| 1. |
- Ahrné, Siv, et al.
(författare)
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Lactobacilli in the intestinal microbiota of Swedish infants
- 2005
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Ingår i: Microbes and Infection. - : Elsevier BV. - 1286-4579 .- 1769-714X. ; 7:11-12, s. 1256-62
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Tidskriftsartikel (refereegranskat)abstract
- Lactobacillus colonisation was examined in 112 Swedish infants. Faecal samples obtained at 1, 2, 4 and 8 weeks and at 6, 12 and 18 months of age were cultivated quantitatively on Rogosa agar. Lactobacilli were speciated by PCR and typed to the strain level by randomly amplified polymorphic DNA (RAPD). Lactobacilli reached a peak at 6 months when 45% of the infants were colonised. L. rhamnosus and L. gasseri were the most common species in this period. Colonisation by lactobacilli in general (P < 0.01) and L. rhamnosus in particular (P < 0.05) was more common in breast-fed than in weaned infants at 6 months of age. Lactobacillus isolation reached a nadir of 17% by 12 months (P < 0.0001), but increased to 31% by 18 months of age P < 0.05). The food-related species L. paracasei, L. plantarum, L. acidophilus and L. delbrueckii dominated in this second phase. A single strain persisted for at least 3 weeks in 17% of the infants during the first 6 months, most commonly L. rhamnosus. Lactobacillus population counts in colonised infants increased from 10(6.4) cfu/g at 1 week to 10(8.8) cfu/g at 6 months, and then dropped to 10(5.4) cfu/g faeces at 12 months of age. Lactobacillus colonisation was not significantly related to delivery mode, or to presence of siblings or pets in the household. Our results suggest that certain Lactobacillus species, especially L. rhamnosus, thrive in the intestinal flora of breast-fed infants. After weaning they are replaced by other Lactobacillus species of types found in food.
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| 2. |
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| 3. |
- Barkman, Cecilia, 1962, et al.
(författare)
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Soluble bacterial constituents down-regulate secretion of IL-12 in response to intact Gram-positive bacteria.
- 2008
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Ingår i: Microbes and infection / Institut Pasteur. - : Elsevier BV. - 1286-4579. ; 10:14-15, s. 1484-93
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Tidskriftsartikel (refereegranskat)abstract
- Intact Gram-positive bacteria induce production of large amounts of IL-12 from freshly isolated human monocytes. Here the bacterial structures and signalling pathways involved were studied and compared with those leading to IL-6 production, and to IL-12 production in response to LPS after IFN-gamma pre-treatment. Intact bifidobacteria induced massive production of IL-12 (1ng/ml) and IL-6 (>30ng/ml) from human PBMC, whereas fragmented bifidobacteria induced IL-6, but no IL-12. IL-12 production induced by intact bifidobacteria was inhibited by pre-treatment with bifidobacterial sonicate, peptidoglycan, muramyl dipeptide, lipoteichoic acid, the soluble TLR2 agonist Pam(3)Cys-SK(4), or anti-TLR2 antibodies. Blocking of phagocytosis by cytochalasin, inhibition of the JNK or NF-kappaB pathways or treatment with Wortmannin also reduced the IL-12 response to intact Gram-positive bacteria. LPS induced moderate levels of IL-12 (0.31ng/ml), but only from IFN-gamma pre-treated PBMC. This IL-12 production was enhanced by Wortmannin and unaffected by blocking the JNK pathway. Thus, intact Gram-positive bacteria trigger monocyte production of large amounts of IL-12 via a distinct pathway that is turned off by fragmented Gram-positive bacteria. This may be a physiological feedback, since such fragments may signal that further activation of the phagocyte via the IL-12/IFN-gamma loop is unnecessary.
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| 4. |
- Bereczky, Sándor, et al.
(författare)
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Multiclonal asymptomatic Plasmodium falciparum infections predict a reduced risk of malaria disease in a Tanzanian population
- 2007
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Ingår i: Microbes and infection. - : Elsevier BV. - 1286-4579 .- 1769-714X. ; 9:1, s. 103-110
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Tidskriftsartikel (refereegranskat)abstract
- Protective immunity to malaria is acquired after repeated exposure to the polymorphic Plasmodium falciparum parasite. Whether the number of concurrent antigenically diverse clones in asymptomatic infections predicts the risk of subsequent clinical malaria needs further understanding. We assessed the diversity of P. falciparum infections by merozoite surface protein 2 genotyping in a longitudinal population based study in Tanzania. The number of clones was highest in children 6–10 years and in individuals with long time to previous anti-malarial treatment. Individual exposure, analysed by circumsporozoite protein antibody levels, was associated with parasite prevalence but not with the number of clones. The risk of subsequent clinical malaria in children free of acute disease or recent treatment was, compared to one clone, reduced in individuals with multiclonal infections or without detectable parasites, with the lowest hazard ratio 0.28 (95% confidence interval 0.10–0.78 Cox regression) for 2–3 clones. The number of clones was not associated with haemoglobin levels. A reduced risk of malaria in asymptomatic individuals with multiclonal persistent P. falciparum infections suggests that controlled maintenance of diverse infections is important for clinical protection in continuously exposed individuals, and needs to be considered in the design and evaluation of new malaria control strategies.
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| 5. |
- Berglund, Carolina, et al.
(författare)
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The genes for Panton Valentine leukocidin (PVL) are conserved in diverse lines of methicillin-resistant and methicillin-susceptible Staphylococcus aureus
- 2008
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Ingår i: Microbes and infection. - Paris : Elsevier. - 1286-4579 .- 1769-714X. ; 10:8, s. 878-884
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Methicillin-resistant Staphylococcus aureus isolated in the community (CA-MRSA) have been reported to carry the loci for Panton Valentine leukocidin (PVL) in high frequency. CA-MRSA in Orebro County, Sweden, constitutes at least 50% of MRSA and the PVL locus is detected in as many as 66% of these CA-MRSA isolates. The aim of this study was to characterize PVL-positive methicillin-resistant and methicillin-susceptible Staphylococcus aureus by molecular methods, to determine the nucleotide sequence of lukS-PV and lukF-PV in S. aureus isolates of different origins, and to investigate the biological consequence of variations occurring in the genes. The PVL-positive MRSA investigated were composed of six different STs (ST8, 36, 80, 152, 154, and 256). Six additional STs (ST5, 22, 25, 30, 88, and 567) were detected when investigating PVL-positive methicillin-susceptible S. aureus with MLST. Despite the different genetic origins of the isolates analyzed, the PVL genes were well conserved and only one mutation was non-synonymous. Evaluation of the consequence of this mutation showed that the mutated toxin and wild-type toxin had comparable biological activity on human polymorphonuclear cells.
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| 6. |
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| 7. |
- Calander, Ann-Marie, 1957, et al.
(författare)
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Matrix metalloproteinase-9 (gelatinase B) deficiency leads to increased severity of Staphylococcus aureus-triggered septic arthritis.
- 2006
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Ingår i: Microbes and infection / Institut Pasteur. - : Elsevier BV. - 1286-4579. ; 8:6, s. 1434-9
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Tidskriftsartikel (refereegranskat)abstract
- Matrix metalloproteinases constitute a family of structurally related endopeptidases that are crucial for the normal turnover of the extracellular matrix. Elevated levels of MMP-9 have been demonstrated in synovial fluids of rheumatoid arthritis patients, and a correlation with the severity of the disease has been described. The aim of this study was to explore the impact of MMP-9 expression on joint inflammation and destruction in a model of bacterially induced septic arthritis. MMP-9 knock-out mice and C57Bl6 congenic controls were inoculated intravenously or intra-articularly with Staphylococcus aureus. Arthritis was evaluated clinically and by means of histology. Zymographic analyses were performed to study ex vivo induction of MMP-9 following exposure to S. aureus. The MMP-9 knock-out mice displayed a significantly higher frequency and severity, but not destructivity, of arthritis than did the wild-type mice. The knock-out mice also proved to harbour an increased number of bacteria locally in joints and systemically in kidneys, possibly by impaired extravasation and recruitment of leukocytes and a deficient early defence against infection. Our findings indicate that deficiency in MMP-9 increases the degree of joint inflammation due to decreased bacterial clearance.
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| 10. |
- Edqvist, Petra J, et al.
(författare)
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Minimal YopB and YopD translocator secretion by Yersinia is sufficient for Yop-effector delivery into target cells.
- 2007
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Ingår i: Microbes and infection. - : Elsevier BV. - 1286-4579 .- 1769-714X. ; 9:2, s. 224-233
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Tidskriftsartikel (refereegranskat)abstract
- Pathogenic Yersinia sp. utilise a common type III secretion system to translocate several anti-host Yop effectors into the cytosol of target eukaryotic cells. The secreted YopB and YopD translocator proteins are essential for this process, forming pores in biological membranes through which the effectors are thought to gain access to the cell interior. The non-secreted cognate chaperone, LcrH, also plays an important role by ensuring pre-secretory stabilisation and efficient secretion of YopB and YopD. This suggests that LcrH-regulated secretion of the translocators could be used by Yersinia to control effector translocation levels. We collected several LcrH mutants impaired in chaperone activity. These poorly bound, stabilised and/or secreted YopB and YopD in vitro. However, these mutants generally maintained stable substrates during a HeLa cell infection and these infected cells were intoxicated by translocated effectors. Surprisingly, this occurred in the absence of detectable YopB- and YopD-dependent pores in eukaryotic membranes. A functional type III translocon must therefore only require minuscule amounts of secreted translocator proteins. Based on these observations, LcrH dependent control of translocation via regulated YopB and YopD secretion would need to be exquisitely tight.
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