Epidemiologic typing of nosocomial microorganisms.

Hospital epidemiologists often rely upon "typing" of microorganisms to help determine their genetic relatedness. Most general clinical microbiology laboratories can determine biologic profiles (biotypes) and antimicrobial susceptibility patterns (antibiograms) of bacteria commonly isolated from specimens; occasionally serologic typing (serotype) is also performed. Special interest laboratories can provide serologic typing, bacteriophage susceptibility patterns (phage typing), bacteriocin production patterns, bacteriocin susceptibility patterns, plasmid analyses and chromosomal DNA analyses for a variety of bacteria, mycobacteria and fungi of nosocomial interest. Such laboratories can also provide serologic typing, restriction enzyme analyses and other special studies of viruses and related microorganisms. A useful and effective "typing" system should be (1) standardized, (2) reproducible, (3) sensitive, (4) stable, (5) available, (6) inexpensive, (7) applicable to a wide range of microorganisms, and (8) field tested in conjunction with epidemiologic investigation. Results should be reported in a standard manner with some discussion of the implications and limitations of the reported results. We suggest that a registry of typing methods be established to facilitate application of available methods to appropriate epidemiologic investigations.