In this paper we analyze three enteropathogenetic opportunistic infections represented by Candida spp., C. difficile and carbapenemase-producing K. pneumoniae. The common pathogenetic pathway is based on an alteration of the intestinal flora, now mainly referred as the human microbiome, with secondary opportunism for infections caused by Candida, C. difficile and carbapenemase-producing Enterobacteriaceae ("CCC"). We highlight the epidemiology, risk factors, clinical syndromes associated with the pathogens and we propose some new issues related to the epidemiology and diagnosis of candidemia, also using hierarchical cluster analysis, definitions of levels of interventions in patients colonized or infected by carbapenemase-producing bacteria. The "enteropathogenetic" opportunistic syndromes are best prevented with antimicrobial stewardship programs aiming at increasing diagnostic specificity of infectious syndromes to reduce the antimicrobial use and costs. Appropriate guidelines for infection control should also be implemented to reduce the nosocomial spread of enteropathogenetic microbes.