Background: Cephalosporins are major antimicrobials used to treat serious infections. However, their effectiveness is being compromised by the emergence of extended spectrum beta lactamases (ESBL). The present study was aimed characterize ESBL producing Escherichia coli from healthy and diarrheic cattle calves. Methods: A total 52 rectal swabs were collected calves between August 2019 March 202...

Eight cephalosporins were tested for their activity against methicillin-susceptible and methicillin-resistant, coagulase-negative staphylococci and for their resistance to beta-lactamase from methicillin-resistant, coagulase-negative staphylococci. Susceptibility testing by the agar plate method was evaluated for the effect of inoculum size and duration of incubation. Methicillin-susceptible, c...

Strains of bacteria resistant to beta-lactam antibiotics have been increasing in number and are becoming troublesome in clinical medicine. The in vitro antibacterial activity of amoxicillin combined with clavulanic acid was determined on selected ampicillin-resistant clinical isolates. Synergistic effects were produced by amoxicillin with clavulanic acid against ampicillin-resistant strains of ...

OBJECTIVE In this work we report the molecular characterization of beta-lactam antibiotics resistance conferred by genes contained in plasmids from enterobacteria producing extended-spectrum beta-lactamases (ESBL). MATERIAL AND METHODS Fourteen enterobacterial clinical isolates selected from a group of strains obtained from seven different hospitals in Mexico during 1990-1992 and 1996-1998 we...

The TEM family of beta-lactamases has evolved to confer resistance to most of the beta-lactam antibiotics, but not to cefepime. To determine whether the TEM beta-lactamases have the potential to evolve cefepime resistance, we evolved the ancestral TEM allele, TEM-1, in vitro and selected for cefepime resistance. After four rounds of mutagenesis and selection for increased cefepime resistance ea...

Clavulanic acid and a penicillanic acid sulfone, when combined individually with piperacillin, synergistically inhibited various Enterobacteriaceae, Staphylococcus aureus, and Bacteroides fragilis. Clavulanic acid and piperacillin synergistically inhibited 91 of 170 (55%) isolates tested. Synergy was most often found against piperacillin-resistant bacteria: 65 of 69 isolates (94%). Although the...

Definitions: Beta-lactam antimicrobials are characterized by having a four-membered cyclic amide (beta-lactam ring) as part of their chemical structure (Figure 1) [1]. This broad group includes the penicillins, cephalosporins, carbapenems, and monobactams [1]. All beta-lactams have a similar mechanism of action; they inhibit bacterial cell wall synthesis [1]. Resistance to beta-lactam antimicro...