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- Sjoestroem, K., et al.
(author)
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Clonal success of piliated penicillin nonsusceptible pneumococci
- 2007
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In: Proceedings of the National Academy of Sciences. - : Proceedings of the National Academy of Sciences. - 1091-6490 .- 0027-8424. ; 104:31, s. 12907-12912
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Journal article (peer-reviewed)abstract
- Antibiotic resistance in pneumococci is due to the spread of strains belonging to a limited number of clones. The Spain(9v)-3 clone of sequence type (ST)156 is one of the most successful clones with reduced susceptibility to penicillin [pneumococci nonsusceptible to penicillin (PNSP)]. In Sweden during 2000-2003, a dramatic increase in the number of PNSP isolates was observed. Molecular characterization of these isolates showed that a single clone of sequence type ST156 increased from 40% to 80% of all serotype 14, thus causing the serotype expansion. Additionally, during the same time period, we examined the clonal composition of two serotypes 9V and 19F: all 9V and 20% of 19F isolates belonged to the clonal cluster of ST156, and overall approximate to 50% of all PNSP belonged to the ST156 clonal cluster. Moreover, microarray and PCR analysis showed that all ST156 isolates, irrespective of capsular type, carried the rlrA pilus islet. This islet was also found to be present in the penicillin-sensitive ST162 clone, which is believed to be the drug-susceptible ancestor of ST156. Competitive experiments between related ST156 serotype 19F strains confirmed that those containing the rlrA pilus islet were more successful in an animal model of carriage. We conclude that the pilus island is an important biological factor common to ST156 isolates and other successful PNSP clones. In Sweden, a country where the low antibiotic usage does not explain the spread of resistant strains, at least 70% of all PNSP isolates collected during year 2003 carried the pilus islet.
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- Albiger, Barbara, et al.
(author)
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Role of the innate immune system in host defence against bacterial infections: focus on the Toll-like receptors.
- 2007
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In: Journal of Internal Medicine. - : Wiley. - 1365-2796 .- 0954-6820. ; 261:6, s. 511-528
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Research review (peer-reviewed)abstract
- The innate immunity plays a critical role in host protection against pathogens and it relies amongst others on pattern recognition receptors such as the Toll-like receptors (TLRs) and the nucleotide-binding oligomerization domains proteins (NOD-like receptors, NLRs) to alert the immune system of the presence of invading bacteria. Since their recent discovery less than a decade ago, both TLRs and NLRs have been shown to be crucial in host protection against microbial infections but also in homeostasis of the colonizing microflora. They recognize specific microbial ligands and with the use of distinct adaptor molecules, they activate different signalling pathways that in turns trigger subsequent inflammatory and immune responses that allows a immediate response towards bacterial infections and the initiation of the long-lasting adaptive immunity. In this review, we will focus on the role of the TLRs against bacterial infections in humans in contrast to mice that have been used extensively in experimental models of infections and discuss their role in controlling normal flora or nonpathogenic bacteria. We also highlight how bacteria can evade recognition by TLRs.
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- Aschtgen, MS, et al.
(author)
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Enterobacteria impair host p53 tumor suppressor activity through mRNA destabilization
- 2022
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In: Oncogene. - : Springer Science and Business Media LLC. - 1476-5594 .- 0950-9232. ; 41:15, s. 2173-2186
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Journal article (peer-reviewed)abstract
- Increasing evidence highlights the role of bacteria in the physiopathology of cancer. However, the underlying molecular mechanisms remains poorly understood. Several cancer-associated bacteria have been shown to produce toxins which interfere with the host defense against tumorigenesis. Here, we show that lipopolysaccharides from Klebsiella pneumoniae and other Enterobacteria strongly inhibit the host tumor suppressor p53 pathway through a novel mechanism of p53 regulation. We found that lipopolysaccharides destabilize TP53 mRNA through a TLR4-NF-κB-mediated inhibition of the RNA-binding factor Wig-1. Importantly, we show that K. pneumoniae disables two major tumor barriers, oncogene-induced DNA damage signaling and senescence, by impairing p53 transcriptional activity upon DNA damage and oncogenic stress. Furthermore, we found an inverse correlation between the levels of TLR4 and p53 mutation in colorectal tumors. Hence, our data suggest that the repression of p53 by Enterobacteria via TLR4 alleviates the selection pressure for p53 oncogenic mutations and shapes the genomic evolution of cancer.
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- Aschtgen, MS, et al.
(author)
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The rise of hyper-virulence
- 2020
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In: Journal of internal medicine. - : Wiley. - 1365-2796 .- 0954-6820. ; 287:3, s. 336-338
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Journal article (other academic/artistic)
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- Barocchi, M A, et al.
(author)
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A pneumococcal pilus influences virulence and host inflammatory responses
- 2006
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In: Proceedings of the National Academy of Sciences. - : Proceedings of the National Academy of Sciences. - 1091-6490 .- 0027-8424. ; 103:8, s. 2857-2862
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Journal article (peer-reviewed)abstract
- Streptococcus pneumoniae (pneumococcus) is a major cause of morbidity and mortality world-wide. The initial event in invasive pneumococcal disease is the attachment of encapsulated pneumococci to epithelial cells in the upper respiratory tract. This work provides evidence that initial bacterial adhesion and subsequent ability to cause invasive disease is enhanced by pili, long organelles able to extend beyond the polysaccharide capsule, previously unknown to exist in pneumococci. These adhesive pili-like appendages are encoded by the pneumococcal rlrA islet, present in some, but not all, clinical isolates. Introduction of the rlrA islet into an encapsulated rlrA-negative isolate allowed pilus expression, enhanced adherence to lung epithelial cells, and provided a competitive advantage upon mixed intranasal challenge of mice. Furthermore, a pilus-expressing rlrA islet-positive clinical isolate was more virulent than a nonpiliated deletion mutant, and it out-competed the mutant in murine models of colonization, pneumonia, and bacteremia. Additionally, piliated pneumococci evoked a higher TNF response during systemic infection, compared with nonpiliated derivatives, suggesting that pneumococcal pili not only contribute to adherence and virulence but also stimulate the host inflammatory response.
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- Blomberg, C, et al.
(author)
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Pattern of Accessory Regions and Invasive Disease Potential in Streptococcus pneumoniae.
- 2009
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In: Journal of Infectious Diseases. - : Oxford University Press (OUP). - 1537-6613 .- 0022-1899. ; 199, s. 1032-1042
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Journal article (peer-reviewed)abstract
- Background. The invasive disease potential (IDP) of Streptococcus pneumoniae differs between serotypes, but the reason for this is unknown. Methods. A total of 47 pneumococcal isolates from 13 serotypes with different IDPs in humans that belonged to 37 multilocus sequence types were compared by whole genome microarrays and mutant analyses. Results. Approximately 34% of the genes were variable, including 95 genes previously shown by signature-tagged mutagenesis (STM) to be required for invasive disease in mice. Many variable genes were localized to 41 accessory regions (ARs), of which 24 contained genes previously identified by STM as required for invasive disease. Only AR6 and AR34 were preferentially found in isolates of serotypes with high IDPs. Neither AR6, which carries a gene previously identified by STM as required for invasive disease and encodes a 6-phospho-beta glucosidase, nor the putative adhesin expressed by AR34 was required for mouse virulence in TIGR4. Conclusions. Pneumococci possess a repertoire of ARs that differ between clones and even between isolates of the same clone. The ARs required for invasive disease in humans may be redundant, as no unique pattern distinguished the most invasive clones from others. The ARs that contained genes previously identified by STM as required for virulence in mice were frequently absent from invasive human isolates. Only 1 AR (AR6) was present in almost all isolates from the serotypes with the highest IDP (1, 4, and 7F), whereas it was missing from many others.
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- Henriques-Normark, B, et al.
(author)
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Bacterial vaccines and antibiotic resistance
- 2014
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In: Upsala journal of medical sciences. - : Uppsala Medical Society. - 2000-1967 .- 0300-9734. ; 119:2, s. 205-208
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Journal article (peer-reviewed)
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