Guideline for Urine Culture and Biochemical Identification of Bacterial Urinary Pathogens in Low-Resource Settings.

Medical diagnosis in low-resource settings is confronted by the lack of suitable guidelines, protocols and checklists. Online-accessible procedural documents are difficult to find, might be mistranslated or interpreted and usually do not address the needs of developing countries. Urinalysis, one of the most frequently performed diagnostic examinations worldwide, involves a series of tests aiming to detect particular disorders, such as urinary tract infections, kidney disease and diabetes. In this guideline, we present an alternative approach for clinical laboratories with limited resources to identify common bacterial uropathogens. We propose dividing the identification plan into two levels. The implicated pathogen will first be assigned into a bacterial group, basic identification, against which a suitable panel of antimicrobial agents shall be selected for the antimicrobial susceptibility testing (AST). Characterization of the pathogen to the genus or species level, advanced identification, will then be performed to ensure correct reading of the AST results and determine the epidemiology of clinically significant pathogens. Most of the proposed steps in our guideline are tailored to meet the needs of clinical laboratories in low-resource settings. Such guidelines are needed to strengthen the capacity of regional pathology laboratories and to enhance international initiatives on antimicrobial resistance and health equity.

Antibody-mediated disruption of the mechanics of CS20 fimbriae of enterotoxigenic Escherichia coli.

Preventive vaccines against enterotoxigenic Escherichia coli (ETEC) are being developed, many of which target common fimbrial colonization factors as the major constituent, based on empirical evidence that these function as protective antigens. Particularly, passive oral administration of ETEC anti-fimbrial antibodies prevent ETEC diarrhea. Little is, however, known regarding the specific mechanisms by which intestinal antibodies against ETEC fimbriae function to prevent disease. Using coli surface antigen 20 (CS20) fimbriae as a model ETEC colonization factor, we show using force spectroscopy that anti-fimbrial antibodies diminish fimbrial elasticity by inhibiting their natural capacity to unwind and rewind. In the presence of anti-CS20 antibodies the force required to unwind a single fimbria was increased several-fold and the extension length was shortened several-fold. Similar measurements in the presence of anti-CS20 Fab fragments did not show any effect, indicating that bivalent antibody binding is required to reduce fimbrial elasticity. Based on these findings, we propose a model for an in-vivo mechanism whereby antibody-mediated disruption of the biomechanical properties of CS20 fimbriae impedes sustained adhesion of ETEC to the intestinal mucosal surface. Further elucidation of the role played by intestinal antibodies in mechanical disruption of fimbrial function may provide insights relevant to ETEC vaccine development.