Reporting antimicrobial susceptibilities and phenotypes of resistance to vancomycin in vancomycin-resistant Enterococcus spp. clinical isolates: A nationwide proficiency study.

Introduction: The ability of Spanish microbiology laboratories to (a) determine antimicrobial susceptibility (AS), and (b) correctly detect the vancomycin resistance (VR) phenotype in vancomycin-resistant Enterococcus spp. (VRE) was evaluated.

Methods: Three VRE isolates representing the VanA (E.

Susceptibility testing and detection of β-lactam resistance mechanisms in Enterobacteriaceae: a multicentre national proficiency study.

A nationwide study was developed to evaluate the ability of 60 Spanish clinical microbiology laboratories to predict the underlying β-lactam resistance mechanisms of 12 Enterobacteriaceae strains (CCS01-CCS12). Results obtained by two reference laboratories were compared with those reported by the participant laboratories that used their own routine susceptibility testing methodology. Clinical and Laboratory Standards Institute (CLSI) interpretive criteria were used in 53.

Establishing the validity of different susceptibility testing methods to evaluate the in vitro activity of amoxicillin-clavulanate against Escherichia coli.

Amoxicillin-clavulanate MICs of 160 Escherichia coli isolates with characterized resistance mechanisms were obtained by 2 MIC gradient strip brands, 3 automated systems, and reference ISO microdilution method using EUCAST (fixed 2μg/mL clavulanate) and CLSI (2:1 ratio) criteria. Discrepancies, mainly obtained with gradient strips, lead to an essential agreement range of 76.2-92.

Inhibitor-resistant TEM- and OXA-1-producing Escherichia coli isolates resistant to amoxicillin-clavulanate are more clonal and possess lower virulence gene content than susceptible clinical isolates.

In a previous prospective multicenter study in Spain, we found that OXA-1 and inhibitor-resistant TEM (IRT) β-lactamases constitute the most common plasmid-borne mechanisms of genuine amoxicillin-clavulanate (AMC) resistance in Escherichia coli. In the present study, we investigated the population structure and virulence traits of clinical AMC-resistant E. coli strains expressing OXA-1 or IRT and compared these traits to those in a control group of clinical AMC-susceptible E.

Role of Klebsiella pneumoniae OmpK35 porin in antimicrobial resistance.

OmpK35 from Klebsiella pneumoniae is the homologue of Escherichia coli OmpF porin. Expression of OmpK35 in K. pneumoniae strain CSUB10R (lacking both OmpK35 and OmpK36) decreased the MICs of cephalosporins and meropenem > or = 128-fold and decreased the MICs of imipenem, ciprofloxacin, and chloramphenicol > or = 8-fold.

Quality control for beta-lactam susceptibility testing with a well-defined collection of Enterobacteriaceae and Pseudomonas aeruginosa strains in Spain.

Eighteen Enterobacteriaceae and Pseudomonas aeruginosa strains, 16 of them with well-defined beta-lactam resistance mechanisms, were sent to 52 Spanish microbiology laboratories. Interpretative categories for 8 extended-spectrum beta-lactams were collected. Participating laboratories used their own routine susceptibility testing procedures (88% automatic systems, 10% disk diffusion, and 2% agar dilution).

Relationship between beta-lactamase production, outer membrane protein and penicillin-binding protein profiles on the activity of carbapenems against clinical isolates of Acinetobacter baumannii.

Twenty blood isolates of Acinetobacter baumannii were studied, representing eight pulsed-field gel electrophoresis patterns and all different antimicrobial susceptibility patterns observed during 1995-97 at the University Hospital Virgen Macarena, Seville, Spain. The MIC(90)s (mg/L) of imipenem and meropenem decreased from 16 to 0.5 and from 8 to 4, respectively, in the presence of BRL 42715 (BRL) but not clavulanic acid.