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1.
Diversity of CTX-M beta-lactamases and their promoter regions from Enterobacteriaceae isolated in three Parisian hospitals 总被引:5,自引:0,他引:5
Saladin M Cao VT Lambert T Donay JL Herrmann JL Ould-Hocine Z Verdet C Delisle F Philippon A Arlet G 《FEMS microbiology letters》2002,209(2):161-168
Nine clinical isolates of Enterobacteriaceae (six Escherichia coli and three Proteus mirabilis) isolated in three Parisian hospitals between 1989 and 2000 showed a particular extended-spectrum cephalosporin-resistance profile characterized by resistance to cefotaxime and aztreonam but not to ceftazidime. CTX-M-1, CTX-M-2, CTX-M-9, CTX-M-14 and two novel plasmid-mediated CTX-M beta-lactamases (CTX-M-20, and CTX-M-21) were identified by polymerase chain reaction and isoelectric focusing (pI>8) and were associated in eight cases with TEM-1 (pI=5.4) or TEM-2 (pI=5.6) beta-lactamases. We used internal ISEcp1 and IS26 forward primers and the CTX-M consensus reverse primer to characterize the CTX-M beta-lactamase promoter regions and showed their high degree of structure diversity. We found upstream of some bla(CTX-M) genes, a 266-bp sequence 100% identical to the sequence upstream of the Kluyvera ascorbata beta-lactamase gene, suggesting that this chromosomal enzyme is the progenitor of the CTX-M-2/5 cluster. 相似文献
2.
Arlet Minassian Junjie Zhang Shanping He Jun Zhao Ebrahim Zandi Takeshi Saito Chengyu Liang Pinghui Feng 《PLoS pathogens》2015,11(7)
Activation of pattern recognition receptors and proper regulation of downstream signaling are crucial for host innate immune response. Upon infection, the NF-κB and interferon regulatory factors (IRF) are often simultaneously activated to defeat invading pathogens. Mechanisms concerning differential activation of NF-κB and IRF are not well understood. Here we report that a MAVS variant inhibits interferon (IFN) induction, while enabling NF-κB activation. Employing herpesviral proteins that selectively activate NF-κB signaling, we discovered that a MAVS variant of ~50 kDa, thus designated MAVS50, was produced from internal translation initiation. MAVS50 preferentially interacts with TRAF2 and TRAF6, and activates NF-κB. By contrast, MAVS50 inhibits the IRF activation and suppresses IFN induction. Biochemical analysis showed that MAVS50, exposing a degenerate TRAF-binding motif within its N-terminus, effectively competed with full-length MAVS for recruiting TRAF2 and TRAF6. Ablation of the TRAF-binding motif of MAVS50 impaired its inhibitory effect on IRF activation and IFN induction. These results collectively identify a new means by which signaling events is differentially regulated via exposing key internally embedded interaction motifs, implying a more ubiquitous regulatory role of truncated proteins arose from internal translation and other related mechanisms. 相似文献
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Abstract Aztreonam-resistant Klebsiella oxytoca strain SL7811 was selected on agar containing 1 μg of aztreonam per ml from a susceptible strain SL781. The MICs for the resistant mutant towards penicillins, aztreonam and ceftriaxone were much higher, to cefotaxime slightly higher and to ceftazidime unchanged. Synthesis of β-lactamase was 223-fold greater in the mutant compared with the susceptible strain. SL781 and its resistant mutant SL7811 produced β-lactamase with the same isoelectric point and substrate profile. The β-lactamase genes from SL781 and SL7811 were cloned in plasmid pBGS18 giving pBOF-1 and pBOF-4 respectively. The sequences of the two putative promoters indicated two modifications in the resistant plasmid pBOF-4: a transversion (G → T) in the first base of the − 10 consensus sequence and a deletion of one C residue four base pairs upstream of the − 10 hexamer. 相似文献
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Barnaud G Labia R Raskine L Sanson-Le Pors MJ Philippon A Arlet G 《FEMS microbiology letters》2001,199(2):185-190
Enterobacter cloacae CHE, a clinical strain with overproduced cephalosporinase was found to be highly resistant to the new cephalosporins, cefepime and cefpirome (MICs> or =128 microg ml(-1)). The strain was isolated from a child previously treated with cefepime. The catalytic efficiency of the purified enzyme with the third-generation cephalosporins, cefepime and cefpirome, was 10 times higher than that with the E. cloacae P99 enzyme. This was mostly due to a decrease in K(m) for these beta-lactams. The clinical isolate produced large amounts of the cephalosporinase because introduction of the ampD gene decreased ampC expression and partially restored the wild-type phenotype. Indeed, MICs of cefepime and cefpirome remained 10 times higher than those for a stable derepressed clinical isolate (OUDhyp) transformed with an ampD gene. Sequencing of the ampC gene showed that 18 nucleotides had been deleted, corresponding to the six amino acids SKVALA (residues 289--294). According to the crystal structure of P99 beta-lactamase, this deletion was located in the H-10 helix. The ampR-ampC genes from the clinical isolates CHE and OUDhyp were cloned and expressed in Escherichia coli JM101. The MICs of cefpirome and cefepime of E. coli harboring ampC and ampR genes from CHE were 100--200 times higher than those of E. coli harboring ampC and ampR genes from OUDhyp. This suggests that the deletion, confirmed by sequencing of the ampC gene, is involved in resistance to cefepime and cefpirome. However, the high level of resistance to cefepime and cefpirome observed in the E. cloacae clinical isolate was due to a combination of hyperproduction of the AmpC beta-lactamase and structural modification of the enzyme. This is the first example of an AmpC variant conferring resistance to cefepime and cefpirome, isolated as a clinical strain. 相似文献
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Małgorzata E. Arlet Lynne A. Isbell Freerk Molleman Ants Kaasik Rebecca L. Chancellor Colin A. Chapman Raivo Mänd James R. Carey 《International journal of primatology》2014,35(2):476-490
Differences among females in infant survival can contribute substantially to variance in fitness. Infant survival is a product of external risk factors and investment by kin, especially the mother, and is thus closely tied with the evolution of behavior and life history. Here we present a 9-yr study (2004–2012) of infant survival and sex ratio relative to age and dominance ranks of mothers and the presence of immigrant males in a free-ranging population of gray-cheeked mangabeys (Lophocebus albigena) in Kibale National Park, Uganda. We consider immigrant males because they are known to increase infant mortality in several other species. We found that infants of older mothers had higher survival than those of younger mothers but that high rank did not confer a significant benefit on infant survival. Female infants had higher survival than male infants. Young, low-ranking females had more male infants than young, high-ranking females, which had slightly more daughters, but this difference declined as females aged because low-ranking females had more daughters as they aged. With limited data, we found a significant relationship between the presence of male immigrants and infant mortality (falls and unexplained disappearances) to 18 mo. Our results suggest that infant survival in gray-cheeked mangabeys is most precarious when mothers must allocate energy to their own growth as well as to their infants, that sons of young mothers are at greatest risk, and that immigrant males can negatively affect infant survival. 相似文献
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Karline R. L. Janmaat William Olupot Rebecca L. Chancellor Malgorzata E. Arlet Peter M. Waser 《International journal of primatology》2009,30(3):443-466
We investigated long-term site fidelity of gray-cheeked mangabey (Lophocebus albigena) groups in Kibale National Park, Uganda. Concurrently, we monitored shifts in home range by individual females and subadult
and adult males. We documented home range stability by calculating the area of overlap in successive years, and by recording
the drift of each group’s monthly centroid from its initial location. Home ranges remained stable for 3 of our 4 groups (overlap
over 10 yr >60%). Core areas were more labile, but group centroids drifted an average of only 530 m over the entire decade.
Deviations from site fidelity were associated with dispersal or group fission. During natal dispersal, subadult males expanded
their home ranges over many months, settling ≤4 home ranges away. Adult males, in contrast, typically dispersed within a few
days to an adjacent group in an area of home range overlap. Adult males made solitary forays, but nearly always into areas
used by their current group or by a group to which they had previously belonged. After secondary dispersal, they expanded
their ranging in the company of their new group, apparently without prior solitary exploration of the new area. Some females
also participated in home range shifts. Females shifted home ranges only within social groups, in association with temporary
or permanent group splits. Our observations raise the possibility that male mangabeys use a finder-joiner mechanism when moving
into new home ranges during secondary dispersal. Similarly, females might learn new resource locations from male immigrants
before or during group fission. 相似文献
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Arlet Małgorzata E. Balasubramaniam Krishna N. Saha Rajarshi Beisner Brianne Marty Pascal R. Kaburu Stefano S. K. Bliss-Moreau Eliza Kaasik Ants Kodandaramaiah Ullasa McCowan Brenda 《International journal of primatology》2021,42(2):220-236
International Journal of Primatology - Female reproductive success depends to a large extent on infants’ ability to survive to maturity. While most studies of female reproductive success have... 相似文献
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Arlet Loza-Huerta Rosario Vera-Estrella Alberto Darszon Carmen Beltrán 《Biochimica et Biophysica Acta (BBA)/General Subjects》2013