plasmid-mediated [beta]-lactamases that are capable of hydrolyzing [beta]-lactams, except for carbapenems and cephamycins
. (11,31) In this regard, the majority of our ESBL-producing isolates were resistant to penicillins and cephalosporins.
ESBLs are plasmid mediated enzymes that hydrolyze the oxyimino p lactams and the monobactams (aztreonam) but have no effect on the cephamycins
(cefoxitin, cefotetan) and the carbapenems (imipenem).
The 14 antibiotics (or antibiotics combination) used in this work were cephamycins
(cefoxitin and cefminox), semisynthetic broad-spectrum penicillins (ampicillin and piperacillin), a first-generation cephalosporin (cefazolin), third-generation cephalosporins (ceftazidime, cefoperazone, cefotaxime, and ceftriaxone), a fourth-generation cephalosporin (cefoselis), a monobactam (aztreonam), an aminoglycoside (kanamycin), and combinations of antibiotics with [beta]-lactamase inhibitors (piperacillin/ tazobactam and imipenem/cilastatin sodium hydrate) (Table 3).
ESBL-producing organisms are capable of hydrolyzing penicillin, broad-spectrum cephalosporins, and monobactams, but they do not affect the cephamycins
or carbapenems, and their activity is inhibited by clavulanic acid.
coli are resistant to penicillins, cephalosporins but are susceptible to cephamycins