Susceptibility of gram-positive cocci from 25 UK hospitals to antimicrobial agents including linezolid. The Linezolid Study Group.
The prevalence of antibiotic resistance amongst Gram-positive cocci from 25 UK hospitals was studied over an 8 month period in 1999. A total of 3770 isolates were tested by the sentinel laboratories using the Etest; these bacteria comprised 1000 pneumococci, 1005 Staphylococcus aureus, 769 coagulase-negative staphylococci (CNS) and 996 enterococci. To ensure quality, 10% of the isolates were retested centrally, as were any found to express unusual resistance patterns. The prevalence of penicillin-resistant Streptococcus pneumoniae, vancomycin-resistant enterococci and methicillin-resistant S. aureus (MRSA) varied widely amongst the sentinel laboratories. The resistance rates to methicillin among S. aureus and CNS were 19.2 and 38.9%, respectively, with MRSA rates in individual sentinel sites ranging from 0 to 43%. No glycopeptide resistance was seen in S. aureus, but 6.5% of CNS isolates were teicoplanin resistant and 0.5% were vancomycin resistant. Vancomycin resistance was much more frequent among Enterococcus faecium (24.1%) than E. faecalis (0.5%) (P<0.05), with most resistant isolates carrying vanA. The rate of penicillin resistance in pneumococci was 8.9%, and this resistance was predominantly intermediate (7.9%), with only six hospitals reporting isolates with high level resistance. The prevalence of erythromycin resistance among pneumococci was 12.3%, with the majority of resistant isolates having the macrolide efflux mechanism mediated by mefE. All the organisms tested were susceptible to linezolid with MICs in the range 0.12-4 mg/L. The modal MICs of linezolid were 1 mg/L for CNS and pneumococci, and 2 mg/L for S. aureus and enterococci. Linezolid was the most potent agent tested against Gram-positive cocci, including multiresistant strains, and as such may prove a valuable therapeutic option for the management of Gram-positive infections in hospitals.
Henwood
C J
CJ
Antibiotic Resistance Monitoring and Reference Laboratory, Central Public Health Laboratory, Colindale Avenue, London NW9 5HT, UK. chenwood@phls.nhs.uk
Livermore
D M
DM
Johnson
A P
AP
James
D
D
Warner
M
M
Gardiner
A
A
D000081:Acetamides / Q000494:pharmacology*; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D006095:Gram-Positive Cocci / Q000187:drug effects*; D006801:Humans; D000069349:Linezolid; D016106:Methicillin Resistance; D008826:Microbial Sensitivity Tests; D023303:Oxazolidinones / Q000494:pharmacology*; D010403:Penicillin Resistance
D000081:Acetamides; D000900:Anti-Bacterial Agents; D023303:Oxazolidinones; D000069349:Linezolid