Air dispersal of meticillin-resistant Staphylococcus aureus in residential care homes for the elderly: implications for transmission during the COVID-19 pandemic.

BACKGROUND: Meticillin-resistant Staphylococcus aureus (MRSA) infections are rampant in hospitals and residential care homes for the elderly (RCHEs). AIM: To analyse the prevalence of MRSA colonization among residents and staff, and degree of environmental contamination and air dispersal of MRSA in RCHEs. METHODS: Epidemiological and genetic analysis by whole-genome sequencing (WGS) in 12 RCHEs in Hong Kong. FINDINGS: During the COVID-19 pandemic (from September to October 2021), 48.7% (380/781) of RCHE residents were found to harbour MRSA at any body site, and 8.5% (8/213) of staff were nasal MRSA carriers. Among 239 environmental samples, MRSA was found in 39.0% (16/41) of randomly selected resident rooms and 31.3% (62/198) of common areas. The common areas accessible by residents had significantly higher MRSA contamination rates than those that were not accessible by residents (37.2%, 46/121 vs. 22.1%, 17/177, P=0.028). Of 124 air samples, nine (7.3%) were MRSA-positive from four RCHEs. Air dispersal of MRSA was significantly associated with operating indoor fans in RCHEs (100%, 4/4 vs. 0%, 0/8, P=0.002). WGS of MRSA isolates collected from residents, staff and environmental and air samples showed that ST 1047 (CC1) lineage 1 constituted 43.1% (66/153) of all MRSA isolates. A distinctive predominant genetic lineage of MRSA in each RCHE was observed, suggestive of intra-RCHE transmission rather than clonal acquisition from the catchment hospital. CONCLUSION: MRSA control in RCHEs is no less important than in hospitals. Air dispersal of MRSA may be an important mechanism of dissemination in RCHEs with operating indoor fans.

3D time of flight MR angiography: acquisition with small field of view and low phase encodes.

The aim of the study was to evaluate and compare the image quality of the 3D TOF MRA acquired with a small FOV and low phase encodes with those MR angiographic images acquired with standard pulse sequence parameters. Twenty patients who were referred to our institution for MR imaging of the brain and strictly satisfied the selection criteria were included in this study. Apart from the routine protocol for MR imaging of the brain, 3D TOF MRA of the circle of Willis with a small FOV and a standard FOV were performed. The image quality of all MRA was evaluated by two independent observers who were blind to the pulse sequence parameters. From the standard FOV MRA, 22.5, 12.5, and 5% of the patients were graded as mild, moderate, and severe stenosis of the internal carotid artery, respectively. On the contrary, no apparent stenosis was observed from the small FOV MRA with low phase encodes. Regarding the reduction in MR artifacts and acquisition time achieved with the small FOV 3D TOF MRA with low phase encodes, this might be a useful MR angiographic technique to be used in routine clinical practice.

c-fos overexpression is associated with the pathoneogenesis of invasive cervical cancer.

The molecular genetics of human cervical cancer remains to be defined to a significant extent. The current study examined the prevalence and significance of proto-oncogene c-fos overexpression in cervical cancer. Immunohistochemical staining of c-fos oncoprotein was performed in 27 invasive cervical carcinomas and 30 cervical intraepithelial neoplasias (CINs) managed in our department. Eight normal cervical specimens were used as controls. In the patients with invasive cervical cancer, 8 were stage I, 12 were stage II, and 7 had stage III-IV disease. Three of the cancers were well differentiated, 18 were moderately differentiated and 6 were poorly differentiated. Twenty invasive cervical carcinomas (59%) and 3 CIN (10%) showed overexpression of c-fos. The difference is statistically significant (p < 0.001). No statistically significant relationship was found between c-fos overexpression and clinical stage, histological grade, or survival in invasive cervical cancer. In this population, c-fos overexpression appears to be common in invasive cervical cancer and correlated with the ability of the tumor to become invasive, but is not associated with the progression of cervical cancer.

An erythromycin derivative produced by targeted gene disruption in Saccharopolyspora erythraea.

Derivatives of erythromycin with modifications at their C-6 position are generally sought for their increased stability at acid pH, which in turn may confer improved pharmacological properties. A recombinant mutant of the erythromycin-producing bacterium, Saccharopolyspora erythraea, produced an erythromycin derivative, 6-deoxyerythromycin A, that could not be obtained readily by chemical synthesis. This product resulted from targeted disruption of the gene, designated eryF (systematic nomenclature, CYP107), that apparently codes for the cytochrome P450, 6-deoxyerythronolide B (DEB) hydroxylase, which converts DEB to erythronolide B (EB). Enzymes normally acting on EB can process the alternative substrate DEB to form the biologically active erythromycin derivative lacking the C-6 hydroxyl group.

Organization of a cluster of erythromycin genes in Saccharopolyspora erythraea.

We used a series of gene disruptions and gene replacements to mutagenically characterize 30 kilobases of DNA in the erythromycin resistance gene (ermE) region of the Saccharopolyspora erythraea chromosome. Five previously undiscovered loci involved in the biosynthesis of erythromycin were found, eryBI, eryBII, eryCI, eryCII, and eryH; and three known loci, eryAI, eryG, and ermE, were further characterized. The new Ery phenotype, EryH, was marked by (i) the accumulation of the intermediate 6-deoxyerythronolide B (DEB), suggesting a defect in the operation of the C-6 hydroxylase system, and (ii) a block in the synthesis or addition reactions for the first sugar group. Analyses of ermE mutants indicated that ermE is the only gene required for resistance to erythromycin, and that it is not required for production of the intermediate erythronolide B (EB) or for conversion of the intermediate 3-alpha-mycarosyl erythronolide B (MEB) to erythromycin. Mutations in the eryB and eryC loci were similar to previously reported chemically induced eryB and eryC mutations blocking synthesis or attachment of the two erythromycin sugar groups. Insertion mutations in eryAI, the macrolactone synthetase, defined the largest (at least 9-kilobase) transcription unit of the cluster. These mutants help to define the physical organization of the erythromycin gene cluster, and the eryH mutants provide a source for the production of the intermediate DEB.

Cloning of genes involved in erythromycin biosynthesis from Saccharopolyspora erythraea using a novel actinomycete-Escherichia coli cosmid.

Two plasmids were constructed that replicate in Saccharopolyspora (Sac.) erythraea, Escherichia coli and Streptomyces (S.) lividans, and used for the cloning of a locus involved in the synthesis of the macrolide antibiotic erythromycin (Er). Plasmid pAL7002 contains the thiostrepton-resistance gene (tsr), a replicon-containing fragment from pJVI and pUC9. Plasmid pNJI contains the lambda cos site but is otherwise similar to pAL7002. A library of total DNA from Sac. erythraea was constructed in pNJI and probed in colony hybridizations with a DNA fragment containing ermE, the Sac. erythraea ErR-encoding gene. Plasmids obtained were subsequently introduced into EryA mutants of Sac. erythraea blocked in synthesis of Er (Ery-) and transformants were screened for restoration of Er production (Ery+). Several plasmids were found to convert two mutants to Ery+, but a third EryA strain could not be restored to Ery+ by any of the plasmids employed. A 5-kb segment, designated eryAI, responsible for restoring the Ery+ phenotype in the EryA strains, was identified and mapped in the segment 12 to 17 kb downstream from ermE. Gene disruption experiments indicated that the 5-kb length of eryAI is fully internal to an eryAI-containing transcript. In Southern blots it was shown that one of the EryA strains carried a small deletion in eryAI and that, in at least some of the transformants restored to Ery+, the deletion had been replaced by the wild-type eryAI allele.(ABSTRACT TRUNCATED AT 250 WORDS)

A study of lymphocyte kinetics in nasopharyngeal carcinoma with indium III oxine-labelled lymphocytes.

The kinetics of lymphocyte migration in 12 pre-treatment patients with nasopharyngeal carcinoma (NPC) and three cancer controls in remission were studied with Indium III oxine-labelled autologous lymphocytes. The migratory patterns of the labelled lymphocytes were defined by serial gamma imaging and blood clearance of Indium over 72 h. Once in the systemic circulation the labelled lymphocytes migrated immediately to the liver and spleen. In all the subjects studied the lymphocytes began to migrate out of the liver at 0.5 h, only to return to the organ gradually between 2 and 72 h. In the control subjects the lymphocytes migrated out of the spleen from about 4 h. This coincided with a hump in the peripheral blood clearance curve after about 4 h signifying re-entry of the lymphocytes into the vascular space from the spleen. In the 'early' NPC subjects (Stage I-III) the rate at which the lymphocytes entered the spleen was much reduced from about 4 to 72 h, suggesting a prolonged transit time of the lymphocyte through the organ. However, there were still prominent humps in the blood clearance curves, suggesting significant re-entry of lymphocytes into the vascular space. In the 'late' NPC subjects (Stage IV-V), the activity of the spleen was low between 4 and 72 h and there was continuous sequestration of lymphocytes in the organ. Consequently the humps in the blood clearance curves were much reduced or absent. The activities of the metastatic lymph nodes were intense between 2 and 48 h, suggesting marked sequestration of lymphocytes in the diseased lymph nodes. Migration of lymphocytes in the metastatic area of the liver was notably absent and presented as cold areas on gamma scanning. The sequestration of lymphocytes in the spleen and metastatic lymph nodes in 'early' and 'late' NPC could lead to a contraction of intravascular lymphocyte pool and could explain the stage-dependent lymphopenia reported in NPC.

Isolation and characterization of vanadate-resistant mutants of Saccharomyces cerevisiae.

Cellular vanadium metabolism was studied in Saccharomyces cerevisiae by isolating and characterizing vanadate [VO4(3-), V(V)]-resistant mutants. Vanadate growth inhibition was reversed by the removal of the vanadate from the medium, and vanadate resistance was found to be a recessive trait. Vanadate-resistant mutants isolated from glucose-grown cells were divided into five complementation classes containing more than one mutant. Among the vanadate-resistant mutants isolated in maltose medium, the majority of mutants were found in only two complementation groups. Three of the classes of vanadate-resistant mutants were resistant to 2.5 mM vanadate but sensitive to 5.0 mM vanadate in liquid media. Two classes of vanadate-resistant mutants were resistant to growth in media containing up to 5.0 mM vanadate. Electron spin resonance studies showed that representative strains of the vanadate-resistant complementation classes contained more cell-associated vanadyl [VO2+, V(IV)] than the parental strains. 51 Vanadium nuclear magnetic resonance studies showed that one of the vanadate resonances previously associated with cell toxicity (G. R. Willsky, D. A. White, and B. C. McCabe, J. Biol. Chem. 259:13273-132812, 1984) did not accumulate in the resistant strains compared with the sensitive strain. The amount of vanadate remaining in the media after growth was larger for the sensitive strain than for the vanadate-resistant strains. All of the strains were able to accumulate phosphate, vanadate, and vanadyl.

Characterization of the gene encoding the major rat liver asialoglycoprotein receptor.

A cloned cDNA encoding the major rat liver asialoglycoprotein receptor has been used to analyze the gene for this protein. Genomic Southern blot analysis reveals that the gene is contained on a single EcoRI restriction fragment and is unique. A clone containing the gene (isolated from a rat liver genomic library) has been characterized by sequence analysis. The mRNA for the receptor is encoded by nine exons separated by eight introns. The first exon is confined to the 5'-untranslated region of the mRNA, the second exon encodes most of the cytoplasmic NH2-terminal domain of the receptor polypeptide, the third exon corresponds to the hydrophobic transmembrane portion of the polypeptide, and the remaining exons encode the extracellular parts of the receptor. Some, but not all, of the divisions between exons correspond to boundaries between functional domains of the polypeptide.

Rat liver asialoglycoprotein receptor lacks a cleavable NH2-terminal signal sequence.

Two cDNA clones encoding the predominant form of the asialoglycoprotein receptor from rat liver (the major rat hepatic lectin; RHL-1) were identified by screening a rat liver cDNA library with a mixed oligonucleotide probe 35 nucleotides long. One clone was a nearly full-length copy of the mRNA for RHL-1, while the other was shortened at both ends. The sequences of these clones demonstrate that this transmembrane receptor is not synthesized with an NH2-terminal signal sequence. The only proteolytic processing occurring in the biosynthesis of RHL-1 is the removal of the NH2-terminal initiator methionine residue. Insertion of RHL-1 into the membrane is postulated to occur by the recognition of the internal transmembrane region as a signal sequence.

Primary structure of the rat liver asialoglycoprotein receptor. Structural evidence for multiple polypeptide species.

When preparations of rat liver receptor for asialoglycoproteins (rat hepatic lectin, (RHL] are examined by dodecyl sulfate-polyacrylamide gel electrophoresis, multiple polypeptide species are found to be present. The predominant polypeptide has an apparent molecular weight of 41,500 (RHL-1), while two less abundant species appear to be of higher molecular weight (49,000 (RHL-2) and 54,000 (RHL-3]. When the several polypeptides are separated and treated with BrCN, the two minor species are found to share at least one large fragment, while the RHL-1 species gives rise to a completely different set of BrCN peptides. All of the BrCN fragments of the major species and the large common fragment from RHL-2 and RHL-3 have been isolated. These fragments serve as the basis for the complete sequence determination of RHL-1. The complete sequence is 283 residues long, although 20% of the protein as isolated is missing the first 2 residues at the NH2 terminus. The overall arrangement of the polypeptide is similar to the chicken receptor for asialoagalactoglycoproteins; it consists of an NH2-terminal stretch of hydrophilic amino acids, a segment of about 30 uncharged residues, and a COOH-terminal portion which contains three oligosaccharide attachment sites. When the COOH terminus of the rat liver receptor is aligned with the corresponding portions of the chicken liver receptor, the two proteins show 28% identity. Little identity is seen near the NH2 terminus. Sequence homology between residues 50-79 and residues 121-150 of the rat receptor suggests that the additional length of this protein compared with the chicken protein may be due to the presence of a duplicated segment within the rat receptor. The complete sequence of the BrCN fragment common to the two minor species has also been determined; this 101-residue sequence is 53% identical with the COOH-terminal sequence of RHL-1. Since these minor species have a primary structure distinct from RHL-1, there must be at least two genes coding for receptor polypeptides. RHL-2 and RHL-3 may differ in their extent of posttranslational modification.

111-Indium platelet imaging, Doppler spectral analysis and angiography compared in patients with transient cerebral ischaemia.

We have evaluated carotid gamma imaging using 111Indium-labelled platelets in the diagnosis of carotid artery disease and measured the accumulation of labelled platelets on endarterectomy specimens. Autologous 111In labelled platelets were injected in 25 patients with TIA. Gamma images were then taken daily and independently interpreted by two observers. Carotid endarterectomy was performed in 11 patients allowing measurement of the radioactivity on the operative specimen. These results were compared to the findings on angiography and Doppler spectral analysis. All endarterectomy specimens accumulated platelets with the most active equivalent to platelets from 1.8 ml blood. Atheromatous ulcers were more active than stenoses with mean (+/- SEM) activities of 1.12 +/- 0.37 and 0.38 +/- 0.10 respectively. These radioactivity levels were at the threshold of gamma camera resolution in a theoretical model. Both observers agreed that 22 of the 50 carotid bifurcations showed platelet accumulation on gamma imaging. Of the 12 atheromatous ulcers demonstrated by angiography 11 were visualized, but only five of ten stenoses greater than 80% were detected. As Doppler identified all stenoses only one angiographically diseased carotid was not detected by combining ultrasound with platelet scanning. Atherosclerotic arteries accumulate 111In platelets and the more thrombogenic ulcerated plaques are identified more frequently than stenoses. Long-term follow-up is required to establish the clinical relevance of platelet deposition.