SummaryFlowering relies on signaling networks that integrate endogenous and external cues. Normally, plants ower at a particular season, re¯ecting day length and/or temperature cues. However, plants can surpass this seasonal regulation and show precocious¯owering under stress environmental conditions. Here, we show that UV-C light stress activates the transition to¯owering in Arabidopsis thaliana through salicylic acid (SA). Moreover, SA also regulates¯owering time in non-stressed plants, as SA-de®cient plants are latē owering. The regulation of¯owering time by SA seems to involve the photoperiod and autonomous pathways, but it does not require the function of the¯owering time genes CONSTANS (CO), FCA, or FLOWERING LOCUS C (FLC ).

A new CTX-M-type ␤-lactamase (CTX-M-9) has been cloned from a clinical cefotaxime-resistant Escherichia coli strain. Despite the close identity that exists between the CTX-M-9 and Toho-2 ␤-lactamases (88%), the 35 amino acids located between residues Ala-185 and Ala-219 are totally different in both enzymes. Outside of this region there are only six amino acids substitutions between both proteins.Not long after the beginning of the use of the extendedspectrum ␤-lactam antibiotics, extended-spectrum ␤-lactamases (ESBLs) were detected in Europe and the United States and have now become a serious problem around the world. ESBLs are most often derivatives of TEM or SHV enzymes. However, there is a small growing family of plasmid-mediated ESBLs of Ambler class A that are not closely related to TEM or SHV ␤-lactamases but that show homology to chromosomal ␤-lactamases of Klebsiella oxytoca, including CTX-M-1 (MEN-1) (3, 5-7), CTX-M-2 (4, 6), CTX-M-3 (14), CTX-M-4 (12, 13), 20), Toho-1 (15), Toho-2 (17), and two different enzymes, both designated CTX-M-5, which will be referred to here as CTX-M-5 (8) and 20). In this report we present a new ␤-lactamase closely related to the ␤-lactamases in this family.In 1996, a cefotaxime-resistant Escherichia coli strain (785-D) against which synergy of cefotaxime with clavulanic acid was found was detected by a conventional disk diffusion susceptibility test. The strain was isolated from the urine of a 65-year-old woman who had a urinary tract infection and diabetes mellitus type 2. Two months before the isolation, the patient underwent a nephroureterectomy because of a renal carcinoma.The MICs of the ␤-lactam antibiotics were determined by the Etest (Biodisk, Solna, Sweden). The ␤-lactamase crude cell extracts were prepared from 250-ml cultures in Luria-Bertani (LB) broth (Oxoid, Basingstoke, United Kingdom). Washed, centrifuged cell pellets were subjected to three cycles of 15-s sonication treatments at 4°C, and the supernatants of the sonic extracts were frozen at Ϫ20°C until they were tested. ␤-Lactamases were characterized initially by isoelectric focusing as described previously (2) in polyacrylamide gels with a pH gradient from 4 to 11 (SERVALYT 4-9 T, 9-11 T; Serva, Heidelberg, Germany). Enzyme activities in the gel were detected by the iodometric method (2).Substrate hydrolysis in sonic extracts was monitored spectrophotometrically with a Biochrom 4060 spectrophotometer (Pharmacia, Uppsala, Sweden) as described previously (19).Conjugation studies were performed in a solid medium as described previously (19) by using E. coli 785-D (susceptible to kanamycin) and E. coli HB101 (Nal r Kan r ) as the donor and the recipient, respectively. Kanamycin (50 g/ml) and cefotaxime (4 g/ml) were used for transconjugant selection. One of the transconjugants (E. coli MSP492) was used for further experiments.Extraction of plasmid DNA was by the alkaline lysis procedure reported previously (18). Cloning of the cefotaxime resistance gene was as follows: plasmid DNA from E. coli MSP492 was pa...

Trends in resistance to antimicrobial agents used for therapy have been evaluated with 3,797 enteropathogenic bacteria, Campylobacter, Salmonella, Shigella, and Yersinia, between 1985-1987 and 1995-1998. The greater increase in the rate of resistance was observed in Campylobacter jejuni for quinolones (from 1 to 82%) and tetracycline (from 23 to 72%) and in gastroenteric salmonellae for ampicillin (from 8 to 44%), chloramphenicol (from 1.7 to 26%), and trimethoprim-sulfamethoxazole and nalidixic acid (from less than 0.5 to 11%). Multidrug resistance was detected in several Salmonella serotypes. In the 1995-1998 period, 76% of Shigella strains were resistant to trimethoprim-sulfamethoxazole, 43% were resistant to ampicillin, and 39% were resistant to chloramphenicol. Seventy-two percent of Yersinia enterocolitica O3 strains were resistant to streptomycin, 45% were resistant to sulfonamides, 28% were resistant to trimethoprim-sulfamethoxazole, and 20% were resistant to chloramphenicol.