The veterinary cephalosporin drug ceftiofur is rapidly degraded in the bovine intestinal tract. A cylinder-plate assay was used to detect microbiologically active ceftiofur, and high-performance liquid chromatography-mass spectrometry analysis was used to quantify the amount of ceftiofur remaining after incubation with bovine intestinal anaerobic bacteria, which were isolated from colon content...

Bacterial -lactamases are the major causes of resistance to -lactam antibiotics. Three classes of these enzymes are believed to have evolved from ancestral penicillin-binding proteins (PBPs), enzymes responsible for bacterial cell wall biosynthesis. Both -lactamases and PBPs are able to efficiently form acyl-enzyme species with -lactam antibiotics. In contrast to -lactamases, PBPs are unable to...

background: extended spectrum β-lactamases (esbls) and ampc β-lactamases enzyme are major sources of resistance to β-lactam antibiotics especially in enterobacteriaceae such as escherichia coli and klebsiella pneumoniae. increasing frequency of the co-existence of esbls with ampc-β-lactamases in bacteria is a serious threat for treating bacterial infections. conclusions: outbreak of isolates co...

The properties and regulation of beta-lactamases produced by certain R factors derived from ampicillin-resistant strains of Escherichia coli and Klebsiella were characterized. beta-Lactamase activity was determined by the acidimetric method with phenol red as indicator. The sensitivity of this assay was increased by employing phosphate buffer at a final concentration of 0.4 mm; as little as 0.0...

β-lactamases are the primary cause of resistance to β-lactams among members of the family Enterobacteriaceae. SHV enzymes have emerged in Enterobacteriaceae causing infections in health care in the last decades of the Twentieth century, and they are now observed in isolates in different epidemiological settings both in human, animal and the environment. Likely originated from a chromosomal peni...

Enterobacteriaceae are major pathogens in both hospital and community. Recently the number of MDR phenotypes (multi drug resistant) increased, with the emergence of XDR phenotypes (extremely drug resistant – susceptible only to colistin and tigecycline). It is extremely important to detect and correct the reporting mechanisms for resistance. Many clinical laboratories have problems detecting ex...

Carbapenem antibiotics have been used to counteract resistant strains of bacteria harboring -lactamases and extended-spectrum -lactamases. Four enzymes from the class A group of -lactamases, NMC-A, IMI-1, SME-1, and KPC-1, efficiently hydrolyze carbapenem antibiotics. Sequence comparisons and structural information indicate that cysteines at amino acid residues 69 and 238, which are conserved i...

In the past 3 decades, classical extended-spectrum beta-lactamases (ESBLs) have probably been the main contributors to gram-negative antimicrobial resistance in Singapore. These appear to be being replaced by the newer CTX-M ESBLs. Metallo-beta-lactamases are found in Pseudomonas aeruginosa but do not seem to have spread widely in Acinetobacter spp. and Enterobacteriaceae. Carbapenem-hydrolysin...