Lectins are generally associated with plant or animal components, selectively bind carbohydrates, and interact with procaryotic and eucaryotic cells. Lectins have various specificities that are associated with their ability to interact with acetylaminocarbohydrates, aminocarbohydrates, sialic acids, hexoses, pentoses, and as other carbohydrates. Microbial surfaces generally contain many of the sugar residues that react with lectins. Lectins are presently used in the clinical laboratory to type blood cells and are used in a wide spectrum of applications, including, in part, as carriers of chemotherapeutic agents, as mitogens, for fractionation of animal cells, and for investigations of cellular surfaces. Numerous studies have shown that lectins can be used to identify rapidly certain microorganisms isolated from a clinical specimen or directly in a clinical specimen. Lectins have been demonstrated to be important diagnostic reagents in the major realms of clinical microbiology. Thus, they have been applied in bacteriology, mycology, mycobacteriology, and virology for the identification and/or differentiation of various microorganisms. Lectins have been used successfully as epidemiologic as well as taxonomic markers of specific microorganisms. Lectins provide the clinical microbiologist with cost-effective and potential diagnostic reagents. This review describes the applications of lectins in clinical microbiology.
A total of 111 Candida isolates representing 11 species were examined for their respective responses to a Tween 80 opacity test. The strains of Candida albicans and C. tropicalis that were examined produced an opacity response around their colonies at 2 to 3 days postinoculation. A second group ofCandida species yielded a halo around their colonies at 8 to 10 days postinoculation. The remaining Candida species did not produce a positive test response through 10 days postinoculation. The strains of C. dubliniensis were easily differentiated from strains of C. albicans by this test. The Tween 80 opacity test is simple and economical to prepare and is easy to interpret.
The distributed genome hypothesis (DGH) states that each strain within a bacterial species receives a unique distribution of genes from a population-based supragenome that is many times larger than the genome of any given strain. The observations that natural infecting populations are often polyclonal and that most chronic bacterial pathogens have highly developed mechanisms for horizontal gene transfer suggested the DGH and provided the means and the mechanisms to explain how chronic infections persist in the face of a mammalian host's adaptive defense mechanisms. Having previously established the validity of the DGH for obligate pathogens, we wished to evaluate its applicability to an opportunistic bacterial pathogen. This
We report a case of cerebral phaeohyphomycosis in a 36-year-old male caused by the neurotropic fungus Ramichloridium obovoideum (Matushima) de Hoog 1977 (Ramichloridium mackenziei Campbell et Al-Hedaithy 1993). This man resided in the Middle East, where the fungus appears to be endemic and, possibly, geographically restricted, since all previous reports of brain abscesses due to this organism have been for patients indigenous to this area. As a servant of the Saudi Arabian royal family, he appeared in the United States seeking treatment for chronic weight loss, fatigue, decreased memory, and a more recent 2-week history of right-hand weakness which worsened to involve the entire right upper extremity. On the day prior to his admission, he had a focal motor seizure with rotation of the head and eyes to the right, followed by secondary generalization. A computerized tomogram showed a ring-enhancing hypodense lesion in the left parietal subcortical region with associated edema and mass effect. Diagnosis of a fungal etiology was made following a parietal craniotomy and excisional biopsy by observation of septate, dematiaceous hyphal elements 2 to 3 μm in width on hematoxylin-and-eosin-stained sections from within areas of inflammation and necrosis. Culture of the excised material grew out a dematiaceous mould which was subsequently identified as R. obovoideum. At two months postsurgery and with a regimen of 200 mg of itraconazole twice a day, the patient was doing well and returned to Saudi Arabia. His condition subsequently deteriorated, however, and following a 7-month course of itraconzole, he expired. We use this case to alert clinicians and personnel in clinical mycology laboratories of the pathogenicity of this organism and its potential occurrence in patients with central nervous system signs and symptoms who have resided in the Middle East and to review and/or compare R. obovoideum with other neurotropic, dematiaceous taxa and similar nonneurotropic, dematiaceous species.
By the use of specific antibody to human chorionic gonadotropin (CG) as well as to its β‐subunit, and the application of the indirect fluorescein‐labeled and peroxidase‐labeled antibody techniques, we have demonstrated the presence of a membrane (wall)‐associated CG‐similar immunoreactive protein in 15 strains of bacteria isolated from tissues of patients bearing malignant neoplasms. These microorganisms were classified as S. epidermidis, (12), E. coli (2), and a single strain of P. maltophilia (ATCC 13637). The absence of the CG‐like antigen in other “cancer associated bacteria”, Streptococcus faecalis (ATCC 12818) and Pseudomonas aeruginosa (from patient with cancer of colon), demonstrated that not every “cancer associated bacteria” has the capability to synthesize the trophoblastic‐like protein. The negative results obtained with a number of “noncancer control” bacteria of known origin, obtained from ATCC and from clinical samples, strongly supported the idea that the existence of these CG‐like protein producing microorganisms is not a ubiquitous finding. The demonstration of a de novo bacterial biosynthesis of a protein having similar antigenic and biophysical properties to those of the human trophoblastic hormone, has great biological implications, especially if its biosynthesis is proven only in bacterial strains growing in the presence of cancer cells in which we have already demonstrated the presence of a similar antigen. The explanation of the phenomenon is unknown. Because of their origin, the potential of “genetic exchange” with subsequent expression of the mammalian gene by the bacterial cells becomes a possibility. It is also possible that the gene coding for the CG‐like protein is normally present but inactive or repressed in all bacteria.
Congo red may be applied as a fluorochrome to rapidly detect fungi in clinical specimens, tissue, and fungal culture preparations. This generally available stain is cost effective and simple to prepare. The stain may be prepared with potassium permanganate as a counterstain or with Formalin or glutaraldehyde as a fungicide. Various fluorescent stains with a high affinity for cellulose or chitin have been applied to stain fungal elements. Accordingly, the fluorescent brightener Calcofluor (Cellofluor, Cal
Three beta-streptococci serogrouping kits, Phadebact, SeroSTAT, and Streptex, were evaluated as to their sensitivity, accuracy, and suitability as methods for serogrouping streptococci in a clinical microbiology laboratory. The majority of the primary isolates examined by the various methods associated with each of the three kits were correctly identified. The Streptex direct mixed-culture procedure was more often associated with the observation of cross-reactivity than with the direct procedures of the other two kits which did not employ mixed growth cultures. Furthermore, the Streptex kit was associated with more falsenegative responses than those determined by the other two kits under evaluation. These results appeared to be due to the relatively poor sensitivity of the Streptex grouping reagents. The Streptex test procedures required more labor than the other kit procedures, requiring a 1-h enzymatic extraction step for the release of the group antigens. The SeroSTAT kit provided only a direct procedure and, thus, is limited in its application. The Phadebact procedures were the most versatile by providing not only a direct and a 24-h grouping procedure, but also by including a 4-h method that may be employed as required by the clinical microbiologist.
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