In vitro study of the retention and mechanical fatigue behavior of four implant overdenture stud-type attachments

This study sought to determine the influence of mechanical fatigue on four varieties of implant overdenture studtype attachments (Supra-Snap, O'Ring, TSIB, ZAAG). Measurements of the initial vertical retentive force and the weight of the implant abutment were recorded. The same procedure was performed after the equivalent of 2 months, 6 months, and 12 months of clinical wear. For the four attachments, weight variation of the abutment between 0 and 1,080 cycles demonstrated no significant difference. Results indicated the TSIB to be significantly most retentive; next most retentive was the O'Ring, followed respectively by Supra-Snap and ZAAG.

Changes in the metabolic and contractile characteristics of muscle in male cattle between 10 and 16 months of age

Samples of semitendinosus muscle from 28 male cattle (18 Salers and 10 Limousins) were taken at 10 months (biopsy) and at 16 months of age (at slaughter). The animals had received the same diet and were slaughtered after the same duration of fattening. The activities of isocitrate dehydrogenase and lactate dehydrogenase were measured in the muscle samples. The five lactate dehydrogenase isoenzymes were separated by electrophoresis under non-denaturing conditions and assayed by densitometry. Fibres were identified by histochemistry by myofibrillar ATPase and succinate dehydrogenase activities as SO (slow oxidative), FOG (fast oxidative glycolytic) or FG (fast glycolytic), and by immunohistochemistry by their reaction to monoclonal antibodies specific to slow and fast myosin heavy chain reactions in I, IIC, IIA, IIAB and IIB type fibres. The isocitrate dehydrogenase activity was not modified between 10 and 16 months of age; the lactate dehydrogenase activity decreased and was correlated with an increase in the proportion of the H isozyme to the detriment of the proportion of the M form. This period was characterized by an increase in fibre size, increased expression of MHC IIa, resulting in more IIA fibres, less IIB fibres, and an increase in the percentage of type IIAB fibres, however the proportions of SO, FOG and FG, when analysed statistically, were not modified between 10 and 16 months of age.

The link between phylogeny and virulence in Escherichia coli extraintestinal infection

Previous studies suggesting a link between Escherichia coli phylogenetic groups and extraintestinal virulence have been hampered by the difficulty in establishing the intrinsic virulence of a bacterial strain. Indeed, unidentified virulence factors do exist, and the susceptibility of the host to infection is highly variable. To overcome these difficulties, we have developed a mouse model of extraintestinal virulence to test the virulence of the strains under normalized conditions. We then assessed the phylogenetic relationships compared to the E. coli reference (ECOR) collection, the presence of several known virulence determinants, and the lethality to mice of 82 human adult E. coli strains isolated from normal feces and during the course of extraintestinal infections. Commensal strains belong mainly to phylogenetic groups A and B1, are devoid of virulence determinants, and do not kill the mice. Strains exhibiting the same characteristics as the commensal strains can be isolated under pathogenic conditions, thus indicating the role of host-dependent factors, such as susceptibility linked to underlying disease, in the development of infection. Some strains of phylogenetic groups A, B1, and D are able to kill the mice, their virulence being most often correlated with the presence of virulence determinants. Lastly, strains of the B2 phylogenetic group represent a divergent lineage of highly virulent strains which kill the mice at high frequency and possess the highest level of virulence determinants. The observed link between virulence and phylogeny could correspond to the necessity of virulence determinants in a genetic background that is adequate for the emergence of a virulent clone, an expression of the interdependency of pathogenicity and metabolic activities in pathogenic bacteria.

Age-related changes and location of type I, III, IV, V and VI collagens during development of four foetal skeletal muscles of double-muscled and normal bovine animals

The aim of this work was to study the variability in the quantities of hydroxyproline, of type I and III collagens and in the location of types, I, III, IV, V, VI in four muscles of normal and double-muscled (DM) cattle. Samples were collected from foetuses at different ages post-conception. Both in the two genetic types and in muscles, from 110 days, types I, III, V, VI were located in perymisium and types I, IV, V, VI in endomysium. The amounts of hydroxyproline and of type I collagen increased from 150 to 180 or 230 days then decreased up to 260 days, with a trend to lower quantities in muscles of DM animals. Depending on the muscle and of the genetic type, amounts of type III, or changed as those of type I, or remained stable. Whatever the genetic type, at the end of gestation, proportions of type I and III in the total collagen are not identical in the four muscles, differences between muscles being particularly marked for type III, CT and MA muscles being the richer in this type. In addition, these two muscles contained less type III in DM animals than in normal ones.

Comparison of foetal metabolic differentiation in three cattle muscles

Metabolic differentiation of Semitendinosus (ST), Cutaneus trunci (CT) and Masseter (MA) in cattle foetuses aged from 110 to 260 days was studied by measuring isocitrate dehydrogenase (ICDH, oxidative) and lactate dehydrogenase (LDH, glycolytic) activities. The five LDH isoenzymes were separated by electrophoresis and assayed by densitometry. ICDH activity increased from 210 days onwards in the three muscles but more intensively in MA (oxidative). LDH activity increased from 170 days onwards in ST, 180 days onwards in CT and only from 210 days onwards in MA and was higher in the glycolytic muscles (ST and CT). The proportion of the LDH-M subunit increased during foetal life in glycolytic muscles. At 110 days, it was higher in CT, intermediate in ST and lower in MA. These results show that 1) metabolic differentiation of bovine muscle begins during the last third of foetal life and 2) the proportion of the LDH-M subunit seems to be related to the contractile type of adult muscle from the first stages of foetal life.

Correlation of topography to bond strength of etched ceramic

PURPOSE

Bonding techniques are commonly used today to ensure the durability of porcelain laminate veneers and ceramic inlay-onlays, which are esthetically pleasing solutions to the problem of dental restoration. Acid etching and silanization of porcelain have been widely used to enhance the retention between bonding resins and ceramic restorations. The purpose of this study was to evaluate the effect of surface modifications with 10% hydrofluoric acid gel and a coupling agent (a dual component silane) on the bond strength of 2 dental feldspathic ceramics (GC and PVS) bonded with an unfilled resin (Super-Bond).

MATERIALS AND METHODS

Eighty samples of GC and eighty samples of PVS were built for a mechanical study. Mechanical tests were conducted using a Lloyd T 6000 R tensile machine, which determined the bond strengths of the 2 ceramics after different surface treatments (etching or silanization). In the next part of the study, 10 surfaces of GC and 10 surfaces of PVS were studied with a scanning mechanical microscope to evaluate the action of hydrofluoric acid gel on the roughness of the 2 ceramics.

RESULTS

Etching ceramic with hydrofluoric acid gel increased the developed surface of feldspathic ceramics, especially for PVS, but this treatment was not sufficient to obtain the highest shear bond strength. The highly positive influence of silanization was shown, particularly for GC ceramic bonded with an unfilled resin.

CONCLUSION

Silane combined with the action of hydrofluoric acid gel is the most effective surface treatment for ceramic.

Insulin-like growth factor II (IGF-II) mRNA expression during skeletal muscle development of double-muscled and normal bovine foetuses

We investigated the IGF-II gene expression in developing Semitendinosus muscle in foetal normal and double-muscled cattle. Samples from normal and double-muscled foetuses ranging from 90 to 210 d post-conception were collected and total RNA extracted. Northern blot analysis was performed using the human IGF-II cDNA probe. Five IGF-II transcripts, 5.1, 4.4, 3.7, 2.6 and 1.7 kb, were detected in muscle samples. Throughout gestation, all transcripts, except for the 5.1 kb one, decreased similarly in both genetic types. In double-muscled foetuses, the amount of the 5.1 kb transcript was higher than those of the other transcripts and its expression remained stable throughout the gestational stages analysed. These results indicated that the regulation of IGF-II gene transcription was distinct in both genetic types. The IGF-II foetal plasma concentrations increased throughout gestation. In bovine foetuses, the first muscle cell differentiation was concomitant with a high autocrine IGF-II mRNA expression and low plasma IGF-II levels in both genetic types. The second step of muscle cell differentiation was associated with high IGF-II plasma concentrations and the autocrine expression of IGF-II was reduced.

Water resistance of resin-bonded joints with time related to alloy surface treatment

OBJECTIVES

This paper attempts to study the resistance of resin-bonded metallic joints to damage in water with time.

METHODS

Unlike the shear or tensile test, a cleavage test (Double Cantilever Beam test) allows us to follow the crack propagation in water, according to the fracture mechanics concept. Moreover, it is possible to follow the kinetic degradation of the metal/resin interface because this test is not totally destructive to the assembly. We have worked on 18 batches according to the nature of the alloys (Pd, Pd-Ag, Au, Co-Cr and Ni-Cr) and the surface treatment (sandblasting, Silicoater MD, Rocatec, V-Primer). The crack length was measured over a period of 20 days. The results are expressed in terms of adherence energy.

RESULTS

The adherence energy dramatically decreased with time in water. The slope of the regression straight line appears to be a good criterion for evaluating the durability of the alloy/adhesive interface. We have demonstrated the importance of silica coating and, especially, the effectiveness of the Rocatec system upon the degree of hydrolytic degradation, and have shown how the development of cracks depends upon surface treatment.

A study of relationships among F17 a producing enterotoxigenic and non-enterotoxigenic Escherichia coli strains isolated from diarrheic calves

We investigated the clonal relationships among 41 enterotoxigenic (ETEC) or non-enterotoxigenic (NETEC) Escherichia coli strains producing the F17 a fimbriae isolated from diarrheic calves in France or Belgium in the early 1980s. Twenty-three of the 26 ETEC strains were highly clonally related, most of them with a O101:K32:H9-serotype. The NETEC strains were also divided in clonal subgroups, most of them with O101:H-serotype. The F17 a positive ETEC strains are no longer isolated from diarrheic calves in these countries. It is postulated that the use of a vaccine including O101, K32 and H9 antigens in addition to K99 (F5) explains the strongly reduced isolation of the O101:K32:H9, K99 (F5) E. coli clone.

Comparison of five typing methods for the epidemiological study of Listeria monocytogenes

Five typing methods were compared in a study designed to adapt a strategy for epidemiologically typing large numbers of Listeria monocytogenes strains. The methods studied were serotyping, electrophoretic typing of esterases (zymotyping), restriction fragment length polymorphism of ribosomal DNA (ribotyping), random amplified polymorphic DNA (RAPD) and pulsed-field gel electrophoresis (PFGE). Data were analysed by computer-assisted statistical analysis. Included in the analysis were 35 strains of L. monocytogenes, including 14 epidemic strains isolated during outbreaks in France in 1992 and 1993, and 21 strains isolated from food and the environment. Five serotypes, eight zymotypes, ten ribotypes, 13 RAPD patterns and 12 PFGE patterns were identified among the 35 strains. The most discriminating combination of typing methods was ribotyping and PFGE typing [27 types, discriminatory index (D.I.) = 0.978]. A factorial analysis of correspondence for each method differentiated the epidemic strains from the environmental strains. This study shows that computer-assisted statistical treatment of the data, combined with the use of discriminating typing methods, is a powerful tool for the epidemiological analysis of Listeria monocytogenes.

Classification of bovine muscle fibres by different histochemical techniques

The classification of bovine muscle fibres is of particular interest for the food industry because meat tenderness depends in part on the proportion of the different types of fibres. It is, therefore, important to define reliable methods for classifying fibre types. There are several classification systems. One is based on contractile type alone, as revealed by myofibrillar ATPase activity or with antibodies against myosin heavy chain. Others take both contractile and metabolic types into account. In this study, the classifications of fibres obtained by these three systems were compared on the semitendinosus and longissimus thoracis muscles of 35 Charolais bulls. Only the use of antibodies allowed the identification of a proportion of hybrid fibres containing two isoforms of fast myosin heavy chain (2a and 2b). In addition, the combination of metabolic types showed that the metabolism of these hybrid fibres differed according to the muscle.

Panmictic structure of Helicobacter pylori demonstrated by the comparative study of six genetic markers

We compared the classifications of strains obtained by analysis of several genetic markers to demonstrate the panmictic structure of Helicobacter pylori, previously suggested by the study of multilocus enzyme electrophoresis. A series of 39 strains, including 37 clinical isolates from patients with gastritis or ulcers from two regions of France, reference strain CIP 101260 and the Sydney strain (strain SSI), were used. They were studied by restriction fragment length polymorphism analysis of ribosomal DNA (ribotyping) using HindIII and HaeIII, by polymorphism analysis of the ureA-ureB and flaA genes by PCR-RFLP using HaeIII and MboI, by vacA genotyping and by the presence or absence of the cagA gene and of the insertion sequence IS605 detected by PCR. There was a high level of genetic polymorphism over the studied strains, with 38 ribotypes, 38 restriction profiles for the ureA-ureB gene, 19 restriction profiles for the flaA gene and five combinations of the signal and mid-region sequences of the vacA gene. Factorial analysis of correspondence and hierarchical clustering performed using each marker revealed that the different classifications of the strains were not correlated. This suggests there is much genetic recombination between strains and supports the hypothesis of a panmictic structure for the H. pylori species.

Phylogenetic analysis of Escherichia coli strains causing neonatal meningitis suggests horizontal gene transfer from a predominant pool of highly virulent B2 group strains

Phylogenetic relationships of 69 neonatal meningitis Escherichia coli strains isolated worldwide were studied. Restriction fragment length polymorphism of rrn operons (rrn RFLP) in these isolates was compared with that of the 72 strains of the ECOR reference collection. Distributions of K1 antigen, of polymerase chain reaction-detected ibe10 gene, pap, afa, sfa/foc, hly, and aer operons, and of a 14.9-kb rrn-containing HindIII fragment previously associated with neonatal meningitis were compared. Oligoclonality was observed for the meningitis strains. Factorial analysis of correspondence on the rrn RFLP data showed a frequency gradient of meningitis strains from the phylogenetic B2 group (68%) to the A group (6%), via the D and B1 groups (26%). The distribution of the virulence determinants argues for their horizontal transfer during the evolution of E. coli. Analysis of the status of some neonates further suggests that neonatal meningitis results from a balance between bacterial genes of virulence and host factors.

Age-related changes and location of type I, III and IV collagens during skeletal muscle development of double-muscled and normal bovine foetuses

The aim of this study was to investigate age-related changes in collagen content in muscles of normal and double-muscled (DM) bovine foetuses. Psoas major (PM) and triceps brachii (TB) muscles were collected from foetuses at 110 to 260 days post-conception (p.c.), frozen and powdered. Cyanogen bromide (CNBr) digestion and hydroxyproline measurements were carried out on the powder. CNBr peptides underwent SDS-polyacrylamide gel electrophoresis, and type I and III collagen relative variations were measured by densitometric analysis. Type I and III procollagen mRNA were located by in situ hybridization and types I, III and IV collagen located by indirect immunofluorescence. Although there was no significant difference between normal and DM animals in the amounts of collagen (except in PM muscle at 180 and 230 days p.c.), there was nevertheless a tendency to lower collagen content in muscles of DM animals. Amounts of hydroxyproline in PM and TB muscles from 110 to 230 days p.c. increased two- and threefold to 8.5 micrograms per mg of dry matter (d.m.) and 12 micrograms per mg d.m., respectively, and then decreased up to 260 days p.c., when they were twice as high in TB muscle (9.1 micrograms per mg d.m.) as in PM (4.5 micrograms per mg d.m.). The same difference in hydroxyproline levels was observed between normal adult PM and TB muscles. These variations were explained, mainly, by those of type I. In foetal muscle, in both genotypes and as in adult muscle, perimysium was types I and III, and endomysium type I, III and IV. Procollagen type I and III mRNA were located in perimysium. In conclusion, this study emphasizes that at the end of foetal life, collagen content is representative of what it will be in adult in muscle of both normal and DM animals.

An epidemiological study of Serratia marcescens isolates from nosocomial infections by enzyme electrophoresis

Serratia marcescens isolates from 164 patients with suspected nosocomial infection in several hospitals in the greater Paris region were investigated by analysis of the electrophoretically demonstrable allelic variations of gene loci coding for five esterases and five other enzymes. All the loci were polymorphic and the mean number of alleles per locus was 6.1. A total of 72 distinctive electrophoretic types (ETs) representing multilocus genotypes was distinguished. The isolates were divided into two groups according to their resistance to antibiotics: 82 multiresistant isolates (MRI) and 82 relatively susceptible isolates (RSI). Seventy-two MRI (88%) were in four genetically related ETs: ET1, ET2, ET8 and ET9; ET1 was found in 48 isolates, whereas the remaining MRI were in 10 ETs, and all RSI in 61 ETs. Three ETs contained both MRI and RSI. The mean coefficients of genetic diversity for the 10 enzyme loci among ETs and isolates were smaller for MRI than for RSI, while the modal ET of MRI resembled that of RSI. The epidemiological significance of isolates varied according to their ET. Thus, isolates belonging to ET1, ET2 and ET8 were responsible for outbreaks or for sporadic infections, whereas isolates of other ETs were responsible for only sporadic infections. The temporal distribution of ET1 isolates among hospitals identified seven outbreaks in seven clinical departments.

Weaning marginally affects glucose transporter (GLUT4) expression in calf muscles and adipose tissues

The nutritional regulation of glucose transporter GLUT4 was studied in eight muscles and four adipose tissues from two groups of preruminant (PR) or ruminant (R) calves of similar age (170 d), empty body weight (194 kg) at slaughter, and level of net energy intake from birth onwards. Isocitrate dehydrogenase (EC 1.1.1.41) activity in muscles was not different between PR and R except in masseter muscle from the cheek (+71% in R; P < 0.003), which becomes almost constantly active at weaning for food chewing. Basal and maximally-insulin-stimulated glucose transport rate (GTR) per g tissue wet weight in rectus abdominis muscle were significantly higher in R calves (+31 and 41% respectively; P < 0.05). GLUT4 protein contents did not differ in muscles from PR and R except in masseter (+74% in R; P < 0.05) indicating that the increased GTR in rectus abdominis cannot be accounted for by an enhanced GLUT4 expression. GLUT4 mRNA levels did not differ between the two groups of animals in all muscles suggesting a regulation of GLUT4 at the protein level in masseter. GLUT4 number expressed on a per cell basis was lower in adipose tissue from R calves (-39%; P < 0.05) and higher in internal than in peripheral adipose tissues. In summary, the regulation of GLUT4 in calves at weaning differs markedly from that previously described in rodents (for review, see Girard et al. 1992). Furthermore, significant inter-individual variations were shown for metabolic activities in muscle and for biochemical variables in adipose tissue.

Epidemiologically related and unrelated strains of Pseudomonas aeruginosa serotype O12 cannot be distinguished by phenotypic and genotypic typing

A clonal origin for European isolates of antibiotic multi-resistant Pseudomonas aeruginosa serotype O12 has been suggested. This study was designed to assess the value and limitations of several typing methods for the investigation of outbreaks due to this serotype. In Hôpital de Rodez, France, this organism is endemic, and a prospective clinical epidemiological study was undertaken over a 15 month period, encompassing all patients at the hospital from whom P. aeruginosa O12 was isolated. All isolates were examined by auxanogram, antibiogram, phage-typing, electrophoresis of esterases and pulsed-field gel electrophoresis of DNA. The results suggest that (1) the methods used did not clearly differentiate between clinically-related and epidemiologically-unrelated European isolates, (2) in Hôpital de Rodez, while some isolates were likely to have been transmitted from patient-to-patient, most infections or colonizations with this organism were sporadic and their origin is unknown. The limits of typing methods for the investigation of outbreaks of nosocomial infection with multi-resistant P. aeruginosa O12 are emphasized.

Regional variations of muscle fibre characteristic in m. semitendinosus of growing cattle

The objectives of the present study were to elaborate an intra-muscular profile of metabolic enzyme equipment, contractile and morphometric features along the longitudinal axis of m. semitendinosus at various ages throughout the growth phase. Thirty-seven male Montbéliard cattle, about half of them castrated, were representatively allocated to various slaughter dates, scheduled at 4, 8, 12 and 16 months of age. Samples were collected from proximal, medial and distal locations of m. semitendinosus. Isocitrate dehydrogenase (aerobic metabolism) and lactate dehydrogenase (anaerobic metabolism) were measured spectrophotometrically. Contractile muscle type was classified by quantification of myosin heavy chain I isoform proportion using the sensitive enzyme-linked immunosorbent assay. Mean muscle fibre area was obtained on histologically-stained cross-sections utilizing an image analysis system. Our results indicate the existence of a regular intra-muscular pattern of muscle fibre traits along the length of m. semitendinosus, with decreasing glycolytic activities and concomitantly an increase in oxidative capacity towards the distal extremity. The metabolic characteristics were in good agreement with decreasing cross-sectional muscle fibre areas and the slow myosin heavy chain I isoform proportion becoming gradually more abundant from proximal to distal regions of the muscle. Moreover, the observed gradient was found to be closely related to age and diminished with advanced physiological maturity. At the final slaughter age (16 months) no differences among the distinct portions were detected, m. semitendinosus was longitudinally homogeneous in all the characteristics studied.

Multicenter evaluating of a commercially available PCR assay for diagnosing enterovirus infection in a panel of cerebrospinal fluid specimens

Thirteen laboratories participated in blind tests of a panel of 20 coded cerebrospinal fluid specimens (7 uninfected samples, 3 samples infected with 1 50% tissue culture infective dose [TCID50]/0.1 ml [nonenterovirus strains], and 10 samples infected with 10, 1, or 0.1 TCID50/0.1 ml [three different enterovirus serotypes]) on the Amplicor enterovirus PCR assay (Roche Diagnostic Systems). The panel was also evaluated by in-house PCR (two nested-PCR and three one-step PCR assay) or tissue culture (eight laboratories). The viral load was shown to influence greatly the sensitivity of the assay. The average sensitivity of the Amplicor test ranged from 67 to 98% for viral titers of 1 to 10 TCID50/0.1 ml, respectively; titers of 0.1 TCID50/0.1 ml resulted in a sensitivity of only 16%. The overall specificity of the Amplicor test was 98%. The Amplicor assay compared favorably to the five in-house PCR tests (no significant difference in either sensitivity or specificity) and was much more sensitive than tissue culture (P < 0.001), even for high viral loads. It was easy to perform, rapid (about 6 h), well-standardized, and appeared to be suitable for the diagnosis of enterovirus meningitis on a routine basis in laboratories trained in molecular biology techniques.

Analysis of genetic relationships among strains of groups A, C and G streptococci by random amplified polymorphic DNA analysis

Random amplified polymorphic DNA (RAPD) analysis was evaluated for its capacity to distinguish species and strains within species of groups A, C and G streptococci. The 99 strains tested, previously typed by multilocus enzyme electrophoresis (MLEE), included 41 group A streptococci (Streptococcus pyogenes), 25 group G Streptococcus spp. (GGS), seven S. dysgalactiae, 11 S. equisimilis, four S. canis, three S. equi and eight S. zooepidemicus. The combined data obtained with three single primers distinguished 82 types. RAPD analysis provided taxonomic results that were in general agreement with previous species classification based on DNA-DNA homology and MLEE. The intraspecies typing efficiency of the technique was significantly improved by the parallel use of several primers. RAPD analysis had greater discriminatory power than MLEE for GAS and GGS. There was not total agreement between the two techniques as RAPD distinguished strains with identical electrophoretic types, whereas MLEE differentiated strains with identical PCR types. RAPD analysis did not distinguish all GAS strains with different biotypes and its already high discriminatory power was further enhanced by concomitant biotyping.

Mechanisms of the spread of penicillin resistance in Streptococcus pneumoniae strains causing meningitis in children in France

The molecular epidemiology of penicillin-resistant Streptococcus pneumoniae strains causing meningitis in children was studied in France. Typing procedures included analysis of total DNA polymorphism by random amplification of polymorphic DNA, restriction fragment length polymorphism (RFLP) analysis of the ribosomal RNA gene regions, and pulsed-field gel electrophoresis. Penicillin-binding protein (PBP) genes pbp2b and pbp2x were studied by RFLP analysis and DNA sequencing in selected cases. Statistical analysis of the data by factorial analysis of correspondence established that the emergence of penicillin-resistant pneumococci in this pathology is the result of the spread of two highly resistant closely related clusters and a cluster of serotype 23 strains with an intermediate level of resistance, the spread of genes confering high resistance to penicillin between the two highly resistant clusters, and complex genetic events involving the pbp genes in a heterogeneous population of strains leading to an intermediate level of resistance.

Molecular epidemiological tools for Salmonella Dublin typing

A total of 32 strains of Salmonella Dublin recovered from cattle were differentiated by electrophoretic typing of their esterases (zymotyping), restriction fragment length polymorphism of ribosomal DNA (ribotyping), arbitrarily primed PCR (AP-PCR) using five primers, PCR based on repetitive extragenic palindromic sequences (REP-PCR) and PCR based on enterobacterial repetitive intergenic consensus sequences (ERIC-PCR). ERIC-PCR and REP-PCR each gave one type, zymotyping gave three, AP-PCR gave five and ribotyping gave seven types. Combination of ribotyping and AP-PCR produced a total of 11 types, whereas 14 different types were obtained by all five methods. Thus a combination of several methods enhanced the discrimination of cattle-adapted strains among the genotypically homogeneous serovar Salmonella Dublin.

Comparison of the foetal development of muscle in normal and double-muscled cattle

Muscle differentiation was studied in foetal Semitendinosus muscle from normal cattle and those with the 'culard' gene of muscular hypertrophy sampled at 90, 130, 170 and 210 days of foetal life. The different fibre types were characterized by immunohistochemistry with antibodies specific to different isoforms of myosin heavy chains. The isoforms were separated by electrophoresis, identified by immunoblotting and quantified by ELISA. In double-muscled animals, there was a slower rate of differentiation in the first generation of cells, most markedly apparent at 90 days. At 130 days, differentiation was retarded mainly in the second generation, while at 170 days there was no longer any difference between the two animal types in the differentiation of first generation cells, which were totally slow in both. At the same stage however, type IIC fibres in double-muscled animals were much slower in appearing and continued to be so at 210 days, albeit to a lesser extent. These findings show that differentiation of the muscle fibres occurs at a slower rate in double-muscled foetuses particularly during the first two-thirds of foetal life.

Activity of beta-lactamase inhibitor combinations on Escherichia coli isolates exhibiting various patterns of resistance to beta-lactam agents

The efficacy of the clinically available beta-lactam/beta-lactamase inhibitor combinations (amoxicillin/clavulanic acid (CA), ticarcillin/CA, amoxicillin/sulbactam, and piperacillin/tazobactam) was evaluated on 300 amoxicillin-resistant Escherichia coli isolates having the main patterns of beta-lactam resistance. The patterns, which reflect the production of various beta-lactamase enzymes, were analyzed by a principal component analysis of susceptibility to 11 beta-lactam antibiotics or beta-lactam/beta-lactamase inhibitor combinations. Sixty-two percent of strains were not very susceptible to penicillins, cephalothin, or any beta-lactam/beta-lactamase inhibitor combinations except for piperacillin/tazobactam; these strains may represent high-level broad-spectrum beta-lactamase (so-called penicillinase) production phenotype or inhibitor-resistant TEM-like enzyme production phenotype. Of the strains, 14.7% were resistant to amoxicillin and ticarcillin compatible with low-level broad-spectrum beta-lactamase production phenotype; 5.7% were cefoxitin resistant and were postulated to present a high-level cephalosporinase production phenotype; and 2.6% were resistant to cephalothin only, attributable to a low-level cephalosporinase production phenotype. Three percent of strains were intermediate or resistant to cefotaxime and may produce an extended-spectrum beta-lactamase, and the remaining strains (12 %), resistant to all tested antibiotics except for cefotaxime and piperacillin/tazobactam, were hypothesized to produce both broad-spectrum beta-lactamase plus cephalosporinase. The minimal inhibitory concentration (MIC) for these phenotype patterns indicated that combinations of CA plus amoxicillin or ticarcillin, or sulbactam plus amoxicillin, restored the activity of penicillins against phenotype 1 strains, whereas these combinations remained inactive against the other phenotype strains. Piperacillin plus tazobactam showed the best in vitro effect against the strains of all resistance phenotypes.

Sex in Escherichia coli does not disrupt the clonal structure of the population: evidence from random amplified polymorphic DNA and restriction-fragment-length polymorphism

Analysis of the Escherichia coli population by multilocus enzyme electrophoresis (MLEE) has established its clonal organization, but there is increasing evidence that horizontal DNA transfer occurs in E. coli. We have assessed the genetic structure of the species E. coli and determined the extent to which recombination can affect the clonal structure of bacteria. A panel of 72 E. coli strains from the ECOR collection was characterized by random amplified polymorphic DNA (RAPD) and restriction-fragment-length polymorphism (RFLP) of the ribosomal RNA gene (rrn) regions. These strains have been characterized by MLEE and are assumed to reflect the range of genotypic variation in the species as a whole. Statistical analysis, including factorial analysis of correspondence (FAC) and hierarchical classifications, established that the data obtained with the three genetic markers are mutually corroborative, thus providing compelling evidence that horizontal transfer does not disrupt the clonal organization of the population. However, there is a gradient of correlation between the different classifications which ranges from the highly clonal structure of B2 group strains causing extraintestinal infections in humans to the less-stringent structure of B1 group strains that came mainly from nonprimate mammals. This group (B1) appears to be the framework from which the remaining non-A group strains have emerged. These results indicate that RAPD analysis is well suited to intraspecies characterization of E. coli. Lastly, treating the RAPD data by FAC allowed description of subgroup-specific DNA fragments which can be used, in a strategy comparable to positional cloning, to isolate virulence genes.

Identification and typing of pyogenic streptococci by enzyme electrophoretic polymorphism

Polyacrylamide-agarose gel electrophoresis was used to study polymorphism of lactate dehydrogenase (LDH), nucleoside phosphorylase (NSP), phosphoglucose isomerase (PGI), hydroxybutyrate dehydrogenase (HBD), adenylate kinase (ADK) and esterases of 44 strains of Streptococcus pyogenes, 25 group G streptococcal strains, 11 "S. equisimilis" strains, seven S. dysgalactiae strains, four S. canis strains, three S. equi strains and seven S. zooepidemicus strains. Analysis of LDH, NSP, PGI, HBD and ADK provided valuable interspecies differentiation, by showing that four groups of strains corresponded to the four known DNA homology groups. Esterases showed greater intraspecies variation than the other enzymes. The combined analysis of the six enzymes indicated 31 zymotypes among S. pyogenes, 14 in group G streptococci and 11 in "S. equisimilis" strains. This was shown to be an effective technique for typing pyogenic streptococci.

Enzyme-linked immunosorbent assay for myosin heavy chains in the horse

The content in slow and fast myosin heavy chains (MHC 1 and MHC 2) of 5 equine muscles was determined using an enzyme-linked immunosorbent assay. The results obtained with this immunoenzymatic method were compared with complementary techniques: electrophoresis and immunohistochemistry. Slices of masseter, diaphragm, tensor faciae latae, semitendinosus and cutaneus trunci were obtained from a 12-year-old saddle horse after slaughter. Muscular proteins were specifically extracted to be analysed by ELISA. The technique used 2 complimentary monoclonal antibodies (MAb). MAb 1 was prepared from a human atrium specimen that reacted specifically against MHC 1. Mab 2 was prepared from myosin of rabbit psoas muscle and reacted against MHC 2. The masseter muscle contained solely MHC 1 (100%) and this was confirmed by electrophoresis and immunohistochemistry. By contrast, the cutaneus trunci was very poor in MHC 1 (1.3%) and was entirely composed of MHC 2 (98.7%) which was confirmed by the other techniques. The diaphragm, tensor fasciae latae and semitendinosus contained 89, 40 and 2% of MHC 1, respectively. It was concluded that this ELISA method made it possible to measure a wide range of MHC contents in equine muscles with a good reproducibility. The results were consistent with those of the other fibre typing techniques. Moreover, this immunoenzymatic method is less time consuming than histological techniques and therefore offers new perspectives for muscle fibre typing in the horse.

Study of the influence of age and weaning on the contractile and metabolic characteristics of bovine muscle

Weaning is an interesting period for the study of the nutritional regulation of muscle energy metabolism, since during this stage the nature of the substrates supplied to the muscle and their energy balance are profoundly changed. The aim of this study was to determine the effect of these modifications on the contractile and metabolic characteristics of bovine muscle. Two similar groups of 7 male Montbéliard calves were used with the same age and weight, and with the same energy intake. One group consisted of milk-fed calves, the other of weaned animals. The latter were progressively weaned over a period between 107 and 128 d. The average age at slaughter in the 2 groups was 170 d. Biopsy specimens of semitendinosus (ST) muscle were taken at the ages of 66 d, 94 d (before the beginning of weaning) and 136 d (at the end of weaning) to follow the evolution of muscle characteristics. Samples of longissimus thoracis (LT) muscle were taken 24 h after slaughter and used to study the changes in protein and DNA content. The proportion and area of the different types of fiber, I (slow, oxidative), IIA (fast, oxido-glycolytic), IIB (fast, glycolytic) and IIC (fast/slow, oxidoglycolytic) were measured by immunohistochemistry and image analysis. The metabolism of the muscles was determined by studying isocitrate dehydrogenase (ICDH, oxidative) and lactate dehydrogenase (LDH, glycolytic) activity. The results obtained between 2 and 6 months of life showed an overall increase in the area of the fibers (I, IIA, IIB and IIC) and a conversion of type IIA fibers into type IIB accompanied by a shift in the energy metabolism towards a glycolytic type. Weaning caused temporary stress, whose main consequences were to decrease overall muscle fiber area and the percentage of type IIB fibers, and increase the proportion of type IIC fibers in weaned animals. These effects may have been due to the nutritional and behavioral disturbances that accompany weaning, because 42 d after the end of weaning there was no difference in the size of ST and LT fibers between the 2 groups whereas the proportion of type IIA fibers was still higher in weaned animals.

Comparison of the foetal development of fibre types in four bovine muscles

The pattern of expression of different types of myosin heavy chains and the development of different generations of muscle cells during foetal life were studied in four bovine muscles with widely varying characteristics, the Masseter, Longissimus thoracis, Cutaneus trunci and Diaphragma. Different complementary techniques were performed: immunocytochemistry, electrophoresis, immunoblotting and ELISA. Monoclonal antibodies against different myosin heavy chain isoforms were used. The results confirmed the existence of at least two generations of cells during foetal development in cattle. A first generation, which appeared at a very early stage, gave rise to adult type I fibres. A second generation, made up of different cell populations, gave rise to adult fast type IIA and IIB fibres, and to type IIC. In the slow muscles, it also seemed to give rise to type I fibres. The beginning of myogenesis was characterized in the different cell generations by the expression of transitory myosin forms that are not found in the adult. Type 1 myosin heavy chain was observed from 90 days whereas the fast types, 2a and 2b, were present from 210 to 230 days, at which stage the foetal form disappeared. Muscles that have greatly different contractile characteristics in the adult exhibit also different profiles of differentiation: the Diaphragma was the first to develop, followed by Cutaneus trunci, Longissimus thoracis and Masseter.

A simple procedure to differentiate ailA and ailNA gene variants among human pathogenic Yersinia enterocolitica strains

The identification and differentiation of the two variants of the ail gene, ailA from the more virulent American serotypes (08, 013a, 13b, 018, 020, 021) and ailNA from the less virulent non-American serotypes (03, 04, 05, 06, 09, 027 and 07, 8) was studied in a panel of 32 Yersinia enterocolitica human pathogenic isolates. A 444 bp fragment corresponding to the ail gene was amplified using a PCR procedure in all tested strains. Subsequent digestion of the PCR product by Rsal and by HaeIII endonucleases, provide electrophoretic patterns that clearly discriminate ailA and ailNA variants. This non-radioactive and reliable procedure allows large clinical and epidemiological studies, and could be proposed to survey the spread of virulent clones.

Genomic fingerprinting of Yersinia enterocolitica species by degenerate oligonucleotide-primed polymerase chain reaction

A novel version of the polymerase chain reaction (PCR) termed degenerate oligonucleotide-primed PCR (DOP-PCR) was used to fingerprint the bacterial genome of Yersinia enterocolitica species. Eight well-characterized reference strains of Y. enterocolitica (ribotype, serotype, biotype and zymotype) were examined. Optimal experimental conditions for reproducibility, sensitivity and specificity were obtained using a single DOP-primer. All the strains gave distinct DOP-PCR profiles composed of 12 to 19 fragments with sizes from 200 to 1.500 bp. Thus, the DOP-PCR, which has so far been used to fingerprint human, mouse, fruitfly and plant DNA, is also well-suited to bacterial DNA.

Genetic heterogeneity of Pseudomonas aeruginosa clinical isolates revealed by esterase electrophoretic polymorphism and restriction fragment length polymorphism of the ribosomal RNA gene region

The intra-species differentiation of Pseudomonas aeruginosa was analysed by comparing the polymorphism of esterases by conventional polyacrylamide-agarose gel electrophoresis, the physicochemical properties of the variants of the major esterase P3 and the restriction fragment length polymorphism of ribosomal RNA gene regions (ribotyping) to O-serotyping for several panels of strains selected from among a series of 257 clinical isolates and two references strains, (ATCC nos. 10145 and 27853). The electrophoretic variation of four main kinds of esterase (P1-P4) and 11 additional esterases distinguished by their spectra of hydrolytic activity with synthetic substrates and by their sensitivity to di-isopropylfluorophosphate, allowed the discrimination of 67 zymotypes. Thirty-two esterase P3 variants were characterized by their pI, electrophoretic mobilities and titration curve analyses. They were distributed into two groups which, by these molecular criteria, seem to be distantly related. Combination of the patterns resulting from HindIII, EcoRI and BclI restriction endonuclease digestions allowed the discrimination of 33 ribotypes among 134 strains. The strains exhibiting esterase P3 variants of group 2 presented a distinct ribotype and belonged to serotype (O)12. They could constitute a distinct group within the species. For the majority of the strains, the absence of correlation between zymotype, ribotype and serotype argues for a high level of heterogeneity within P. aeruginosa and indicates that the parallel use of the first two methods represent a potential tool for epidemiological study.

Clonal relationships among Escherichia coli serogroup O78 isolates from human and animal infections

We investigated the clonal relationships among 63 Escherichia coli strains of antigen serogroup O78 isolated from infections in humans, cattle, sheep, pigs, and chickens. Both septicemic and enterotoxigenic isolates were included in the study. A main group of 55 E. coli strains consisting of 52 septicemic isolates and 3 human enterotoxigenic E. coli isolates were clustered in related clones. The remaining eight strains, four human and four animal isolates, were clonally heterogeneous. The main group of 55 clonally related strains included isolates from human and animal infections. This result indicates that animals are a possible source of serogroup O78 septicemic E. coli infections in humans.

Correlation between esterase electrophoretic polymorphism and virulence-associated traits in extra-intestinal invasive strains of Escherichia coli

The electrophoretic variations of carboxylesterase B and of esterases A, C and I, the presence of mannose resistant haemagglutinin, alpha-haemolysin, cytotoxic necrotizing factor type 1 (CNF1) and certain O antigens were compared in 150 strains of Escherichia coli responsible for extra-intestinal infections. Electrophoretic mobilities of outer membrane proteins (OMP) were also studied for strains belonging to O4, O6, O7, O8 and O75 serogroups. Fast migrating allozymes of carboxylesterase B (pattern B1) were correlated with slow migrating allozymes of esterase C, serogroups O7 and O8, lack of virulence factor, and particular OMP patterns, whereas slow migrating allozymes of carboxylesterase B (pattern B2) were correlated with fast migrating allozymes of esterase C, serogroups O2, O4, O6, O18 and O75, virulence factor production, and distinct OMP patterns. Allozymes of esterases A and I were not clearly correlated with the distribution of virulence factors. The pattern B2 was more strongly associated with CNF1 than with alpha-haemolysin and mannose resistant haemagglutinin. These results substantiate the view that the electrophoretic pattern B2 of carboxylesterase B identified most of the highly pathogenic strains implicated in extra-intestinal infection of humans.

O, K, and H antigens predict virulence factors, carboxylesterase B pattern, antimicrobial resistance, and host compromise among Escherichia coli strains causing urosepsis

The O:K:H serotypes of 75 Escherichia coli blood isolates from patients with urosepsis were compared for the presence and expression of determinants for P fimbriae, hemolysin, and aerobactin; antimicrobial resistance; the carboxylesterase B phenotype; and associated compromising host conditions. O groups, K types, and O:K:H serotypes previously associated with urovirulence accounted for 69%, 60%, and 31% of the population, respectively. Chromosomal determinants for P fimbriae, hemolysin, and aerobactin were present in combination more commonly among strains belonging to urovirulence-associated O groups, K types, and O:K:H serotypes. Similarly, antimicrobial resistance was strikingly less prevalent, the B2 carboxylesterase phenotype more common, and associated host compromise less common among such strains. These data demonstrate that the O groups, K types, and O:K:H serotypes traditionally associated with urovirulence are prominent among E. coli strains causing urosepsis, in which they are associated with presence and expression of multiple chromosomal virulence factor determinants, susceptibility to antimicrobial agents, the B2 carboxylesterase phenotype, and noncompromised hosts.

Genetic structures of the B2 and B1 Escherichia coli strains responsible for extra-intestinal infections

Escherichia coli strains causing human extra-intestinal infections may be divided into two groups, B1 and B2 according to the electrophoretic patterns of carboxylesterase B. This study compares the restriction fragment length polymorphism (RFLP) of ribosomal DNA (rDNA) for 45 B1 strains and 45 B2 strains to examine the genetic structure of B2 strains and to distinguish them from B1 strains. The isolates were chosen for diversity in their allozymes of esterases, B, A, C and I, their production of virulence factors (alpha-haemolysin, mannose resistant haemagglutinin and cytotoxic necrotizing factor) and certain O antigens, and their pathological and geographical origins. DNA was digested with HindIII and BamHI restriction enzymes and analysed by Southern blotting. The resulting rDNA RFLP patterns of B2 strains were distinct from those of the B1 strains. Moreover, the B2 strains appeared to be less heterogeneous than the B1 strains. The B2 strains gave 13 ribotypes (resulting from the combination of the rDNA RFLP patterns obtained with HindIII and BamHI digestions) while the B1 strains gave 32 ribotypes. Correspondence analysis of the data showed that several clusters of strains were identified in the B2 strains by particular ribotypes, certain associations of esterase B and A electrophoretic variants, O serotypes and virulence factor production. In contrast, these parameters appeared to be unrelated in the B1 strains, reflecting their heterogeneity. These findings, which differentiate two levels of genetic heterogeneity within E. coli pathogenic isolates, indicate that the B2 strains constitute a phylogenetically distinct group within the species.

The absence of correlation between allozyme and rrn RFLP analysis indicates a high gene flow rate within human clinical Pseudomonas aeruginosa isolates

Two hundred and fifty seven human clinical Pseudomonas aeruginosa strains isolated between 1984 and 1990 in several regions of France, as well as two reference strains, were studied by computer-assisted statistical analysis of the data from their esterase electrophoretic patterns and rrn restriction fragment length polymorphisms. No correlation was found between the two sets of data except for some strains of serotype O12 which, thus, may constitute a distinct group within the species. This absence of correlation indicates a high gene flow rate within human isolates of the P. aeruginosa species. A possible explanation is that, because of an as yet unidentified selective advantage, the esterase loci are a major target for recombinational events. Alternatively, horizontal genetic transfers between strains may have occurred at so high a rate that the clonal structure usually observed in bacterial populations has been disrupted. This study highlights clearly the need for caution in inferring bacterial population structure from any single class of genetic markers.

Characterization of Escherichia hermannii by ribosomal DNA restriction fragment length polymorphism

Ribosomal DNA polymorphism was used to characterize strains of Escherichia hermannii and to differentiate them from E. coli. DNA from 11 E. hermannii strains previously separated into three zymotypes by enzyme electrophoretic polymorphism was digested with HindIII and EcoRI restriction enzymes and analyzed by Southern blotting. The 10 ribotypes obtained with EcoRI fell into 3 groups which correlated with the corresponding zymotypes, and the 5 ribotypes obtained with HindIII were clearly distinct from those of E. coli strains.

Purification and characterization of three carboxylesterases from Enterobacteriaceae

The carboxylesterases from Proteus vulgaris, Salmonella enterica and Citrobacter amalonaticus were purified 104-, 95- and 120-fold, respectively by chromatography. The enzymes had similar catalytic activities but differed considerably in their inactivation by heat, di-isopropyl fluorophosphate and Cd2+, Zn2+, Hg2+ and Cu2+. Quantitative neutralization of hydrolytic activity with specific immunoglobulins indicated that the three enzymes were antigenically distinct.