From phenotyping to the study of clonal relationship of microbial isolates

The term “typing” is generally used with two meanings: a methods to establish the correct taxonomic collocation of a genus/specie/biotype, b methods for discriminating different bacterial isolates of the same species in order to establish the genetic relationship among the microorganisms involved in a possible outbreak. In this paper we focus our attention on the second aspect, that represents a relevant epidemiological tools in infection prevention and control. Typing systems are traditionally based on two steps workup: the first is the study of phenotypes such as serotype, biotype, phage-type, or antimicrobial susceptibilities of the isolates and this can be easily performed in every microbiology laboratory; the second, examines the relatedness of isolates at a molecular level. Over the years many molecular methods have been developed and efficiently applied in several hospital settings. The large panorama of methods put the microbiologists in trouble to operate the proper choice. Thus, in the present paper, we have reviewed old as well new molecular typing methods in order to provide a useful guide that can represent an overview on molecular methods and particularly of their specific pro and cons.