- Volume 48, Issue 6, 1999
Volume 48, Issue 6, 1999
- Short Article
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Distribution of aggA and aafA gene sequences among Escherichia coli isolates with genotypic or phenotypic characteristics, or both, of enteroaggregative E. coli
More LessTwo types of fimbriae, designated aggregative adherence fimbria I and II (AAF/I and AAF/II) have been described in enteroaggregative Escherichia coli (EAEC) strains. These fimbriae mediate the aggregative pattern of adherence (AA) to epithelial cells. The genes encoding the structural subunit of each fimbria have been designated aggA and aafA, respectively. The prevalence of these genes was investigated in 155 faecal EAEC isolates that displayed AA to HeLa cells and were isolated from children in Sao Paulo, Brazil. Hybridisation assays with aggA and aafA sequences showed that 9.7% of these isolates carried aggA, 3.9% aafA, and none hybridised with both sequences. Of the 78 isolates displaying AA that reacted with the previously described EAEC probe (CVD432), 19.2% and 7.7% hybridised with the aggA and aafA probes, respectively. None of the 77 isolates displaying AA but lacking the EAEC probe sequence hybridised with either probe. These results clearly indicate that additional factors are involved in the AA phenotype in these EAEC strains.
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- Editorial
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- Host Response To Infection
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Mycobacterium avium infection in BALB/c and SCID mice
BALB/c and severe combined immunodeficient (SCID) mice were inoculated intraperitoneally with Mycobacterium avium and the numbers of cfu were monitored for 70 days in spleen, liver, lung, kidney, brain and peritoneum. While BALB/c mice formed typical granulomas and controlled bacterial growth in organs, a delay in development of lesions and a modest containment of infection were observed in SCID mice. In the spleen of BALB/c mice, in which bacterial growth was contained, macrophages (M⊘) and natural killer (NK) cell numbers increased ≥4.2 times and T- and B-cell numbers increased ≥1.8 times after 42 days of infection; conversely, a low recruitment of mononuclear cells was observed in the spleen of SCID mice, where M. avium proliferated efficiently. Unlike visceral organs, a pronounced decrease in the number of cfu was observed in the peritoneum of BALB/c mice, concomitantly with a ≥31.7-fold increase in M⊘ and NK cells and a ≥9.1-fold increase in T and B cells. In the peritoneum of SCID mice only a bacteriostatic effect was observed despite a ≥56.7-fold increase in M⊘ and NK cells and a ≥22.3-fold increase in T and B cells. These results suggest that while an intact immune response can efficiently control M. avium infection in the spleen and peritoneum of BALB/c mice, cells of the innate immune system such as M⊘ and NK cells play a role in the containment of bacterial growth in the peritoneum, but not spleen, of SCID mice.
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- Antimicrobial Resistance
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Occurrence of methicillin-resistant and -susceptible Staphylococcus aureus within a single colony contributing to MRSA mis-identification
More LessMany methods have been described for the detection of methicillin-resistant Staphylococcus aureus (MRSA), but the homogeneous or heterogeneous expression of methicillin resistance affects the reliability of those methods. This study demonstrates that close association between methicillin-susceptible S. aureus (MSSA) and MRSA strains in the host colonisation site can present additional problems for the detection of MRSA in clinical laboratories, which may contribute to failure in the control of MRSA infection in hospital. Worse, this association may also account for the emergence of MRSA during antibiotic therapy.
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- Epidemiological Typing
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Phenotypic and genotypic typing of food and clinical isolates of Enterobacter sakazakii
More LessEnterobacter sakazakii, designated a unique species in 1980, has been implicated as the causative organism in a rare but severe form of neonatal meningitis. Dried infant formula milk has been identified as a potential source of the organism. E. sakazakii isolates from dried infant formula available in Canada and clinical isolates obtained from Canadian hospital culture collections were characterised by phenotypic (biotype and antibiograms) and genotypic (ribotyping, random amplification of polymorphic DNA and pulsed-field gel electrophoresis) methods. Three biotypes and four antibiogram patterns were observed in the 18 isolates examined. Ribotyping with the Dupont Ribopiinter™ microbial identification system divided the 18 isolates into 10 ribotypes. Three isolates from the same hospital had indistinguishable ribotyping patterns although each was isolated in a different year, as did three food isolates from one company. Pulsed-field gel electrophoresis (PFGE) and random amplification of polymorphic DNA (RAPD) profiles indicated minor differences between the isolates that were indistinguishable by ribotyping. PFGE (with the restriction endonucleases Xba1 and Spel) and RAPD gave discrete patterns that enabled easy comparison of E. sakazakii isolates, with a high degree of discrimination. The discriminatory index showed RAPD and PFGE were shown to be the most discriminatory typing schemes for E. sakazakii, followed by ribotyping, biotyping and antibiograms.
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- Clinical Microbiology
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Significance of Cryptosporidium in acute diarrhoea in North-Eastern India
More LessIn a hospital-based study, stool samples from 2095 patients of all ages were examined for different fungal, protozoal and bacterial enteropathogens over a period of 2 years (July 1994-June 1996). Cryptosporidium was detected in 151 specimens (7.2%) and was the third commonest pathogen found. The highest prevalence of this organism was in the group aged 16-45 years and during the rainy months (July-Oct.). Diarrhoea caused by the protozoon was of mild to moderate severity and features of dysentery were absent. Amongst other enteropathogens, Candida albicans was the most frequently isolated, followed by enteropathogenic and enterotoxigenic Escherichia coli, Salmonella spp., Campylobacter jejuni, Entamoeba histolytica, Giardia duodenalis (lamblia), Shigella spp., Vibrio cholerae and Aeromonas spp.
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- Technical Note
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Isolation and partial characterisation of the Triton X-100 solubilised protein antigen from Mycobacterium tuberculosis
More LessThis report describes extraction of a new native antigen fraction from Mycobacterium tuberculosis without massive degradation of proteins by Triton X-100. The Triton X-100 solubilised protein (TSP) antigen showed a characteristic antigen profile and reproducible extraction pattern. To characterise the nature of their composition, the TSP antigen was fractionated by Triton X-114 phase partitioning. The TSP antigen contained a variety of lipids and glycoconjugates as well as diverse proteins. Most proteins were partitioned into the aqueous phase during phase fractionation, whereas non-protein molecules and lipoproteins were recovered in the detergent phase. The lymphoproliferative responses to the TSP aqueous fraction in healthy tuberculin reactors were significantly higher than those to the purified protein derivative (PPD) and unfractionated TSP. In contrast, the antibody responses to TSP aqueous fraction in tuberculosis patients showed weak reactivity. This study suggests that the TSP aqueous fraction can be used as a T-cell antigen associated with protective immunity against tuberculosis.
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Absorption of IgG does not enhance toxoplasma IgM and IgA immunoblotting
More LessTotal IgG, IgM and IgA levels and toxoplasma IgG. IgM and IgA immunoblotting patterns were assayed in 10 sera before and after IgG absorption with Protein G -Sepharose 4. Removal of IgG (mean reduction 96%) was accompanied by a significant reduction in the level of IgM (mean reduction 56%) and IgA (mean reduction 53%) in nine of the 10 sera. The absorbed supernates showed fewer and weaker IgM bands in five sera, but IgA immunoblotting patterns were unaffected by absorption. There was no benefit in removing IgG in toxoplasma IgM and IgA immunoblotting.
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- Case Report
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Fatal Campylobacter jejuni bacteraemia in patients with AIDS
More LessTwo fatal cases of Campylobacter jejuni septicaemia in patients with AIDS were characterised by severe HIV-related immunodeficiency, negative stool cultures and presentation during hospitalisation, developing a clinical picture of fulminant septic shock despite therapy with appropriate antibiotics. Campylobacter spp. are important opportunist pathogens in HIV disease and may cause a septicaemic illness in the absence of enteric disease.
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- Bacterial Pathogenicity
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Growth, cellular differentiation and virulence factor expression by Proteus mirabilis in vitro and in vivo
More LessA uropathogenic strain of Proteus mirabilis was grown in vitro in human and mouse urine and brain-heart infusion broth (BHIB) and in vivo in subcutaneous open chambers (SOC) in mice, intraperitoneal diffusion chambers (IPC) in rats and by ascending urinary tract infection in mice in order to compare growth pattern, cellular differentiation and expression of virulence factors. Although the growth rate was slower in vivo than in vitro, the extent of growth was similar after 24 h. P. mirabilis differentiated into filamentous swarmer cells in all in-vitro culture conditions, but no filamentous cells were observed in either of the in-vivo chamber models. Transurethrally infected mice showed a rapid release or loss of filamentous cells and these could not be seen in kidney or bladder homogenates 7 days after infection. Bacteria showed increasing haemagglutination titres for fresh and tanned red blood cells after subculturing in BHIB, but bacteria grown in vivo did not show haemagglutination. An increasing resistance to normal serum was found when bacteria were grown in vivo. Significant haemolytic activity was detected with bacteria grown in BHIB and IPC, but almost no activity was found when bacteria had grown in urine. These findings improve the understanding of the role of P. mirabilis uropathogenic virulence factors in vivo.
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Effect of glucose and pH on uropathogenic and non-uropathogenic Escherichia coli: studies with urine from diabetic and non-diabetic individuals
More LessIt is generally assumed that one of the reasons why diabetics are more susceptible to urinary tract infections than non-diabetics is their ‘sweet urine’. However, very little information is available on this subject. Therefore, the growth rates of different Escherichia coli strains were studied in human urine with and without added glucose and with and without a constant pH, and compared with their growth rates in MuellerHinton broth (MHB). Eight isolates were used (three from blood cultures from urosepsis patients, two urinary isolates, two faecal isolates and one laboratory strain K12). All isolates grew better in MHB than in urine, but with the exception of the laboratory strain, they had the same growth rate in urine. No significant difference was found between the growth rate in urine from diabetics without glucosuria and that in urine from non-diabetics. The addition of glucose (up to a concentration of 1000 mg/dl) to urine and MHB enhanced the growth rate of all isolates. However, very high concentrations of glucose (up to 10 000 mg/dl) in urine and MHB caused a decrease in bacterial growth rate when the urinary pH was not kept constant. The stationary phase was reached later and the final bacterial yield was greater when the urine was made less acidic. As the uropathogenic strains did not grow better in urine than the other isolates, it may be concluded that better growth in urine is not one of the causes of the greater virulence of these strains.
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Ability of lactoferrin to promote the growth of Bifidobacterium spp. in vitro is independent of receptor binding capacity and iron saturation level
More LessLactoferrin (Lf) is an iron-binding protein which has been shown to inhibit the growth of various bacterial pathogens and promote the growth of anaerobic bacteria of the genus Bifidobacterium in vitro. The present study was designed to investigate whether the bifidobacteria growth promotion activity of Lf is correlated with either the binding of Lf to bifidobacterial cells or the iron saturation of Lf. Bovine Lf (bLf) from mature milk increased the growth of B. infantis and B. breve in vitro in a dose-dependent fashion, while much less growth promotion activity was found for B. bifidum. In contrast, human Lf (huLf) from mature milk promoted the growth of B. bifidum and was inactive for B. infantis and B. breve, while bLf from colostrum was devoid of bifidobacteria growth promotion activity. Changes in the iron content of Lf did not alter the bifidobacteria growth promotion activity of either bLf or huLf preparations. Competitive binding studies with biotinylated milk bLf showed that binding of bLf was inhibited by unlabelled bLf and huLf but not by β-lactoglobulin, α-lactalbumin or transferrin. Binding of bLf to B. bifidum and B. breve was c. 4C-fold higher than binding to Escherichia coli. Colostrum bLf was also found to bind to B. bifidum and B. breve, despite a lack of in-vitro growth promotion activity. Collectively, these results demonstrate that the ability of Lf to promote the growth of Bifidobacterium spp. in vitro is independent of the iron saturation level for Lf and suggest that binding of Lf to bifidobacteria cells may be involved but is not sufficient for stimulation of bifidobacterial growth.
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A novel mucin-sulphatase activity found in Burkholderia cepacia and Pseudomonas aeruginosa
More LessLung infections due to Burkholderia cepacia and Pseudomonas aeruginosa in patients with cystic fibrosis (CF) are common, are associated with respiratory morbidity and are a cause of mortality. Respiratory mucin in CF patients is highly sulphated, which increases its resistance to bacterial degradation. Desulphation increases the susceptibility of mucin to degradation by bacterial glycosidases and proteinases, and subsequent deglycosylation may facilitate bacterial colonisation by increasing available substrates and binding sites. This study determined whether clinical and environmental strains of B. cepacia and P. aeruginosa had the ability to desulphate mucin. Mucin-sulphatase activity was tested by incubating bacterial cell suspensions with 35S-sulphated mucins purified from LS174T and HT29-MTX human colon carcinoma cell lines. These mucins were also used to test for differences in substrate specificities. Mucin-sulphatase activity was detected in all nine B. cepacia strains and in four of six P. aeruginosa strains. There was strain variability in the level of mucin-sulphatase activity. Aryl-sulphatase activities of Pseudomonas isolates (determined with methylumbelliferyl sulphate) were c. 20-fold higher than those of B. cepacia strains, and were independent of mucin-sulphatase activity. This is the first report to demonstrate desulphation of mucin by B. cepacia and P. aeruginosa. It is concluded that B. cepacia and P. aeruginosa produce one or more cell-bound glycosulphatase(s), in addition to aryl-sulphatase activity. Mucin-sulphatase activity of B. cepacia and P. aeruginosa may contribute to their association with airway infections in patients with cystic fibrosis.
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- Virology
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Molecular epidemiology of poliovirus infection in Tunisia
This report is an overview of poliomyelitis surveillance in Tunisia from 1991 to 1996. In all, 2088 stool specimens, collected from 152 acute flaccid paralysis (AFP) cases and from 1747 of their healthy contacts were investigated. Virus isolation was done systematically in RD and HEp-2C cell lines and isolated viruses were typed by seroneutralisation as polioviruses or non-polio enteroviruses. Poliovirus isolates were analysed systematically for their wild or vaccine-related origin by two methods - one based on antigenic differences and one on genetic differences between strains. All type 2 polioviruses were vaccine-related and most wild viruses belonged to polio serotype 3. Wild polio type 3 viruses were detected in 1991 and 1992 in six cases of paralytic polio. A silent circulation of wild polio 1 and wild polio 3 was detected in 1994. No wild virus was detected in Tunisia from 1995 onwards. Wild polioviruses were sequenced and compared with Tunisian wild strains isolated during the 1980s, as well as other genotypes from the international database. These investigations revealed a single Tunisian polio 3 genotype that has been circulating from 1985 to 1994 and two different polio 1 genotypes. These results reflect effective control strategies within the country and contribute to the improvement of the polio eradication programme effectiveness at national and global levels.
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- Proceedings Of The Pathological Society Of Great Britain And Ireland
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- Book Review
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Volumes and issues
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