- Volume 53, Issue 7, 2004
Volume 53, Issue 7, 2004
- Review
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Switches, cross-talk and memory in Escherichia coli adherence
More LessEscherichia coli is a successful commensal and pathogen. Its pathogenic diversity stems from the acquisition and expression of multiple virulence-associated loci. Many of the key virulence factors are surface structures involved in adherence and motility. These are important antigens and their expression is limited by phase-variable genetic switches that are considered to act randomly. This review considers the possibility that such stochastic expression within a bacterial population belies sequential or co-ordinate control at the level of the individual bacterium. Co-ordinated expression or cross-talk between virulence loci can lead to a programmed set of events within a bacterium analogous to a simple form of electronic memory that is of benefit during infection.
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- Diagnostics, Typing And Identification
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PCR-based assays for detection of Streptococcus pneumoniae serotypes 3, 14, 19F and 23F in respiratory specimens
More LessCurrent culture-based assays are insensitive for detection of simultaneous respiratory tract colonization by more than one pneumococcal serotype. Separate single-tube, nested PCR-based assays have been developed to detect Streptococcus pneumoniae serotypes 3, 14, 19F and 23F by amplifying unique DNA sequences in the capsular polysaccharide gene cluster of each serotype. Pairs of 27–32-base outer primers and 20–21-base inner primers and a 20–22-base probe were designed to amplify and detect a 200–221-base sequence by dot blotting using the labelled probe. Sensitivity of the assays was 0.01–10 fg using chromosomal DNA and ⩽ 1 viable cell using DNA extracted from exponential-phase bacteria. Each serotype-specific assay detected chromosomal DNA from all of five to ten clinical isolates of the homologous type and did not detect DNA sequences from any of 190–204 strains from 51–52 different serotypes or 28 non-pneumococcal bacterial strains. Sixteen throat swabs from children that had been cultured for S. pneumoniae were tested in PCR assays following DNA extraction. All of six that grew S. pneumoniae serotype 3, 14, 19F or 23F were positive in the PCR assay for the homologous serotype (and in a PCR assay for sequences in lytA, present in all pneumococci) and were negative in assays for other serotypes. Of eight culture-negative specimens in children not receiving antimicrobials, three were positive for both the lytA assay and an assay for one of the four serotypes, suggesting true positive results; in three others all five PCR assays were negative and, in the remaining two, the lytA assay was positive but each of the four assays for individual serotypes was negative, suggesting either false-positive results or presence of DNA sequences from an S. pneumoniae serotype other than 3, 14, 19F or 23F. These preliminary clinical data suggest that these PCR-based assays are sensitive and specific for detection of individual serotypes of pneumococci and may be used with respiratory tract specimens.
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Comparison between real-time PCR, conventional PCR and different staining techniques for diagnosing Pneumocystis jiroveci pneumonia from bronchoalveolar lavage specimens
Between January 2002 and July 2003, 173 bronchoalveolar lavage (BAL) specimens from 150 patients (19 HIV-infected and 131 non-HIV-infected patients) were evaluated for identification of Pneumocystis jiroveci (formerly known as Pneumocystis carinii f. sp. hominis) using staining techniques, conventional PCR (mtLSUrRNA gene) and real-time PCR (MSG gene). Test results were compared to Pneumocystis pneumonia (PCP) confirmed by typical clinical findings and response to treatment. Sensitivity and specificity of the techniques were 60 and 100 % for staining (where either one or both techniques were positive), 100 and 87.0 % for conventional PCR and 100 and 84.9 % for real-time PCR, respectively. The use of a concentration of 103 copies of DNA per capillary of BAL as a cut-off (determined by real-time PCR) increased specificity from 84.9 to 98.6 % without reducing the sensitivity of the technique. This technique is rapid (<3 h) and therefore of major interest in differentiating between asymptomatic carriage and PCP. A BAL specimen with <103 copies per capillary of Pneumocystis-specific DNA is more likely to indicate a chronic carrier state, but in such cases follow-up is required to ensure that the patient is not in the early stage of an active PCP.
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Identification and characterization of transmissible Pseudomonas aeruginosa strains in cystic fibrosis patients in England and Wales
More LessMost past studies of cross-infection with Pseudomonas aeruginosa among cystic fibrosis (CF) patients in the UK suggest that it is a rare occurrence. However, two recent reports of highly transmissible strains in patients in regional centres in England (Liverpool and Manchester) have raised questions as to the extent of the problem and prompted a nationwide survey to establish the distribution of P. aeruginosa strain genotypes among these patients. Isolates of P. aeruginosa were requested from over 120 hospitals in England and Wales and a sample size of approximately 20 % of the CF patient population in each centre was recommended. In total, 1225 isolates were received from 31 centres (range 1 to 330). Single patient isolates were typed by SpeI macrorestriction and PFGE. A panel of strains of the common genotypes including representatives of reported transmissible strains was assembled and further characterized by fluorescent amplified fragment length polymorphism (FAFLP) genotyping. At least 72 % of all patients harboured strains with unique genotypes. Small clusters of related strains were evident in some centres, presumably indicating limited transmission of local strains. The most prevalent strain was indistinguishable from that previously described as the ‘Liverpool’ genotype, and accounted for approximately 11 % of patient isolates from 15 centres in England and Wales. The second most common genotype (termed Midlands 1) was recovered from 86 patients in nine centres and the third genotype, which matched closely the PFGE profile of Clone C, a genotype originally described in Germany, was found in eight centres and was isolated from 15 patients. A fourth genotype, identical to the published Manchester strain, was found in three centres. FAFLP analysis revealed some microheterogeneity among strains of the Liverpool genotype but all isolates of this genotype were positive by PCR for a strain-specific marker. These data suggest that cross-infection with P. aeruginosa has occurred both within and widely between CF centres in England and Wales. The two most common genotypes accounted for more than one-fifth of patients’ isolates examined and transmissible genotypes were found in all but three centres studied. These results emphasize the need for continued surveillance of P. aeruginosa genotypes in CF patients to provide informed infection control policy in treatment centres.
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Improvement in the detection rate of diarrhoeagenic bacteria in human stool specimens by a rapid real-time PCR assay
More LessA rapid laboratory system has been developed and evaluated that can simultaneously identify major diarrhoeagenic bacteria, including Salmonella enterica, Vibrio parahaemolyticus, Campylobacter jejuni and Shiga toxin-producing Escherichia coli, in stool specimens by real-time PCR. Specific identification was achieved by using selective TaqMan probes, detecting two targets in each pathogen. A positive result was scored only when both targets of a pathogen were amplified and the difference between threshold cycles for detection was less than five. Diagnosis of enteric bacterial infections using this highly sensitive method, including DNA extraction and real-time PCR, requires only 3 h. Forty stool specimens related to suspected food poisoning outbreaks were analysed: 16 (40 %) of these samples were found to be positive for diarrhoeagenic bacteria using a conventional culture method; 28 (70 %) were positive using the real-time PCR assay. Of the 12 PCR-positive but culture-negative cases, 11 patients had consumed pathogen-contaminated or high-risk food. Analysis of faecal samples from 105 outpatients who complained of diarrhoea and/or abdominal pain identified 19 (18 %) patients as being positive for diarrhoeagenic bacteria using the culture method. An additional six (6 %) patients were found to be positive by PCR analysis.
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Non-invasive diagnosis of Helicobacter pylori infection in adult dyspeptic patients by stool antigen detection: does the rapid immunochromatography test provide a reliable alternative to conventional ELISA kits?
More LessStool antigen-testing allows non-invasive detection of Helicobacter pylori that is indicative of active infection. Three commercial kits are currently marketed in the UK for stool antigen-testing. The aim of this study was to conduct a comparative evaluation of the performances of each of these tests, compared with culture and histological examination of gastric biopsies, for pre-treatment diagnosis of infection in an adult dyspeptic population in south-east England. Examination of 112 stool samples by the Premier Platinum HpSA ELISA (Meridian Diagnostics) and by the Amplified IDEIA HpStAR ELISA (DakoCytomation) kits demonstrated that the latter was more sensitive (81.3 versus 93.8 %, respectively) and specific (91.7 versus 100.0 %, respectively). Additionally, the IDEIA HpStAR was easier to interpret, with OD readings of positive and negative results being far from the recommended cut-off, whereas equivocal results that were generated by the HpSA kit were difficult to interpret. Additional testing of 87 of the 112 stools by the ImmunoCard STAT! HpSA kit (Meridian Diagnostics) demonstrated that this test was easier to perform than ELISA and was more sensitive than the HpSA kit but, compared with the IDEIA HpStAR kit, the ImmunoCard test was less sensitive (87.8 versus 95.9 %, respectively) and specific (89.4 versus 100.0 %, respectively). Furthermore, the ImmunoCard test generated weakly positive results, correlating with lower OD readings for both ELISA kits, that were difficult to interpret. The Amplified IDEIA HpStAR kit is therefore the most sensitive and specific of the three tests that are available for pre-treatment, non-invasive detection of H. pylori in stool samples in an English adult dyspeptic population.
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Preliminary evaluation of one conventional nested and two real-time PCR assays for the detection of Toxoplasma gondii in immunocompromised patients
Toxoplasma reactivation is a serious complication in patients receiving allogenic stem cell transplantation. Real-time PCR assays allow a rapid diagnosis of toxoplasma infection; however, no comparative data are available on the performance of real-time PCR protocols under routine conditions. Therefore, the aim of this study was to amplify Toxoplasma gondii DNA from routine samples of allogenic stem cell recipients using two real-time PCR assays on a LightCycler, and using conventional nested PCR. Conventional nested PCR revealed T. gondii DNA in 16 samples. Only 12 of the 16 samples yielded a positive result in both real-time PCRs. The accuracy of the conventional PCR results was demonstrated by direct sequencing. Amplification and detection of the amplicon was completed in only 1 h using the real-time PCR assays. Thus, real-time PCR substantially accelerates the detection of T. gondii DNA in the majority of positive specimens; however, conventional nested PCR is required for detection of T. gondii DNA in some samples.
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Isolation and molecular identification of Candida dubliniensis from non-human immunodeficiency virus-infected patients in Kuwait
More LessCandida dubliniensis is an emerging pathogen capable of causing oropharyngeal, vaginal and bloodstream infections. Although C. dubliniensis is similar to Candida albicans in several phenotypic characteristics, it differs from it with respect to epidemiology, certain virulence factors and the ability to develop resistance to fluconazole rapidly. In this study, the first seven isolations of C. dubliniensis from Kuwait are described, all originating from non-human immunodeficiency virus (HIV)-infected patients. The isolates were initially identified by the Vitek 2 yeast identification system, positive germ tube test, production of rough colonies and chlamydospores on Staib agar and by their inability to assimilate xylose, trehalose or methyl α-d-glucoside. The species identity of the isolates was subsequently confirmed by specific amplification of rDNA targeting the internally transcribed spacer 2 (ITS2), restriction endonuclease digestion of the amplified DNA and direct DNA sequencing of the ITS2. Using the E-test method, the MICs of C. dubliniensis test isolates were in the range 0.125–0.75 μg ml−1 for fluconazole, 0.002–0.75 μg ml−1 for itraconazole, 0.006–0.125 μg ml−1 for ketoconazole, 0.002–0.5 μg ml−1 for amphotericin B and 0.002–0.016 μg ml−1 for voriconazole. Two of the isolates were resistant to 5-flucytosine (>32 μg ml−1), but none against fluconazole. The study reinforces the current view that C. dubliniensis has a much wider geographical and epidemiological distribution.
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Do procalcitonin and C-reactive protein levels have a place in the diagnosis and follow-up of Helicobacter pylori infections?
The aims of this study were to determine the levels of procalcitonin (PCT) and C-reactive protein (CRP) in Helicobacter pylori-positive (HP+) patients diagnosed with duodenal and gastric ulcer and to evaluate the correlation of PCT and CRP levels with other invasive and non-invasive diagnostic methods for determination of H. pylori eradication in post-treatment follow-up. Thirty-five HP+ patients with dyspepsia were included in this study. Serum samples (5 ml) were collected at admission and after 24 h. Antimicrobial therapy (omeprazole, amoxycillin and clarithromycin) was given for 1 week to HP+ patients who were positive only by culture or by urease test plus pathology. After 1 month, serum samples (5 ml) were collected again and culture, urease and pathology investigations were performed on endoscopic samples. PCT and CRP levels were measured in the collected blood samples. Thirty-five H. pylori-negative (HP−) cases with dyspepsia, 38 cases with bacteraemia and 35 healthy blood donors were included in this study as control groups. The mean and minimum–maximum levels of PCT were 1.39 (0.25–6.75), 0.35 (0.12–0.71), 7.45 (0.68–51.5) and 0.40 (0.12–0.71) ng ml−1 for the groups of HP+, HP− and bacteraemia patients and healthy donors, respectively. Mean CRP levels were 1.00 (<0.5–8.11), 0.62 (<0.5–3.2), 11.5 (3.2–43.5) and 0.63 (<0.5–5.46) mg dl−1 for the same groups. A statistically significant difference was found between HP+ patients and both HP− cases and healthy blood donors for PCT levels, and higher PCT levels were found on admission in cases of bacteraemia than in the other groups (P < 0.05). PCT levels of HP+ cases decreased significantly (from 1.39 to 0.86) between admission and the post-treatment period (30 days); however, PCT levels remained higher than the cut-off value (0.5 ng ml−1). Similar ranges of CRP levels were found over the same time-period. The sensitivity of PCT was found to be higher than that of CRP on admission, but the specificity of PCT was found to be lower than that of CRP on the day of admission (65 and 74 %, respectively). The sensitivity of PCT was the same as that of CRP for the post-treatment period, but specificity of PCT was higher than that of CRP for the post-treatment period (83 and 76 %, respectively). It was concluded that PCT and CRP are not very effective markers for H. pylori infection in primary diagnosis or in eradication follow-up after therapy when used in parallel with conventional diagnostic methods, even if there is a difference in PCT and CRP levels between HP+ and HP− cases on admission.
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- Epidemiology
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Aetiology of acute pharyngitis: the role of atypical bacteria
In order to establish the role of atypical bacteria and compare characteristics of different infectious agents in acute pharyngitis, 127 patients with acute pharyngitis (66 males; median age, 5.33 years; range, 6 months to 14 years) and 130 healthy subjects of similar sex and age were studied. Serology with paired samples and PCR on nasopharyngeal aspirates and throat cultures were used to identify bacteria and viruses. Viruses were identified in 43 patients (33.8 %) and five controls (3.8 %; P < 0.0001), potential bacterial pathogens in 34 patients (26.8 %) and 26 controls (20 %; P = 0.256) and mixed viral/bacterial pathogens in 26 patients (20.5 %) and none of the controls (P < 0.0001). The main aetiological agents were adenovirus, respiratory syncytial virus (RSV), Mycoplasma pneumoniae, Streptococcus pyogenes and Chlamydia pneumoniae. M. pneumoniae was the agent found most frequently as a single pathogen. A history of recurrent pharyngitis, having older siblings and a negative outcome were significantly more common among patients with acute M. pneumoniae infection than among those with infections due to other pathogens or healthy controls. This study demonstrates that: (i) adenovirus and RSV have a prominent role in acute pharyngitis; (ii) S. pyogenes is found frequently, but it is not possible to distinguish simple carriers from patients with a true infection; (iii) M. pneumoniae appears to be able to cause acute pharyngitis per se; and (iv) C. pneumoniae seems to be mainly a co-pathogen. To avoid the risk of an incorrect therapeutic approach, simple laboratory investigations that allow rapid identification of M. pneumoniae infections are urgently needed.
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Typing and characterization of carbapenem-resistant Acinetobacter calcoaceticus–baumannii complex in a Chinese hospital
More LessThis study was designed to investigate the prevalence of carbapenem-resistant Acinetobacter calcoaceticus–baumannii complex (Acb complex) and to type carbapenemases. The relatedness of 45 isolates of carbapenem-resistant Acb complex collected from a clinical setting was analysed by PFGE. The carbapenemases produced by these isolates were typed by IEF, a three-dimensional test, 2-mercaptopropanoic acid inhibition assay, PCR and DNA cloning and sequencing. Results showed that all 45 isolates were resistant to multiple antibiotics including meropenem. The resistance rates to cefoperazone/sulbactam and ampicillin/sulbactam were 2.2 and 6.5 %, respectively. About 71.7–78.3 % of these isolates were intermediately resistant to cefepime, ceftazidime and cefotaxime. Forty-five isolates were classified into type A (98 %) and B (2 %) based on their PFGE patterns. Most of type A isolates were from the ICU. Type A was the dominant isolate, including subtypes A1 (22 %), A2 (71 %), A3 (2 %) and A4 (2 %). Only one isolate, from the haematology department, belonged to type B. Forty-three isolates (96 %) were positive for carbapenemase. One isolate had two bands by IEF, the pIs of which were 6.64 and 7.17. The band with the pI of 6.64 was OXA-23. The other 42 isolates produced two bands with pIs of 6.40 and 7.01 which could not be inhibited by clavulanic acid, cloxacillin or 2-mercaptopropanoic acid. It can be concluded that the prevalent carbapenem-resistant Acb complex isolates from this hospital all had similar β-lactamase patterns.
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Characterization of Neisseria meningitidis isolates collected from 1974 to 2003 in Japan by multilocus sequence typing
Analysis of 182 Neisseria meningitidis strains isolated over the past 30 years in Japan by serogroup typing and multilocus sequence typing (MLST) was performed. The serogroups of the 182 Japanese isolates were B (103 isolates), Y (39), W135 (1) and non-groupable (39). By MLST analysis, 65 different sequence types (ST) were identified, 42 of which were not found in the MLST database as of January 2004 and seemed to be unique to Japan. Statistical analysis of the MLST results revealed that, although the Japanese isolates seemed to be genetically divergent, they were classified into six major clonal complexes and other minor complexes. Among these isolates, well-documented ST complexes found worldwide were present, such as ST-23 complex (49 isolates), ST-44 complex (41 isolates) and ST-32 complex (8 isolates). On the other hand, a new clonal complex designated ST-2046 complex (28 isolates), which has not been identified in other countries, was also found, suggesting that this clone was indigenous to Japan. Taken together, it was speculated that meningococcal isolates in Japan comprised heterogeneous clones, which were derived both from clones identified in other countries and clones unique to Japan.
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Epidemiology of Burkholderia cepacia complex species recovered from cystic fibrosis patients: issues related to patient segregation
Studies of the prevalence of Burkholderia cepacia complex species amongst cystic fibrosis (CF) patients in different geographical regions, and the association between cross-infection and putative transmissibility markers, will further our understanding of these organisms and help to address infection-control issues. In this study, B. cepacia complex isolates from CF patients in different regions of Europe were analysed. Isolates were examined for B. cepacia complex species and putative transmissibility markers [cable pilin subunit gene (cblA) and the B. cepacia epidemic strain marker (BCESM)]. Sporadic and cross-infective strains were identified by random amplification of polymorphic DNA (RAPD). In total, 79 % of patients were infected with Burkholderia cenocepacia (genomovar III), 18 % with Burkholderia multivorans (genomovar II) and less than 5 % of patients with B. cepacia (genomovar I), Burkholderia stabilis (genomovar IV) or Burkholderia vietnamiensis (genomovar V). The cblA and BCESM transmissibility markers were only detected in strains of B. cenocepacia. The BCESM was a more sensitive marker for transmissible B. cenocepacia strains than cblA, although sporadic B. cenocepacia strains containing the BCESM, but lacking cblA, were also observed. Furthermore, clusters of cross-infection with transmissibility marker-negative strains of B. multivorans were identified. In conclusion, B. cenocepacia was the greatest cause of cross-infection, and the most widely distributed B. cepacia complex species, within these CF populations. However, cross-infection was not exclusive to B. cenocepacia and cblA and the BCESM were not absolute markers for transmissible B. cenocepacia, or other B. cepacia complex strains. It is therefore suggested that CF centres cohort patients based on the presence or absence of B. cepacia complex infection and not on the basis of transmissibility marker-positive B. cenocepacia as previously suggested.
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- Clinical Microbiology And Virology
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Microevolution between paired antral and paired antrum and corpus Helicobacter pylori isolates recovered from individual patients
Sequence variations located at the signal sequence and mid-region within the vacA gene, the 3′-end of the cagA gene, the indel motifs at the 3′-end of the cag pathogenicity island and the regions upstream of the vacA and ribA genes were determined by PCR in 19 paired antral or antrum and corpus Helicobacter pylori isolates obtained at the same endoscopic session, and three antral pairs taken sequentially. Random amplification of polymorphic DNA (RAPD)-PCR and fluorescent amplified fragment length polymorphism (FAFLP)-PCR fingerprinting were applied to these paired clinical isolates. The FAFLP-PCR profiles generated were phylogenetically analysed. For the 22 paired isolates there were no differences within pairs at five of the genetic loci studied. However, six pairs of isolates (27 %), of which four were antrum and corpus pairs, showed differences in the numbers of repeats located at the 3′-end of the cagA gene. RAPD-PCR fingerprinting showed that 16 (73 %) pairs, nine of which were antrum and corpus pairs, possessed identical profiles, while six (27 %) displayed distinctly different profiles, indicating mixed infections. Three of the six pairs showing differences at the 3′-end of the cagA gene yielded identical RAPD-PCR fingerprints. FAFLP-PCR fingerprinting and phylogenetic analysis revealed that all 16 pairs that displayed identical RAPD-PCR profiles had highly similar, but not identical, fingerprints, demonstrating that these pairs were ancestrally related but had undergone minor genomic alterations. Two antrum and corpus pairs of isolates, within the latter group, were isolates obtained from two siblings from the same family. This analysis demonstrated that each sibling was colonized by ancestrally related strains that exhibited differences in vacA genotype characteristics.
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Alginate production affects Pseudomonas aeruginosa biofilm development and architecture, but is not essential for biofilm formation
Extracellular polymers can facilitate the non-specific attachment of bacteria to surfaces and hold together developing biofilms. This study was undertaken to qualitatively and quantitatively compare the architecture of biofilms produced by Pseudomonas aeruginosa strain PAO1 and its alginate-overproducing (mucA22) and alginate-defective (algD) variants in order to discern the role of alginate in biofilm formation. These strains, PAO1, Alg+ PAOmucA22 and Alg− PAOalgD, tagged with green fluorescent protein, were grown in a continuous flow cell system to characterize the developmental cycles of their biofilm formation using confocal laser scanning microscopy. Biofilm Image Processing (bip) and Community Statistics (comstat) software programs were used to provide quantitative measurements of the two-dimensional biofilm images. All three strains formed distinguishable biofilm architectures, indicating that the production of alginate is not critical for biofilm formation. Observation over a period of 5 days indicated a three-stage development pattern consisting of initiation, establishment and maturation. Furthermore, this study showed that phenotypically distinguishable biofilms can be quantitatively differentiated.
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- Veterinary Microbiology
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Immunocytochemical studies of Salmonella Typhimurium invasion of porcine jejunal epithelial cells
More LessAlthough infection of pigs with Salmonella Typhimurium represents a serious problem, most studies on Salmonella infection have been carried out in other species. The purpose of the current study was to examine the route(s) of entry of Salmonella Typhimurium in pigs, using a jejunal loop model. The infection process was followed over 240 min using single to triple immunocytochemical detection of Salmonella and intestinal cell markers. Salmonella invasion was observed in both cytokeratin-18-positive and -negative cylindrical absorptive cells within 5–10 min. Subepithelial invasion of ordinary villi was consistently less marked than invasion of the subepithelial layer of Peyer's patches. Our results show that several epithelial cell types were invaded by Salmonella, and that Peyer's patches represent the main portal of entry in early Salmonella infection. Additionally, infection was associated with alterations in the keratin and F-actin cytoskeleton of intestinal epithelial cells, probably reflecting toxin-mediated actions. Such changes were confined to the proximal region of the jejunum, demonstrating a regional heterogeneity of intestinal epithelial cell responses to Salmonella infection.
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- Oral Microbiology
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Genotypic diversity and virulence traits of Streptococcus mutans in caries-free and caries-active individuals
The present study evaluated the relationship between clonal diversity and some virulence traits of Streptococcus mutans isolated from eight caries-free and eight caries-active subjects. A total of 155 S. mutans isolates from caries-free subjects and 144 isolates from caries-active subjects were obtained from samples of saliva, dental plaque and tongue surface and identified by PCR. The isolates were submitted to arbitrarily primed (AP)-PCR (OPA-2 and OPA-13) and multilocus enzyme electrophoresis (MLEE) to establish the genotypic diversity. Production of water-insoluble glucan (WIG) (monitored by SDS-PAGE), final pH of cultures and the ability of bacterial cells to adhere to smooth glass in the presence of sucrose were measured. High and comparable abilities of MLEE and AP-PCR were found to distinguish S. mutans genotypes, using Simpson's index of discrimination (0.971 and 0.968, respectively). The results showed a significant difference (P < 0.01) in the number of genotypes when caries-free and caries-active groups were compared by both fingerprinting methods used. Final pH (P = 0.32) and the percentage of adherence to a glass surface (P = 0.62) did not show differences between the two groups; however, the intensities of WIG bands from the caries-active group were greater than those from the caries-free group (P < 0.01). In addition, WIG was positively correlated with the ability of S. mutans to adhere to a glass surface (r = 0.34, P = 0.02) from caries-active subjects. These data showed that AP-PCR analysis and MLEE are both effective methods for assessing the genetic relatedness of S. mutans. Using these techniques, it was found that there is a larger number of genotypes of S. mutans with increased ability to synthesize WIG in caries-active individuals.
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- Models Of Infection
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Protection in a mouse peritonitis model mediated by iron-regulated outer-membrane protein of Salmonella typhi coupled to its Vi antigen
More LessVi polysaccharide and iron-regulated outer-membrane proteins (IROMPs) were extracted and purified from the standard strain of Salmonella typhi, Ty2. These were then conjugated by chemical coupling using the carbodimide method. Vi–IROMP conjugate was tested for its ability to protect against colonization by S. typhi in different organs. Mice immunized with 2.5 μg Vi–IROMP conjugate showed the most protection, as the least bacterial colonization of spleen, liver and Peyer's patches was observed. Peritoneal macrophages obtained from conjugate-treated mice phagocytosed bacteria efficiently. Circulating antibodies and the delayed type hypersensitivity response elucidated by mouse foot-pad swelling was significantly higher in conjugate-treated animals. These results clearly demonstrate that an IROMP and polysaccharide conjugate of S. typhi prepared from the same strain has the potential to protect animals against challenge.
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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 3 (1970)
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Volume 2 (1969)
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Volume 1 (1968)