The aim of this study was to evaluate MIC trends for clinical isolates of Staphylococcus aureus to vancomycin over a 5 year period (2002–06) in a hospital in Spain. All clinical isolates of S. aureus (one per patient) from clinical samples of patients at Hospital Universitario de Getafe from January 2002 to December 2006 were used. MICs of vancomycin were determined by the CLSI broth microdilution procedure. For analysis of MIC trends over the 5 years, we grouped the isolates into those with MIC ≤1 mg/L [2428 methicillin-susceptible S. aureus (MSSA) and 518 methicillin-resistant S. aureus (MRSA)] and those with MIC ≥2 mg/L (MIC = 2 mg/L: 141 MSSA and 47 MRSA; MIC = 4 mg/L: 5 MSSA and 1 MRSA). MICs for the different groups in the different years were compared with the linear-trend χ² test. A total of 3141 strains of S. aureus collected over the 5 year period was included in this analysis. Of these, 2574 (82%) strains were MSSA and 566 (18%) strains were MRSA. One of the 566 MRSA strains (0.18%) and 5 of the 2574 MSSA strains (0.19%) were vancomycin-intermediate (not significant). The rest were susceptible. The overall percentage of MRSA isolates with a vancomycin MIC of ≥2 mg/L was much higher than that of MSSA during the 5 year period [8.5% (48/566) versus 5.7% (146/2574); P = 0.012]. No statistically significant change in the percentage of isolates with a vancomycin MIC of ≥2 mg/L was observed over the years for MRSA (χ² = 0.01; P = 0.91) or MSSA (χ² = 0.08; P = 0.78). Annual consumption of parenteral vancomycin in our hospital in daily defined doses/100 stays was: 2002 (1.91), 2003 (1.63), 2004 (1.74), 2005 (2.06) and 2006 (1.64). In a setting of low consumption of vancomycin and with a large collection of S. aureus clinical isolates, we have demonstrated the stability of vancomycin MICs over time.

Background: The treatment of complicated urinary tract infections may require the use of a parenteral antibiotic with potent activity against the most common urinary pathogens. Ertapenem is a broad-spectrum 1β-methyl carbapenem with a long plasma half-life that allows administration of a single daily dose. Methods: The purpose of this work was to test the in vitro susceptibility to ertapenem, ampicillin, cefazolin, cefuroxime, cefotaxime, co-amoxiclav, piperacillin/tazobactam, imipenem, gentamicin, amikacin, fosfomycin, ciprofloxacin and co-trimoxazole of 482 strains of urinary pathogens of the family Enterobacteriaceae isolated from patients in the community of Madrid (40% from males). The distribution was as follows: Escherichia coli (n = 315), Proteus mirabilis (n = 42), Klebsiella spp. (n = 14) and AmpC-producing Enterobacteriaceae (n = 111). The strains studied were selected based on their resistance to quinolones and aminoglycosides, and their production of extended-spectrum β-lactamases (ESBLs) or AmpC-type β-lactamases. Results: All the strains were susceptible to ertapenem, imipenem and amikacin. The MIC₉₀ of ertapenem ranged from a minimum of 0.03 mg/L for Proteus vulgaris and a maximum of 1 mg/L for Enterobacter spp. Ertapenem was the most active of all drugs tested in all cases. On comparing antibiotic resistance among ESBL-producing strains of E. coli (n = 35) and E. coli strains not producing ESBLs (n = 280), statistically significant differences were obtained for ciprofloxacin (P = 0.002) and gentamicin (P = 0.011). Regarding ertapenem, only a slight increase in MIC₅₀ was seen, the value being 0.015 mg/L for strains not producing ESBLs versus 0.03 mg/L for ESBL-producing strains. Conclusions: In view of its significant antibiotic potency against antibiotic-resistant Enterobacteriaceae, ertapenem may constitute a good therapeutic alternative in urinary infections caused by these pathogens.