- Volume 52, Issue 7, 2003
Volume 52, Issue 7, 2003
- Editorial
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- Review
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Microbial dinner-party conversations: the role of LuxS in interspecies communication
More LessBacteria have a tendency to be gregarious by nature. Whether on abiotic surfaces in the environment or on the mucosal surfaces of humans, bacteria accumulate in complex multi-species communities. In these dynamic accretions, bacteria can be densely packed and often depend on each other for the provision of metabolic substrates. Under these circumstances, it will be advantageous for bacteria to be able to detect the presence of their neighbours, to communicate with them and to co-ordinate various physiological activities. Such cell–cell sensing and communication systems can be established through the release and detection of chemical signalling molecules. While originally considered a feature characteristic of eukaryotes, the exchange of chemical signals has now been demonstrated in many bacterial species and ecosystems. Indeed, it has even been suggested that assemblages of bacterial species can be considered as proto-multicellular organisms, whereby biological processes are controlled for the benefit of the entire community. Regardless of the extent to which bacterial communication represents a step on the road to multicellularity, it is becoming increasingly apparent that the signalling systems devised by bacteria are essential for successful relationships with other bacteria and with eukaryotic hosts.
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- Pathogenicity And Virulence
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Correlation between enterococcal biofilm formation in vitro and medical-device-related infection potential in vivo
More LessHospital-acquired infections caused by enterococci have increased dramatically since the 1970s. Many nosocomial enterococcal bloodstream infections are associated with medical devices such as central venous catheters. The ability to form biofilm on medical devices is a potential virulence trait that may allow enterococci to cause infections in the expanding population of patients managed with such devices. In this study, the hypothesis that increased ability to form biofilm in vitro is associated with medical-device-related infection in vivo was tested. A microplate assay was employed to assess biofilm-forming characteristics of enterococci in 0.9 % (w/v) sodium chloride, an oligotrophic environment, and BHI, a nutrient-rich environment. Results were compared in isolates from different sources of infection. One hundred and nine enterococcal bloodstream isolates were assayed. Biofilm formation on microplates was demonstrated by all Enterococcus faecalis isolates and 16/38 (42 %) Enterococcus faecium isolates. E. faecalis isolates produced significantly more biofilm than E. faecium isolates in both media (P < 0.0001, Mann–Whitney U test). E. faecalis isolates from intravascular-catheter-related bloodstream infections (CRBSIs) produced significantly more biofilm than non-CRBSI isolates (P < 0.0001), or isolates of uncertain clinical significance (P < 0.0001). Biofilm formed by E. faecium isolates was not significantly affected by culture medium and did not differ between isolates from the different clinical categories. In conclusion, there was significantly more biofilm formed by E. faecalis isolates causing CRBSI compared with isolates from other types of infection or from isolates of uncertain clinical significance. The ability of E. faecalis isolates to form biofilm in vitro appears to be a marker of a virulence trait that enhances the ability of isolates to cause CRBSI.
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- Host Response
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Inability of outer-surface protein C (OspC)-primed mice to elicit a protective anamnestic immune response to a tick-transmitted challenge of Borrelia burgdorferi
A one-inoculation regimen of recombinant outer-surface protein C (OspC), which has been demonstrated to elicit protective immunity against a tick-borne challenge of Borrelia burgdorferi, was administered to outbred mice. Following seroconversion, the serum antibody titre against OspC was allowed to wane with time until there was little or no detection of anti-OspC antibodies by immunoblot. The mice were then challenged with an infectious dose of B. burgdorferi by tick transmission. Eleven of 12 OspC-primed mice subsequently became infected by B. burgdorferi, demonstrating that a protective anamnestic response was not generated in these mice following the introduction of infectious OspC-expressing spirochaetes.
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- Diagnostics, Typing And Identification
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Rapid identification and susceptibility testing of Mycobacterium tuberculosis from MGIT cultures with luciferase reporter mycobacteriophages
In a prospective study conducted in a diagnostic laboratory in Mexico City, luciferase reporter mycobacteriophages (LRPs) were evaluated for their utility and performance in identification and antibiotic-susceptibility testing of Mycobacterium tuberculosis complex (MTC) isolates from MGIT-960 cultures. Eighty-four consecutive MGIT cultures recovered from 54 patients were included in this study. The LRPs confirmed mycobacterial growth in 79 (94 %) of 84 MGIT cultures. Failure to confirm growth was due to low inoculum (n = 1) or growth with non-tuberculous mycobacteria (n = 4). The median time to confirmation of MGIT cultures was 1 day (range 1–55). Confirmed cultures were identified with p-nitro-α-acetylamino-β-hydroxypropiophenone (NAP), a selective inhibitor of MTC species, and results obtained with LRPs were compared with those obtained by BACTEC-460. The sensitivity and specificity of the LRP NAP test were respectively 97 and 100 %, and the median turnaround time for identification was 3 days with both methods. The accuracy and speed of the LRPs for susceptibility testing with rifampicin, streptomycin, isoniazid and ethambutol were compared with BACTEC-460 and discrepant results were tested by the conventional agar proportion method. In total, 72 MTC cultures were tested. The overall agreement between the LRPs and BACTEC-460 was 98.6 %. Four isolates (5.6 %) were falsely identified as ethambutol-resistant. The median turnaround time for susceptibility testing was 3 days (range 3–57) with the LRPs and 9 days (range 7–29) with BACTEC-460. LRPs offer an accurate and rapid approach for identification and susceptibility testing of M. tuberculosis from MGIT-960 cultures.
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Improved serodiagnosis of erythema migrans using novel recombinant borrelial BBK32 antigens
The performances of recombinant borrelial BBK32 proteins as antigens in the serology of erythema migrans (EM) were evaluated in an ELISA. Serum samples were obtained from 75 patients from different geographic areas where three borrelial species, Borrelia burgdorferi sensu stricto, Borrelia afzelii or Borrelia garinii, cause Lyme borreliosis. Antibodies to variant BBK32 proteins were compared with anti-flagella or with anti-IR6 peptide antibodies. In IgG ELISA at presentation of EM, 65/75 (87 %) patients had antibodies to one or more variants of BBK32, 29/75 (39 %) had antibodies to flagella and 29/75 (39 %) had antibodies to the VlsE IR6 peptide antigen. The immunoreactivity against variant BBK32 proteins differed in patients from different geographic regions. The present results suggest that the BBK32 proteins used in combination or in parallel may improve the laboratory diagnosis of EM.
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Analysis of saliva for antibodies to the LPS of Escherichia coli O157 in patients with serum antibodies to E. coli O157 LPS
More LessThe salivary antibody response to the Escherichia coli O157 LPS antigen was assessed in 44 patients with serum antibodies binding to the LPS of E. coli O157. Saliva from 477 controls was also examined to assess the specificity of the immunoassay used. Twenty of the 44 patients had salivary antibodies to E. coli O157 LPS, giving the salivary antibody test a sensitivity of 0.45 and a predictive positive value for seropositivity of 1.00. The presence of these antibodies appeared not to relate to the time interval between serum sampling and saliva sampling. None of the 477 volunteers had salivary antibodies binding to the LPS of E. coli O157 alone; however, 15 had antibodies which bound non-specifically to both O157 LPS and BSA.
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- Epidemiology
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Clostridium difficile in a geriatric unit: a prospective epidemiological study employing a novel S-layer typing method
More LessClostridium difficile is the major identifiable cause of antibiotic-associated diarrhoea in the UK. The aim of this study was to employ traditional culture, toxin detection and a novel typing method to determine the level of C. difficile colonization and disease in a population of elderly patients and to investigate the association between strains in the patients and their environment. Three hundred and ninety patients between 62 and 101 years of age admitted to a geriatric unit in the Royal Victoria Hospital (RVH), Edinburgh, were investigated for the presence of C. difficile. C. difficile was cultured from 100 (26 %) patients using pre-reduced cycloserine-cefoxitin egg yolk agar, and toxin(s) was detected in the faeces of 34 of these patients using the Techlab ELISA test kit for the detection of C. difficile toxins A and/or B. Toxin(s) was detected in a further 18 patients from whom no C. difficile was detected in culture. Of the patients in whom C. difficile was detected, 49 % had diarrhoea, with the highest proportion of patients with diarrhoea being both culture- and toxin-positive for C. difficile. Environmental sampling of the patient environment yielded C. difficile from 14 % of samples. The organism was most frequently isolated from floors, sluice-rooms and toilet areas. The variation in the molecular mass of the C. difficile S-layer proteins was exploited as the basis of a novel typing method for C. difficile. Isolates from patients in the RVH were given a four-digit ‘S-type’ number based on their S-layer protein profile. A total of seven S-types were identified, with one type, toxigenic S-type 5236, accounting for 73 % of all clinical isolates and 91 % of environmental isolates.
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- Clinical Microbiology And Virology
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Comparative viral frequency in Mexican children under 5 years of age with and without upper respiratory symptoms
More LessIn Mexico, there is a lack of up-to-date published data that show viruses to be the main cause of acute respiratory infection (ARI). The objective of this study was to estimate the comparative viral frequency between children under the age of 5 years with and without ARI (n = 179 in each group) in a suburban community (Nezahualcóyotl City). A nasopharyngeal sample was collected for viral culture and identification was carried out by indirect immunofluorescence (IIF) using mAbs. There were no sex differences between the two groups. Children under 1 year of age with ARI showed a higher frequency (56 %) of viral infections; this was statistically significant (P < 0.05) when compared with the same age group in ARI-free children (17 %). Respiratory syncytial virus (RSV) was the most prevalent type of virus isolated from both groups (38 vs 18 %). A statistically significantly higher number of subjects with ARI (33/179) than without (12/179) were infected with RSV (P < 0.003). Prevalences of four other viruses studied were similar in the two groups. The highest viral incidence of ARI in children was detected in the winter–spring seasonal period.
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- Models Of Infection
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Identification of a novel antigen of pathogenic Leptospira spp. that reacted with convalescent mice sera
More LessThe virulence of leptospires isolated from human patients against C3H/HeJ mice was investigated. Infection with clinical isolates from patients with severe leptospirosis was lethal to C3H/HeJ mice, suggesting that C3H/HeJ mice are suitable as an acute lethal model of severe leptospirosis. Using this model, a novel antigen of pathogenic Leptospira spp. (named LAg42), which reacted with convalescent mice sera, was identified. LAg42 is a 42 kDa inner-membrane protein and its immunogenic region is located in the C-terminal region. The gene for LAg42 is conserved among pathogenic leptospires but not among non-pathogenic leptospires, which suggests its involvement in virulence.
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- Human And Animal Microbial Ecology
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Molecular analysis of bacterial flora associated with chronically inflamed maxillary sinuses
More LessChronic maxillary sinusitis is a chronic inflammatory condition in which the role of microbial infection remains undefined. Bacteria have been isolated from chronically inflamed sinuses; however, their role in the chronicity of inflammation is unknown. The objective of this study was to determine whether bacteria are present in clinical samples from chronic maxillary sinusitis and to assess the diversity of the flora present. Washes and/or tissue samples from endoscopic sinus surgery on 11 patients with chronic maxillary sinusitis were subjected to PCR amplification of bacterial 16S rDNA using three universal primer pairs, followed by cloning and sequencing. The samples were also assessed for the presence of bacteria and fungi by conventional culture methods. Viable bacteria and/or bacterial 16S rDNA were detected from maxillary sinus samples of five of the 11 patients examined (45 %). Three sinus samples were positive by both PCR and culture methods, one was positive only by PCR, and one only by culture. Thirteen bacterial species were identified: Abiotrophia defectiva, Enterococcus avium, Eubacterium sp., Granulicatella elegans, Neisseria sp., Prevotella sp., Pseudomonas aeruginosa, Serratia marcescens, Staphylococcus aureus, Stenotrophomonas maltophilia, Streptococcus gordonii, Streptococcus mitis/Streptococcus oralis and Streptococcus sp. Fungi were not detected. In one patient Streptococcus mitis/Streptococcus oralis, and in another patient Pseudomonas aeruginosa, were detected from both the sinus and the oral cavity using species-specific PCR primers. These results suggest that both aerobic and anaerobic bacteria can be detected in nearly half of chronic maxillary sinusitis cases.
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- Case Report
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Septicaemia due to Corynebacterium striatum: molecular confirmation of entry via the skin
More LessSepticaemia due to Corynebacterium striatum occurs infrequently. A case of C. striatum septicaemia with a known skin focus is reported in a 69-year-old male with ischaemia, refractory anaemia and treated for thyroid cancer. The characterization and typing of blood and cutaneous isolates was carried out using biochemical and DNA molecular typing methods to analyse the isolates. This is the first reported case with a documented source.
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Volumes and issues
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Volume 73 (2024)
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Volume 72 (2023 - 2024)
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Volume 71 (2022)
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Volume 70 (2021)
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Volume 69 (2020)
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Volume 68 (2019)
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Volume 67 (2018)
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Volume 66 (2017)
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Volume 65 (2016)
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Volume 64 (2015)
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Volume 63 (2014)
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Volume 62 (2013)
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Volume 61 (2012)
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Volume 60 (2011)
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Volume 59 (2010)
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Volume 58 (2009)
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Volume 57 (2008)
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Volume 56 (2007)
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Volume 55 (2006)
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Volume 54 (2005)
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Volume 53 (2004)
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Volume 52 (2003)
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Volume 51 (2002)
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Volume 50 (2001)
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Volume 49 (2000)
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Volume 48 (1999)
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Volume 47 (1998)
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Volume 46 (1997)
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Volume 45 (1996)
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Volume 44 (1996)
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Volume 43 (1995)
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Volume 42 (1995)
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Volume 41 (1994)
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Volume 40 (1994)
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Volume 39 (1993)
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Volume 38 (1993)
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Volume 37 (1992)
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Volume 36 (1992)
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Volume 35 (1991)
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Volume 34 (1991)
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Volume 33 (1990)
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Volume 32 (1990)
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Volume 31 (1990)
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Volume 30 (1989)
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Volume 29 (1989)
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Volume 28 (1989)
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Volume 27 (1988)
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Volume 26 (1988)
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Volume 25 (1988)
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Volume 24 (1987)
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Volume 23 (1987)
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Volume 22 (1986)
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Volume 21 (1986)
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Volume 20 (1985)
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Volume 19 (1985)
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Volume 18 (1984)
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Volume 17 (1984)
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Volume 16 (1983)
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Volume 15 (1982)
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Volume 14 (1981)
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Volume 13 (1980)
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Volume 12 (1979)
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Volume 11 (1978)
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Volume 10 (1977)
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Volume 9 (1976)
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Volume 8 (1975)
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Volume 7 (1974)
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Volume 6 (1973)
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Volume 5 (1972)
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Volume 4 (1971)
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Volume 3 (1970)
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Volume 2 (1969)
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Volume 1 (1968)