Reduced expression of the atl autolysin gene and susceptibility to autolysis in clinical heterogeneous glycopeptide-intermediate Staphylococcus aureus (hGISA) and GISA strains.
OBJECTIVE
To assess a link between resistance to Triton X-100 induced autolysis (TIA) and lowered atl expression in a collection of clinical glycopeptide-intermediate Staphylococcus aureus (GISA) and heterogeneous GISA (hGISA).


METHODS
Nine clinical GISA, 11 hGISA and 11 glycopeptide-susceptible S. aureus (GSSA), including three pairs of related isolates, were analysed using TIA assays. Lysostaphin MICs were determined by a broth microdilution technique and reverse transcriptase PCR was used to compare atl expression levels in all isolates.


RESULTS
Eight of nine clinical GISA and six of 11 hGISA exhibited lower susceptibility to TIA and higher MICs of lysostaphin than GSSA. Eight of nine GISA and all hGISA strains had lowered atl expression levels compared with GSSA.


CONCLUSIONS
The majority of GISA and hGISA isolates exhibited lowered susceptibility to TIA and lysostaphin and reduced atl expression when compared with GSSA isolates. These factors could contribute to, or predispose to the development of, a thickened cell wall and glycopeptide-intermediate resistance.
Wootton
Mandy
M
Bristol Centre for Antimicrobial Research and Evaluation, Department of Cellular and Molecular Medicine, Medical Sciences, University of Bristol, Bristol BS1 8TD, UK. mandy.wooton@bristol.ac.uk
Bennett
Peter M
PM
MacGowan
Alasdair P
AP
Walsh
Timothy R
TR
D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001433:Bacteriolysis / Q000235:genetics; D024881:Drug Resistance, Bacterial; D015870:Gene Expression; D006020:Glycopeptides / Q000494:pharmacology*; D006801:Humans; D008248:Lysostaphin / Q000378:metabolism; D008826:Microbial Sensitivity Tests; D009238:N-Acetylmuramoyl-L-alanine Amidase / Q000235:genetics* / Q000378:metabolism; D017830:Octoxynol / Q000494:pharmacology; D012329:RNA, Bacterial / Q000032:analysis; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013203:Staphylococcal Infections / Q000382:microbiology; D013211:Staphylococcus aureus / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*
D000900:Anti-Bacterial Agents; D006020:Glycopeptides; D012329:RNA, Bacterial; D012333:RNA, Messenger; D017830:Octoxynol; D008248:Lysostaphin; D009238:N-Acetylmuramoyl-L-alanine Amidase