Gram-positive hospital acquired infection in the ITU setting

The intensive therapy unit (ITU) is a prime site for the development and emergence of antimicrobial resistance. The majority of Staphylococcus aureus isolates in ITU patients are methicillin-resistant S. aureus (MRSA). In general, other Gram-positive pathogens including coagulase-negative staphylococci (mainly Staphylococcus epidermidis) and enterococci (primarily Enterococcus faecalis and Enterococcus faecium) are also increasingly becoming increasing antibiotic resistant. In a recent US study, bacteraemias in ITU patients accounted for about half of all cases, and significant increases were observed in the prevalence of MRSA, coagulase-negative staphylococci and vancomycin-resistant enterococci (all P<0.001). Almost all of these resistant pathogens remain susceptible to linezolid, and additionally to daptomycin and tigecycline, two new agents that are already licenced in some countries. Comparative studies are few but do suggest possible superiority for linezolid in comparison with vancomycin both for the treatment of MRSA hospital-acquired pneumonia (including ventilator associated pneumonia), and for the treatment of complicated skin structure infection caused by MRSA. Linezolid was also superior to teicoplanin in patients with Gram-positive infection, notably in those with S. aureus bacteraemia. Thus, new antimicrobials offer a welcome addition to the hitherto limited therapeutic alternatives for prevalent Gram-positive pathogens in ITU patients.