High-level ciprofloxacin resistance among hospital-adapted Enterococcus faecium (CC17)

Abstract

Hospital-adapted Enterococcus faecium differ from their colonising variants in humans and animals by additional genomic content. Molecular typing based on multilocus sequence typing (MLST) allows allocation of isolates to specific clonal complexes (CCs), such as CC17 for hospital-adapted strains. Acquired ampicillin resistance is a specific feature of these hospital isolates, especially in Europe. A few recent reports have described acquired high-level ciprofloxacin resistance as a supposed feature of hospital-adapted E. faecium strains. In the present retrospective analysis, ciprofloxacin minimum inhibitory concentrations (MICs) of 609 clinical isolates from German hospital patients (1997-2007) were determined and a breakpoint for high-level resistance was deduced (>16mg/L). Acquired high-level ciprofloxacin resistance was distributed among isolates of 26 different MLST types (all CC17), indicating a wide prevalence of this acquired resistance trait among the hospital-adapted E. faecium population. High-level ciprofloxacin resistance was linked to gyrA and parC mutations in 98 investigated isolates. Eleven different allele types or combinations thereof were identified. Their allocation to specific MLST and pulsed-field gel electrophoresis (PFGE) types revealed differences in the emergence and spread of corresponding mutations and strains.

Performance of three chromogenic VRE screening agars, two Etest® vancomycin protocols, and different microdilution methods in detecting vanB genotype Enterococcus faecium with varying vancomycin MICs

“…The numbers of infections and colonizations with vanB type VRE increased in a number of European countries during recent years ( Bourdon et al, 2011, Klare et al, 2010and Soderblom et al, 2010. The supposed growing incidence of vanB type enterococci may have different reasons and could only be partly explained by an increased incidence of vanB type resistant strains.…”

“…Diagnostic and university laboratories send strains to us for (vancomycin/teicoplanin) resistance confirmation and molecular typing. Our enterococcal strain collection currently contains > 10,000 isolates, mainly from hospital surveillance and infections, but also from animals, food products, the environment, and stool colonisations in outpatients (Klare et al, 1995a, Klare et al, 1995b, Klare et al, 1999, Klare et al, 2005, Werner et al, 2007, Werner et al, 2010and Werner et al, 2011a. Until now, we collected and identified 1060 vanB strains including 982 vanB-positive E. faecium and 74 vanB-positive E. faecalis which were all from hospital patients.…”

“…Classification into susceptible/intermediate/resistant (S-I-R) differs between European Committee on Antimicrobial Susceptibility Testing (EUCAST) and Clinical Laboratory Standard Institutes (CLSI) (CLSI, 2011); EUCAST defines MICs for vancomycin with S ≤ 4 mg/L and R > 4 mg/L (no intermediate range) and CLSI defines S ≤ 4 mg/L, I = 8-16 mg/L, and R ≥ 32 mg/L. We used the EUCAST clinical breakpoints when available; for other antibiotics, we applied breakpoints derived from CLSI, DIN, and based on other criteria, e.g., for high-level ciprofloxacin resistance defined as an MIC > 16 mg/L ( Leavis et al, 2006 andWerner et al, 2010). Strains were classified as resistant with MICs (in milligrams per liter) as follows: penicillin/ampicillin > 8, teicoplanin > 2, erythromycin > 4, linezolid > 4, tetracycline > 4, rifampicin > 0.5, chloramphenicol > 16, tigecycline > 0.5, daptomycin > 4, gentamicin (high-level) > 128, streptomycin (high-level) > 512, quinupristin/dalfopristin > 4.…”

“…The dramatic increase in vanB type prevalence among VRE in a number of European countries ( Bourdon et al, 2011, Klare et al, 2010and Soderblom et al, 2010 …”

Current Trends of Emergence and Spread of Vancomycin-Resistant Enterococci

“…and the necessity of specific mutations in one or both A subunit genes to confer what is specified as high-level ciprofloxacin resistance (Onodera et al, 2002;Oyamada et al, 2006a;Oyamada et al, 2006b). Molecular studies with high-level ciprofloxacin-resistant clinical isolates revealed mutations in both A subunits associated with different levels of ciprofloxacin resistance, whereas mutations in gyrB and parE alleles were only infrequently found Leavis et al, 2006;Valdezate et al, 2009;Werner et al, 2010a).…”