Novel infectious diseases and emerging gram-positive multi-resistant pathogens in hospital and community acquired infections

Abstract

Gram-positive pathogens are a major cause of healthcare-associated and community-acquired bacterial infections. Staphylococci (mostly Staphylococcus aureus but also coagulase-negative staphylococci), enterococci, streptococci, and Clostridium difficile are the most important species of clinical interest. Antibiotic resistance issues are common among Gram-positive pathogens, especially among staphylococci and enterococci. Methicillin-resistant Staphylococcus aureus (MRSA) and glycopeptide-resistant enterococci (GRE) are paradigms for difficult-to-treat multi-resistant pathogen capable of global-scale diffusion, with remarkable impact on morbidity, mortality, and healthcare-associated costs. MRSA, in particular, is the most relevant Gram-positive multi-resistant pathogen in terms of diffusion and overall clinical impact, being a leading cause for healthcare-associated infections worldwide, as well as an emerging cause of community-acquired infections that are often associated with novel MRSA strains. Resistance to anti-MRSA and anti-VRE drugs remains uncommon or exceptional among the respective species. However, invasive infections caused by MRSA strains resistant to glycopeptides, linezolid, or daptomycin, and by VRE strains resistant to linezolid or daptomycin have increasingly been reported, especially after prolonged drug exposure, and a transferable resistance mechanism to linezolid and other anti-ribosomal agents has recently emerged among staphylococci and enterococci. This evolving scenario underscores the need for continuing efforts aimed at surveillance and control of infections caused by multi-resistant Gram-positives, and at the discovery and development of new drugs active against these pathogens.