Molecular Characteristics of Extended Spectrum beta-Lactamases in Escherichia coli and Klebsiella pneumoniae and the Prevalence of qnr in Extended Spectrum beta-Lactamase Isolates in a Tertiary Care Hospital in Korea

PURPOSE: Extended spectrum beta-lactamases (ESBLs) are cephalosporinases that confer resistance to a wide variety of oxyimino cephalosporins and create serious therapeutic problems. In addition, the quinolone resistance qnr genes are becoming increasingly prevalent in clinical isolates, some of which also produce ESBL. This study was designed to evaluate the occurrence and genotypic distribution of ESBL producing Escherichia coli (E. coli) and Klebsiella pneumoniae (K. pneumoniae) as well as the prevalence and distribution of qnr genes in ESBL-producing isolates in a tertiary care hospital in Korea. MATERIALS AND METHODS: We tested a total of 111 ESBL-producing isolates of E. coli and K. pneumoniae, which were collected at Kyung Hee Medical Center from November 2006 to June 2008. ESBL production was determined by the Clinical and Laboratory Standards Institute (CLSI) ESBL confirmatory test. The cefotaxime and ceftazidime resistance of the ESBL-producers were transferred to azide-resistant E. coli J53 by conjugation. The presence and identity of ESBL and qnr genes were determined by polymerase chain reaction (PCR) and nucleotide sequencing. RESULTS: The prevalence of ESBLs was 17.7% (297/1,680) of E. coli and 26.5% (240/904) of K. pneumoniae in our hospital during the study periods. Of the 111 collected isolates, 69 isolates were E. coli and 42 isolates were K. pneumoniae. The most prevalent ESBL genotype was CTX-M15. Among the ESBL-producing isolates, 4 E. coli (5.8%) and 17 K. pneumoniae (40.5%) contained qnr genes. qnrB4 was the most frequent type in both E. coli and K. pneumoniae. CONCLUSION: CTX-M15 was the most frequently encountered ESBL. In addition, a high prevalence of qnr genes among ESBL-producing K. pneumoniae was identified in this study.

Isolation of 34 kDa protein from spinach chloroplasts having ferrooxidase and H2O2-dependent dark O2 evolution activities.

A latent form of 'Ferrooxidase' exhibiting ferrocyanide-dependent O2 uptake was detected in the isolated spinach chloroplasts. Presence of a cationic detergent hexadecyl trimethyl ammonium bromide (CTAB) in the medium was essential to induce this activity. The association of this enzyme activity with photosystem II (PSII) particles as well as the ability of PSII particles to show oxidation of H2O2 (catalase like activity) indicated its possible relationship with water oxidation system. The protein catalysing this activity was purified to homogeneity and its molecular mass was found to be 34 kDa. The purified protein showed a complete dependence on an electron acceptor, namely ferricyanide, for the oxidation of H2O2. While with ferrocyanide in the presence of CTAB, the protein exhibits the ferrooxidase activity. For both activities, a sharp pH optima at 6.1 was observed. The km for H2O2 was 12.2 mM. The purified enzyme protein contained 4 atoms of calcium and 2 atoms of iron per mole of the enzyme. Unlike catalase, the enzyme reaction was insensitive to sodium azide even at 500 microM concentration. The enzyme was found to be sensitive to metal chelators like ethylene-glycol-bis-(beta-aminoethylether) N, N+ tetra acetic acid (EGTA) (2mM), alpha,alpha-dipyridyl (500 microM) and 1,10-orthophenanthroline (200 microM). The sensitivity of the reaction to alpha,alpha-dipyridyl and 1,10-orthophenanthroline suggested the involvement of Fe2+ in the reaction. Inhibition of enzyme activity by EGTA and restoration of activity by supplementation of CaCl2 to the EGTA-dialysed sample confirmed the absolute requirement for calcium for this activity. Calcium was absent in the EGTA-dialysed enzyme. Apart from these inhibitors, NaF and NH2OH were potent inhibitors of the enzyme reaction.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of Emblica officinalis Gaertn. (Indian gooseberry) fruit extract on sodium azide and 4-nitro-o-phenylenediamine induced mutagenesis in Salmonella typhimurium.

Water, acetone and chloroform extracts of E. officinalis fruit reduced sodium azide and NPD induced his+ revertants significantly in TA100 and TA97 a strains respectively of S. typhimurium. The chloroform extract was less active as compared to water and acetone extracts. Autoclaving of water extract for 15 min did not reduce its activity. The enhanced inhibitory activity of the extracts on pre-incubation suggests the possibility of desmutagens in the extracts. Besides ascorbic acid, a constituent of the extract, the role of other antimutagenic factors in the extract cannot be ruled out.