New extended-spectrum ␤-lactamase GES-11 was detected in Acinetobacter baumannii BM4674. The enzyme conferred resistance to ␤-lactams, including aztreonam, and reduced susceptibility to carbapenems. The structural gene was part of a class 1 integron borne by self-transferable plasmid pIP847. GES-type ␤-lactamases have not been reported previously in A. baumannii.Acinetobacter baumannii is a predominant species associated with outbreaks of nosocomial infections, such as pneumonia, urinary tract infections, septicemia, and meningitis. Its clinical significance is due to its ability either to upregulate indigenous efflux pumps (5) or to acquire numerous resistance mechanisms (7) that lead to therapeutic failure. A rapid, global emergence of A. baumannii strains resistant to all ␤-lactams, including carbapenems, aminoglycosides, quinolones, tetracyclines-glycylcyclines, polymyxins, and trimethoprim-sulfamethoxazole, has been observed (1). A. baumannii clinical specimens resistant to all known antibiotics, including polymyxins, have been reported, illustrating the genetic flexibility of this pathogen (13).Resistance to ␤-lactams in A. baumannii is due mainly to the production of ␤-lactamases but can also result from several other mechanisms, including changes in outer membrane proteins, overexpression of multidrug efflux pumps, and alterations in the affinity or production of penicillin-binding proteins (9). ␤-Lactamases with carbapenemase activity, i.e., class D carbapenem-hydrolyzing oxacillinases or, less frequently, class B metallo-␤-lactamases, represent the major clinical concern. To the best of our knowledge, Ambler class A carbapenemases KPC, GES, SME, NMC, and IMI have not yet been reported in A. baumannii (18).A. baumannii BM4674 was isolated from the tibia fracture of a patient hospitalized at the Centre Hospitalier Universitaire in Nancy, France, in September 2008. MICs of antimicrobial agents for this strain were determined by Etest (AB Biodisk, Combourg, France) on Mueller-Hinton agar (bioMerieux, Marcy l'Etoile, France), and the breakpoints delivered by the Comité de l'Antibiogramme de la Société Française de Microbiologie were used for interpretations of results (3). A. baumannii BM4674 was resistant to all ␤-lactams, with decreased susceptibility to carbapenems (MIC imipenem ϭ 4 g/ ml; MIC meropenem ϭ 8 g/ml). It was also resistant to aminoglycosides, co-trimoxazole, quinolones, and chloramphenicol but remained susceptible to tetracyclines-glycylcyclines, colistin, and rifampin (rifampicin).The transfer of ␤-lactam resistance from A. baumannii BM4674 to A. baumannii BM4652 was performed by conjugation on solid medium, as described previously (11). Transconjugants selected on agar containing apramycin (80 g/ml) and ceftazidime (16 g/ml) were obtained at a high frequency of ca. 1 ϫ 10 Ϫ3 per recipient cell. They exhibited a broad spectrum of resistance to ␤-lactams, including aztreonam, diminished susceptibility to imipenem (MIC ϭ 0.75 g/ml) and meropenem (MIC ϭ 1.5 g/ml) compared to that of the recipi...

Helicobacter pylori resistance to macrolides is increasing, and the need for susceptibility testing has become crucial. The only standardized method is agar dilution, which is not adapted to clinical practice. The present work aimed: (1) to optimize the technical conditions and to assess the reproducibility of the E-test and disk diffusion method for macrolides susceptibility testing of H. pylori, and (2) to assess the performances of these two phenotypic methods in detecting strains harboring a resistance mechanism to macrolides. We used 191 isolates collected in nine centers of France and Belgium. Phenotypic tests were performed on Mueller-Hinton agar supplemented with 10% horse blood, inoculated with a 2-day-old H. pylori suspension (10(8) CFU/ml), and incubated for 72 hr at 37 degrees C under microaerophilic conditions. The reproducibility studied on two randomly selected strains was better for disk diffusion than for the E-test for both clarithromycin and erythromycin. For a subset of 10 strains, the MICs of erythromycin and clarithromycin did not differ from more than one two-fold dilution when determined by E-test or agar dilution method. The breakpoints were for MICs: 1 mg/L for both clarithromycin and erythromycin and for inhibition diameters, 22 mm for clarithromycin and 17 mm for erythromycin. There was a 100% concordance between susceptibility to erythromycin and clarithromycin. However, the susceptible and resistant populations were better separated by testing erythromycin. Of 34 resistant strains, two lacked the A2142G and A2143G point mutations in 23S rRNA by PCR-RFLP. None of 15 tested sensitive strains were positive for one of these two point mutations. For clinical practice, we recommend to assess macrolide susceptibility of H. pylori by using one of these two phenotypic methods under the described technical conditions.

No abstract

The aim of this prospective study was to compare differential blood cultures and quantitative catheter tip cultures for the diagnosis of catheter-related sepsis. Over a period of 2 years, 283 central venous catheters were inserted in 190 adult patients. Catheters were removed when they were no longer needed or when infection was suspected. Immediately before removal of the central venous catheters, blood cultures were performed, with blood drawn simultaneously from the catheter and the peripheral vein. After removal, quantitative catheter culture was performed according to the Brun-Buisson modified Cleri technique. Fifty-five quantitative catheter cultures were positive. They were classified as contaminated (n = 18), colonized (n = 23), or infected (n = 14). Differential blood cultures correctly identified 13 infections. With a catheter/peripheral cfu ratio of 8, differential blood cultures had a sensitivity of 92.8% and a specificity of 98.8%. When the catheters were removed because of suspected infection, differential blood cultures had a sensitivity of 92.8% and a specificity of 100%. Differential blood culture, a technique that does not necessitate catheter removal, seems effective in the diagnosis of catheter-related sepsis in patients in the intensive care unit.

In vitro or animal models have been used to investigate the pathogenesis of Helicobacter pylori infection. However, extrapolation to humans of results obtained with these heterologous models remains difficult. We have developed a new model for the study of H. pylori infection that uses human entire embryonic stomachs engrafted in nude mice. At 80 days after implantation, 22 of these xenografts, which exhibited a mature gastric epithelium, were inoculated with 107 to 108 CFU of eitherH. pylori LB1, a freshly isolated H. pyloristrain (n = 12), or H. pylori ATCC 49503 (n = 10). After 12-week examination, H. pylori LB1 persistently colonized the antrum of all inoculated grafts, as assessed by culture (mucus and mucosa), immunohistochemistry (mucosa), and a rapid urease test (mucus). H. pylori ATCC 49503, either before or after in vivo passage, permitted only a transient 2-week colonization in one of the five inoculated grafts in both groups. Colonization was always associated with an increase of gastric juice pH. A mild neutrophil infiltration of the gastric mucosa was noted solely in infected grafts. Transmission electron microscopy showed adherence of H. pylori organisms to epithelial cell surface. In six animals, intracytoplasmic location of this bacterium was observed in the antrum or the fundus. These results allow us to propose this model as a new ex vivo model for the study of specificH. pylori-gastric cell interactions.