Helicobacter pylori, one of the most common bacterial pathogens of humans, colonizes the gastric mucosa, where it appears to persist throughout the host's life unless the patient is treated. Colonization induces chronic gastric inflammation which can progress to a variety of diseases, ranging in severity from superficial gastritis and peptic ulcer to gastric cancer and mucosal-associated lymphoma. Strain-specific genetic diversity has been proposed to be involved in the organism's ability to cause different diseases or even be beneficial to the infected host and to participate in the lifelong chronicity of infection. Here we compare the complete genomic sequences of two unrelated H. pylori isolates. This is, to our knowledge, the first such genomic comparison. H. pylori was believed to exhibit a large degree of genomic and allelic diversity, but we find that the overall genomic organization, gene order and predicted proteomes (sets of proteins encoded by the genomes) of the two strains are quite similar. Between 6 to 7% of the genes are specific to each strain, with almost half of these genes being clustered in a single hypervariable region.

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Fucosylated carbohydrate structures are involved in a variety of biological and pathological processes in eukaryotic organisms including tissue development, angiogenesis, fertilization, cell adhesion, inflammation, and tumor metastasis. In contrast, fucosylation appears less common in prokaryotic organisms and has been suggested to be involved in molecular mimicry, adhesion, colonization, and modulating the host immune response. Fucosyltransferases (FucTs), present in both eukaryotic and prokaryotic organisms, are the enzymes responsible for the catalysis of fucose transfer from donor guanosine-diphosphate fucose to various acceptor molecules including oligosaccharides, glycoproteins, and glycolipids. To date, several subfamilies of mammalian FucTs have been well characterized; these enzymes are therefore delineated and used as models. Non-mammalian FucTs that possess different domain construction or display distinctive acceptor substrate specificity are highlighted. It is noteworthy that the glycoconjugates from plants and schistosomes contain some unusual fucose linkages, suggesting the presence of novel FucT subfamilies as yet to be characterized. Despite the very low sequence homology, striking functional similarity is exhibited between mammalian and Helicobacter pylori alpha1,3/4 FucTs, implying that these enzymes likely share a conserved mechanistic and structural basis for fucose transfer; such conserved functional features might also exist when comparing other FucT subfamilies from different origins. Fucosyltranferases are promising tools used in synthesis of fucosylated oligosaccharides and glycoconjugates, which show great potential in the treatment of infectious and inflammatory diseases and tumor metastasis.

The gyrA gene of Campylobacterjejuni UA580, which encodes the A subunit of DNA gyrase, was cloned and its nucleotide sequence was determined. An open reading frame of 2,589 nucleotides was identified, which could code for a polypeptide of 863 amino acids with a Mr of 97 kDa. Both the nucleotide sequence and the putative amino acid sequence show ca. 50% identity with those of other gyrA genes from gram-positive and gram-negative bacteria. Similar mutations were also identified in ciprofloxacin-resistant isolates of S. aureus (10,27).Gootz and Martin (9) demonstrated that the DNA gyrases from Nalr mutants of C. jejuni UA535 were 100-fold less susceptible than the wild-type enzyme to inhibition by quinolones in the DNA supercoiling reaction. Subunit switching experiments with purified A and B subunits from the wild type and one of the quinolone-resistant mutants indicated that an alteration in the A subunit was responsible for resistance. Here, we report the cloning and nucleotide sequence of the C. jejuni gyrA gene and the location of the gene on both C. jejuni and C. coli chromosomes. Several mutations responsible for quinolone resistance were detected in the gyrA sequence. MATERUILS AND METHODSStrains and culture conditions. The Campylobacter spp. employed in this study were C. jejuni UA67 (Nalr mutant [35]); UA536, UA543, and UA549 (Nalr clinical isolates from H. Lior); UA580 (35); UA58OR1 and UA580R3 (Nalr mutant from UA580 [this study]); and C. coli UA417 (Nalr clinical isolates [35]). E. coli DH5at (23) was also used. The plasmids and phages employed were pUC19, M13mpl8, M13mpl9 (38), pBluescript II SK (Stratagene), pK194 (16), and pT7-5 (30).Campylobacters were grown at 37°C on Mueller-Hinton agar medium containing 7% CO2. E. coli was grown in 2x YT medium or on Luria-Bertani agar (23) at 37°C. When necessary, the medium was supplemented with ampicillin (100 ,ug/ml), kanamycin (15 jig/ml), or nalidixic acid (24 ig/ml).DNA isolation, transformation, and nucleotide sequence analysis. Plasmid DNA was isolated by a modification of the alkaline lysis method of Birnboim and Doly (2) and purified by the "magic miniprep" (Promega) when used for restriction analysis and sequencing. M13 phage DNA was prepared by the method described by Sambrook et al. (23).

Growing cells of Campylobacter coli and C. jejuni were naturally transformed by naked DNA without the requirement for any special treatment. Transformation frequencies for homologous chromosomal DNA were approximately 10(-3) transformants per recipient cell in C. coli and 10(-4) in C. jejuni. Maximum competence was found in the early log phase of growth. Campylobacters preferentially took up their own DNA in comparison with Escherichia coli chromosomal DNA, which was taken up very poorly. Three new Campylobacter spp.-to-E. coli shuttle plasmids, which contained additional cloning sites and selectable markers, were constructed from the shuttle vector pILL550A. These plasmid DNAs were taken up by campylobacters much less efficiently than was homologous chromosomal DNA, and transformation into plasmid-free cells was very rare. However, with the use of recipients containing a homologous plasmid, approximately 10(-4) transformants per cell were obtained. The tetM determinant, originally obtained from Streptococcus spp. and not heretofore reported in Campylobacter spp., was isolated from an E. coli plasmid and was introduced, selecting for tetracycline resistance, by natural transformation into C. coli.

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Infection with Campylobacter jejuni is now considered to be the most common cause of acute bacterial gastroenteritis in humans worldwide. It occurs more frequently than infections caused by Salmonella species, Shigella species, or Escherichia coli O157:H7. Although C. jejuni is also recognized for its association with serious post-infection neurological complications, most patients with C. jejuni infections have a self-limited illness. Nevertheless, a substantial proportion of these infections are treated with antibiotics. These include severe and prolonged cases of enteritis, infections in immune-suppressed patients, septicaemia and other extra-intestinal infections. Under these circumstances, erythromycin is often recommended as the drug of first choice. However, erythromycin-resistant Campylobacter have emerged during therapy with macrolides. Moreover, the widespread use of macrolides, including erythromycin, in veterinary medicine has accelerated this resistance trend. Several countries including Canada, Japan and Finland have reported C. jejuni isolates with low and stable rates of macrolide resistance. In contrast, the increasing level of macrolide resistance in C. jejuni is becoming a major public health concern in other parts of the world such as the United States, Europe and Taiwan. Macrolide resistance in Campylobacter is mainly associated with point mutation(s) occurring in the peptidyl-encoding region in domain V of the 23S rRNA gene, the target of macrolides. Several rapid and practical techniques have recently been developed for the identification of macrolide-resistant isolates of C. jejuni. The aim of this mini-review is to give an overview of the worldwide distribution of macrolide resistance in C. jejuni and Campylobacter coli as well as its possible association with the massive use of these agents in food animals. Mechanisms implicated in macrolide resistance in C. jejuni and also techniques that have been developed for the efficient detection of macrolide-associated mutation(s) will be discussed in detail.