Molecular differentiation of Renibacterium salmoninarum isolates from worldwide locations.
(1/1937)
Renibacterium salmoninarum is a genospecies that is an obligate pathogen of salmonid fish and is capable of intracellular survival. Conventional typing systems have failed to differentiate isolates of R. salmoninarum. We used two methods to assess the extent of molecular variation which was present in isolates from different geographic locations. In one analysis we investigated possible polymorphisms in a specific region of the genome, the intergenic spacer (ITS) region between the 16S and 23S rRNA genes. In the other analysis we analyzed differences throughout the genome by using randomly amplified polymorphic DNA (RAPD). We amplified the spacer region of 74 isolates by using PCR and performed a DNA sequence analysis with 14 geographically distinct samples. The results showed that the 16S-23S ribosomal DNA spacer region of R. salmoninarum is highly conserved and suggested that only a single copy of the rRNA operon is present in this slowly growing pathogen. DNA sequencing of the spacer region showed that it was the same length in all 14 isolates examined, and the same nucleotide sequence, sequevar 1, was obtained for 11 of these isolates. Two other sequevars were found. No tRNA genes were found. We found that RAPD analysis allows reproducible differentiation between isolates of R. salmoninarum obtained from different hosts and different geographic regions. By using RAPD analysis it was possible to differentiate between isolates with identical ITS sequences. (+info)
Biodiversity of Lactococcus garvieae strains isolated from fish in Europe, Asia, and Australia.
(2/1937)
Lactococcus garvieae (junior synonym, Enterococcus seriolicida) is a major pathogen of fish, producing fatal septicemia among fish species living in very diverse environments. The phenotypic traits of L. garvieae strains collected from three different continents (Asia, Europe, and Australia) indicated phenotypic heterogeneity. On the basis of the acidification of D-tagatose and sucrose, three biotypes were defined. DNA relatedness values and a specific PCR assay showed that all the biotypes belonged to the same genospecies, L. garvieae. All of the L. garvieae strains were serotyped as Lancefield group N. Ribotyping proved that one clone was found both in Japan, where it probably originated, and in Italy, where it was probably imported. PCR of environmental samples did not reveal the source of the contamination of the fish in Italy. Specific clones (ribotypes) were found in outbreaks in Spain and in Italy. The L. garvieae reference strain, isolated in the United Kingdom from a cow, belonged to a unique ribotype. L. garvieae is a rising zoonotic agent. The biotyping scheme, the ribotyping analysis, and the PCR assay described in this work allowed the proper identification of L. garvieae and the description of the origin and of the source of contamination of strains involved in outbreaks or in sporadic cases. (+info)
Comparative activity of quinupristin/dalfopristin and RPR 106972 and the effect of medium on in-vitro test results.
(3/1937)
Quinupristin/dalfopristin and RPR 106972 were active in vitro against a wide range of aerobic Gram-positive organisms including Enterococcus faecium. However, most isolates of Enterococcus faecalis were resistant or of intermediate sensitivity. Against Staphylococcus aureus quinupristin/dalfopristin was more active but for all other species the range of activity of the two drugs was the same or RPR 106972 was more active. RPR 106972 was also more active against the respiratory pathogens Haemophilus influenzae and Moraxella catarrhalis. Quinupristin/dalfopristin MICs for isolates of H. influenzae (1-8 mg/L) clustered around the breakpoint. There were differences in the quality of growth, but little difference in MICs or zone diameters was obtained on three different media: Mueller-Hinton (MHA), Iso-Sensitest (ISA), and Diagnostic Sensitivity Test (DST) agars. The addition of blood to the medium increased MICs 2- to 4-fold, with MHA showing the greatest increase, and reduced zone diameters around quinupristin/dalfopristin discs by 3-4 mm, with the greatest effect on ISA. (+info)
The in-vitro activity of linezolid (U-100766) and tentative breakpoints.
(4/1937)
The in-vitro activity of linezolid, a novel oxazolidinone, was investigated in comparison with those of amoxycillin, cefuroxime, quinupristin/dalfopristin, trovafloxacin and vancomycin against 420 recent Gram-positive and anaerobic clinical isolates. Linezolid was equally active (MIC90 1 mg/L) against methicillin-susceptible and -resistant Staphylococcus aureus. It demonstrated uniform activity against streptococci and enterococci and no cross-resistance with other agents. The time-kill kinetic data demonstrated that the in-vitro activity of linezolid was predominantly bacteriostatic; slow bactericidal activity was only observed at the higher concentration with streptococci. An increase in inoculum from 10(4) to 10(6) cfu on selected strains had little effect on the MICs (MIC90 within one dilution step) of linezolid and an increase in inoculum from 10(5) to 10(7) cfu/mL had no notable effect on the in-vitro bactericidal activity. A tentative linezolid breakpoint of 2 mg/L was chosen after analysis of distribution of susceptibilities. (+info)
Transmission dynamics of epidemic methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococci in England and Wales.
(5/1937)
A simple epidemiological framework for the analysis of the transmission dynamics of hospital outbreaks of epidemic methicillin-resistant Staphylococcus aureus (EMRSA) and vancomycin-resistant enterococci (VRE) in hospitals in England and Wales is presented. Epidemic strains EMRSA-15 and EMRSA-16 are becoming endemic in hospitals in the United Kingdom, and theory predicts that EMRSA-15 and EMRSA-16 will reach respective endemic levels of 158 (95% confidence interval [CI], 143-173) and 116 (95% CI, 109-123) affected hospitals with stochastic fluctuations of up to 30 hospitals in each case. An epidemic of VRE is still at an early stage, and the incidence of hospitals newly affected by VRE is growing exponentially at a rate r=0.51/year (95% CI, 0.48-0.54). The likely impact of introducing surveillance policies if action is taken sufficiently early is estimated. Finally, the role of heterogeneity in hospital size is considered: "Super-spreader hospitals" may increase transmission by 40%-132% above the expected mean. (+info)
DNA banding pattern polymorphism in vancomycin-resistant Enterococcus faecium and criteria for defining strains.
(6/1937)
The degree of DNA banding pattern polymorphism exhibited by vancomycin-resistant Enterococcus faecium (VREM) strains isolated on a renal unit over an 11-month period was investigated. Thirty VREM strains from different patients were analyzed by pulsed-field gel electrophoresis (PFGE; with extended run and optimal pulse times), ribotyping, plasmid profile analysis, biotyping, pyrolysis mass spectrometry, and antibiogram analysis. PFGE resolved 17 banding patterns which formed four distinct clusters at the 82% similarity level. Intercluster band differences ranged from 14 to 31 bands. The strains in one cluster, which contained seven patterns that differed from each other by one to seven bands and from the common pattern by five bands, were confirmed to be a single strain by four of the five other typing methods. The strains in a second cluster with eight patterns, which differed from each other by 1 to 12 bands, contained two subclusters. This subdivision was supported by ribotyping and biotyping. However, it was unclear whether these subclusters represented distinct strains. In one strain, marked polymorphism (patterns that differed from each other by up to four bands) was observed in the ribotype pattern. This study demonstrates the high degree of DNA banding pattern polymorphism found for some strains of VREM and illustrates the complexity involved in defining such strains. (+info)
Proficiency of clinical laboratories in and near Monterrey, Mexico, to detect vancomycin-resistant enterococci.
(7/1937)
Early detection of vancomycin-resistant enterococci is important for preventing its spread among hospitalized patients. We surveyed the ability of eight hospital laboratories in and near Monterrey, Mexico, to detect vancomycin resistance in Enterococcus spp. and found that although laboratories can reliably detect high-level vancomycin resistance, many have difficulty detecting low-level resistance. (+info)
Isolation of Enterococcus faecalis clinical isolates that efficiently adhere to human bladder carcinoma T24 cells and inhibition of adhesion by fibronectin and trypsin treatment.
(8/1937)
The adherence of Enterococcus faecalis strains to human T24 cells was examined by scanning electron microscopy. Five highly adhesive strains were identified from 30 strains isolated from the urine of patients with urinary tract infections. No efficiently adhesive strains were found among the 30 strains isolated from the feces of healthy students. The five isolated strains also adhered efficiently to human bladder epithelial cells. Analysis of restriction endonuclease-digested plasmid DNAs and chromosome DNAs showed that the five strains were different strains isolated from different patients. The adhesiveness of these strains was inhibited by treatment with fibronectin or trypsin, implying that a specific protein (adhesin) on the bacterial cell surface mediates adherence to fibronectin on the host cell surfaces, and the adhesin differs from the reported adhesins. (+info)