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Volume 57,
Issue 7,
2008
Volume 57, Issue 7, 2008
- Pathogenicity And Virulence
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Campylobacter jejuni response to human mucin MUC2: modulation of colonization and pathogenicity determinants
More LessCampylobacter jejuni is the main cause of bacterial acute gastroenteritis worldwide. In its colonization of the host intestinal tract, it encounters secreted mucins in the mucus layer and surface mucins in the epithelial cells. Mucins are complex glycoproteins that comprise the major component of mucus and give mucus its viscous consistency. MUC2 is the most abundant secreted mucin in the human intestine; it is a major chemoattractant for C. jejuni, and the bacterium binds to it. There are no studies on the transcriptional response of the bacterium to this mucin. Here, cell-culture techniques and quantitative RT-PCR were used to characterize in vitro the effects of MUC2 on C. jejuni growth and the changes in expression of 20 C. jejuni genes related to various functions. The genes encoding cytolethal distending toxin protein (cdtABC), vacuolating cytotoxin (vacB), C. jejuni lipoprotein (jlpA), Campylobacter invasion antigen (ciaB), the multidrug efflux system (cmeAB), putative mucin-degrading enzymes (cj1344c, cj0843c, cj0256 and cj1055c), flagellin A (flaA) and putative rod-shape-determining proteins (mreB and mreC) were upregulated, whereas those encoding Campylobacter adhesion fibronectin-binding protein (cadF) and sialic acid synthase (neuB1) were downregulated. These results showed that C. jejuni utilizes MUC2 as an environmental cue for the modulation of expression of genes with various functions including colonization and pathogenicity.
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Biochemical properties and primary structure of elastase inhibitor AFUEI from Aspergillus fumigatus
More LessAn elastase inhibitor from Aspergillus fumigatus (AFUEI) was isolated, and its biochemical properties and primary structure examined. The inhibitor was purified by column chromatography using DE52 cellulose and Sephadex G-75, and was found to be homogeneous as indicated by a single band following discontinuous PAGE and SDS-PAGE. A molecular mass of 7525.1 Da was observed by matrix-assisted desorption/ionization time-of-flight mass spectroscopy. The elastolytic activity of elastases from A. fumigatus, Aspergillus flavus and human leukocytes was inhibited by AFUEI. However, the elastolytic activity of porcine pancreas elastase, Pseudomonas aeruginosa elastase and elastase from snake venom was not affected by AFUEI. No inhibitory effect of DTT or 2-mercaptoethanol on the elastase inhibitory activity of AFUEI was observed. The amino acid sequence of AFUEI peptides derived from digests utilizing clostripain was determined by Edman sequencing. AFUEI was composed of 68 aa and had a calculated molecular mass of 7526.2 Da. The search for amino acid homology with other proteins demonstrated that aa 1–68 of AFUEI are 100 % identical to aa 20–87 of the hypothetical protein AFUA 3G14940 of A. fumigatus.
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Attenuation of Pseudomonas aeruginosa virulence by medicinal plants in a Caenorhabditis elegans model system
More LessExpression of a myriad of virulence factors and innate antibiotic resistance enables the opportunistic human pathogen Pseudomonas aeruginosa to create intractable infections. Using a nematode model, we screened for novel inhibitors of this pathogen. Aqueous extracts of three plants, Conocarpus erectus, Callistemon viminalis and Bucida buceras, were examined for their effects on P. aeruginosa killing of the nematode Caenorhabditis elegans. The results were evaluated in toxin-based and infection-based assays using P. aeruginosa strains PAO1 and PA14. The tested plant extracts prevented mortality via gut infection in approximately 60 % of the worms and caused a 50–90 % reduction in death from toxin production. All extracts inhibited nematode death by P. aeruginosa without host toxicity, indicating their potential for further development as anti-infectives.
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- Diagnostics, Typing And Identification
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Urease-positive bacteria in the stomach induce a false-positive reaction in a urea breath test for diagnosis of Helicobacter pylori infection
More LessThis study investigated the influence of urease-positive non-Helicobacter pylori bacteria on the results of a urea breath test (UBT) to evaluate the diagnostic utility of a UBT using film-coated [13C]urea tablets. The UBT was performed in 102 patients treated with a proton pump inhibitor and antibiotics for the eradication of H. pylori. Urease-producing bacteria other than H. pylori were isolated and identified from the oral cavity and stomach. In 4/102 patients, the UBT gave false-positive results. These false-positive results were found to be caused by the presence of urease-positive bacteria in the oral cavity and stomach. Five bacterial species with urease activity (Proteus mirabilis, Citrobacter freundii, Klebsiella pneumoniae, Enterobacter cloacae and Staphylococcus aureus) were subsequently isolated from the oral cavity and/or stomach. As there was no correlation between the in vitro urease activity of urease-positive non-H. pylori bacteria and the UBT value, and all of the patients with a false-positive UBT result were suffering from atrophic gastritis, it is possible that the false-positive results in the UBT were a result of colonization of urease-positive bacteria and gastric hypochlorhydric conditions. Thus, for the diagnosis of H. pylori infection using a UBT, the influence of stomach bacteria must be considered when interpreting the results.
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A novel method for rapid detection of Streptococcus pneumoniae antigen in sputum and its application in adult respiratory tract infections
A highly sensitive immunochromatography test kit, ODK0501, was developed using specific polyclonal antibodies against the C-polysaccharide moiety of Streptococcus pneumoniae for the rapid detection of S. pneumoniae antigen in sputum samples. The clinical utility of ODK0501 for this detection was evaluated prospectively in 52 adult patients with respiratory infections and compared with that of a urinary antigen detection kit. Overall, 21 patients (40.4 %) showed positive results with ODK0501, compared with 16 patients (30.8 %) using the urinary antigen detection kit, and S. pneumoniae was cultured from 18 patients. ODK0501 and the urinary antigen detection kit exhibited a sensitivity of 94.4 and 55.6 % (P<0.01), respectively, and a specificity of 88.2 and 82.4 %, respectively. Eleven of thirteen patients with conflicting results between the two test kits exhibited consistent results for sputum cultures. Moreover, eight out of nine patients positive for ODK0501 and negative for the urinary antigen detection kit were S. pneumoniae culture-positive, including five who exhibited phagocytosis, indicating S. pneumoniae as a causative agent of infection, in Gram staining of sputum samples. These results suggest that the ODK0501 direct sputum detection kit is more clinically useful than the urinary antigen detection kit in adult patients with respiratory infections.
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Extended phage locus typing of Salmonella enterica serovar Typhimurium, using multiplex PCR-based reverse line blot hybridization
More LessSalmonella enterica serovar Typhimurium (S. Typhimurium) is the commonest pathogen causing food-borne disease among humans and animals in Australia. A multiplex PCR-based reverse line blot (mPCR/RLB) system was developed to rapidly identify S. Typhimurium phage types and strains within them. The system comprised 32 biotin-labelled primer sets and 38 amino-labelled probes, based on sequences that were either phage-type-related or derived from temperate phages ST64B, P22, Gifsy-1 or Gifsy-2. The system was developed and evaluated using 168 S. Typhimurium isolates, representing 46 phage types. RLB patterns, based on a combination of positive hybridization and grading of signal intensities, validated by sequencing, differentiated S. Typhimurium isolates into 102 types. Some clusters contained isolates belonging to a single phage type while others contained isolates belonging to more than one. Most phage types exhibited at least two RLB profiles. The feasibility of this system was evaluated during investigations of three outbreaks, due to two different phage types. Within each outbreak, isolates showed identical RLB patterns, whereas sporadic isolates of corresponding phage types showed various patterns. The mPCR/RLB system was compared with multilocus variable-number tandem-repeat analysis (MLVA). The two methods demonstrated similar discriminatory abilities. Based on these preliminary results, the mPCR/RLB system is a promising tool for molecular identification of most common S. Typhimurium phage types. It could be used as an alternative to, or in conjunction with, MLVA for rapid strain typing during outbreaks.
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Molecular assessment of invasive Streptococcus pneumoniae serotype 1 in Brazil: evidence of clonal replacement
In Brazil, serotype 1 Streptococcus pneumoniae is one of the most prevalent causes of severe infection. This study investigated the genetic relatedness of 134 serotype 1 isolates obtained from invasive diseases during the period 1977–2005. Molecular typing by PFGE revealed two major lineages using visual inspection and computer analysis. Type A comprised 94 isolates (70.2 %) with four subtypes, whereas type B comprised 40 isolates (29.8 %) with eight subtypes. Subtype A3, the most frequent genotype, accounting for 65 % of the total isolates, was identified as a representative of clone Sweden1-40 (ST304). Type B was predominant in the period 1977–1988. In contrast, an increase in the type A lineage was detected from 1990 in Brazil, significantly associated with isolates recovered from pneumonia cases and from young patients. This study clearly established a temporal switch between two lineages of S. pneumoniae serotype 1 in Brazil, with a wide dispersion of clone Sweden1-40 in recent years.
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Use of the serum reactivity against Toxoplasma gondii excreted–secreted antigens in cerebral toxoplasmosis diagnosis in human immunodeficiency virus-infected patients
Despite the development of serological and molecular methods in recent years, the diagnosis of cerebral toxoplasmosis in human immunodeficiency virus (HIV)-infected patients still presents difficulties. In the present study, we investigated whether cerebral toxoplasmosis induced changes in the reactivity of serum toward Toxoplasma gondii excreted–secreted antigens (ESA) in order to develop an assay for evaluating HIV-infected patients with cerebral toxoplasmosis. The antigen selection was based on those produced by tachyzoites, since it is the form of the organism responsible for disseminating the infection, as well as stimulation of the humoral and cellular immune responses. By using an ELISA containing pooled ESA recovered from infected culture supernatants with tachyzoites-RH strain (ESA-ELISA), we found that ESA had a high specificity for sera from patients with cerebral toxoplasmosis. The reactions were compared with an ELISA using crude tachyzoites antigen, widely used in traditional serology. The assays were performed on 293 serum samples separated as follows: 100 sera from patients with cerebral toxoplasmosis and AIDS (symptomatic), 99 sera from individuals with chronic toxoplasmosis (asymptomatic) and 94 sera from healthy individuals without toxoplasmosis (control). The crude tachyzoite antigen in ELISA was able to distinguish both groups of sera with toxoplasmosis, as similar reactivity were observed in sera from patients with cerebral toxoplasmosis and those from chronic individuals. In contrast, ESA-ELISA distinguished sera from symptomatic and asymptomatic individuals (three times more reactive in the former group, 12.6 versus 4.2). The assays were reproducible based on immunoblotting and statistical analysis. These data suggest the utility of ESA-ELISA in the diagnosis of cerebral toxoplasmosis in HIV-infected patients, since it provided clear evidence that anti-ESA antibodies are present principally in patients with active infection. The absence of a significant amount of antibodies distinguished the patients without clinical symptoms of infection.
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- Antimicrobial Agents And Chemotherapy
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Effect of putative efflux pump inhibitors and inducers on the antimicrobial susceptibility of Campylobacter jejuni and Campylobacter coli
More LessThe CmeABC efflux pump plays an important role in the antimicrobial resistance of Campylobacter jejuni and Campylobacter coli. The aim of this investigation was to study the effect of putative efflux pump inhibitors, phenyl-arginine-β-naphthylamide (PAβN) and 1-(1-naphthylmethyl)-piperazine (NMP), as well as the effect of putative efflux pump inducers, sodium salicylate and sodium deoxycholate, on the MIC levels of erythromycin, ciprofloxacin, kanamycin, tetracycline and rifampicin for C. jejuni and C. coli. Our results indicated that susceptibility to erythromycin and rifampicin increased, respectively, 8- to 32- and 8- to 64-fold in the presence of PAβN and to a lesser extent in the presence of NMP. Salicylate produced a 2- to 4-fold increase in ciprofloxacin MIC values, whereas little effect was observed in the presence of deoxycholate.
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Molecular characterization of multidrug-resistant Shigella species isolated from epidemic and endemic cases of shigellosis in India
Shigella species represent one of the growing numbers of antimicrobial-resistant bacteria in developing countries. Fluoroquinolone-resistant strains of Shigella dysenteriae type1 and Shigella flexneri type 2a emerged in India during 2002 and 2003, respectively. Sixty strains of Shigella from different parts of India were analysed for antimicrobial susceptibility, the presence of the qnr plasmid, mutations in the quinolone resistance determining regions (QRDRs), fluoroquinolone accumulation, and the presence of other genes encoding resistance to various antimicrobials. Fluoroquinolone-resistant strains had mutations in gyrA and parC genes and had an active efflux system. They were also resistant to several other antimicrobials but were susceptible to azithromycin and ceftriaxone. The majority of the strains harboured genes encoding resistance to ampicillin (97 %), tetracycline (95 %), streptomycin (95 %) and chloramphenicol (94 %). PFGE analysis revealed clonality among strains of S. dysenteriae types 1 and 5, S. flexneri type 2a and Shigella boydii type 12.
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- Epidemiology
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Genetic profiling of Mycobacterium tuberculosis in Tunisia: predominance and evidence for the establishment of a few genotypes
Typing analyses of 378 Mycobacterium tuberculosis isolates collected between the years 2001 and 2005 from three northern representative regions of Tunisia revealed a highly homogeneous population. Indeed, 84.9 % of all tuberculosis (TB) cases were attributed to the Haarlem, LAM or T families. Strikingly, within each family, more than 60 % of TB cases were due to a single genotype. ST50 (Haarlem3) and ST42 (LAM9) genotypes were exceptionally predominant, representing 46.3 % of all typed isolates. ST50 showed an increased tendency for clustering and was more predominant in the extreme north of the country. By contrast, the more widespread ST42, which was apparently prevalent 17 years ago, displayed weak cluster individualization and a low transmission rate, consistent with its stable association with the Tunisian population. It is believed that both mass BCG vaccination, strictly applied for four decades, and the high endogamy rate that characterizes the Tunisian population could have profoundly shaped the population structure of M. tuberculosis by concurrently favouring the selection and accommodation of particular genotypes.
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Promising loci of variable numbers of tandem repeats for typing Beijing family Mycobacterium tuberculosis
More LessWe analysed the genotypes of 325 Mycobacterium tuberculosis clinical isolates obtained during 2002 throughout Japan. The genotyping methods included insertion sequence IS6110 RFLP, spoligotyping and variable number of tandem repeat (VNTR) analyses. Clustered isolates revealed by IS6110 RFLP analysis accounted for 18.5 % (60/325) of the isolates. Beijing genotype tuberculosis (TB) accounted for 73.8 % (240/325) of the isolates. Using VNTR, we analysed 35 loci, including 12 standard mycobacterial interspersed repetitive units and 4 exact tandem repeats. The discriminatory power of these 16 loci was low. Using VNTR analyses of the 35 loci, 12 loci (VNTRs 0424, 0960, 1955, 2074, 2163b, 2372, 2996, 3155, 3192, 3336, 4052 and 4156) were selected for the genotyping of Beijing genotype strains. Comparison of the discriminatory power of the 12-locus VNTR [Japan Anti-Tuberculosis Association (JATA)] to that of the 15-locus and 24-locus VNTRs proposed by Supply et al. (2006) showed that our established VNTR system was superior to the reported 15-locus VNTR and had almost equal discriminatory power to the 24-locus VNTR. This 12-locus VNTR (JATA) can therefore be used for TB genotyping in areas where Beijing family strains are dominant.
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- Clinical Microbiology And Virology
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Emergence of CTX-M-15 type extended-spectrum β-lactamase-producing Salmonella spp. in Kuwait and the United Arab Emirates
More LessCephalosporins are major antimicrobials used to treat serious Salmonella infections. However, their effectiveness is being compromised by the emergence of extended-spectrum β-lactamases (ESBLs). The genetic determinants encoding ESBL in Salmonella spp. isolated from patients in Kuwait and United Arab Emirates (UAE) were studied over a 2 year period. Out of a total of 407 isolates, 116 isolates possessed the resistance phenotypes consistent with possible ESBL production. Of these, 69 (59.5 %) were ESBL positive. PCR and sequencing were used to determine the genetic determinant(s) responsible for ESBL phenotypes. A total of 14 (12.1 %) and 29 (24.6 %) isolates were CTX-M-15 ESBL producers and TEM producers, respectively. Ten CTX-M-15 producers carried the insertion sequence ISEcpI gene. PFGE analysis revealed identical profiles in 4 of the 13 Kuwaiti strains. This study reports the presence of the bla CTX-M-15 gene in Salmonella spp. and Salmonella enterica serotype Typhi from Kuwait and UAE for what is believed to be the first time. This is of great concern as the gene is also found in association with the ISEcpI gene, which may easily facilitate its spread. These isolates originated mostly from non-Kuwaiti Arabs rather than from people of Asian origin.
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- Veterinary Microbiology
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Heterogeneity of Escherichia coli STb enterotoxin isolated from diseased pigs
More LessTo investigate the presence and frequency of estB variant(s), a collection of 100 STb-positive enterotoxigenic Escherichia coli (ETEC) strains isolated from 1980 to 2007 inclusively and randomly selected from diseased pigs in Québec, Canada, was analysed. A wide diversity of virulence gene profiles (virotypes) was detected in the strain collection. The estB gene was amplified by PCR using primers designed from the signal sequence and the C-terminal end, and the amplified fragment was sequenced using the forward primer. The translated DNA sequence revealed a His12→Asn change in 23 of the 100 ETEC isolates tested. The STb-variant strains were observed throughout the sampling period covered in the study. No other STb-variant type was found in this study. All 23 variant strains were also positive for the STa enterotoxin and were resistant to tetracycline, as for strain 2173. The STb variant was associated with Stx2-positive strains (5/6) and STa : STb strains that did not harbour any of the tested porcine fimbrial adhesins (13/17). The remaining variant strains were associated with fimbriae F4 (1/40), F5 (1/6), F6 (1/1) and F18 (2/7; excluding F18 : Stx2 strains).
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- Oral Microbiology
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Molecular characterization of Streptococcus mutans strains isolated from the heart valve of an infective endocarditis patient
More LessStreptococcus mutans, known to be an aetiological agent of dental caries, is occasionally isolated from patients with infective endocarditis (IE). S. mutans strains with a defect in all three types of glucosyltransferase (GTF) obtained from an infected heart valve extirpated from an IE patient have been reported previously. In this study, molecular analyses of strains detected in heart valve (strain V1) and dental plaque (strain P1) samples taken from the same patient were performed. Complete nucleotide alignments of the gtfB, gtfC and gtfD regions in strains V1 and P1, as well as in the reference strain MT8148, were determined, which revealed the existence of alignments with a high similarity to erythromycin- and spectinomycin-resistance genes in the middle of the gtfB–gtfC and gtfD genes, respectively, of V1. Strain V1 also showed a higher MIC for these two antibiotics compared with strain P1. Next, primers to detect the specific sequences of the antibiotic-resistance genes in strain V1 were constructed and PCR amplification was performed with template DNA from dental plaque and infected valve tissue samples taken from the patient. Attenuated expression of GTFs in V1 caused a significantly lower susceptibility to phagocytosis by human polymorphonuclear leukocytes compared with the reference strain. These results suggest that the blood isolate V1 found in the oral cavity invaded and survived in the bloodstream for a long duration and that this was related to its virulence in IE in our patient.
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- Case Reports
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Leclercia adecarboxylata in an immunocompetent patient
More LessLeclercia adecarboxylata is a rarely reported human pathogen, most commonly affecting immunocompromised individuals. In reported cases of immunocompetent patients infected with this organism, it is seen exclusively in the context of polymicrobial infections. We report here the case of an abscess in an immunocompetent patient that grew out L. adecarboxylata as a pure culture. The limited literature available on this organism is reviewed, and the potential implication of this finding is discussed.
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First clinical case of Corynebacterium auriscanis isolated from localized dog bite infection
More LessCorynebacterium auriscanis has only previously been isolated from dogs and to our knowledge no cases of zoonotic transmission to humans have been reported. A case of a leg wound infection following a dog bite in a previously healthy human patient is described and confirms this organism to be a potential human pathogen.
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Capnocytophaga canimorsus: infection, septicaemia, recovery and reconstruction
More LessA case is presented of a life-threatening septicaemia and associated peripheral necrosing microembolic phenomenon, resulting from a dog lick to an insignificant burn wound. The isolated bacterium was Capnocytophaga canimorsus, a slow-growing Gram-negative bacillus commonly found in dog saliva. Any clinician seeing patients with a history of dog bite/saliva contact and progressive illness should consider this bacterium as a possible offender and take special care to elicit an accurate history, specifically including questions regarding animal contact.
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Staphylococcus caprae meningitis following intraspinal device infection
A case is reported of Staphylococcus caprae meningitis due to infection of an intraspinal analgesia pump. The subclinical and pauci-symptomatic clinical course of the infection strongly suggested a chronic device contamination.
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Isolation of Helcococcus kunzii from plantar phlegmon in a vascular patient
More LessHelcococcus kunzii has previously been considered to belong to the normal skin flora of podiatry patients. Here, H. kunzii was isolated in abundance from a pus specimen collected by incision and drainage of plantar phlegmon. This fastidious Gram-positive species was unambiguously identified with the colorimetric VITEK 2 GP card identification system. This suggests that this phenotypic identification system is able to identify promptly H. kunzii, which should be considered a potential pathogen.
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Volumes and issues
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Volume 72 (2022 - 2023)
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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 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 49 (2000)
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Volume 46 (1997)
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Volume 45 (1996)
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Volume 41 (1994)
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Volume 36 (1992)
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Volume 34 (1991)
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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)
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