Evaluation of three techniques for detection of low-level methicillin-resistant Staphylococcus aureus (MRSA): a disk diffusion method with cefoxitin and moxalactam,the Vitek 2 system,and the MRSA-screen latex agglutination test

Very-low-level methicillin-resistant Staphylococcus aureus (MRSA), or class 1 MRSA, is often misdiagnosed as methicillin-susceptible S. aureus (MSSA). We evaluated the performances of three methods for detection of low-level methicillin resistance: the disk diffusion method using the cephamycin antibiotics cefoxitin and moxalactam, the Vitek 2 system (bioMérieux), and the MRSA-screen test (Denka). Detection of the mecA gene by PCR was considered to be the "gold standard." We also determined the sensitivity of the oxacillin disk diffusion method with 5- and 1-microg disks and that of the Oxascreen agar assay with 6 mg of oxacillin liter(-1) for detection of MRSA. We compared the distributions of MICs of oxacillin and cefoxitin by the E-test (AB Biodisk), and those of moxalactam by dilutions in agar, for MRSA and MSSA isolates. The 152 clinical isolates of S. aureus studied were divided into 69 MSSA (mecA-negative) and 83 MRSA (mecA-positive) isolates, including 63 heterogeneous isolates and 26 class 1 isolates (low-level resistance). The cefoxitin and moxalactam disk diffusion tests detected 100% of all the MRSA classes: cefoxitin inhibition zone diameters were <27 mm, and moxalactam inhibition zone diameters were <24 mm. The Vitek 2 system and the MRSA-screen test detected 94 and 97.6% of all MRSA isolates, respectively. The sensitivities of the 5- and 1-microg oxacillin disks were 95.2 and 96.4%, respectively, whereas that of the Oxascreen agar screen assay was 94%. All of the tests except the 1-microg oxacillin disk test were 100% specific. For the class 1 MRSA isolates, the sensitivity of the Vitek 2 test was 92.3%, whereas those of the MRSA-screen test and the disk diffusion method with cefoxitin and moxalactam were 100%. Therefore, the cefoxitin and moxalactam disk diffusion methods were the best-performing tests for routine detection of all classes of MRSA.     

Presence and characterization of extraintestinal pathogenic Escherichia coli virulence genes in F165-positive E. coli strains isolated from diseased calves and pigs

The virulence genotype profile and presence of a pathogenicity island(s) (PAI) were studied in 18 strains of F165-positive Escherichia coli originally isolated from diseased calves or piglets. On the basis of their adhesion phenotypes and genotypes, these extraintestinal pathogenic strains were classified into three groups. The F165 fimbrial complex consists of at least two serologically and genetically distinct fimbriae: F165(1) and F165(2). F165(1) is encoded by the foo operon (pap-like), and F165(2) is encoded by fot (sfa related). Strains in group 1 were foo and fot positive, strains in group 2 were foo and afa positive, and strains in group 3 were foo positive only. The strains were tested for the presence of virulence genes found mainly in extraintestinal pathogenic E. coli (ExPEC) strains. Although all the strains were positive for the papA variant encoding F11 fimbriae incD, traT, and papC, the prevalence of virulence genes commonly found in PAIs associated with ExPEC strains was highly variable, with strains of group 2 harboring most of the virulence genes tested. papG allele III was detected in all strains in group 1 and in one strain in group 3. All other strains were negative for the known alleles encoding PapG adhesins. The association of virulence genes with tRNA genes was characterized in these strains by using pulsed-field gel electrophoresis and DNA hybridization. The insertion site of the foo operon was found at the pheU tRNA locus in 16 of the 18 strains and at the selC tRNA locus in the other 2 strains. Furthermore, 8 of the 18 strains harbored a high-pathogenicity island which was inserted in either the asnT or the asnV/U tRNA locus. These results suggest the presence of one or more PAIs in septicemic strains from animals and the association of the foo operon with at least one of these islands. F165-positive strains share certain virulence traits with ExPEC, and most of them are pathogenic in piglets, as tested in experimental infections.     

Specificities and functions of the recA and pps1 intein genes of Mycobacterium tuberculosis and application for diagnosis of tuberculosis

The worldwide recrudescence of tuberculosis and the widespread appearance of antibiotic resistance have strengthened the need for rapid and specific diagnostic tools. The prevailing microbiological identification of Mycobacterium tuberculosis, the causative agent of tuberculosis, which implies the use of in vitro cultures and acid-fast staining microscopy, is time-consuming. Detection of M. tuberculosis directly in clinical samples through PCR amplification of mycobacterium-specific genes, designed to shorten diagnostic delay, demonstrated reliability and high sensitivity. However, the quality of the diagnosis depends on the specificity of the target sequence for M. tuberculosis complex strains. In the present study, we demonstrated the specificity of recA and pps1 inteins for this complex and thus the feasibility of using intein-coding sequences as a new target for PCR diagnosis. Indeed, the recA and pps1 genes of 36 clinical isolates of M. tuberculosis and 10 field strains of M. bovis were found to be interrupted by an intein sequence at the RecA-a and Pps1-b sites, respectively, while a large number of nontuberculous mycobacterial species failed to demonstrate these insertions. Besides, the MtuPps1, which was cloned and expressed in Escherichia coli, was shown to possess an endonuclease activity. The intein cleaves the 40-bp sequence spanning the intein insertion site Pps1-b in the inteinless pps1 gene. In addition to the PCR amplification of recA and pps1 intein genes as a tool for diagnosis, the specific endonuclease activity could represent a new molecular approach to identify M. tuberculosis.     

Bilateral cataract and high serum ferritin: a new dominant genetic disorder?

This paper reports the cosegregation in a three generation pedigree of dominantly inherited cataract with an abnormally high level of serum ferritin. In this family, circulating L ferritin was raised in all subjects affected by cataract independently of iron overload. We suggest that a disorder of ferritin metabolism could be a new genetic disorder leading to lens opacity. Cataract-hyperferritaemia syndrome could also be a new contiguous gene syndrome involving the L ferritin gene and the gene coding for the lens membrane protein (MP19), which both map to the same region of chromosome 19q.     

Hydroxytelechelic polybutadiene, 12. Polymerization reactions between hydroxytelechelic polybutadiene with hexamethylene diisocyanate or 4,4′-methylenedi(phenyl isocyanate). Kinetics of polymerization in toluene and in the bulk

Addition polymerization of hydroxytelechelic polybutadiene (HTPB) with hexamethylene diisocyanate (HMDI) with a mole ratio NCO/OH = 0,8 in dilute solution of toluene as well as in bulk follows apparent 3rd order kinetics. The polymerization rates are twice as sensitive to temperature as in toluene, an effect which is attributed to intra- and/or intermolecular (OH, OH) auto-association. The three alcoholic functions in HTPB are catalyzed equally by dibutyltin dilaurate. Even with high excess of NCO, free alcoholic functions were found in the product. They were determined quantitatively in moulded polyurethane sheets from HTPB + HMDI and HTPB + 4,4′-methylenedi(phenyl isocyanate) which should be partially crosslinked:     

Murine Dendritic Cells Pulsed In Vitro with Toxoplasma gondii Antigens Induce Protective Immunity In Vivo

The activation of a predominant T-helper-cell subset plays a critical role in disease resolution. In the case of Toxoplasma gondii, the available evidence indicates that CD4⁺ protective cells belong to the Th1 subset. The aim of this study was to determine whether T. gondii antigens (in T. gondii sonicate [TSo]) presented by splenic dendritic cells (DC) were able to induce a specific immune response in vivo and to protect CBA/J mice orally challenged with T. gondii cysts. CBA/J mice immunized with TSo-pulsed DC exhibited significantly fewer cysts in their brains after oral infection with T. gondii 76K than control mice did. Protected mice developed a strong humoral response in vivo, with especially high levels of anti-TSo immunoglobulin G2a antibodies in serum. T. gondii antigens such as SAG1 (surface protein), SAG2 (surface protein), MIC1 (microneme protein), ROP2 through ROP4 (rhoptry proteins), and MIC2 (microneme protein) were recognized predominantly. Furthermore, DC loaded with TSo, which synthesized high levels of interleukin-12 (IL-12), triggered a strong cellular response in vivo, as assessed by the proliferation of lymph node cells in response to TSo restimulation in vitro. Cellular proliferation was associated with gamma interferon and IL-2 production. Taken together, these results indicate that immunization of CBA/J mice with TSo-pulsed DC can induce both humoral and Th1-like cellular immune responses and affords partial resistance against the establishment of chronic toxoplasmosis.     

Inflammatory malignant fibrous histiocytomas and dedifferentiated liposarcomas: histological review, genomic profile, and MDM2 and CDK4 status favour a single entity

Inflammatory malignant fibrous histiocytoma (inflammatory MFH) is a very rare tumour that occurs most often in the retroperitoneum. So far, it has been considered to be a special subtype of MFH. As it is now widely accepted that most retroperitoneal pleomorphic MFHs are dedifferentiated liposarcomas, the present study compared histological features, genomic profile (CGH analysis), and MDM2 and CDK4 status (immunohistochemistry, FISH, and quantitative PCR) in inflammatory MFHs from 12 patients and dedifferentiated liposarcomas that had an inflammatory MFH component from eight patients. Metaphase cytogenetic and FISH analyses were also performed on one inflammatory MFH. Histological review showed areas of well-differentiated liposarcoma in nine inflammatory MFHs. CGH analysis showed 12q13-15 amplification or gain in six of seven inflammatory MFHs and in seven of seven dedifferentiated liposarcomas. Immunohistochemistry showed positivity of tumour cells for MDM2 in every tumour in both groups and for CDK4 in ten and seven inflammatory MFHs and dedifferentiated liposarcomas, respectively. Metaphase cytogenetic and FISH analysis performed on one inflammatory MFH showed the presence of a supernumerary large marker chromosome and ring chromosome with high-level amplification of both MDM2 and CDK4 genes. FISH analysis on paraffin wax-embedded sections showed amplifications of MDM2 and CDK4 in seven of seven inflammatory MFHs and in seven of seven dedifferentiated liposarcomas. Quantitative PCR showed amplification of MDM2 in six and of CDK4 in seven of nine inflammatory MFHs. In conclusion, this study strongly suggests that most so-called inflammatory MFHs are dedifferentiated liposarcomas.     

Pneumocystis carinii f. sp. hominis is not infectious for SCID mice

The infectious power of Pneumocystis carinii f. sp. hominis was explored by inoculating SCID mice intranasally with either P. carinii f. sp. hominis or P. carinii f. sp. muris isolates. Only mice inoculated with mouse parasites developed Pneumocystis pneumonia, as assessed by microscopy and PCR. These results suggest that humans do not contract pneumocystosis from animals.     

Regulation of gelatinase B in human monocytic and endothelial cells by PECAM-1 ligation and its modulation by interferon-beta.

Platelet endothelial cell adhesion molecule-1 (PECAM-1 or CD31) and gelatinase B are coexpressed at sites of inflammation, where an intense interaction occurs between leukocytes and endothelial cells. To investigate whether a functional link exists between PECAM-1 activation and gelatinase B production, the regulatory role of PECAM-1, IFN-gamma, IFN-beta, LPS, and PMA on the production of gelatinase B (MMP-9) was studied in vitro in normal human umbilical vein endothelial cells (HUVECs), human peripheral blood mononuclear cells (PBMCs), and in a human monocytic leukemia cell line. In THP-1 cells, progelatinase B levels were slightly up-regulated by immobilized PECAM-1-specific monoclonal antibody (mAb) and soluble recombinant PECAM-1 when compared with strong induction by LPS and PMA. IFN-beta inhibited the induced and basal gelatinase B production but had no modulating effect on the expression of PECAM-1. HUVECs mainly produced progelatinase A (proMMP-2). Treatment with LPS and triggering of the endothelial cells with PECAM-1 mAb or recombinant PECAM-1 had no effect on gelatinase A or B production, whereas PMA stimulated the production of progelatinase B. IFN-beta significantly up-regulated the expression of PECAM-1 in HUVECs but did not affect gelatinase secretion. Finally, in PBMCs, progelatinase B production was increased by soluble PECAM-1 mAb, recombinant PECAM-1, LPS, and PMA, whereas IFN-beta reduced gelatinase B secretion. IFN-beta did not alter PECAM-1 expression on PBMCs. Thus, PECAM-1 and gelatinase B are differently regulated in leukocytes and endothelial cells.