The Journal of Medical Microbiology, Vol 8, Issue 2 337-347, Copyright © 1975 by Society for General Microbiology
Further evolution of a strain of Staphylococcus aureus in vivo: evidence for significant inactivation of flucloxacillin by penicillinase
R. W. Lacey and E. L. Lewis
A strain of Staphylococcus aureus (no. FAR4) has been isolated at
intervals, for 32 months, from the sputum of a patient with cystic fibrosis
of the lung. Changes in the properties of isolates of this strain over the
first 18 months have been reported previously (Lacey et al., 1973 and
1974). During the last 14 months (May 1973 to July 1974), further evolution
has occurred to produce a total of 31 distinct phenotypes. Recent changes
are as follows. 1. The ability of isolates to produce penicillinase in
vitro was closely correlated with flucloxacillin therapy. Inactivation of
flucloxacillin by penicillinase was demonstrated by diffusion testing (but
not MIC determination) in vitro and may have occurred to a significant
extent in vivo. 2. Lincomycin-resistant mutants slowly disappeared from the
sputum after the termination of clindamycin therapy. 3. All of the recent
isolates were resistant to erythromycin, possibly because of the linkage of
the genes coding for erythromycin resistance with those coding for the
production of delta-haemolysin; delta-haemolysin may be an important
"virulence factor".
