Objective To investigate antibiotic resistance of Klebsiella pneumoniae and Escherichia coli in old patients with lower respiratory tract infections. Methods Kirby Bauer agar diffusion method was used to evaluate the drug sensitivity in 240 strains of Klebsiella pneumoniae and Escherichia coli isolated from patients with lower respiratory tract infection. Phenotypic confirmatory test recommended by NCCLS1999 was used to detect extended spectrum beta lactamases(ESBLs). Results The resistant rates of Klebsiella pneumoniae and Escherichia coli to 14 antibiotics in old patients and in non old patients with lower respiratory tract infections were amoxicillin 93 2% vs 87 3%, piperacillin 57 1% and 42 9%, cefuroxime 51 4% and 33 3%, cefotaxime 40 1% and 17 5%, ceftazidime 13 6% and 3 2%, ceftriaxone 39 0% and 17 5%, cefoperazone 37 3% and 15 9%, cefepime 10 2% and 3 2%, amikacin 47 5% and 34 9%, ciprofloxacin 54 2% and 38 1%, imipenem 0, cefoperazone/sulbactam 0, piperacillin/tazobactam 1 1% vs 0, and cefmetazole 9 6% and 4 8% respectively. Out of 240 clinical strains of Klebsiella pneumoniae and Escherichia coli, 78(32 5%) were considered ESBLs producers by phenotypic confirmatory test. The prevalence of ESBLs in old patients was 38 4%, which was much higher than that in non old patients(15 9%). The resistant rate of ESBLs producing strains to imipinem, cefoperazone/sulbactam, piperacillin/tazobactam and cefmetazole was the lowest, being 0, 0, 2 6% and 12 8%. Conclusions The resistant rates of Klebsiella pneumoniae and Escherichia coli to most antibiotics and the prevalence of ESBLs in old patients with lower respiratory tract infection were higher than that in non old patients. Imipinem, cefoperazone/sulbactam, piperacillin/tazobactam and cefmetazole were the effective antibiotics to infections caused by ESBLs producing strains.

Aminopeptidase H (APH) is an universally distributed aminoendopeptidase in the tissue of many organism. However, it is hard to investigate its mechanism underlying the catalysis and the function in cell. In this paper, the full DNA sequence of this enzyme was cloned from chicken liver, then subcloned to the vector pET22 b(+). The recombined vector was transformed into E. coli Rosetta(DE3), and the APH gene was expressed by the induction of IPTG. It was found the recombinant protein exhibited same mo lecular weight as authentic APH on SDS-PAGE analysis; the expression level increased with induction time and approached maximum of 94.7 mg/L till 6 hours, which contained 16.7% of the total protein. Moreover, this recombinant protein showed similar prop erties of subunit composition, thermal stability and optimum pH with native APH, based on the enzymatic assay, purification and analysis of enzymological properties. Therefore, it is confirmed that APH was expressed in this prokaryote system with a high-level of 1636 u/L aminopeptidase activity. These results would help to elucidate the catalysis mechanism and biological function of APH by providing enough material.
Aminopeptidases ; biosynthesis ; genetics ; Animals ; Chickens ; Endopeptidases ; biosynthesis ; genetics ; Enzyme Stability ; Escherichia coli ; genetics ; metabolism ; Recombinant Proteins ; biosynthesis ; genetics ; isolation & purification