In vitro Activity of Daptomycin versus Linezolid and Vancomycin against Gram-Positive Uropathogens and Ampicillin against Enterococci, Causing Complicated Urinary Tract Infections

<i>Objectives:</i> The existing therapeutic options for complicated urinary tract infections (UTI) caused by gram-positive uropathogens are not always optimal. Therefore, newer antimicrobials have to be assessed. <i>Methods:</i> The antimicrobial activity of daptomycin was tested versus linezolid, vancomycin, and ampicillin (enterococci on ly), against pathogens from three different collections: (1) Uropathogens from hospitalized urological patients with complicated and/or hospital-acquired UTIs of the Urologic Clinic, Hospital St. Elisabeth, Straubing. (2) Uropathogens from a multicenter study comprising 37 urological centers throughout Germany. (3) Methicillin-resistant <i>Staphylococcus aureus</i> (MRSA) isolates of patients and staff within the Hospital St. Elisabeth, Straubing. Genotyping of the latter isolates was performed by pulsed-field gel electrophoresis. The minimal inhibitory concentrations (MIC) of daptomycin, linezolid, vancomycin, and ampicillin (only tested against enterococci) were determined by an agar dilution method using a multipointer with an inoculum of 10⁴ CFU per point. <i>Results:</i> For all methicillin-susceptible <i>Staphylococcus aureus</i> (n = 25), MRSA (n = 49), methicillin-susceptible coagulase-negative staphylococci (n = 129), methicillin-resistant coagulase-negative staphylococci (n = 33), for <i>Enterococcus faecalis</i> (n = 289), and for <i>Enterococcus faecium</i> (n = 4) the MICs ranged up to 2 mg/l (daptomycin, linezolid), up to 4 mg/l (vancomycin), and up to 8 mg/l (ampicillin, enterococci only) indicating that all strains were susceptible to the antibiotics tested. <i>Conclusions:</i> According to the in vitro activity daptomycin may be considered a promising antibacterial agent for the treatment of complicated UTI caused by gram-positive uropathogens. Thus, daptomycin should be evaluated in a clinical study