Search

Les bactéries du genre Campylobacter, commensales du tube digestif de divers animaux, sont responsables d’infections variées chez l’homme, principalement de gastroentérites partout dans le monde. En 2010, l’OMS estime à 96 millions le nombre mondial de cas de gastroentérites à Campylobacterspp. et à environ 4 millions celui à Salmonellanon typhi. Campylobacter jejuniet dans une moindre mesure Campylobacter colisont les espèces les plus fréquemment isolées mais d’autres espèces plus récemment identifiées sont responsables d’infections digestives et également extradigestives. Dans les pays industrialisés, la contamination se fait le plus souvent par consommation de volaille insuffisamment cuite, les infections sont sporadiques avec une saisonnalité estivale, la prévalence du portage est faible. Dans les pays en voie de développement, la prévalence du portage est plus élevée, les infections sont endémiques sans saisonnalité. La contamination peut être interhumaine ou via l’environnement souillé. Différents facteurs clés conduisant à l’infection ont été caractérisés : la mobilité, l’adhésion, l’invasion, la production de toxines, l’échappement au système défensif de l’hôte, la capacité de survie en conditions hostiles. Ces bactéries sont naturellement sensibles aux aminopénicillines, aux carbapénèmes, aux aminosides, aux tétracyclines, aux macrolides et aux fluoroquinolones. Cependant, l’utilisation massive des antibiotiques pour le traitement des infections mais surtout comme facteurs de croissance pour l’élevage des animaux a conduit à l’émergence et à l’augmentation rapide du nombre de souches résistantes aux fluoroquinolones, aux macrolides et aux tétracyclines, avec, dans certains pays, des taux de résistance aux quinolones et aux cyclines supérieurs à 90 %.

Campylobacterest un agent pathogène ubiquitaire responsable d’infections intestinales extrêmement fréquentes dans le monde. La contamination humaine se fait principalement par voie alimentaire après ingestion de volailles (principal réservoir) ou d’eau contaminée. Les espèces les plus fréquemment retrouvées en pathologie humaine sont Campylobacter jejuniet Campylobacter coli. Campylobacterpeut causer un spectre très large de manifestations cliniques dont la gastro-entérite aiguë est la plus fréquente avec des diarrhées souvent sanglantes. Des atteintes extra-intestinales peuvent être observées, en particulier des septicémies. Les manifestations cliniques varient en fonction de l’espèce impliquée. Ainsi, Campylobacter fetusest connu pour être fréquemment responsable de bactériémies chez des patients présentant des comorbidités. Les infections à Campylobacterpeuvent se compliquer de manifestations immunologiques post-infectieuses rares mais graves (arthrite réactionnelles et syndrome de Guillain-Barré). Le diagnostic est microbiologique par l’isolement de la bactérie dans la coproculture ou les hémocultures. L’évolution est bénigne la plupart du temps et ne nécessite qu’un traitement symptomatique. L’antibiothérapie est à réserver aux formes sévères ou aux patients présentant des comorbidités. Les macrolides sont alors le traitement de choix. Plus récemment, de nouvelles espèces émergentes de Campylobacteront été identifiées. Ces données ouvrent la voie à la recherche concernant le rôle du microbiote dans de nombreuses affections digestives dont les maladies inflammatoires du tube digestif.

Le foie est l’organe le plus à même de développer des abcès. L’abcès hépatique (AH) est une maladie rare, touchant principalement les hommes de 60 ans avec plusieurs comorbidités, notamment diabète, transplantation hépatique et néoplasie digestive. Les principales causes de formation des AH sont l’obstacle biliaire (néoplasie, lithiase, cholangite ischémique), ou un foyer infectieux d’origine portale ou systémique. Les AH d’origine biliaire ou portale sont souvent polymicrobiens et les germes retrouvés sont des entérobactéries, des bacilles à Gram négatif anaérobies, Enterococcussp., Streptococcussp. Les AH d’origine systémique sont généralement monomicrobiens ; l’AH à Klebsiella pneumoniaehypervirulente, maladie émergente en Asie du Sud Est depuis quelques années, est maintenant rapporté dans le monde entier. Les AH à bacille à Gram négatif non fermentant, et les AH fongiques sont plus rares, et touchent des patients immunodéprimés, dans des contextes d’infections associées aux soins. Le diagnostic d’AH repose sur l’imagerie (échographie ou scanner). Pour rechercher la porte d’entrée de l’AH, il est nécessaire de pratiquer une exploration fine des voies biliaires, et du tube digestif (échographie, scanner±endoscopie). La documentation microbiologique est essentielle pour optimiser le traitement. Pour ce faire, il faut associer les hémocultures périphériques à la culture du pus de l’AH en respectant les conditions strictes d’anaérobiose. Le traitement repose sur le drainage de l’AH (par ponction simple ou associée à la pose d’un drain), une antibiothérapie prolongée et le traitement de la porte d’entrée. Les AH d’origine biliaire ont des taux de récidive et de mortalité plus élevés que les AH d’origine extrabiliaire.

Les entérocoques sont les cocci à Gram positif les plus fréquemment retrouvés dans les abcès hépatiques. Leur pathogénicité propre a longtemps été discutée dans les infections intra-abdominales. L’objectif de cette étude était de décrire les caractéristiques des patients ayant un abcès hépatique documenté à entérocoques, en les comparant à celles des patients ayant un abcès documenté à un autre germe.

Morbidity and mortality after a totally implantable venous access port (TIVAP)-related infection in oncology patients have rarely been studied. We conducted this study to assess the incidence and factors associated with the following outcome endpoints: severe sepsis or septic shock at presentation, cancellation of antineoplastic chemotherapy, and mortality at week 12. We conducted a prospective single-center observational study including all adult patients with solid cancer who experienced a TIVAP-related infection between February 1, 2009, and October 31, 2010. Patients were prospectively followed for 12 weeks. Among 1728 patients receiving antineoplastic chemotherapy during the inclusion time, 72 had an episode of TIVAP-related infection (4.2) and were included in the study (median age, 60 yr; range, 28–85 yr). The incidence of complications was 18 for severe sepsis or septic shock (1372 patients), 30 for definitive cancellation of antineoplastic chemotherapy (1446 patients who still had active treatment), and 46 for death at week 12 (3372 patients). Factors associated with severe sepsis or septic shock were an elevated C-reactive protein (CRP) level and an infection caused by Candidaspecies; 4 of the 13 severe episodes (31) were due to coagulase-negative staphylococci (CoNS). Factors associated with death at week 12 were a low median Karnofsky score, an elevated Charlson comorbidity index, the metastatic evolution of cancer, palliative care, and an elevated CRP level at presentation. Hematogenous complications (that is, infective endocarditis, septic thrombophlebitis, septic pulmonary emboli, spondylodiscitis, septic arthritis, or organ abscesses) were found in 8 patients (11). In conclusion, patients’ overall condition (comorbidities and autonomy) and elevated CRP level were associated with an unfavorable clinical outcome after a TIVAP-related infection. Candidaspecies and CoNS were responsible for severe sepsis or septic shock.

ABSTRACTEscherichia coliis the species most frequently associated with clinical infections by extended-spectrum-ß-lactamase (ESBL)-producing isolates, with the CTX-M ESBL enzymes being predominant and found in genetically diverse E. coliisolates. The main objective of this study was to compare, on the basis of a case-control design, the phylogenetic diversity of 152 CTX-M-producing and 152 non-ESBL-producing clinical E. coliisolates. Multilocus sequence typing revealed that even though CTX-M enzymes were largely disseminated across the diversity of E. coliisolates, phylogenetic group B2 showed a particularly heterogeneous situation. First, clone ST131 of group B2 was strongly associated with CTX-M production (55 [79%] of 70 isolates), with CTX-M-15 being predominant. Second, the remaining members of group B2 were significantly less frequently associated with CTX-M production (9 [12%] of 75) than E. coliphylogenetic groups A, B1, and D (88 [55%] of 159). CTX-M-producing ST131 E. coliisolates were significantly more frequent in patients hospitalized in geriatric wards or long-term care facilities. Besides, the non-ESBL ST131 isolates significantly more frequently showed resistance to penicillins than the non-ESBL, non-ST131 isolates did. In conclusion, the present study emphasizes the particular antimicrobial resistance and epidemiologic characteristics of clone ST131 within group B2, which could result from the higher antibiotic exposure of this clone, as it is the predominant clone of group B2 carried in the human gut.

The relationship between efflux system overexpression and cross-resistance to cefoxitin, quinolones, and chloramphenicol has recently been reported in Klebsiella pneumoniae. In 3 previously published clinical isolates and 17 in vitro mutants selected with cefoxitin or fluoroquinolones, mutations in the potential regulator genes of the AcrAB efflux pump (acrR, ramR, ramA, marR, marA, soxR, soxS, and rob) were searched, and their impacts on efflux-related antibiotic cross-resistance were assessed. All mutants but 1, and 2 clinical isolates, overexpressed acrB. No mutation was detected in the regulator genes studied among the clinical isolates and 8 of the mutants. For the 9 remaining mutants, a mutation was found in the ramR gene in 8 of them and in the soxR gene in the last one, resulting in overexpression of ramA and soxS, respectively. Transformation of the ramR mutants and the soxR mutant with the wild-type ramR and soxR genes, respectively, abolished overexpression of acrB and ramA in the ramR mutants and of soxS in the soxR mutant, as well as antibiotic cross-resistance. Resistance due to efflux system overexpression was demonstrated for 4 new antibiotics: cefuroxime, cefotaxime, ceftazidime, and ertapenem. This study shows that the ramR and soxR genes control the expression of efflux systems in K. pneumoniae and suggests the existence of efflux pumps other than AcrAB and of other loci involved in the regulation of AcrAB expression.

ABSTRACTThe relationship between efflux system overexpression and cross-resistance to cefoxitin, quinolones, and chloramphenicol has recently been reported in Klebsiella pneumoniae. In 3 previously published clinical isolates and 17 in vitromutants selected with cefoxitin or fluoroquinolones, mutations in the potential regulator genes of the AcrAB efflux pump (acrR, ramR, ramA, marR, marA, soxR, soxS, and rob) were searched, and their impacts on efflux-related antibiotic cross-resistance were assessed. All mutants but 1, and 2 clinical isolates, overexpressed acrB. No mutation was detected in the regulator genes studied among the clinical isolates and 8 of the mutants. For the 9 remaining mutants, a mutation was found in the ramRgene in 8 of them and in the soxRgene in the last one, resulting in overexpression of ramAand soxS, respectively. Transformation of the ramRmutants and the soxRmutant with the wild-type ramRand soxRgenes, respectively, abolished overexpression of acrBand ramAin the ramRmutants and of soxSin the soxRmutant, as well as antibiotic cross-resistance. Resistance due to efflux system overexpression was demonstrated for 4 new antibiotics: cefuroxime, cefotaxime, ceftazidime, and ertapenem. This study shows that the ramRand soxRgenes control the expression of efflux systems in K. pneumoniaeand suggests the existence of efflux pumps other than AcrAB and of other loci involved in the regulation of AcrAB expression.

ABSTRACTCross-resistance to cefoxitin (FOX), chloramphenicol (CMP), and quinolones (nalidixic acid [NAL]) related to a putative efflux system overexpression has recently been reported for Klebsiella pneumoniae. The potential impact of this multidrug resistance (MDR) on the virulence of K. pneumoniaewas evaluated in the Caenorhabditis elegansmodel. For 2 of the 3 MDR clinical isolates studied, a significant increase in acrBtranscription was found in comparison with their antibiotic-susceptible revertants. ATCC 138821 and MDR, revertant, and derivative strains with altered porin expression were studied. Strains proved or suspected to overexpress an efflux system were significantly more virulent than the ATCC and revertant strains (time to kill 50% of nematodes [LT50] in days: 3.4 to 3.8 ± 0.2 versus 4.1 to 4.4 ± 0.3, P< 0.001). Inversely, strains with altered porin expression were significantly less virulent, independently of the expression level of efflux system (LT50= 5.4 to 5.6 ± 0.2, P< 0.001). Altered porin expression did not change MICs of CMP and NAL but did those of FOX (4 to 16× MIC) and ertapenem (16 to 64× MIC). The strains with a normally or an overexpressed efflux system that received the β-lactamase CTX-M-15 became more widely resistant without modification of their virulence potential, suggesting that balance between resistance and virulence is dependent on the type of resistance mechanisms. In conclusion, this study shows that the expression of both efflux systems and porins is a key factor not only for antibiotic resistance but also virulence potential in K. pneumoniae.

ABSTRACTAmong patients with cirrhosis, infections caused by Escherichia coliorganisms that translocate from the gut are a frequent and severe complication. One hundred ten E. coliisolates from 110 cirrhotic patients with spontaneous bacterial peritonitis and/or spontaneous bacteremia were characterized for their phylogenetic group and virulence genotype (34 extraintestinal virulence factor genes). Genetic relatedness was investigated by enterobacterial repetitive intergenic consensus sequence type 2 (ERIC-2) PCR typing and multilocus sequence typing. Phylogenetic groups A, B1, B2, and D accounted for 24%, 4%, 48%, and 24% of the population, respectively. Overall, 68 distinct ERIC-2 profiles were encountered. Eleven clonal groups, represented by multiple isolates (2 to 11) from the same sequence type (ST) or sequence type complex, were identified. These clonal groups accounted for 54 (49%) isolates overall. Membership in one of these clonal groups was more frequent among B2 isolates than non-B2 isolates (67% versus 32%, P< 0.001). The most frequent sequence types were ST95 (n= 13) and ST73 (n= 8), followed by the ST14 and ST10 complexes (n= 7). ST131 and ST69 were represented by three isolates each. Clonal group-associated isolates exhibited a greater prevalence of 11 virulence genes, including papelements, than the other isolates. However, no association between clonal groups and host factors, type of infection, or mortality was observed. In conclusion, E. coliisolates causing spontaneous bacterial peritonitis and bacteremia in cirrhotic patients are genetically diverse. However, approximately half of the isolates belong to familiar clonal groups and exhibit extensive virulence profiles that may be associated with greater invasive potential.

ABSTRACTThe diagnosis of extrapulmonary tuberculosis is difficult because of the paucibacillary nature of these infections. We developed a culture-enhanced PCR assay combining a preliminary step of broth culture in BacT/Alert MP bottles with the subsequent detection of Mycobacterium tuberculosisusing the GenoType Mycobacteria Direct test. First, the procedure was applied to 10-fold-diluted suspensions of M. tuberculosisprepared in vitro. These experiments showed that a 15-day incubation time was required to detect bacilli in the suspension, with the lowest inoculum size yielding a single colony on Lowenstein-Jensen slants. The efficacy of culture-enhanced PCR at day 15 was subsequently evaluated with 225 nonrespiratory specimens from 189 patients with suspected tuberculosis. All these specimens were smear negative, and 31 (13.8%) from 27 patients were culture positive. The result of culture-enhanced PCR at day 15 was consistent with final culture results in all specimens tested. Compared to culture results, the sensitivity, specificity, positive predictive value, and negative predictive value were 100%. Four patients with a negative culture and a negative PCR result were diagnosed as having tuberculosis on the basis of histological findings or therapeutic response. When using a positive diagnosis of tuberculosis as a gold standard, the sensitivity, specificity, positive predictive value, and negative predictive value were 88.6%, 100%, 100%, and 97.9%, respectively. These results indicate that culture-enhanced PCR is a highly sensitive and specific method for the early detection of M. tuberculosisin extrapulmonary specimens.

ABSTRACTQuinolone-resistant and CTX-M-15-producing Escherichia coliisolates belonging to clone ST131 have been reported in the community. This study was designed to identify these E. coliisolates in the stools of 332 independent healthy subjects living in the area of Paris, France. Stools were plated on media without antibiotics, in order to obtain the dominant (Dm) fecal E. colistrain, and with nalidixic acid (NAL) and cefotaxime. Quinolone susceptibility, phylogenetic groups, and molecular profiles, including multilocus sequence types (ST), were determined for all NAL-resistant (NAL-R) isolates. Groups were also determined for the Dm strains from participants with NAL-R isolates and from a subgroup without NAL-R isolates. All B2 isolates were typed; pulsed-field gel electrophoresis was performed for the ST131 isolates, and the results were compared with those for intercontinental clone ST131. Two participants (0.6%) had extended-spectrum ß-lactamase-producing (SHV-2, TEM-52) fecal E. coliisolates, and 51 (15%) had NAL-R isolates; 51% of NAL-R isolates belonged to phylogenetic group A, 31% to group D, 16% to group B2, and 2% to group B1. The Dm strain was NAL-R in 3.3% of the 332 subjects. Forty-nine percent of the NAL-R isolates belonged to clones: ST10 and ST606 for group A isolates, ST117 and ST393 for group D isolates. Of all B2 isolates studied from 100 subjects (8 NAL-R strains; 19 NAL-susceptible dominant strains), 52% belonged to three clones: ST131 (n= 7), ST95 (n= 4), and ST141 (n= 3). This is the first study to show the presence of fecal E. coliisolates of clone ST131 in 7% of independent healthy subjects not colonized by CTX-M-15-producing isolates.

ABSTRACTThree types of multidrug-resistant Escherichia coliisolates, called GEN S, GEN R, and AMG S, according to their three different aminoglycoside resistance patterns, were responsible for urinary tract colonization or infection in 87, 12, and 13 new patients, respectively, in a French 650-bed geriatric hospital over a 13-month period. The three E. colitypes belonged to the same clone and phylogenetic group (group B2) and had identical transferable plasmid contents (a 120-kb plasmid), β-lactam and fluoroquinolone resistance genotypes (blaTEM-1B, blaCTX-M-15, and double mutations in both the gyrAand the parCgenes), and virulence factor genotypes (aer, fyuA, and irp2). They disseminated in the geriatric hospital, where the antibiotics prescribed most often were fluoroquinolones and ceftriaxone, but not in the affiliated acute-care hospital, where isolation precautions were applied to the transferred patients. Thus, E. coliisolates, both CTX-M-type β-lactamase producers and fluoroquinolone-resistant isolates, might present a new challenge for French health care settings.

ABSTRACTEnterobacterial strains of Raoultellaspp. display a penicillinase-related β-lactam resistance pattern suggesting the presence of a chromosomal blagene. From whole-cell DNA of Raoultella planticolastrain ATCC 33531Tand Raoultella ornithinolyticastrain ATCC 31898T, blagenes were cloned and expressed into Escherichia coli. Each gene encoded an Ambler class A β-lactamase, named PLA-1 and ORN-1 for R. planticolaand R. ornithinolytica, respectively. These β-lactamases (291 amino acids), with the same pI value of 7.8, had a shared amino acid identity of 94%, 37 to 47% identity with the majority of the chromosome-encoded class A β-lactamases previously described for Enterobacteriaceae, and 66 to 69% identity with the two β-lactamases LEN-1 and SHV-1 from Klebsiella pneumoniae. However, the highest identity percentage (69 to 71%) was found with the plasmid-mediated β-lactamase TEM-1. PLA-1, which displayed very strong hydrolytic activity against penicillins, also displayed significant hydrolytic activity against cefepime and, to a lesser extent, against cefotaxime and aztreonam, but there was no hydrolytic activity against ceftazidime. Such a substrate profile suggests that the Raoultellaβ-lactamases PLA-1 and ORN-1 should be classified into the group 2be of the β-lactamase classification of K. Bush, G. A. Jacoby, and A. A. Medeiros (Antimicrob. Agents Chemother. 39:1211-1233, 1995). The highly homologous regions upstream of the blaPLA-1Aand blaORN-1Agenes comprised a nucleotide sequence identical to the −35 region and another one very close to the −10 region of the blaLEN-1gene. From now on, as the blagene sequences of the most frequent Raoultellaand Klebsiellaspecies are available, the blagene amplification method can be used to differentiate these species from each other, which the biochemical tests currently carried out in the clinical laboratory are unable to do.

ABSTRACTThe two genetic groups (oxy-1 and oxy-2) previously identified in the Klebsiella oxytocataxon are recognizable by four independent molecular markers: (i) ERIC-1R profiles, (ii) 16S ribosomal DNA (rDNA) signature sequences, (iii) singular nucleotides in a defined fragment of the rpoBgene, and (iv) the type of the strain's blaOXYgene (i.e., blaOXY-1or blaOXY-2). K. oxytocastrains SG266 and SG271 could not be classified into these genetic groups based on their ERIC-1R profile and blaOXYgene sequence. With regard to the gene identity percentages between the blaOXY-1and blaOXY-2gene groups (86.8% ± 0.4%) and within a blaOXYgene group (>99%), it was concluded that the blaOXYgene of strain SG271 was representative of a new blaOXYgene group (blaOXY-3), since the mean identity percentages between it and the two blaOXYgene groups were 85.5% ± 0.2% and 84.4% ± 0.4%, respectively. Since the corresponding percentages were 95.0% ± 0.4% and 86.2% ± 0.3% for strain SG266, it was impossible to classify its blaOXYgene, which was therefore named blaOXY-4. The 16S rDNA signature sequences of the two strains could be determined only after cloning experiments. The SG266 clones displayed the same signature sequence as that of the genetic group oxy-1, whereas the SG271 clones displayed three different 16S rDNA signature sequences that also differed from those of the two genetic groups. Singular nucleotides were found within the rpoBsequence of the two strains, allowing for their distinction from the two genetic groups. All of these results, combined with those previously obtained by the ERIC-1R PCR method, indicate that strain SG271 is representative of a new K. oxytocagenetic group (oxy-3), whereas strain SG266 could not be classified.

The two genetic groups (oxy-1 and oxy-2) previously identified in the Klebsiella oxytoca taxon are recognizable by four independent molecular markers: (i). ERIC-1R profiles, (ii). 16S ribosomal DNA (rDNA) signature sequences, (iii). singular nucleotides in a defined fragment of the rpoB gene, and (iv) the type of the strain's bla(OXY) gene (i.e., bla(OXY-1) or bla(OXY-2)). K. oxytoca strains SG266 and SG271 could not be classified into these genetic groups based on their ERIC-1R profile and bla(OXY) gene sequence. With regard to the gene identity percentages between the bla(OXY-1) and bla(OXY-2) gene groups (86.8% +/- 0.4%) and within a bla(OXY) gene group (>99%), it was concluded that the bla(OXY) gene of strain SG271 was representative of a new bla(OXY) gene group (bla(OXY-3)), since the mean identity percentages between it and the two bla(OXY) gene groups were 85.5% +/- 0.2% and 84.4% +/- 0.4%, respectively. Since the corresponding percentages were 95.0% +/- 0.4% and 86.2% +/- 0.3% for strain SG266, it was impossible to classify its bla(OXY) gene, which was therefore named bla(OXY-4). The 16S rDNA signature sequences of the two strains could be determined only after cloning experiments. The SG266 clones displayed the same signature sequence as that of the genetic group oxy-1, whereas the SG271 clones displayed three different 16S rDNA signature sequences that also differed from those of the two genetic groups. Singular nucleotides were found within the rpoB sequence of the two strains, allowing for their distinction from the two genetic groups. All of these results, combined with those previously obtained by the ERIC-1R PCR method, indicate that strain SG271 is representative of a new K. oxytoca genetic group (oxy-3), whereas strain SG266 could not be classified.

ABSTRACTTwo multidrug-resistant Salmonella entericaserovar Wien strains (SW468 and SW1107) were isolated in 2001 in Tunis. Both strains produced the β-lactamases TEM-1, SHV-2a, and CMY-4, whereas strain SW1107 also produced the β-lactamase CTX-M-3. The imipenem-resistant strain (SW468) was totally devoid of the OmpF-immunorelated porin. Imipenem resistance was shown as being related to porin loss and CMY-4 β-lactamase production.

Purpose:The purpose of this study was to compare the efficacy of rifampin-bonded gelatin-sealed and silver acetate/collagen-coated knitted polyester prostheses for the prevention of bacteremic graft infection in an animal model. Methods:Eighteen 6.0-mm polyester grafts (length, 5.0 cm) were implanted in dogs end-to-end into the infrarenal aorta. The dogs were divided into four groups as a function of type of prosthesis implanted. The dogs in groups I (n = 3) and II (n = 3) received control gelatin-sealed or collagen-coated polyester prostheses, respectively. In group III (n = 6), the dogs received rifampin-bonded gelatin-sealed polyester prostheses. In group IV (n = 6), the dogs received silver/collagen-coated polyester prostheses. Two days after implantation, the grafts were challenged with 6 × 109Staphylococcus aureusintravenously. One week after implantation, the grafts were harvested with sterile technique. Quantitative cultures were obtained from all the harvested grafts. The results were expressed as colony-forming units per cm2of graft material. Bacteriologic study was also performed on various tissue samples. The χ2test was used to compare the culture proven infection of control and antimicrobial grafts. Results:All the control grafts were infected with S aureusat the time of removal. Five of the six silver/collagen-coated grafts were infected, whereas none of the six rifampin-bonded gelatin-sealed grafts grew S aureus(P<.01). There was no significant difference in the number of positive culture results of organ samples between the different groups of dogs. Conclusion:These results indicate that rifampin-bonded gelatin-sealed polyester grafts are significantly more resistant to bacteremic infection than are silver/collagen-coated polyester grafts in a highly challenging model. (J Vasc Surg 2002;35:1260-3.)