Cephalosporin resistance, particularly due to bla(TEM) encoded β-lactamases, among Enterobacteriaceae is, though, an increasing public health problem in India; their circulating genetic variants remain unknown. The present study deals with determination of bla(TEM) variants among 134 pathogenic Enterobacteriaceae of Indian origin. Their resistance profile against 3rd generation cephalosporins w...

To evaluate the validity of our in vitro evolution method as a model for natural evolutionary processes, the TEM-1 beta-lactamase gene was evolved in vitro and was selected for increased resistance to cefotaxime, cefuroxime, ceftazadime, and aztreonam, i.e., the "extended-spectrum" phenotype. The amino acid substitutions recovered in 10 independent in vitro evolvants were compared with the amin...

The aims of this study were to investigate drug resistance rates, types of extended spectrum beta lactamases (ESBLs), and molecular epidemiological characteristics of 43 Shigella sonnei isolates. Ampicillin-sulbactam, amoxicillin-clavulanate, chloramphenicol, and ciprofloxacin were the most active antibiotics. Five isolates harbored bla SHV-12, bla(TEM-1) and bla(CTX-M-15). More than 90% of the...

Ninety-one ampicillin-resistant Shigella flexneri strains from Hong Kong and Shanghai were studied for production of beta-lactamases. TEM-1-like and OXA-1-like enzymes were identified in 21 and 79% of the strains, respectively, by isoelectric focusing (IEF). No difference in the pattern of beta-lactamase production was found between strains from Hong Kong and Shanghai. Four ribotypes were detec...

bla(TEM-1) expression results in penicillin resistance, whereas expression of many bla(TEM-1) descendants, called extended-spectrum beta-lactamases (ESBLs), results simultaneously in resistance to penicillins and extended-spectrum cephalosporins. Despite the expanded resistance phenotypes conferred by many ESBLs, bla(TEM-1) is still the most abundant bla(TEM) allele in many microbial population...

Extended-spectrum β-lactamases (ESBL) of the CTX-M, SHV, and TEM families were recognized in 76 (67%), 31 (27%), and 6 (5%) isolates, respectively, among 162 ESBL-producing Klebsiella pneumoniae (ESBL-Kp) strains obtained in a multicenter study in Spain. Predisposing factors for ESBL-Kp acquisition included invasive procedures, mechanical ventilation, and previous antimicrobial use.

Carbapenem-resistant Gram-negative bacilli resulting from β-lactamases have been reported to be an important cause of nosocomial infections and are a critical therapeutic problem worldwide. This study aimed to describe the prevalence of imipenem-resistant Gram-negative bacilli isolates and detection of bla VIM, bla TEM, bla SHV, bla CTX-M-1, and bla CTX-M-9 genes in these clinical isolates in E...

Of 59 clinical isolates of Enterobacter cloacae from a teaching hospital in Sichuan, China, 18 isolates were shown to be resistant to oxyimino cephalosporins and aztreonam. Enterobacterial repetitive consensus PCR revealed that these isolates comprised 7 distinct genotypes. The presence of plasmids in the 18 clinical isolates was revealed by conjugational transfer of plasmids from E. cloacae to...

Widespread use of beta-lactam antibiotics has promoted the evolution of beta-lactamase mutant enzymes that can hydrolyze ever newer classes of these drugs. Among the most pernicious mutants are the inhibitor-resistant TEM beta-lactamases (IRTs), which elude mechanism-based inhibitors, such as clavulanate. Despite much research on these IRTs, little is known about the structural bases of their a...