- Volume 20, Issue 2, 1985
Volume 20, Issue 2, 1985
- Articles
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A Resistance Determinant to Nucleic Acid-Binding Compounds in Methicillin-Resistant Staphylococcus Aureus
More LessSummaryRecent isolates of methicillin-resistant Staphylococcus aureus from Australia and several other countries carry a plasmid coding for high levels of resistance to propamidine isethionate and low levels of resistance to cetyltrimethyl-ammonium bromide. The reasons for the acquisition and retention of such a determinant are not known. To define the properties of this resistance determinant in more detail, the minimum inhibitory concentrations of a series of cationic agents, including ethidium bromide, were determined and a cationic-resistance profile prepared for several strains of S. aureus and their isogenic, sensitive derivatives. The compounds for which resistance is coded by this determinant all bind to nucleic acids. Hence the determinant has been designated the NAB (nucleic acid-binding compounds)-resistance determinant.
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Lysogenicity of Methicillin-Resistant Strains of Staphylococcus Aureus
More LessSummaryThe lysogenic status of 23 strains of methicillin-resistant Staphylococcus aureus, isolated at the Royal Prince Alfred Hospital, Sydney, since 1980, was studied. Twenty strains, belonging to the four predominant phage types isolated in this hospital, carried the same lysogenic phage which we have designated C. Three other phages were isolated from five strains belonging to phage type 84/85/90. The presence of phage C had little effect on the phage-typing pattern of the strains. Similarly, lysogenisation with the other three phages did not result in a significant change in phage-typing patterns. However, when strain 1489, isolated in 1969, was lysogenised with these three phages, there was a change in phage-typing pattern. Lysogenisation of this strain with phage 47T resulted in a marked loss of sensitivity to both group-I and group-III phages. The lysogenic status of these methicillin-resistant strains of S. aureus was compared with that of strains isolated between 1967 and 1970. There was no evidence that the strains isolated recently were either related to, or derived from, the earlier ones.
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Susceptibility to Antimicrobial Agents and Analysis of Plasmids in Gentamicin- and Methicillin-Resistant Staphylococcus Aureus From Dublin Hospitals
More LessSummaryMethicillin- and gentamicin-resistant Staphylococcus aureus (MGRSA) strains isolated from Dublin Hospitals were classified into two groups (phenotypes). Phenotype-I strains expressed high level resistance to gentamicin and were susceptible to fusidic acid; strains resistant to tetracycline harboured a 3 x 106-mol. wt plasmid. Strains in phenotype II usually expressed low level resistance to gentamicin, were resistant to fusidic acid and often harboured a (22-24) x 106-mol. wt plasmid that specified resistance to ethidium bromide, tetracycline, kanamycin, neomycin and trimethoprim, or to combinations of these markers. A few phenotype-II strains expressed higher levels of resistance to gentamicin and other aminoglycosides. All MGRSA strains carried a 21 x 106-mol. wt plasmid conferring resistance to penicillin, ethidium bromide, cadmium and mercury. Gentamicin resistance was invariably chromosomal and all strains carried chromosomal resistance to methicillin, erythromycin, streptomycin and spectinomycin.
Several methicillin-resistant S. aureus (MRSA) strains isolated before the emergence of gentamicin resistance harboured a 21 x 106-mol. wt penicillinase plasmid with the same restriction endonuclease profile as that from some MGRSA strains. Some MRSA strains carried other plasmids related to those found in MGRSA strains.
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Transfer of Plasmid-Borne Aminoglycoside-Resistance Determinants in Staphylococci
More LessSummaryAminoglycoside-resistance determinants in staphylococci are borne on conjugative and non-conjugative plasmids. The conjugative plasmids were found in methicillin-resistant strains of Staphylococcus aureus isolated recently in Darwin and Sydney, Australia and in Houston, Texas, USA. These plasmids and the class-2 conjugative plasmid reported by Archer and Johnston (1983) had similar patterns of EcoR1 restriction-endonuclease fragments, encoded resistance to gentamicin, kanamycin and neomycin, transferred to a non-lysogenic recipient in conditions that promoted close cell-to-cell contact and mobilised a small, non-conjugative plasmid. A further plasmid, pWG14, encoding resistance to kanamycin, neomycin, streptomycin, erythromycin and lincomycin, also displayed conjugative properties but did not mobilise the small, non-conjugative plasmid. The transfer frequency of all conjugative plasmids was stimulated by the addition of polyethylene glycol, particularly at concentrations above 20%, to mixtures of donor and recipient broth cultures. Polyethylene glycol appeared to promote close cell-to-cell contact between donor and recipient cells. A representative of the most common aminoglycoside-resistance plasmids in Australian isolates of methicillin-resistant S. aureus was non-conjugative and transferred by a bacteriophage-mediated system to a lysogenic recipient. With the exception of plasmid pWG14, the conjugative plasmids were also transferred by a bacteriophage-mediated system. Furthermore, cultural conditions that favoured conjugative transfer of plasmids inhibited bacteriophage-mediated transfer and vice versa. The efficacy of the two transfer systems for analysing the plasmids of gentamicin-resistant, methicillin-resistant isolates of S. aureus has been compared.
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Transferable Resistance and Aminoglycoside-Modifying Enzymes in Enterococci
More LessSummaryTen isolates of Streptococcus faecalis and two isolates of S. faecium were studied together with an NCTC strain of each species. Antibiotic susceptibility tests showed different patterns of high-level resistance to aminoglycosides. Three S. faecalis strains were highly resistant to gentamicin and other aminoglycosides. By means of a filter membrane technique, transfer of high-level resistance to aminoglycosides was demonstrated from S. faecalis to S. faecalis, from S. faecium to S. faecalis and from S. faecalis to S. faecium, the last of which has not previously been described.
Aminoglycoside-modifying enzymes were assayed with radio-labelled cofactors. High-level resistance to gentamicin and other aminoglycosides could be attributed to the production of 3„-O-phosphotransferases, 3‚-O-phosphotransferases, 6‚-O-adenylyltransferases and 6‚-N-acetyltransferases. Other resistance mechanisms accounted for resistance in two strains of S. faecalis and one strain of S. faecium that were highly resistant only to streptomycin and one S. faecalis strain that was moderately resistant to all aminoglycosides. A low level of 6'-N-acetyltransferases was detected in the three strains of S. faecium but this did not confer high-level resistance to aminoglycosides and this trait could not be transferred.
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Auxotypes of Neisseria Gonorrhoeae in Toronto: Relationship to Penicillin Resistance and to Sex of Patient
More LessSummaryThe relationship of auxotype to penicillinase production, penicillin susceptibility, and sex of the patient, has been studied in 8446 non-penicillinase-producing and 153 penicillinase-producing Neisseria gonorrhoeae (PPNG) strains isolated during 1980-1983 in Toronto. Proline-requiring types constituted 51% of the PPNG and 13% of the non-PPNG strains; ornithine-requiring types constituted only 4% of the PPNG compared with 12% of the non-PPNG isolates. The various auxotypes of the non-PPNG isolates showed marked differences in their degree of resistance to penicillin; and the proportions of each auxotype from male and female patients were dissimilar.
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A Comparative Study of the Type-3 Fimbriae of Klebsiella Species
More LessSummaryType-3 fimbriae isolated from members of five different species of Klebsiella were 4-5 nm in diameter and agglutinated the tannic acid-treated erythrocytes of ox and, in some cases, the untanned erythrocytes of fowl. In sodium dodecyl sulphate-polyacrylamide gel electrophoresis, the type-3 fimbrial proteins had mol. wts in the range 19 500-21 500. Hydrophobic amino acids comprised 39.6% of all the amino acids of the type-3 fimbrial protein of K. oxytoca strain 70/1. The type-1 fimbrial protein of Klebsiella had a mol. wt of c. 18 000 and the type-1 fimbriae were serologically distinct from the type-3 fimbriae. Our results for the type-3 fimbriae of Klebsiella were compared with those of others for morphologically similar and serologically related thin fimbriae of Salmonella and Yersinia.
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Experimental Infection of Gnotobiotic Mice With Campylobacter Jejuni: Colonisation of Intestine and Spread to Lymphoid and Reticulo-Endothelial Organs
More LessSummaryAxenic and monoxenic C3H mice were used to develop an animal model for enteroinvasiveness and translocation of Campylobacter jejuni. After oral administration of 107-108 viable cells of C. jejuni on day 0 (D0), bacterial colonisation was followed quantitatively during 23 days by counting free luminal bacteria and tissue-associated bacteria in the duodenum, ileum and colon. The kinetics of bacterial colonisation were the same in axenic and monoxenic mice; bacteria were more numerous in distal than in proximal intestinal segments.
Electronmicroscope studies of axenic infected mice showed C. jejuni free in the intestinal lumen on D2 and D7, and adhering to microvilli or included in enterocyte vacuoles in the colon on D2 without inflammatory reaction; C. jejuni was isolated from mesenteric lymph nodes until D23, but from blood, spleen, liver and bile until D1 only. In monoxenic infected mice, C. jejuni was found from D1 to D4 in mesenteric lymph nodes and Peyer's patches, whereas the associated bacterium (Clostridium perenne) was never cultured from any organs.
On the basis of our observations in this gnotobiotic model, C. jejuni appears to be an enteroinvasive bacterium with a particular affinity for lymphoid organs.
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Protection Against Yersinia Infection Induced by Non-Virulence-Plasmid-Encoded Antigens
M. Simonet, P. Berche, D. Mazigh and M. VeronSummarySpecific immunity against Yersinia was induced by plasmid-encoded antigens not associated with virulence. Mice were immunised with viable bacteria from a virulence-plasmid-cured strain of Y. pseudotuberculosis. This antigenic stimulation generated specific protection against virulence-plasmid-harbouring strains of Y. pseudotuberculosis and Y. pestis, demonstrating that protection can be generated by organisms lacking plasmid-encoded virulence antigens.
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Biotransformation of Bile Acids by Clostridia
More LessSummaryThe metabolism of bile acids by nuclear dehydrogenating clostridia (NDC) was studied. NDC were able to desaturate the A-ring of 5β-cholan-3-oxo-24-oic acid, 12 α-hydroxy-5β-cholan-3-oxo-24-oic acid, 7α-hydroxy-5β-cholan-3-oxo-24-oic acid, 6α-hydroxy-5β-cholan-3-oxo-24-oic acid, 7α, 12α-dihydroxy-5β-cholan-3-oxo-24-oic acid, 3,12-dioxo-5β-cholan-24-oic acid but not 3,6-dioxo-5β-cholan-24-oic acid, 3,7-dioxo-5β-cholan-24-oic acid and 3,7,12-trioxo-5β-cholan-24-oic acid. In each case the sole product possessed a 4-ene-3-one structure. Desaturation of bile acids was more efficient than that of androstanes. NDC are, therefore, capable of introducing double bonds into the nucleus of bile acids as well as that of androstanes. The physiological significance of such reactions in relation to large bowel cancer has yet to be elucidated.
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Detection of Mycobacterial Antigen and Antibodies in the Cerebrospinal Fluid of Patients With Tuberculous Meningitis
More LessSummaryAn immunodiagnostic test for the detection of a soluble nonprotein mycobacterial antigen by reverse passive haemagglutination with IgM murine monoclonal antibody was developed. The test was used to analyse the cerebrospinal fluid of 89 patients with tuberculous meningitis (TBM) from India and 127 control subjects from India and the UK. The antigen was demonstrable in 88% of culture-positive and 73% of culture-negative TBM patients. However, it was also detected in 21% of Indian patients with pyogenic meningitis, and in 8% of Indian and 1% of UK control subjects. Antibodies binding to a soluble mycobacterial extract were detected at low titre in 68% of all subjects with TBM and in 37% of Indian cases of pyogenic meningitis. Because patients with TBM had raised levels of the antigen and of antibodies to the antigen, the possible role of immune complexes in the pathogenesis of the disease is briefly discussed.
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Protein-Mediated Adhesion of Staphylococcus Aureus to Silicone Implant Polymer
More LessSummaryInvestigation was made of the role of protein A and clumping factor in the adhesion of Staphylococcus aureus to the silicone polymer used for manufacture of cerebrospinal fluid shunting systems. The two proteins were judged to contribute non-specifically to adhesion. S. aureus was also shown to be capable of hydrophobic binding, but this was found to be distinct from the demonstrated protein-mediated adhesion.
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IMMUNE RESPONSES TO THE PROTEIN, CARBOHYDRATE AND LIPID ANTIGENS OF NOCARDIA ASTEROIDES IN EXPERIMENTAL NOCARDIOSIS IN MICE
More LessSummaryThe intravenous injection of Nocardia asteroides into mice produced systemic nocardiosis involving all the vital organs. Infection of the kidneys and adrenals was more persistent and progressive than in other organs as evidenced by increased bacterial counts and histopathological findings. During the course of the experimental infection, no humoral immune response was detected against various protein antigens up to 4 weeks after challenge, but significant cell-mediated immunity (CMI) was found. Phospholipid antigens elicited only a humoral immune response. The increased CMI responses with protein antigens correlated well with the decreasing bacterial load, which suggested that CMI against proteins was important in the pathogenesis of this disease.
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Immunological Responses to Protein, Carbohydrate and Lipid Fractions of Nocardia Asteroides in Mice
More LessSummaryThe protein, polysaccharide and phospholipid constituents of Nocardia asteroides have been partially purified and their immunogenicity studied in mice. Humoral and cellular immune responses were demonstrated against a crude cytoplasmic protein fraction (CPF). Two fractions of CPF were prepared on a Sephadex G-200 column; a high mol. wt fraction, fraction-1(F1) was capable of eliciting both types of immune responses, whereas fraction-2(F2) behaved more like a hapten. Phosphatides elicited only humoral responses whereas polysaccharides were non-immunogenic.
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The Expression of Capsule in Serum-Soft Agar by Staphylococcus Aureus Isolated From Human Clinical Sources
More LessSummaryStaphylococcus aureus isolates from human clinical sources were incubated for various times in modified 110 medium and tested for production of capsule by the serum-soft agar technique. Ten (5·7%) of 175 isolates were encapsulated after incubation for 24 h. A more detailed examination of 77 isolates showed that incubation period affected the production of capsule. After 2 h, 31% were encapsulated, but after 6 h and 24 h this decreased to 17% and 4% respectively. Rapid passage in vitro induced the expression of capsule in four of 50 unencapsulated strains. Only three of 20 encapsulated strains could be typed with standard antisera.
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Volumes and issues
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Volume 73 (2024)
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