S Merino

Publications (52)143.35 Total impact

• Article: The cell division genes (ftsE and X) of Aeromonas hydrophila and their relationship with opsonophagocytosis.

  S Merino, M Altarriba, R Gavín, L Izquierdo, J M Tomás
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  ABSTRACT: A transposon mutant from Aeromonas hydrophila AH-3 was obtained which was highly resistant to opsonophagocytosis. The mutation was identified in the ftsE gene and we characterised the operon ftsY, E and X from this bacterium. These genes, as in enteric bacteria, are neighbours to rpoH. The A. hydrophilia ftsE and X genes were fully able to complement Escherichia coli ftsE mutants, and also complement the opsonophagocytosis-resistant phenotype of the A. hydrophila mutant strain. This phenotype seems to be related to the filamentous phenotype at 37 degrees C exhibited by the A. hydrophila ftsE mutant.
  FEMS Microbiology Letters 06/2001; 198(2):183-8. · 2.04 Impact Factor
• Article: The MgtE Mg2+ transport protein is involved in Aeromonas hydrophila adherence.

  S Merino, R Gavín, M Altarriba, L Izquierdo, M E Maguire, J M Tomás
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  ABSTRACT: Aeromonas hydrophila AH-3 strains carrying mutations in mgtE, which encodes a Mg2+ and Co2+ transport system, showed a 50% reduction of in vitro adherence to HEp-2 cells, a reduction in swarming in semisolid swarming agar, and decrease in biofilm formation of over 60% in comparison to the wild-type strain. The cloned A. hydrophila mgtE expressed from a plasmid complements a Salmonella typhimurium strain deleted for all Mg2+ transporters both phenotypically and by measurement of 57Co2+ uptake. Likewise, plasmid-borne mgtE was able to complement the changes observed in A. hydrophila mgtE mutants. We suggest that MgtE and thus Mg2+ and possibly Co2+ have a role in A. hydrophila related to their swarming ability and related consequences such as adherence and biofilm formation.
  FEMS Microbiology Letters 06/2001; 198(2):189-95. · 2.04 Impact Factor
• Article: Role of flm locus in mesophilic Aeromonas species adherence.

  I Gryllos, J G Shaw, R Gavín, S Merino, J M Tomás
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  ABSTRACT: The adherence mechanism of Aeromonas caviae Sch3N to HEp-2 cells was initially investigated through four mini-Tn5 mutants that showed a 10-fold decrease in adherence. These mutants lost motility, flagella, and their lipopolysaccharide (LPS) O antigen (O-Ag). Three genes, flmB-neuA-flmD, were found to be interrupted by the transposon insertions; additionally, two other genes, one lying upstream (flmA) and one downstream (neuB), were found to be clustered in the same operon. While the flmA and flmB genes were present in all mesophilic Aeromonas spp. (A. hydrophila, A. caviae, A. veronii bv. veronii, and A. veronii bv. sobria) tested, this was not the case for the neuA-flmD-neuB genes. Construction and characterization of flmB insertion mutants in five other mesophilic Aeromonas strains revealed the loss of motility, flagella, and adherence but did not alter the LPS composition of these strains. Taking the above findings into consideration, we conclude (i) that flagella and possibly the LPS O-Ag are involved in the adherence of the mesophilic Aeromonas to human epithelial cells; (ii) flmA and flmB are genes widely distributed in the mesophilic Aeromonas and are involved in flagella assembly, and thus adherence; and (iii) in A. caviae Sch3N the flmA and flmB genes are found in a putative operon together with neuA, flmD, and neuB and are involved in LPS O-Ag biosynthesis and probably have a role in flagellum assembly.
  Infection and Immunity 02/2001; 69(1):65-74. · 4.16 Impact Factor
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  Available from: Maria Mercedes Nogueras

  Article: Cloning and sequencing of the Klebsiella pneumoniae O5 wb gene cluster and its role in pathogenesis.

  S Merino, M Altarriba, L Izquierdo, M M Nogueras, M Regué, J M Tomás
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  ABSTRACT: One representative recombinant clone encoding Klebsiella pneumoniae O5-antigen lipopolysaccharide (LPS) was found upon screening for serum resistance in a cosmid-based genomic library of K. pneumoniae KT769 (O5:K57) introduced into Escherichia coli DH5alpha. A total of eight open reading frames (wb(O5) gene cluster) were necessary to produce K. pneumoniae O5-antigen LPS in E. coli K-12. The enzymatic activities proposed for the wb(O5) gene cluster are in agreement with the activities proposed for the biosynthesis of K. pneumoniae O5-antigen LPS. Using the complete DNA sequence of the K. pneumoniae wb(O5) gene cluster, we obtained (by single or double recombination) genetically well-characterized mutants devoid only of this O5-antigen LPS. Finally, using these O5(-) mutants and the corresponding wild-type strains or complemented mutants with the wb(O5) gene cluster (O5(+) strains), we found that the presence of K. pneumoniae O5-antigen LPS is essential for some pathogenic features like serum resistance, adhesion to uroepithelial cells, and colonization (experimental infections) of the urinary tract in rats.
  Infection and Immunity 06/2000; 68(5):2435-40. · 4.16 Impact Factor
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  Available from: Maria Mercedes Nogueras

  Article: Cloning, sequencing, and role in serum susceptibility of porin II from mesophilic Aeromonas hydrophila.

  M M Nogueras, S Merino, A Aguilar, V J Benedi, J M Tomás
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  ABSTRACT: We cloned and sequenced the structural gene for Aeromonas hydrophila porin II from strain AH-3 (serogroup O:34). The genetic position of this gene, like that of ompF in Escherichia coli, is adjacent to aspC and transcribed in the same direction. However, upstream of the porin II gene no similarities with E. coli were found. We obtained defined insertion mutants in porin II gene either in A. hydrophila (O:34) or A. veronii sobria (serogroup O:11) serum-resistant or -sensitive strains. Furthermore, we complemented these mutants with a plasmid harboring only the porin II gene, which allowed us to define the role of porin II as an important surface molecule involved in serum susceptibility and C1q binding in these strains.
  Infection and Immunity 05/2000; 68(4):1849-54. · 4.16 Impact Factor
• Article: Capsular polysaccharide is a major complement resistance factor in lipopolysaccharide O side chain-deficient Klebsiella pneumoniae clinical isolates.

  D Alvarez, S Merino, J M Tomás, V J Benedí, S Albertí
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  ABSTRACT: We have previously demonstrated the existence of Klebsiella pneumoniae clinical isolates deficient in the lipopolysaccharide O side chain, the major factor for resistance to complement-mediated killing in this bacterial species. These isolates are complement resistant, and their mechanisms to resist complement were investigated by selecting transposon-generated complement-sensitive mutants. One mutant with a drastically reduced capacity to grow in nonimmune human serum carried the transposon inserted in an open reading frame of a gene cluster involved in capsule synthesis. This mutant produced less capsule, bound more molecules of the complement component C3, and was more sensitive to complement-mediated and opsonophagocytic killings than was the parent strain. Four additional clinical isolates representing four different K serotypes were studied, and results showed that capsular polysaccharide is a major complement resistance factor in these O side chain-deficient isolates.
  Infection and Immunity 03/2000; 68(2):953-5. · 4.16 Impact Factor
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  Available from: Maria Mercedes Nogueras

  Article: Cloning, sequencing, and role in virulence of two phospholipases (A1 and C) from mesophilic Aeromonas sp. serogroup O:34.

  S Merino, A Aguilar, M M Nogueras, M Regue, S Swift, J M Tomás
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  ABSTRACT: Two different representative recombinant clones encoding Aeromonas hydrophila lipases were found upon screening on tributyrin (phospholipase A1) and egg yolk agar (lecithinase-phospholipase C) plates of a cosmid-based genomic library of Aeromonas hydrophila AH-3 (serogroup O34) introduced into Escherichia coli DH5alpha. Subcloning, nucleotide sequencing, and in vitro-coupled transcription-translation experiments showed that the phospholipase A1 (pla) and C (plc) genes code for an 83-kDa putative lipoprotein and a 65-kDa protein, respectively. Defined insertion mutants of A. hydrophila AH-3 defective in either pla or plc genes were defective in phospholipase A1 and C activities, respectively. Lecithinase (phospholipase C) was shown to be cytotoxic but nonhemolytic or poorly hemolytic. A. hydrophila AH-3 plc mutants showed a more than 10-fold increase in their 50% lethal dose on fish and mice, and complementation of the plc single gene on these mutants abolished this effect, suggesting that Plc protein is a virulence factor in the mesophilic Aeromonas sp. serogroup O:34 infection process.
  Infection and Immunity 09/1999; 67(8):4008-13. · 4.16 Impact Factor
• Article: Genetic analysis of the Serratia marcescens N28b O4 antigen gene cluster.

  F Saigí, N Climent, N Piqué, C Sanchez, S Merino, X Rubirés, A Aguilar, J M Tomás, M Regué
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  ABSTRACT: The Serratia marcescens N28b wbbL gene has been shown to complement the rfb-50 mutation of Escherichia coli K-12 derivatives, and a wbbL mutant has been shown to be impaired in O4-antigen biosynthesis (X. Rubirés, F. Saigí, N. Piqué, N. Climent, S. Merino, S. Albertí, J. M. Tomás, and M. Regué, J. Bacteriol. 179:7581-7586, 1997). We analyzed a recombinant cosmid containing the wbbL gene by subcloning and determination of O-antigen production phenotype in E. coli DH5alpha by sodium dodecyl sulfate-polyacrylamide electrophoresis and Western blot experiments with S. marcescens O4 antiserum. The results obtained showed that a recombinant plasmid (pSUB6) containing about 10 kb of DNA insert was enough to induce O4-antigen biosynthesis. The same results were obtained when an E. coli K-12 strain with a deletion of the wb cluster was used, suggesting that the O4 wb cluster is located in pSUB6. No O4 antigen was produced when plasmid pSUB6 was introduced in a wecA mutant E. coli strain, suggesting that O4-antigen production is wecA dependent. Nucleotide sequence determination of the whole insert in plasmid pSUB6 showed seven open reading frames (ORFs). On the basis of protein similarity analysis of the ORF-encoded proteins and analysis of the S. marcescens N28b wbbA insertion mutant and wzm-wzt deletion mutant, we suggest that the O4 wb cluster codes for two dTDP-rhamnose biosynthetic enzymes (RmlDC), a rhamnosyltransferase (WbbL), a two-component ATP-binding-cassette-type export system (Wzm Wzt), and a putative glycosyltransferase (WbbA). A sequence showing DNA homology to insertion element IS4 was found downstream from the last gene in the cluster (wbbA), suggesting that an IS4-like element could have been involved in the acquisition of the O4 wb cluster.
  Journal of Bacteriology 04/1999; 181(6):1883-91. · 3.83 Impact Factor
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  Available from: ncbi.nlm.nih.gov

  Article: Surface antigen exposure by bismuth dimercaprol suppression of Klebsiella pneumoniae capsular polysaccharide.

  P Domenico, J M Tomas, S Merino, X Rubires, B A Cunha
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  ABSTRACT: The bacterial capsule is an important virulence determinant in animal and plant disease. Bacterial capsule and slime can be inhibited by bismuth compounds, especially when complexed with lipophilic thiol chelators. Bismuth dimercaprol (BisBAL) at 1 ppm of Bi3+ repressed Klebsiella pneumoniae capsule expression in defined medium by nearly 90%, which exposed subsurface structures. The phagocytic index for BisBAL-treated bacteria increased from <10 to 360 bacteria per 100 neutrophils in the presence of complement and anticapsular or anti-O antigen antiserum. BisBAL treatment also enhanced the reactivity of monoclonal antibodies (MAbs) specific for the O1-antigen lipopolysaccharide (LPS) or the LPS core in a dose-dependent manner as indicated by the results of enzyme-linked immunosorbent assays. When anti-O1 MAb was used, the reactivity increased significantly for fully encapsulated O1:K1 or O1:K2 cells but not for O1:K- cells. Deposition of C3b also increased significantly for BisBAL-treated O1:K1 or O1:K2 cells but not for O1:K- cells. Survival of a serum-sensitive strain was <0.1% when nonimmune human serum absorbed with O1:K1 cells was used and 107% when BisBAL-treated cells were used for absorption. Outer membrane proteins were also more accessible on the surface of K. pneumoniae after BisBAL treatment. Thus, at subinhibitory levels, BisBAL inhibited capsule expression, which promoted phagocytosis, enhanced the reactivity of specific antibodies for LPS O antigen, LPS core epitopes, or outer-membrane proteins, and enhanced complement interaction with encapsulated K. pneumoniae. By unmasking bacterial surface structures and enhancing the immune system reactivity to bacteria, bismuth thiols may prove useful as adjuncts for vaccination.
  Infection and Immunity 03/1999; 67(2):664-9. · 4.16 Impact Factor
• Article: Klebsiella pneumoniae lipopolysaccharide O typing: revision of prototype strains and O-group distribution among clinical isolates from different sources and countries.

  D S Hansen, F Mestre, S Alberti, S Hernández-Allés, D Alvarez, A Doménech-Sánchez, J Gil, S Merino, J M Tomás, V J Benedí
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  ABSTRACT: We have previously described an inhibition enzyme-linked immunosorbent assay method for the O typing of O1 lipopolysaccharide from Klebsiella pneumoniae which overcomes the technical problems and limitations of the classical O-typing method. In this study, we have extended the method to all of the currently recognized O types. The method was validated by studying the prototype strains that have defined the O groups by the classical tube agglutinatination O-typing method. Based on these results, we confirmed the O types of 60 of 64 typeable strains, and we propose a revised O-antigenic scheme, with minor but necessary changes, consisting of serogroups or serotypes O1, O2, O2ac, O3, O4, O5, O7, O8, and O12. Application of this typing method to 638 K. pneumoniae clinical isolates from Denmark, Spain, and the United States from different sources (blood, urine, and others) showed that up to 80% of these isolates belong to serotypes or serogroups O1, O2, O3, and O5, independently of the source of isolation, and that a major group of nontypeable isolates, representing about 17% of the total, consists of half O+ and half O- strains. Differences were observed, however, in the prevalence of the lipopolysaccharide O types or groups, depending on the country and isolation source.
  Journal of Clinical Microbiology 02/1999; 37(1):56-62. · 4.15 Impact Factor
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  Available from: Maria Mercedes Nogueras

  Article: Activation of the complement classical pathway (C1q binding) by mesophilic Aeromonas hydrophila outer membrane protein.

  S Merino, M M Nogueras, A Aguilar, X Rubires, S Albertí, V J Benedí, J M Tomás
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  ABSTRACT: The mechanism of killing of Aeromonas hydrophila serum-sensitive strains in nonimmune serum by the complement classical pathway has been studied. The bacterial cell surface component that binds C1q more efficiently was identified as a major outer membrane protein of 39 kDa, presumably the porin II described by D. Jeanteur, N. Gletsu, F. Pattus, and J. T. Buckley (Mol. Microbiol. 6:3355-3363, 1992), of these microorganisms. We have demonstrated that the purified form of porin II binds C1q and activates the classical pathway in an antibody-independent manner, with the subsequent consumption of C4 and reduction of the serum total hemolytic activity. Activation of the classical pathway has been observed in human nonimmune serum and agammaglobulinemic serum (both depleted of factor D). Binding of C1q to other components of the bacterial outer membrane, in particular to rough lipopolysaccharide, could not be demonstrated. Activation of the classical pathway by this lipopolysaccharide was also much less efficient than activation by the outer membrane protein. The strains possessing O-antigen lipopolysaccharide bind less C1q than the serum-sensitive strains, because the outer membrane protein is less accessible, and are resistant to complement-mediated killing. Finally, a similar or identical outer membrane protein (presumably porin II) that binds C1q was shown to be present in strains from the most common mesophilic Aeromonas O serogroups.
  Infection and Immunity 09/1998; 66(8):3825-31. · 4.16 Impact Factor
• Article: Mesophilic Aeromonas strains from different serogroups: the influence of growth temperature and osmolarity on lipopolysaccharide and virulence.

  S Merino, A Aguilar, X Rubires, J M Tomás
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  ABSTRACT: Growth of mesophilic Aeromonas sp. strains from serogroups O:13, O:33 and O:44 at different temperatures and osmolarity resulted in changes in the lipopolysaccharide (LPS) and virulence of the strains tested, as we had previously reported for strains from serogroup O:34. The effect of osmolarity could be observed when the cells grew at 37 degrees C but not at 20 degrees C. Purified LPS from cells cultivated at 20 degrees C (high or low osmolarity) or at 37 degrees C at high osmolarity was smooth, whereas the LPS extracted from the cells cultivated on low osmolarity was rough. The smooth strains were resistant to the bactericidal activity of non-immune serum, while the rough strains were sensitive and showed better adhesion to Hep-2 cells than the rough strains. Furthermore, the smooth strains were more virulent for fish and mice than the rough strains. For mesophilic Aeromonas sp. strains from serogroups O:1 to O:44, these changes were not observed, except for serogroups O:13, O:33, O:34 and O:44.
  Research in Microbiology 07/1998; 149(6):407-16. · 2.76 Impact Factor
• Article: Bacteriophage PM2 nomenclature revision.

  S Merino, J M Tomás, J Maniloff
  Archives of Virology 02/1998; 143(9):1852-3. · 2.11 Impact Factor
• Article: A gene (wbbL) from Serratia marcescens N28b (O4) complements the rfb-50 mutation of Escherichia coli K-12 derivatives.

  X Rubirés, F Saigi, N Piqué, N Climent, S Merino, S Albertí, J M Tomás, M Regué
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  ABSTRACT: A cosmid-based genomic library of Serratia marcescens N28b was introduced into Escherichia coli DH5alpha, and clones were screened for serum resistance. One clone was found resistant to serum, to bacteriocin 28b, and to bacteriophages TuIa and TuIb. This clone also showed O antigen in its lipopolysaccharide. Subcloning and sequencing experiments showed that a 2,124-bp DNA fragment containing the rmlD and wbbL genes was responsible for the observed phenotypes. On the basis of amino acid similarity, we suggest that the 288-residue RmlD protein is a dTDP-L-rhamnose synthase. Plasmid pJT102, containing only the wbbL gene, was able to induce O16-antigen production and serum resistance in E. coli DH5alpha. These results suggest that the 282-residue WbbL protein is a rhamnosyltransferase able to complement the rJb-50 mutation in E. coli K-12 derivatives, despite the low level of amino acid identity between WbbL and the E. coli rhamnosyltransferase (24.80%). S. marcescens N28b rmlD and wbbL mutants were constructed by mobilization of suicide plasmids containing a portion of rmlD or wbbL. These insertion mutants were unable to produce O antigen; since strain N28b produces O4 antigen, these results suggest that both genes are involved in O4-antigen biosynthesis.
  Journal of Bacteriology 01/1998; 179(23):7581-6. · 3.83 Impact Factor
• Article: The role of O1-antigen in the adhesion to uroepithelial cells of Klebsiella pneumoniae grown in urine.

  S Merino, X Rubires, A Aguilar, J M Tomás
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  ABSTRACT: We obtained mutants devoid of the O1-antigen, the capsular polysaccharide (K antigen) or both from Klebsiella pneumoniae clinical isolates (urinary infection). These mutants were grown in urine, and their ability to fimbriate and to adhere were studied. Mutants lacking the O1-antigen, independently of the other surface molecules (capsule and fimbriae), showed a great decrease in adhesion to these cells.
  Microbial Pathogenesis 08/1997; 23(1):49-53. · 1.94 Impact Factor
• Article: The role of flagella and motility in the adherence and invasion to fish cell lines by Aeromonas hydrophila serogroup O:34 strains.

  S Merino, X Rubires, A Aguilar, J M Tomás
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  ABSTRACT: We compared the ability of Aeromonas hydrophila wild-type strains of serogroup O:34, non-motile Tn5 aflagellar mutants and the same mutants harboring a recombinant cosmid DNA from a library of A. hydrophila AH-3 (O:34, wild-type) that allows these mutants to make flagella and to be motile, to adhere and invade two fish cell lines. We found that motility is essential in these strains for adhesion, and also that possession of flagella is essential for the ability to invade the fish cell lines. We cannot rule out that flagella may be an adhesin, or that motility may also be involved in A. hydrophila serogroup O:34 bacterial invasion of both fish cell lines.
  FEMS Microbiology Letters 07/1997; 151(2):213-7. · 2.04 Impact Factor
• Article: Complement resistance of capsulated strains of Aeromonas salmonicida.

  S Merino, A Aguilar, J M Tomás, R Bonet, M J Martinez, D Simón-Pujol, F Congregado
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  ABSTRACT: The complement resistance of Aeromonas salmonicida strains grown under conditions promoting capsule formation was investigated using well characterized strains and their isogenic mutants. Complement resistance was previously studied using the same strains growing under non-capsulating conditions. The serum resistant strains were found to activate complement, but rapidly degrade C3b preventing productive formation of the lytic complex C5b-9. Isogenic lipopolysaccharide rough mutants grown under non-capsulating conditions were serum sensitive, binding a large amount of C3b and leading to productive formation of C5b-9. When grown under conditions promoting capsule formation, these mutants were partially resistant to complement because less C3b is bound to them and also partially degraded, with a concomitant reduction in lytic C5b-9.
  Microbial Pathogenesis 06/1997; 22(5):315-20. · 1.94 Impact Factor
• Article: Influence of osmolarity on lipopolysaccharides and virulence of Aeromonas hydrophila serotype O:34 strains grown at 37 degrees C.

  A Aguilar, S Merino, X Rubires, J M Tomas
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  ABSTRACT: Growth of Aeromonas hydrophila serotype O:34 strains at 37 degrees C at low and high osmolarity resulted in changes in the lipopolysaccharide (LPS) and virulence of the strains tested. We previously described the effect of growth temperature on LPS and virulence of these strains (S. Merino et al., Infect. Immun. 60:4343-4349, 1992). The effect of osmolarity can be observed when the cells grow at 37 degrees C but not when they grow at 20 degrees C. Purified LPS from cells cultivated at 37 degrees C and high osmolarity was smooth, while the LPS extracted from the cells cultivated at low osmolarity was rough. Furthermore, the strains were more virulent for fish and mice when they were grown at high osmolarity than when they were grown at low osmolarity and also showed increased extracellular activities when they were grown at high osmolarity. Finally, cells grown at high osmolarity showed better adhesion to HEp-2 cells than the same cells grown at low osmolarity, and furthermore the cells grown at high osmolarity were resistant to the bactericidal activity of nonimmune serum, while the same cells grown at low osmolarity were sensitive.
  Infection and Immunity 05/1997; 65(4):1245-50. · 4.16 Impact Factor
• Article: Molecular characterization of a 17-kDa outer-membrane protein from Klebsiella pneumoniae.

  N Climent, S Ferrer, X Rubires, S Merino, J M Tomás, M Regué
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  ABSTRACT: A cosmid-based genomic library of Klebsiella pneumoniae 52145 (O1:K2) was introduced into Escherichia coli, and clones were screened for the bacteriocin 28b resistance phenotype. One clone was found which conferred partial resistance to bacteriocin 28b. By using Tn5tac1 insertions, it was shown that this phenotype was due to the expression, in E. coli, of an outer-membrane protein (OMP) with an apparent molecular mass of 17 kDa (OmpK17). The DNA region defined by insertion mutagenesis was sequenced and found to contain an ORF of 510 bp. The deduced amino acid sequence has 170 residues with a theoretical molecular mass of 18.4 kDa. The protein contains an N-terminal signal sequence of 24 amino acid residues. When compared with other enterobacterial OMPs, OmpK17 most closely resembles members of a family of small OMPs of Enterobacteriaceae the known functions of which appear to be related to virulence. Immunoblotting experiments showed that OmpK17 is also present in various K. pneumoniae strains belonging to different O and K serotypes.
  Research in Microbiology 03/1997; 148(2):133-43. · 2.76 Impact Factor
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  Available from: nih.gov

  Article: Mesophilic Aeromonas sp. serogroup O:11 resistance to complement-mediated killing.

  S Merino, X Rubires, A Aguilar, S Albertí, S Hernandez-Allés, V J Benedí, J M Tomas
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  ABSTRACT: The complement activation by and resistance to complement-mediated killing of Aeromonas sp. strains from serogroup O:11 were investigated by using different wild-type strains (with an S-layer characteristic of this serogroup) and their isogenic mutants characterized for their surface components (S-layer and lipopolysaccharide [LPS]). All of the Aeromonas sp. serogroup O:11 wild-type strains are unable to activate complement, which suggested that the S-layer completely covered the LPS molecules. We found that the classical complement pathway is involved in serum killing of susceptible Aeromonas sp. mutant strains of serogroup O11, while the alternative complement pathway seems not to be involved, and that the complement activation seems to be independent of antibody. The smooth mutant strains devoid of the S-layer (S-layer isogenic mutants) or isogenic LPS mutant strains with a complete or rather complete LPS core (also without the S-layer) are able to activate complement but are resistant to complement-mediated killing. The reasons for this resistance are that C3b is rapidly degraded, and therefore the lytic membrane attack complex (C5b-9) is not formed. Isogenic LPS rough mutants with an incomplete LPS core are serum sensitive because they bind more C3b than the resistant strains, the C3b is not completely degraded, and therefore the lytic complex (C5b-9) is formed.
  Infection and Immunity 01/1997; 64(12):5302-9. · 4.16 Impact Factor