27.5 W/m2 collection efficiency solar laser using a diffuse scattering cooling liquid: erratum.

In this erratum we clarify our previously published paper [Appl. Opt.57, 4008 (2018)APOPAI0003-693510.1364/AO.57.004008], where we used a solar spectrum truncated to a maximum wavelength of 830 nm in the numerical modelling, but did not state this in the paper. Here, we present a graph of the numerically modelled absorption in the Nd:YAG rod as a function of the diffuse reflectivity of the chamber walls using the full solar spectrum, confirming that the theoretical maximum possible absorption we predict is in agreement with literature values.

27.5 W/m2 collection efficiency solar laser using a diffuse scattering cooling liquid.

We report a solar pumped solid state laser using a 20 mm long, 3 mm diameter neodymium-doped yttrium aluminum garnet laser rod. This rod was placed in a liquid cooling chamber using a water-white-emulsion-paint mix. This mix provides cooling for the laser crystal and also doubles as a diffuse light scattering liquid. This enhances sunlight scattering and leads to a greater absorption in the laser rod. We numerically model the solar absorption in the laser rod using a ray-tracing model and predict a 2.6 times enhancement in absorption when a 98% reflective diffuse scatter is modelled compared to 0% scattering. We experimentally demonstrated this, showing a 2.58 times increase in average output power of the solar laser compared to the use of pure water as a cooling liquid. Using the water-white-paint scattering cooling liquid, we demonstrated a laser with an output power of 2.3 W and with a collection efficiency of 27.5 W/m2.

Molecular epidemiology of group B streptococci in Ireland: associations between serotype, invasive status and presence of genes encoding putative virulence factors.

Group B streptococcal isolates (n = 159) from the three Dublin maternity hospitals, were serotyped and analysed for the bac, bca, hylB, pepB, and rib genes. The serotype distribution of the isolates was Ia, 19.5%; Ib, 18.9%; II, 10.7%; III, 29.5%; IV, 1.9%; V, 15.1%; non-typeable, 4.4%. There was a statistically significant association between the serotype and invasive status (carriage or infection) of isolates (P < 0.005), but no significant association between serotype and degree of invasiveness was demonstrated. The presence or absence of each analysed gene was not associated with the invasive status of isolates. Statistically significant associations were revealed between bca and hylB (IS1548) (P = 0.0004) and between bac and bca (P=0.014). The bac, bca, hylB (IS1548) and rib genes and the numbers of tandem repeats in the bca gene showed significant associations with serotype. Almost 50% of serotype III isolates possessed at least one of the bac and bca genes and 55-65% of strains of serotypes Ia, Ib and II possessed the rib gene. Most serotype III isolates had IS1548 in their hylB genes. Serotype Ib was the only serotype in which more than half of the strains contained more tandem repeats in the bca gene than the overall mean for the GBS population studied of 7.4 repeats. These findings indicate that some previously reported associations between putative virulence factors and GBS disease require further study and clarification.

Characterization of a putative pathogenicity island from bovine Staphylococcus aureus encoding multiple superantigens.

Previous studies have demonstrated that a proportion of Staphylococcus aureus isolates from bovine mastitis coproduce toxic shock syndrome toxin (TSST) and staphylococcal enterotoxin C (SEC). In this study, molecular genetic analysis of one such strain, RF122, revealed the presence of a 15,891-bp putative pathogenicity island (SaPIbov) encoding the genes for TSST (tst), the SEC bovine variant (sec-bovine), and a gene (sel) which encodes an enterotoxin-like protein. The island contains 21 open reading frames specifying hypothetical proteins longer than 60 amino acids including an integrase-like gene. The element is bordered by 74-bp direct repeats at the left and right junctions, and the integration site lies adjacent to the 3' end of the GMP synthase gene (gmps) in the S. aureus chromosome. SaPIbov contains a central region of sequence identity with the previously characterized tst pathogenicity island SaPI1 (J. A. Lindsay et al., Mol. Microbiol. 29:527-543, 1998). A closely related strain, RF120, of the same multilocus enzyme electrophoretic type, random amplified polymorphic DNA type, and ribotype, does not contain the island, implying that the element is mobile and that a recent insertion/deletion event has taken place. TSST and TSST/SEC-deficient mutants of S. aureus strain RF122 were constructed by allele replacement. In vitro bovine Vbeta-specific lymphocyte expansion analysis by culture supernatants of wild-type strains and of tst and sec-bovine allele replacement mutants revealed that TSST stimulates BTB13-specific T cells whereas SEC-bovine stimulates BTB93-specific T cells. This suggests that the presence of SaPIbov may contribute to modulation of the bovine immune response.

Population characteristics of Irish Helicobacter pylori isolates: a tRNA-associated locus.

BACKGROUND: A strain-variable transfer RNA-associated-locus (trl) was present in 50% of Irish Helicobacter pylori (H. pylori), isolates and did not correlate with the origin of the isolates. AIM: To associate a particular genotype or phenotype to trl status in H. pylori by further screening the isolates from the original study for the presence of known genotypic and phenotypic characteristics. METHODS: Forty two clinical isolates were screened for the presence of the cagA, vacA, iceA1 and vapD genes by Southern or DNA dot blot analysis. Western blot analysis was performed using antibodies to CagA, VacA, Lewis X (Le(x)) and Lewis Y (Le(y)). Plasmids were identified by the alkaline lysis method. RESULTS: The cagA gene was present in 29 (69%) of isolates screened and 21 (50%) produced the CagA protein. The vacA gene was detected in all of the isolates while VacA was expressed in 71.4%. The iceA1 and vapD loci were detected in 73.8% and 71.4% respectively. Le(x) was expressed in 42.9% and Le(y) in 38.1% of the isolates. Expression of both Lewis antigens was detected in 7.1% while in 30.9% neither antigen was detected. Plasmids were present in 47.6%. There was no association between the trl status of isolates and any of the above. There were no significant associations between the phenotypic and genotypic characteristics studied and peptic ulcer disease or non-ulcer dyspepsia. CONCLUSION: The strain-variable tRNA-associated locus is independent of the vacA/VacA, cagA/CagA, Lewis X, Lewis Y, iceA1, vapD and plasmid status in the population of Irish H. pylori isolates studied.

Molecular population and virulence factor analysis of Staphylococcus aureus from bovine intramammary infection.

Staphylococcus aureus isolates from cows in Ireland (n = 102) and the USA (n = 42) were characterized by RAPD-PCR and analysed for the production of a number of putative virulence factors. Of these strains 63 representative isolates were screened for the corresponding virulence factor genes by PCR or Southern hybridization or both. The isolates were divided into 12 distinct clonal types on the basis of their RAPD fingerprint profiles. Of the isolates, 107 (74.3%) tested positive for clumping factor in a slide agglutination test, all 24 RAPD type 7 isolates being negative for clumping factor. PCR analysis of region R, a repeat region of the clfA gene, revealed eight region-R sizes. There was a strong association between RAPD type and the clfA region-R genotype among Irish isolates. Of the RAPD type 7 isolates, 21 (87.5%) coproduced toxic shock syndrome toxin-1 (TSST-1) and staphylococcal enterotoxin C (SEC). Over 90% of isolates demonstrated haemolytic activity on sheep or rabbit red blood cells and all isolates harboured the gamma-haemolysin (hlg) locus. Of the Irish isolates, all those of RAPD type 7 were sensitive to penicillin G, whereas 86% of RAPD types 4 and 5 strains were resistant. Furthermore, RAPD types 5 and 7 were more likely to be associated with clinical mastitis whereas RAPD type 4 isolates were more often associated with a latent infection. The current study identifies some of the putative virulence factors produced by the predominant clonal types of bovine Staph. aureus that may be considered as components of a vaccine.

Lack of a relationship between Lewis antigen expression and cagA, CagA, vacA and VacA status of Irish Helicobacter pylori isolates.

The cagA gene, vacA gene, CagA (cytotoxin-associated gene A product) and VacA (vacuolating cytotoxin) status of a collection of Helicobacter pylori isolates from the geographically distinct Irish population was determined, the potential association of these traits with Lewis (Le) antigen expression was assessed, and the relationship between these bacterial properties and the pathology associated with H. pylori infection was evaluated. Of the 57 isolates, a higher proportion from ulcer than from non-ulcer patients expressed VacA (71% vs. 53%). H. pylori isolates which were cagA-positive were no more significantly associated with peptic ulcers than non-ulcer disease (71% vs. 67%, P = 0.775), nor were CagA-positive isolates (57% vs. 50%, P = 0.783), but 80% of the isolates from duodenal ulcer patients were cagA-positive. Thirty-seven of the 57 isolates were tested for Le antigen expression. No statistically significant relationship (P > 0.05) was found between the occurrence and level of expression of Le(x) or Le(y) and cagA, vacA, or VacA status. This lack of an association in the Irish H. pylori isolates contrasts with that previously reported for predominantly North American isolates, and may be attributable to the adaptation of H. pylori strains with differing attributes to different human populations.

Fine-structure molecular epidemiological analysis of Staphylococcus aureus recovered from cows.

Sixty-three Staphylococcus aureus isolates recovered from bovine sources in the USA and the Republic of Ireland were characterized by multilocus enzyme electrophoresis (MLEE), ribotyping, and random amplified polymorphic DNA polymerase chain reaction (RAPD-PCR) typing at two separate laboratories. The S. aureus isolates were assigned by MLEE to 10 electrophoretic types (ETs) (Index of Discrimination, D = 0.779). In contrast, the same isolates were assigned to 13 ribotypes (D = 0.888), and to 12 RAPD types (D = 0.898). A common clone, ET3, of worldwide distribution, was represented by six distinct combinations of ribotypes and RAPD types. S. aureus clones recovered from cows in Ireland were also associated with mastitis in dairy cows in the USA. These findings are consistent with the hypothesis that only a few specialized clones of S. aureus are responsible for the majority of cases of bovine mastitis, and that these clones have a broad geographic distribution.

Rheumatologic view of the rheumatoid foot.

Rheumatoid arthritis is a common systemic disease that affects between 0.3% and 1.5% of the general population worldwide. In 1988, it was estimated by the National Arthritis Foundation that there were 4 to 6 million cases of rheumatoid arthritis in the United States. There is general agreement that the feet are a major source of pain and disability at some point in the course of the illness. The frequency of involvement of the feet among 1000 patients with rheumatoid arthritis studied by Vainio was 91% in females and 85% in males. The clinical features and pathogenesis of the rheumatoid foot and an approach to initial nonsurgical treatment will be discussed.

Fimbrial adhesins: similarities and variations in structure and biogenesis.

Fimbriae are wiry (2 to 4 nm diam.) or rod-shaped (6 to 8 nm diam.), fibre-like structures on the surfaces of bacteria which mediate attachment to host cells. Much has been learned in recent years about the biogenesis, structure and regulation of expression of these adhesive organelles in Gram-negative bacteria. Analyses of the genetic determinants encoding the biogenesis of fimbriae has revealed that the adhesive interaction of fimbriae can be mediated by major subunits (CFA/I and CS1 fimbriae) or minor subunits (P, S, and type 1 fimbriae), with the adhesin being located either at the tip of the fimbria or along the length of the fimbrial shaft. Minor subunits can also act as adapters, anchors, initiators or elongators. Post-translational glycosylation of the type 4 pilins of Neisseria gonorrhoeae, Neisseria meningitidis and Pseudomonas aeruginosa has been demonstrated. The structures of the PapD chaperone of Escherichia coli and of N. gonorrhoeae type 4 fimbrin have been resolved at 2.0-2.6 A. Rod-shaped fimbriae should not be thought of as being rigid inflexible structures but rather as dynamic structures which can undergo transition from a helicoidal to a fibrillar conformation to provide a degree of elasticity and plasticity to the fimbriae so that they can resist shear forces, rather like a bungee cord. At least four mechanisms have been identified in the assembly of fimbriae from fimbrin subunits, namely the chaperone-usher pathway (e.g., P-fimbriae of uropathogenic E. coli), the general secretion assembly pathway (e.g., type 4 fimbriae or N-methylphenylalanine fimbriae of P. aeruginosa, the extracellular nucleation-precipitation pathway (e.g., curli of E. coli) and the CFA/I, CS1 and CS2 fimbrial pathway.

Genomic DNA fingerprinting of clinical isolates of Helicobacter pylori using short oligonucleotide probes containing repetitive sequences.

The ability of oligonucleotide probes containing short repetitive sequence motifs to differentiate between isolates of Helicobacter pylori was investigated. Genomic DNA preparations from H. pylori were digested with the restriction enzyme HindIII, electrophoresed in agarose gels and transferred to nylon filters. Five separate oligonucleotide probes were tested for hybridization sequentially to fingerprint the digested DNA from a panel of 29 clinical isolates and one type strain of H. pylori, and their relative discriminatory abilities were assessed. Four probes, (GACA)4, (GT)8, (GTG)5 and (GGAT)4, were each shown to yield highly informative hybridization band profiles allowing differentiation of H. pylori isolates. The DNA fingerprints of individual isolates obtained with each probe were distinct and reproducible. Direct comparison with ribotyping revealed that oligonucleotide fingerprinting had far superior discriminatory power. Computer-assisted similarity analysis of (GGAT)4-generated hybridization profiles of pairwise combinations of H. pylori isolates revealed that there was no correlation between ribotype and oligonucleotide fingerprint patterns. The results of this study demonstrate that oligonucleotide probes containing microsatellite sequences provide a new and powerful tool for isolate discrimination of H. pylori.

Molecular analysis of the cso operon of enterotoxigenic Escherichia coli reveals that CsoA is the adhesin of CS1 fimbriae and that the accessory genes are interchangeable with those of the cfa operon.

A deletion mutation in csoA, the gene encoding the structural subunit protein of CS1 fimbriae of enterotoxigenic Escherichia coli of serotype O6:K15:H16 or H-, was constructed in the subcloned CS1 genetic determinant. The mutation resulted in the abolition of CS1 fimbrial adhesiveness. Complementation, in trans, involving the determinant with the csoA deletion mutation and the gene encoding the structural subunit protein, CsoA, expressed from compatible plasmids, restored the expression and adhesive ability of CS1 fimbriae. In addition, trans-complementation was achieved between the cso determinant with the aforementioned deletion mutation and the cfaB gene encoding the structural subunit protein (CfaB) of CFA/I fimbriae, resulting in the expression of CFA/I fimbriae. The observation that heterologous assembly was possible between these two fimbrial systems, together with the knowledge that the adhesin of CFA/I fimbriae is the structural subunit, was exploited to investigate whether CsoA had adhering properties. A deletion mutation in cfaB was created in the CFA/I fimbrial determinant. Complementation of this mutation with csoA in trans resulted in expression of the CsoA antigen on the bacterial cell surface and restoration of bacterial adherence. As no minor subunits act as the adhesin in CFA/I fimbriae, adhesion was mediated by CsoA. Nucleotide sequencing of the DNA region downstream from csoA confirmed the absence of genes encoding minor subunits which might act as the adhesin. Two open reading frames were revealed which encoded proteins sharing considerable homology with proteins encoded by corresponding ORFs in the CFA/I fimbrial operon. These proteins underlie the functional similarities between the CS1 and CFA/I fimbrial systems, allowing heterologous expression of their respective subunits.

Recrudescence of Helicobacter pylori after apparently successful eradication: novel application of randomly amplified polymorphic DNA fingerprinting.

The aim of this study was to find out if reinfection or recrudescence accounted for the recurrence of Helicobacter pylori infections after apparent eradication of the bacterium. Three hundred and twenty patients were treated with colloidal bismuth subcitrate (120 mg four times daily for four weeks), metronidazole and tetracycline (400 mg and 500 mg, respectively, thrice daily for the first week). H pylori was eradicated four weeks after the end of treatment as assessed by the rapid urease test, histological examination, Gram staining, and culture. However, the infection recurred in 29 (9.1%) of the patients one year after apparent eradication. Pre and posteradication isolates from five patients were available. DNA was extracted and used for restriction endonuclease analysis with Hind III and Hae III, and for polymerase chain reaction (PCR) based randomly amplified polymorphic DNA fingerprinting with a combination of two 10 nucleotide primers. Sodium dodecyl sulphate polyacrylamide gel electrophoretic analysis was performed also. Randomly amplified polymorphic DNA fingerprinting was unique in that it yielded highly discriminatory fingerprints, which showed that the pretreatment and recurrent isolates obtained from each of the five patients were indistinguishable from one another. This shows that recurrence of H pylori infection is probably caused by recrudescence and that the discriminatory power of randomly amplified polymorphic DNA fingerprinting is a practicable and discriminatory typing scheme for H pylori.

Molecular analysis of Helicobacter pylori populations in antral biopsies from individual patients using randomly amplified polymorphic DNA (RAPD) fingerprinting.

In the present study, randomly amplified polymorphic DNA (RAPD) fingerprinting has been used to analyse multiple single colony isolates of Helicobacter pylori from antral biopsies in an attempt to ascertain whether or not multiple strains are present in individual patients using single biopsy samples. The RAPD fingerprints derived from single colonies obtained from the same biopsy specimen were in all cases indistinguishable. The previously noted heterogeneity between H. pylori strains from different individuals was confirmed. RAPD fingerprinting, combined with a simple method of template preparation, was shown to be an excellent method for H. pylori strain differentiation. The results of this study indicate that the H. pylori population is homogeneous in individual patients at a single gastric site.

Identification of erythrocyte-binding antigens in Helicobacter pylori.

The surface antigens of Helicobacter pylori conferring erythrocyte-binding activity were obtained by adsorption onto formaldehyde-treated dog and goat erythrocytes from supernatant fractions of sonicated bacteria and elution using a high concentration of NaCl. The desorbed material was analysed by SDS-PAGE and immunoblotting with anti-whole-cell serum to agar-grown bacteria which had been absorbed with broth-grown, non-haemagglutinating cells (haemagglutination-associated antiserum). Two polypeptides with molecular masses of 25 and 59 kDa were revealed as erythrocyte-binding antigens. Strains which agglutinated both dog and goat erythrocytes possessed both these erythrocyte-binding antigens, whereas an antigenically cross-reactive 24 kDa polypeptide was present in a strain which only agglutinated goat erythrocytes. Haemagglutinin material was extracted from H. pylori using n-octylglucopyranoside and purified by Sepharose chromatography and sucrose density gradient ultracentrifugation. The purified extract directly agglutinated erythrocytes in a neuraminyl-lactose-sensitive and neuraminidase-sensitive manner. The 59 kDa polypeptide was not present in the purified haemagglutinin preparation. The haemagglutination-associated antiserum reacted strongly with the 25 kDa polypeptide band which was the most prominent polypeptide band on analysis of the purified haemagglutinin preparation by SDS-PAGE and silver staining. Thus, H. pylori possesses at least two adhesins, one of which recognises a N-acetylneuraminic acid (alpha 2-3) moiety of receptors, the other being of unknown receptor specificity. Differences in the antigenicity and molecular masses of these adhesins in individual strains may underlie differences in receptor-binding specificities and haemagglutination profiles.

Legionella in Dublin hospital water supplies.

An environmental survey was carried out which consisted of periodic and random sampling of water tanks and showers in two large Dublin hospitals. Of the samples 5.3% yielded Legionella bacteria. Legionella pneumophila of serogroups 3, 5 and 6 were isolated from these sites with viable counts ranging from 3.0 x 10(2) - 2.5 x 10(3) c.f.u./litre. The implementation of periodic sampling may, however, not be a worthwhile exercise unless an environmental site has been associated with cases of legionellosis. Emphasis should be placed on the prevention of contamination of environmental sites with legionellae and on the development and implementation of protocols and procedures for the isolation of legionellae to gain the necessary expertise should an epidemiological survey be required.

Electron microscopy of adhesive interactions between Gardnerella vaginalis and vaginal epithelial cells, McCoy cells and human red blood cells.

Exfoliated vaginal epithelial cells with attached bacteria, termed 'clue cells', which were procured from a patient with non-specific vaginitis, were stained with ruthenium red and examined by transmission electron microscopy. The attached bacteria appeared to adhere by means of an outer fibrillar coat. An epithelial tissue culture cell line (McCoy) and human red blood cells to which strains of Gardnerella vaginalis attached were similarly examined. The adherence of G. vaginalis to the epithelial cell line appeared to be mediated by an outer fibrillar coat while adherence to red cells appeared to be mediated by fimbriae. Transmission electron microscopy was performed on the Gardnerella strains used. Thin sections of tissue-culture-adherent strains revealed a dense outer fibrillar coat whereas the surface of the haemagglutinating strains showed fine fimbriae. Negative staining of haemagglutinating strains demonstrated fimbriae on a minority of organisms.

Nucleotide sequence of the gene encoding the major subunit of CS3 fimbriae of enterotoxigenic Escherichia coli.

The complete nucleotide sequence of a 612-base-pair DNA fragment containing the gene for the major fimbrial subunit of CS3 of enterotoxigenic Escherichia coli is presented. A possible promoter region, a ribosome-binding site, and two potential signal peptidase cleavage sites are indicated. Unlike the best-studied fimbrial proteins, the predicted CS3 sequence has no Cys residues.

Molecular cloning of the plasmid-located determinants for CS1 and CS2 fimbriae of enterotoxigenic Escherichia coli of serotype O6:K15:H16 of human origin.

The plasmid pCS001, isolated from an enterotoxigenic strain of Escherichia coli, mediates expression of the CS1 or CS2 and CS3 fimbrial adhesins in appropriate E. coli hosts. To characterize this further, HindIII-generated DNA fragments of this plasmid were cloned into the vector plasmid pBR322. A chimaera, called pCS200, which mediated expression of the CS1 or CS2 fimbrial antigen but not of CS3 fimbrial antigen in appropriate host strains, was obtained. The DNA inserted into the vector sequences of plasmid pCS200 comprised HindIII fragments of 4.7 kbp and 0.8 kbp. Plasmid pCS200-carrying wild-type E. coli hosts of serotype O6:K15:H16 that expressed the CS1 or CS2 antigen also caused mannose-resistant agglutination of bovine red blood cells, suggesting that functional fimbriae were present on the bacterial surface. As previously observed with strain K12 recipients of CS-fimbriae-associated plasmids mobilized from wild-type enterotoxigenic E. coli, K12 recipients of the chimaeric plasmid pCS200 did not express the CS1 or CS2 fimbrial antigen. An oligonucleotide probe, synthesized on the basis of the published N-terminal amino acid sequence of the CS2 fimbrial subunit, hybridized to plasmid pCS200, indicating that the gene for the structural subunit of this fimbria resided on the plasmid.

Haemagglutination and tissue culture adhesion of Gardnerella vaginalis.

Six strains of Gardnerella vaginalis were studied to examine the adhesin-receptor mechanism involved in their attachment to human red blood cells and an epithelial tissue culture cell line (McCoy). The adhesins involved in the attachment of the bacteria to each of these cells were proteinaceous but showed marked differences after various chemical or physical treatments, indicating that separate adhesins were present. Haemagglutinating strains were more hydrophobic than tissue-culture-adherent strains. Haemagglutination of human red blood cells by strains of G. vaginalis was inhibited by galactose, lactose, N-acetylneuraminic acid and phosphatidylserine. In contrast, the tissue-culture adherence of strains was not inhibited by these substances.