No abstract

We report on a detailed study on the molecular diversity and evolutionary relationships of Tn1546-like elements in vancomycin-resistant enterococci (VRE) from humans and animals. Restriction fragment length polymorphism (RFLP) analysis of the VanA transposon of 97 VRE revealed seven different Tn1546 types. Subsequent sequencing of the complete VanA transposons of 13 VRE isolates representing the seven RFLP types followed by sequencing of the identified polymorphic regions in 84 other VanA transposons resulted in the identification of 22 different Tn1546derivatives. Differences between the Tn1546 types included point mutations in orf1, vanS,vanA, vanX, and vanY. Moreover, insertions of an IS1216V-IS3-like element inorf1, of IS1251 in the vanS-vanHintergenic region, and of IS1216V in thevanX-vanY intergenic region were found. The presence of insertion sequence elements was often associated with deletions in Tn1546. Identical Tn1546 types were found among isolates from humans and farm animals in The Netherlands, suggesting the sharing of a common vancomycin resistance gene pool. Application of the genetic analysis of Tn1546 to VRE isolates causing infections in hospitals in Oxford, United Kingdom, and Chicago, Ill., suggested the possibility of the horizontal transmission of the vancomycin resistance transposon. The genetic diversity in Tn1546 combined with epidemiological data suggest that the DNA polymorphism among Tn1546 variants can successfully be exploited for the tracing of the routes of transmission of vancomycin resistance genes.

In order to determine the prevalence of vancomycin-resistant enterococci (VRE) in The Netherlands, 624 hospitalized patients from intensive care units or hemato-oncology wards in nine hospitals and 200 patients living in the community were screened for VRE colonization. Enterococci were found in 49% of the hospitalized patients and in 80% of the patients living in the community. Of these strains, 43 and 32%, respectively, were Enterococcus faecium. VRE were isolated from 12 of 624 (2%) and 4 of 200 (2%) hospitalized patients and patients living in the community, respectively. PCR analysis of these 16 strains and 11 additional clinical VRE isolates from one of the participating hospitals revealed 24 vanA gene-containing, 1 vanB gene-containing, and 2 vanC1 gene-containing strains. All strains were cross-resistant to avoparcin but were sensitive to the novel glycopeptide antibiotic LY333328. Genotyping of the strains by arbitrarily primed PCR and pulsed-field gel electrophoresis revealed a high degree of genetic heterogeneity. This underscores a lack of hospital-driven endemicity of VRE clones. It is suggested that the VRE in hospitalized patients have originated from unknown sources in the community. Enterococcus spp. have recently emerged as important nosocomial pathogens (35). According to the data from the National Nosocomial Infections Surveillance System, enterococci are the fourth leading cause of nosocomial infections in the United States (12). Enterococcal infections that have frequently been reported include urinary tract infections, bacteremia, endocarditis, intra-abdominal infections, and surgical wound infections (27). Enterococcus faecalis is commonly isolated from the human gastrointestinal tract, whereas Enterococcus faecium is less frequently isolated from that site (31). This latter species, however, is noted for its antimicrobial resistance. Vancomycin-resistant E. faecium (VREF) strains have emerged in a setting of increasing high-level resistance of enterococci to penicillins and aminoglycosides (28). During the last few years, nosocomial outbreaks due to VREF have been described (17, 25). The emergence of VREF has raised serious concerns (28), and in response, the Hospital Infections Control Practices Advisory Committee (HICPAC), in collaboration with the Centers for Disease Control and Prevention, has developed recommendations for preventing the spread of vancomycin-resistant enterococci (VRE) (18). Given the concern that vancomycin resistance genes may transfer from enterococci to Staphylococcus aureus, a phenomenon that has been observed in vitro (31), control measures have already been proposed, should vancomycin-resistant S. aureus strains eventually arise (10). MATERIALS AND METHODS Prevalence study. Five Dutch university hospitals in Rotterdam, Utrecht, Nijmegen, and Amsterdam and four regional teaching hospitals in Breda and Tilburg participated in the study. Six hundred twenty-four patients who were hospitalized in the following wards were screened for gastrointestinal carriage of VRE...

Campylobacter jejuni isolates (n ‫؍‬234

No abstract

Guillain-Barré syndrome (GBS) and Miller-Fisher syndrome (MFS) are correlated with prior infection byCampylobacter jejuni in up to 40% of cases. Nucleotide sequence-based typing of 25 C. jejuni isolates associated with neuropathy permitted robust comparisons with equivalent data from approximately 800 C. jejuni isolates not associated with neuropathy. A total of 13 genetic lineages and 20 flaA short variable region nucleotide sequences were present among the 25 isolates. A minority of isolates (4 of 25) had the flaA short variable region nucleotide sequences that were previously proposed as a marker for GBS-associated isolates. These 4 isolates probably represented the Penner serotype 19 lineage, which has been proposed to have an association with GBS.

Ertapenem (MK-0826, L-749,345) is a 1-␤-methyl carbapenem with a long serum half-life. Its in vitro activitywas determined by broth microdilution against 3,478 bacteria from 12 centers in Europe and Australia, with imipenem, cefepime, ceftriaxone, and piperacillin-tazobactam used as comparators. Ertapenem was the most active agent tested against members of the family Enterobacteriaceae, with MICs at which 90% of isolates are inhibited (MIC 90 s) of <1 g/ml for all species. Ertapenem also was more active than imipenem against fastidious gram-negative bacteria and Moraxella spp.; on the other hand, ertapenem was slightly less active than imipenem against streptococci, methicillin-susceptible staphylococci, and anaerobes, but its MIC 90 s for these groups remained <0.5 g/ml. Acinetobacter spp. and Pseudomonas aeruginosa were also much less susceptible to ertapenem than imipenem, and most Enterococcus faecalis strains were resistant. Ertapenem resistance, based on a provisional NCCLS MIC breakpoint of >16 g/ml, was seen in only 3 of 1,611 strains of the family Enterobacteriaceae tested, all of them Enterobacter aerogenes. Resistance was also seen in 2 of 135 anaerobes, comprising 1 Bacteroides fragilis strain and 1 Clostridium difficile strain. Ertapenem breakpoints for streptococci have not been established, but an unofficial susceptibility breakpoint of <2 g/ml was adopted for clinical trials to generate corresponding clinical response data for isolates for which MICs were as high as 2 g/ml. Of 234 Streptococcus pneumoniae strains tested, 2 required ertapenem MICs of 2 g/ml and one required an MIC of 4 g/ml, among 67 non-Streptococcus pyogenes, non-Streptococcus pneumoniae streptococci, single isolates required ertapenem MICs of 2 and 16 g/ml. These streptococci also had diminished susceptibilities to other ␤-lactams, including imipenem as well as ertapenem. The Etest and disk diffusion gave susceptibility test results in good agreement with those of the broth microdilution method for ertapenem.

Vancomycin-resistant enterococci (VRE) pose an emerging health risk, but little is known about the precise epidemiology of the genes coding for vancomycin resistance. To determine whether the bacterial flora of consumer poultry serves as a gene reservoir, the level of contamination of poultry products with VRE was determined. VRE were genotyped by pulsed-field gel electrophoresis (PFGE), and transposon structure mapping was done by PCR. ThevanX-vanY intergenic regions of several strains were further analyzed by sequencing. A total of 242 of 305 (79%) poultry products were found to be contaminated with VRE. Of these VRE, 142 (59%) were high-level-vancomycin-resistant Enterococcus faecium strains (VREF). PFGE revealed extensive VREF heterogeneity. Two genotypes were found nationwide on multiple occasions: type A (22 of 142 VREF [15%]) and type B (14 of 142 VREF [10%]). No PFGE-deduced genetic overlap was found when VREF from humans were compared with VREF from poultry. TwovanA transposon types were identified among poultry strains. In 59 of 142 (42%) of the poultry VREF, the size of the intergenic region between vanX and vanY was ∼1,300 bp. This transposon type was not found in human VREF. In contrast, all human strains and 83 of 142 (58%) of the poultry VREF contained an intergenic region 543 bp in size. Sequencing of this 543-bp intergenic vanX-vanY region demonstrated full sequence conservation. Though preliminary, these data suggest that dissemination of the resistance genes carried on transposable elements may be of greater importance than clonal dissemination of resistant strains. This observation is important for developing strategies to control the spread of glycopeptide resistance.