Adherence of mycoplasmas to specific tissue surfaces is a crucial step in the establishment of infection. Several pathogenic mycoplasmas are flask-shaped and possess specialized tips that permit a highly oriented surface parasitism of host target cells. Mycoplasma pneumoniae, which causes primary atypical pneumonia in humans, requires a network of interactive adhesins and accessory proteins to cytadhere. The adhesins must cluster at the mycoplasma tip organelle in close association with cytadherence-related accessory proteins and a naplike structure, which together appear to comprise a primitive cytoskeleton-like system. Proline-rich regions associated with these proteins play critical roles in the maintenance of the structural and functional integrity of the tip. Mycoplasma genitalium, originally isolated from the human urogenital tract of patients with nongonococcal urethritis, also colonizes airway cells along with M. pneumoniae. The molecular basis for cytadherence of these mycoplasmas is discussed in terms of the identification, cloning, and sequencing of the implicated mycoplasma genes, their common DNA and amino acid homologies and structural and functional domains, and the organizational similarities in their cytadherence-related operons. In addition, the multiorgan protean manifestations of mycoplasma infection are discussed in terms of the role that mycoplasma adhesins may play in molecular mimicry, postinfectious autoimmunity, and immune-mediated damage.

b Shiga-toxigenic Escherichia coli (STEC) strains were isolated from a variety of fresh produce, but mostly from spinach, with an estimated prevalence rate of 0.5%. A panel of 132 produce STEC strains were characterized for the presence of virulence and putative virulence factor genes and for Shiga toxin subtypes. About 9% of the isolates were found to have the eae gene, which encodes the intimin binding protein, and most of these belonged to known pathogenic STEC serotypes, such as O157:H7 and O26: H11, or to serotypes that reportedly have caused human illness. Among the eae-negative strains, there were three O113:H21 strains and one O91:H21 strain, which historically have been implicated in illness and therefore may be of concern as well. The ehxA gene, which encodes enterohemolysin, was found in ϳ60% of the isolates, and the saa and subAB genes, which encode STEC agglutinating adhesin and subtilase cytotoxin, respectively, were found in ϳ30% of the isolates. However, the precise roles of these three putative virulence factors in STEC pathogenesis have not yet been fully established. The stx 1a and stx 2a subtypes were present in 22% and 56%, respectively, of the strains overall and were the most common subtypes among produce STEC strains. The stx 2d subtype was the second most common subtype (28% overall), followed by stx 2c (7.5%), and only 2 to 3% of the produce STEC strains had the stx 2e and stx 2g subtypes. Almost half of the produce STEC strains had only partial serotypes or were untyped, and most of those that were identified belonged to unremarkable serotypes. Considering the uncertainties of some of these Stx subtypes and putative virulence factors in causing human illness, it is difficult to determine the health risk of many of these produce STEC strains. Increases in the consumption of fresh produce have resulted in increases in food-borne outbreaks and illness associated with these products, prompting federal agencies to monitor the microbial quality of fresh produce. The FDA has implemented import and domestic compliance programs to check produce samples for the presence of pathogens. Also, the USDA Agricultural Marketing Service initiated the Microbiological Data Program (MDP) in 2001 to conduct microbial surveys of fresh produce samples collected from wholesale distribution centers across the country. On average, 10,000 to 15,000 samples were tested by MDP yearly for the presence of Salmonella, enterotoxigenic Escherichia coli (ETEC), E. coli serotype O157:H7, and other Shiga-toxigenic E. coli (STEC) types. The annual MDP reports (http://www.ams .usda.gov/AMSv1.0/mdp) showed that many of these bacteria can be found in various types of fresh produce. STEC strains are characterized by the production of Shiga toxins (Stx), of which there are two main types, designated Stx1 and Stx2. Within each toxin are many subtypes; currently, there are three known Stx1 (Stx1a, Stx1c, and Stx1d) and seven known Stx2 (Stx2a, Stx2b, Stx2c, Stx2d, Stx2e, Stx2f, and Stx2g) subtypes (1). Some of these subtypes have ...

Potential biomarkers for Crohn's disease (CD) and ulcerative colitis (UC) were identified from two sets of full thickness pathologic samples utilizing DermArray and PharmArray DNA microarrays relative to uninvolved (Un) colon or normal colon. Seven of the over-expressed genes were verified using quantitative RT-PCR (i.e., TMPT, FABP1, IFI27, LCN2, COL11A2, HXB, and metallothionein). By correlating gene expression profiles between inflammatory bowel disease (IBD) tissue samples and IBD drug-treated cell cultures it might be possible to identify new candidate molecular target genes for IBD therapy and drug discovery. Potential biomarkers for CaCo2 cell cultures, which are routinely used as a GI tract surrogate model for in vitro pharmacokinetic studies, treated with azathioprine, 5-aminosalicylic acid, metronidazole, and prednisone were also identified from another experiment. Metallothionein mRNA expression was found to be down-regulated in azathioprine-treated CaCo2 cells, and was coincidentally up-regulated in the CD sample, thus resulting in an anti-correlation. These results suggest that this new screening methodology is feasible, that metallothioneins might be biomarkers for azathioprine therapy in vivo in CD, and that azathioprine might mechanistically down-regulate metallothionein gene expression. Correlations were also observed between IBD samples and either metronidazole- or 5-aminosalicylic acid-treated CaCo2 cells. Similar comparisons of disease tissue samples in vivo vs drug-treated cell cultures in vitro might reveal new mechanistic insights concerning established or experimental drug therapies. This affordable in vitro methodology is promising for expanded studies of IBD and other diseases.

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Adhesins and adhesin-related accessory proteins of pathogenic mycoplasmas are required for cytadherence and the subsequent development of disease pathology. The classic example has been Mycoplasma pneumoniae, which causes primary atypical pneumonia in humans. Mutants of M. pneumoniae defective in adhesins (P1 and P30) or in adherence-accessory proteins (HMW1 through HMW4) are unable to colonize host tissues and are avirulent. Mycoplasma genitalium, implicated in nongonococcal, nonchlamydial urethritis, pneumonia, arthritis, and AIDS progression, was found to encode a 140-kDa adhesin that shared both DNA and protein sequence similarities with P1, a major adhesin of M. pneumoniae. In this report, we show that M. genitalium possesses additional homolog sequences to well-characterized adherence-related genes and proteins of M. pneumoniae. The pathogenic human mycoplasmas, Mycoplasma pneumoniae and Mycoplasma genitalium, have genome sizes of 500 and 400 MDa, respectively, with the latter mycoplasm considered the smallest self-replicating biological cell (2, 40). These pathogens possess terminal structures, or tip organelles, which mediate their adherence to target cells. The characterization of these cytadherence events has identified specific mycoplasma membrane adhesins and adherence-related accessory proteins as essential for successful surface parasitism (2). For example, the P1 (170-kDa) and P30 (30-kDa) adhesins of M. pneumoniae and the P140 (140-kDa) adhesin of M. genitalium have been shown through biochemical, genetic, immunological, and ultrastructural studies to be required for cytadherence (2). Mutants lacking these proteins are incapable of cytadherence and are avirulent, spontaneous cytadhering revertants regain the ability to synthesize these adhesins, antibodies reactive against these proteins block cytadherence, and immunoelectron microscopy has shown the adhesins to be localized and densely clustered at the specialized tip attachment organelles (2,4,8,24,29). The complexity of mycoplasma cytadherence has been demonstrated by the involvement of other M. pneumoniae proteins, including HMW1 through HMW4, which have been implicated in cytoskeleton-like functions, such as the maintenance and integrity of the tip structure and the clustering of the adhesin proteins at the specialized tip (2, 25, 39).For several reasons, we have been interested in identifying additional proteins in M. genitalium that might be considered homologs of M. pneumoniae cytadherence-related proteins. M. genitalium was first isolated in 1980 from urethral specimens of patients attending a clinic for sexually transmitted disease and, more recently, was detected in urethral samples from approximately 25% of individuals with acute nongonococcal, nonchlamydial urethritis (21,47,48). Furthermore, M. genitalium has been isolated along with M. pneumoniae from nasopharyngeal throat swabs of patients with acute respiratory disease (3) and from synovial fluids from patients with arthritis (43, 45). Furthermore, M. genitalium, like other mycop...